Cells and Metabolism Big Ideas. L.O. 1.15 – The student is able to describe specific examples of...
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Cells and Metabolism Big Ideas. L.O. 1.15 – The student is able to describe specific examples of conserved core biological processes and features shared
L.O. 1.15 The student is able to describe specific examples of
conserved core biological processes and features shared by all
domains or within one domain of life, and how these shared,
conserved core processes and features support the concept of common
ancestry for all living organisms.
Slide 3
Essential knowledge 2.A.1: All living systems require constant
input of free energy. a. Life requires a highly ordered system. 1.
Order is maintained by constant free energy input into the system.
2. Loss of order or free energy flow results in death. 3. Increased
disorder and entropy are offset by biological processes that
maintain or increase order. b. Living systems do not violate the
second law of thermodynamics, which states that entropy increases
over time. 1. Order is maintained by coupling cellular processes
that increase entropy (and so have negative changes in free energy)
with those that decrease entropy (and so have positive changes in
free energy). 2. Energy input must exceed free energy lost to
entropy to maintain order and power cellular processes. 3.
Energetically favorable exergonic reactions, such as ATPADP, that
have a negative change in free energy can be used to maintain or
increase order in a system by being coupled with reactions that
have a positive free energy change.
Slide 4
c. Energy-related pathways in biological systems are sequential
and may be entered at multiple points in the pathway. [See also
2.A.2] Krebs cycle Glycolysis Calvin cycle Fermentation d.
Organisms use free energy to maintain organization, grow and
reproduce. 1. Organisms use various strategies to regulate body
temperature and metabolism. Endothermy (the use of thermal energy
generated bymetabolism to maintain homeostatic body temperatures.
Ectothermy (the use of external thermal energy to help regulate and
maintain body temperature) Elevated floral temperatures in some
plant species 2. Reproduction and rearing of offspring require free
energy beyond that used for maintenance and growth. Different
organisms use various reproductive strategies in response to energy
availability. Seasonal reproduction in animals and plants
Life-history strategy (biennial plants, reproductive diapause) 3.
There is a relationship between metabolic rate per unit body mass
and the size of multicellular organisms generally, the smaller the
organism, the higher the metabolic rate. 4. Excess acquired free
energy versus required free energy expenditure results in energy
storage or growth. 5. Insufficient acquired free energy versus
required free energy expenditure results in loss of mass and,
ultimately, the death of an organism
Slide 5
e. Changes in free energy availability can result in changes in
population size. f. Changes in free energy availability can result
in disruptions to an ecosystem. Change in the producer level can
affect the number and size of other trophic levels. Change in
energy resources levels such as sunlight can affect the number and
size of the trophic levels. Learning Objectives: LO 2.1 The student
is able to explain how biological systems use free energy based on
empirical data that all organisms require constant energy input to
maintain organization, to grow and to reproduce. [See SP 6.2] LO
2.2 The student is able to justify a scientific claim that free
energy is required for living systems to maintain organization, to
grow or to reproduce, but that multiple strategies exist in
different living systems. [See SP 6.1] LO 2.3 The student is able
to predict how changes in free energy availability affect
organisms, populations and ecosystems. [See SP 6.4]
Slide 6
The Laws of Energy Transformation Thermodynamics is the study
of energy transformations A isolated system, such as that
approximated by liquid in a thermos, is isolated from its
surroundings In an open system, energy and matter can be
transferred between the system and its surroundings Organisms are
open systems 2011 Pearson Education, Inc.
Slide 7
The First Law of Thermodynamics According to the first law of
thermodynamics, the energy of the universe is constant Energy can
be transferred and transformed, but it cannot be created or
destroyed The first law is also called the principle of
conservation of energy 2011 Pearson Education, Inc.
Slide 8
The Second Law of Thermodynamics During every energy transfer
or transformation, some energy is unusable, and is often lost as
heat According to the second law of thermodynamics Every energy
transfer or transformation increases the entropy (disorder) of the
universe 2011 Pearson Education, Inc.
Slide 9
Figure 8.3 (a) First law of thermodynamics (b) Second law of
thermodynamics Chemical energy Heat
Slide 10
Free-Energy Change, G A living systems free energy is energy
that can do work when temperature and pressure are uniform, as in a
living cell The free-energy change of a reaction tells us whether
or not the reaction occurs spontaneously 2011 Pearson Education,
Inc.
Slide 11
The change in free energy (G) during a process is related to
the change in enthalpy, or change in total energy (H), change in
entropy (S), and temperature in Kelvin (T) G = H TS Only processes
with a negative G are spontaneous Spontaneous processes can be
harnessed to perform work 2011 Pearson Education, Inc.
Slide 12
Free Energy, Stability, and Equilibrium Free energy is a
measure of a systems instability, its tendency to change to a more
stable state During a spontaneous change, free energy decreases and
the stability of a system increases Equilibrium is a state of
maximum stability A process is spontaneous and can perform work
only when it is moving toward equilibrium 2011 Pearson Education,
Inc.
Slide 13
Figure 8.5 More free energy (higher G) Less stable Greater work
capacity In a spontaneous change The free energy of the system
decreases ( G 0) The system becomes more stable The released free
energy can be harnessed to do work Less free energy (lower G) More
stable Less work capacity (a) Gravitational motion (b) Diffusion(c)
Chemical reaction
Slide 14
Exergonic and Endergonic Reactions in Metabolism An exergonic
reaction proceeds with a net release of free energy and is
spontaneous An endergonic reaction absorbs free energy from its
surroundings and is nonspontaneous 2011 Pearson Education,
Inc.
Slide 15
Figure 8.6 (a) Exergonic reaction: energy released, spontaneous
(b) Endergonic reaction: energy required, nonspontaneous Reactants
Energy Products Progress of the reaction Amount of energy released
( G 0) Reactants Energy Products Amount of energy required ( G 0)
Progress of the reaction Free energy
Slide 16
Equilibrium and Metabolism Reactions in a closed system
eventually reach equilibrium and then do no work Cells are not in
equilibrium; they are open systems experiencing a constant flow of
materials A defining feature of life is that metabolism is never at
equilibrium A catabolic pathway in a cell releases free energy in a
series of reactions Closed and open hydroelectric systems can serve
as analogies 2011 Pearson Education, Inc.
Slide 17
Figure 8.7 (a) An isolated hydroelectric system (b) An open
hydro- electric system (c) A multistep open hydroelectric system G
0 G 0
Slide 18
Concept 8.3: ATP powers cellular work by coupling exergonic
reactions to endergonic reactions A cell does three main kinds of
work Chemical Transport Mechanical To do work, cells manage energy
resources by energy coupling, the use of an exergonic process to
drive an endergonic one Most energy coupling in cells is mediated
by ATP 2011 Pearson Education, Inc.
Slide 19
The Structure and Hydrolysis of ATP ATP (adenosine
triphosphate) is the cells energy shuttle ATP is composed of ribose
(a sugar), adenine (a nitrogenous base), and three phosphate groups
2011 Pearson Education, Inc.
Slide 20
Figure 8.8 (a) The structure of ATP Phosphate groups Adenine
Ribose Adenosine triphosphate (ATP) Energy Inorganic phosphate
Adenosine diphosphate (ADP) (b) The hydrolysis of ATP
Slide 21
How the Hydrolysis of ATP Performs Work The three types of
cellular work (mechanical, transport, and chemical) are powered by
the hydrolysis of ATP In the cell, the energy from the exergonic
reaction of ATP hydrolysis can be used to drive an endergonic
reaction Overall, the coupled reactions are exergonic 2011 Pearson
Education, Inc.
Slide 22
Figure 8.9 Glutamic acid Ammonia Glutamine (b) Conversion
reaction coupled with ATP hydrolysis Glutamic acid conversion to
glutamine (a) (c) Free-energy change for coupled reaction Glutamic
acid Glutamine Phosphorylated intermediate Glu NH 3 NH 2 Glu G Glu
= +3.4 kcal/mol ATP ADP NH 3 Glu P P i ADP Glu NH 2 G Glu = +3.4
kcal/mol Glu NH 3 NH 2 ATP G ATP = 7.3 kcal/mol G Glu = +3.4
kcal/mol + G ATP = 7.3 kcal/mol Net G = 3.9 kcal/mol 1 2
Slide 23
ATP drives endergonic reactions by phosphorylation,
transferring a phosphate group to some other molecule, such as a
reactant The recipient molecule is now called a phosphorylated
intermediate 2011 Pearson Education, Inc.
Slide 24
Figure 8.10 Transport protein Solute ATP P P i ADP P i ADP ATP
Solute transported Vesicle Cytoskeletal track Motor proteinProtein
and vesicle moved (b) Mechanical work: ATP binds noncovalently to
motor proteins and then is hydrolyzed. (a) Transport work: ATP
phosphorylates transport proteins.
Slide 25
The Regeneration of ATP ATP is a renewable resource that is
regenerated by addition of a phosphate group to adenosine
diphosphate (ADP) The energy to phosphorylate ADP comes from
catabolic reactions in the cell The ATP cycle is a revolving door
through which energy passes during its transfer from catabolic to
anabolic pathways 2011 Pearson Education, Inc.
Slide 26
Free Energy Equations and Diagrams Delta G? Activation
energy?
Slide 27
Essential knowledge 2.A.2: Organisms capture and store free
energy for use in biological processes. a. Autotrophs capture free
energy from physical sources in the environment. 1. Photosynthetic
organisms capture free energy present in sunlight. 2.
Chemosynthetic organisms capture free energy from small inorganic
molecules present in their environment, and this process can occur
in the absence of oxygen. b. Heterotrophs capture free energy
present in carbon compounds produced by other organisms. 1.
Heterotrophs may metabolize carbohydrates, lipids and proteins by
hydrolysis as sources of free energy. 2. Fermentation produces
organic molecules, including alcohol and lactic acid, and it occurs
in the absence of oxygen.
Slide 28
c. Different energy-capturing processes use different types of
electron acceptors. NADP+ in photosynthesis Oxygen in cellular
respiration d. The light-dependent reactions of photosynthesis in
eukaryotes involve a series of coordinated reaction pathways that
capture free energy present in light to yield ATP and NADPH, which
power the production of organic molecules. 1. During
photosynthesis, chlorophylls absorb free energy from light,
boosting electrons to a higher energy level in Photosystems I and
II. 2. Photosystems I and II are embedded in the internal membranes
of chloroplasts (thylakoids) and are connected by the transfer of
higher free energy electrons through an electron transport chain
(ETC). [See also 4.A.2] 3. When electrons are transferred between
molecules in a sequence of reactions as they pass through the ETC,
an electrochemical gradient of hydrogen ions (protons) across the
thykaloid membrane is established. 4. The formation of the proton
gradient is a separate process, but it is linked to the synthesis
of ATP from ADP and inorganic phosphate via ATP synthase. 5. The
energy captured in the light reactions as ATP and NADPH powers the
production of carbohydrates from carbon dioxide in the Calvin
cycle, which occurs in the stroma of the chloroplast.
Slide 29
e. Photosynthesis first evolved in prokaryotic organisms;
scientific evidence supports that prokaryotic (bacterial)
photosynthesis was responsible for the production of an oxygenated
atmosphere; prokaryotic photosynthetic pathways were the foundation
of eukaryotic photosynthesis. f. Cellular respiration in eukaryotes
involves a series of coordinated enzyme-catalyzed reactions that
harvest free energy from simple carbohydrates. 1. Glycolysis
rearranges the bonds in glucose molecules, releasing free energy to
form ATP from ADP and inorganic phosphate, and resulting in the
production of pyruvate. 2. Pyruvate is transported from the
cytoplasm to the mitochondrion, where further oxidation occurs.
[See also 4.A.2] 3. In the Krebs cycle, carbon dioxide is released
from organic intermediates ATP is synthesized from ADP and
inorganic phosphate via substrate level phosphorylation and
electrons are captured by coenzymes. 4. Electrons that are
extracted in the series of Krebs cycle reactions are carried by
NADH and FADH2 to the electron transport chain.
Slide 30
g. The electron transport chain captures free energy from
electrons in a series of coupled reactions that establish an
electrochemical gradient across membranes. 1. Electron transport
chain reactions occur in chloroplasts (photosynthesis),
mitochondria (cellular respiration) and prokaryotic plasma
membranes. 2. In cellular respiration, electrons delivered by NADH
and FADH2 are passed to a series of electron acceptors as they move
toward the terminal electron acceptor, oxygen. In photosynthesis,
the terminal electron acceptor is NADP+. 3. The passage of
electrons is accompanied by the formation of a proton gradient
across the inner mitochondrial membrane or the thylakoid membrane
of chloroplasts, with the membrane(s) separating a region of high
proton concentration from a region of low proton concentration. In
prokaryotes, the passage of electrons is accompanied by the outward
movement of protons across the plasma membrane. 4. The flow of
protons back through membrane-bound ATP synthase by chemiosmosis
generates ATP from ADP and inorganic phosphate. 5. In cellular
respiration, decoupling oxidative phosphorylation from electron
transport is involved in thermoregulation. h. Free energy becomes
available for metabolism by the conversion of ATPADP, which is
coupled to many steps in metabolic pathways.
Slide 31
Learning Objectives: LO 2.4 The student is able to use
representations to pose scientific questions about what mechanisms
and structural features allow organisms to capture, store and use
free energy. [See SP 1.4, 3.1] LO 2.5 The student is able to
construct explanations of the mechanisms and structural features of
cells that allow organisms to capture, store or use free energy.
[See SP 6.2]
Slide 32
Figure 9.2 Light energy ECOSYSTEM Photosynthesis in
chloroplasts Cellular respiration in mitochondria CO 2 H 2 O O 2
Organic molecules ATP powers most cellular work ATP Heat
energy
Slide 33
Catabolic pathways yield energy by oxidizing organic fuels to
produce ATP The breakdown of organic molecules is exergonic
Fermentation is a partial degradation of sugars that occurs without
O2 Aerobic respiration consumes organic molecules and O2 and yields
ATP Anaerobic respiration is similar to aerobic respiration but
consumes compounds other than O2 2011 Pearson Education, Inc.
Slide 34
Cellular respiration includes both aerobic and anaerobic
respiration but is often used to refer to aerobic respiration
Although carbohydrates, fats, and proteins are all consumed as
fuel, it is helpful to trace cellular respiration with the sugar
glucose C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy (ATP + heat) 2011
Pearson Education, Inc.
Slide 35
The Principle of Redox Chemical reactions that transfer
electrons between reactants are called oxidation- reduction
reactions, or redox reactions In oxidation, a substance loses
electrons, or is oxidized In reduction, a substance gains
electrons, or is reduced (the amount of positive charge is reduced)
2011 Pearson Education, Inc. becomes oxidized (loses electron)
becomes reduced (gains electron)
Slide 36
Oxidation of Organic Fuel Molecules During Cellular Respiration
During cellular respiration, the fuel (such as glucose) is
oxidized, and O2 is reduced 2011 Pearson Education, Inc. becomes
oxidized becomes reduced
Slide 37
Stepwise Energy Harvest via NAD+ and the Electron Transport
Chain In cellular respiration, glucose and other organic molecules
are broken down in a series of steps Electrons from organic
compounds are usually first transferred to NAD+, a coenzyme As an
electron acceptor, NAD+ functions as an oxidizing agent during
cellular respiration Each NADH (the reduced form of NAD+)
represents stored energy that is tapped to synthesize ATP 2011
Pearson Education, Inc.
Slide 38
Figure 9.4 Nicotinamide (oxidized form) NAD (from food)
Dehydrogenase Reduction of NAD Oxidation of NADH Nicotinamide
(reduced form) NADH Dehydrogenase
Slide 39
NADH passes the electrons to the electron transport chain
Unlike an uncontrolled reaction, the electron transport chain
passes electrons in a series of steps instead of one explosive
reaction O2 pulls electrons down the chain in an energy-yielding
tumble The energy yielded is used to regenerate ATP 2011 Pearson
Education, Inc.
Slide 40
Figure 9.5 (a) Uncontrolled reaction (b) Cellular respiration
Explosive release of heat and light energy Controlled release of
energy for synthesis of ATP Free energy, G H 2 1 / 2 O 2 2 H 1 / 2
O 2 H2OH2O H2OH2O 2 H + 2 e 2 e 2 H + ATP Electron transport chain
(from food via NADH)
Slide 41
Electron shuttles span membrane MITOCHONDRION 2 NADH 6 NADH 2
FADH 2 or 2 ATP about 26 or 28 ATP Glycolysis Glucose 2 Pyruvate
Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Oxidative
phosphorylation: electron transport and chemiosmosis CYTOSOL
Maximum per glucose: About 30 or 32 ATP Moving into matrix on your
picture, point to matrix, cristae, inner mitochondrial membrane,
and intermembrane space NADH from glycolysis 1.5 ATP vs. 2.5 ATP
per NADH depending on which shuttle working
Slide 42
Electron shuttles span membrane MITOCHONDRION 2 NADH 6 NADH 2
FADH 2 or 2 ATP about 26 or 28 ATP Glycolysis Glucose 2 Pyruvate
Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Oxidative
phosphorylation: electron transport and chemiosmosis CYTOSOL
Maximum per glucose: About 30 or 32 ATP Now moving to the inner
mitochondrial membrane 4. Electrons that are extracted in the
series of Krebs cycle reactions are carried by NADH and FADH2 to
the electron transport chain.
Slide 43
g. The electron transport chain captures free energy from
electrons in a series of coupled reactions that establish an
electrochemical gradient across membranes. 1. Electron transport
chain reactions occur in chloroplasts (photosynthesis),
mitochondria (cellular respiration) and prokaryotic plasma
membranes.
Slide 44
Figure 9.13 NADH FADH 2 2 H + 1 / 2 O 2 2 e H2OH2O NAD
Multiprotein complexes (originally from NADH or FADH 2 ) I II III
IV 50 40 30 20 10 0 Free energy (G) relative to O 2 (kcal/mol) FMN
Fe S FAD Q Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 Fe S 2. In cellular
respiration, electrons delivered by NADH and FADH2 are passed to a
series of electron acceptors as they move toward the terminal
electron acceptor, oxygen. The electrons carried by FADH2 have
lower free energy and are added to a later point in the chain.
Slide 45
3. The passage of electrons is accompanied by the formation of
a proton gradient across the inner mitochondrial membrane or the
thylakoid membrane of chloroplasts, with the membrane(s) separating
a region of high proton concentration from a region of low proton
concentration. In prokaryotes, the passage of electrons is
accompanied by the outward movement of protons across the plasma
membrane.
Slide 46
Figure 9.15 Protein complex of electron carriers (carrying
electrons from food) Electron transport chain Oxidative
phosphorylation Chemiosmosis ATP synth- ase I II III IV Q Cyt c FAD
FADH 2 NADH ADP P i NAD HH 2 H + 1 / 2 O 2 HH HH HH 21 HH H2OH2O
ATP
Slide 47
4. The flow of protons back through membrane-bound ATP synthase
by chemiosmosis generates ATP from ADP and inorganic phosphate. ATP
synthase uses the exergonic flow of H + to drive phosphorylation of
ATP This is an example of chemiosmosis, the use of energy in a H +
gradient to drive cellular work The H + gradient is referred to as
a proton-motive force, emphasizing its capacity to do work Figure
9.14 INTERMEMBRANE SPACE Rotor Stator HH Internal rod Catalytic
knob ADP + P i ATP MITOCHONDRIAL MATRIX
Slide 48
Figure 9.16 Electron shuttles span membrane MITOCHONDRION 2
NADH 6 NADH 2 FADH 2 or 2 ATP about 26 or 28 ATP Glycolysis Glucose
2 Pyruvate Pyruvate oxidation 2 Acetyl CoA Citric acid cycle
Oxidative phosphorylation: electron transport and chemiosmosis
CYTOSOL Maximum per glucose: About 30 or 32 ATP
Slide 49
5. In cellular respiration, decoupling oxidative
phosphorylation from electron transport is involved in
thermoregulation. Used by hibernating mammals Brown fat, high in
mitochondria, with ETC uncoupling protein Protein is activated
during hibernation Allows protons to flow back down their gradient
without making ATP (uncoupled) Ongoing oxidation of stored fuel
generates heat to keep body temp warmer than environment If ATP
were made, would build up to high levels that would shut down the
cell respiration pathways
Slide 50
Temp regulation
Slide 51
Fermentation produces organic molecules, including alcohol and
lactic acid, and it occurs in the absence of oxygen. See Ch. 9
slide 78 Animation
Slide 52
In alcohol fermentation, pyruvate is converted to ethanol in
two steps. First, pyruvate is converted to a two-carbon compound,
acetaldehyde by the removal of CO 2. Second, acetaldehyde is
reduced by NADH to ethanol. Alcohol fermentation by yeast is used
in brewing and winemaking. Fig. 9.17a
Slide 53
During lactic acid fermentation, pyruvate is reduced directly
by NADH to form lactate (ionized form of lactic acid). Lactic acid
fermentation by some fungi and bacteria is used to make cheese and
yogurt. Muscle cells switch from aerobic respiration to lactic acid
fermentation to generate ATP when O 2 is scarce. The waste product,
lactate, may cause muscle fatigue, but ultimately it is converted
back to pyruvate in the liver. Fig. 9.17b
Slide 54
Some organisms (facultative anaerobes), including yeast and
many bacteria, can survive using either fermentation or
respiration. At a cellular level, human muscle cells can behave as
facultative anaerobes, but nerve cells cannot. For facultative
anaerobes, pyruvate is a fork in the metabolic road that leads to
two alternative routes. Fig. 9.18
Slide 55
The Evolutionary Significance of Glycolysis Ancient prokaryotes
are thought to have used glycolysis long before there was oxygen in
the atmosphere Very little O 2 was available in the atmosphere
until about 2.7 billion years ago, so early prokaryotes likely used
only glycolysis to generate ATP Glycolysis is a very ancient
process 2011 Pearson Education, Inc.
Slide 56
Control of catabolism is based mainly on regulating the
activity of enzymes at strategic points in the catabolic pathway.
One strategic point occurs in the third step of glycolysis,
catalyzed by phosphofructokinase. Fig. 9.20
Slide 57
Carbohydrates, fats, and proteins can all be catabolized
through the same pathways. Fig. 9.19
Slide 58
Slide 59
Slide 60
Slide 61
Chloroplasts: The Sites of Photosynthesis in Plants Leaves are
the major locations of photosynthesis Their green color is from
chlorophyll, the green pigment within chloroplasts Chloroplasts are
found mainly in cells of the mesophyll, the interior tissue of the
leaf Each mesophyll cell contains 3040 chloroplasts 2011 Pearson
Education, Inc.
Slide 62
CO 2 enters and O 2 exits the leaf through microscopic pores
called stomata The chlorophyll is in the membranes of thylakoids
(connected sacs in the chloroplast); thylakoids may be stacked in
columns called grana Chloroplasts also contain stroma, a dense
interior fluid 2011 Pearson Education, Inc.
Slide 63
Figure 10.4 Mesophyll Leaf cross section Chloroplasts Vein
Stomata Chloroplast Mesophyll cell CO 2 O2O2 20 m Outer membrane
Intermembrane space Inner membrane 1 m Thylakoid space Thylakoid
Granum Stroma Lets look at model
Slide 64
Photosynthesis as a Redox Process Photosynthesis reverses the
direction of electron flow compared to respiration Photosynthesis
is a redox process in which H 2 O is oxidized and CO 2 is reduced
Photosynthesis is an endergonic process; the energy boost is
provided by light 2011 Pearson Education, Inc. Energy 6 CO 2 6 H 2
O C 6 H 12 O 6 6 O 2 becomes reduced becomes oxidized
Slide 65
The Two Stages of Photosynthesis: A Preview Photosynthesis
consists of the light reactions (the photo part) and Calvin cycle
(the synthesis part) The light reactions (in the thylakoids) Split
H 2 O Release O 2 Reduce NADP + to NADPH Generate ATP from ADP by
photophosphorylation 2011 Pearson Education, Inc.
Slide 66
The Calvin cycle (in the stroma) forms sugar from CO 2, using
ATP and NADPH The Calvin cycle begins with carbon fixation,
incorporating CO 2 into organic molecules 2011 Pearson Education,
Inc.
Slide 67
Light Light Reactions Calvin Cycle Chloroplast [CH 2 O] (sugar)
ATP NADPH NADP ADP + P i H2OH2O CO 2 O2O2 Figure 10.6-4
Slide 68
While light travels as a wave, many of its properties are those
of a discrete particle, the photon. Photons are not tangible
objects, but they do have fixed quantities of energy and amount
depends on wavelength.
Slide 69
(b) Action spectrum (a) Absorption spectra Engelmanns
experiment (c) Chloro- phyll a Chlorophyll b Carotenoids Wavelength
of light (nm) Absorption of light by chloroplast pigments Rate of
photosynthesis (measured by O 2 release) Aerobic bacteria Filament
of alga 400 500600700 400 500600700 400 500600700 RESULTS Figure
10.10
Slide 70
Chlorophyll a is the main photosynthetic pigment Accessory
pigments, such as chlorophyll b, broaden the spectrum used for
photosynthesis Accessory pigments called carotenoids absorb
excessive light that would damage chlorophyll 2011 Pearson
Education, Inc.
Slide 71
Excited electrons are unstable. Generally, they drop to their
ground state in a billionth of a second, releasing heat energy.
Some pigments, including chlorophyll, release a photon of light, in
a process called fluorescence, as well as heat. Fig. 10.10
Slide 72
Fig. 10.9
Slide 73
Figure 10.18 STROMA (low H concentration) THYLAKOID SPACE (high
H concentration) Light Photosystem II Cytochrome complex
Photosystem I Light NADP reductase NADP + H To Calvin Cycle ATP
synthase Thylakoid membrane 2 13 NADPH Fd Pc Pq 4 H + +2 H + H+H+
ADP + P i ATP 1/21/2 H2OH2O O2O2
Slide 74
A Photosystem: A Reaction-Center Complex Associated with Light-
Harvesting Complexes A photosystem consists of a reaction-center
complex (a type of protein complex) surrounded by light-harvesting
complexes The light-harvesting complexes (pigment molecules bound
to proteins) transfer the energy of photons to the reaction center
2011 Pearson Education, Inc.
Slide 75
Figure 10.13 (b) Structure of photosystem II (a) How a
photosystem harvests light Thylakoid membrane Photon Photosystem
STROMA Light- harvesting complexes Reaction- center complex Primary
electron acceptor Transfer of energy Special pair of chlorophyll a
molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)
Chlorophyll STROMA Protein subunits THYLAKOID SPACE ee Each
photosystem consists of chlorophylls, accessory pigments, and
proteins. The black arrows represent photons being passed like a
wave to reaction center chlorophylls that actually donate their
electrons.
Slide 76
Figure 10.14-5 Cytochrome complex Primary acceptor H2OH2O O2O2
2 H + 1/21/2 P680 Light Pigment molecules Photosystem II (PS II )
Photosystem I (PS I ) Pq Pc ATP 1 235 6 7 8 Electron transport
chain P700 Light + H NADP NADPH NADP reductase Fd ee ee ee ee 4 ee
ee Linear Electron Flow
Slide 77
Photosystem II Photosystem I Mill makes ATP ATP NADPH ee ee ee
ee ee ee ee Photon Figure 10.15
Slide 78
Lets watch animation of Phase I
http://www.mhhe.com/biosci/genbio/biolink
/j_explorations/ch09expl.htmhttp://www.mhhe.com/biosci/genbio/biolink
/j_explorations/ch09expl.htm
Slide 79
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria
Chloroplasts and mitochondria generate ATP by chemiosmosis, but use
different sources of energy Mitochondria transfer chemical energy
from food to ATP; chloroplasts transform light energy into the
chemical energy of ATP Spatial organization of chemiosmosis differs
between chloroplasts and mitochondria but also shows similarities
2011 Pearson Education, Inc.
Slide 80
In mitochondria, protons are pumped to the intermembrane space
and drive ATP synthesis as they diffuse back into the mitochondrial
matrix In chloroplasts, protons are pumped into the thylakoid space
and drive ATP synthesis as they diffuse back into the stroma 2011
Pearson Education, Inc.
Slide 81
Mitochondrion Chloroplast MITOCHONDRION STRUCTURE CHLOROPLAST
STRUCTURE Intermembrane space Inner membrane Matrix Thylakoid space
Thylakoid membrane Stroma Electron transport chain HH Diffusion ATP
synthase HH ADP P i KeyHigher [H ] Lower [H ] ATP Figure 10.17
Slide 82
ATP and NADPH are produced on the side facing the stroma, where
the Calvin cycle takes place In summary, light reactions generate
ATP and increase the potential energy of electrons by moving them
from H 2 O to NADPH 2011 Pearson Education, Inc.
Slide 83
Input 3 (Entering one at a time) CO 2 Phase 1: Carbon fixation
Rubisco 3PP P6 Short-lived intermediate 3-Phosphoglycerate 6 6 ADP
ATP 6PP 1,3-Bisphosphoglycerate Calvin Cycle 6 NADPH 6 NADP 6 P i6
P i 6P Phase 2: Reduction Glyceraldehyde 3-phosphate (G3P) P 5 G3P
ATP 3 ADP Phase 3: Regeneration of the CO 2 acceptor (RuBP) 3P P
Ribulose bisphosphate (RuBP) 1P G3P (a sugar) Output Glucose and
other organic compounds 3 Figure 10.19-3 For every one net G3P,
requires 9 ATP and 6 NADPH from the light reaction. Calvin
Cycle
Slide 84
Cyclic Electron Flow Cyclic electron flow uses only photosystem
I and produces ATP, but not NADPH No oxygen is released Cyclic
electron flow generates surplus ATP, satisfying the higher demand
in the Calvin cycle 2011 Pearson Education, Inc.
Slide 85
Figure 10.16 Photosystem I Primary acceptor Cytochrome complex
Fd Pc ATP Primary acceptor Pq Fd NADPH NADP reductase NADP + H
Photosystem II
Slide 86
In photosynthesis, the energy that enters the chloroplasts as
sunlight becomes stored as chemical energy in organic compounds.
Photosynthesis is the biospheres metabolic foundation - About 50%
of the organic material made is consumed as fuel for cellular
respiration in plant mitochondria. Rest is stored or used to build
other organic compounds.
Slide 87
On a global scale, photosynthesis is the most important process
to the welfare of life on Earth. Each year photosynthesis
synthesizes 160 billion metric tons of carbohydrate per year.
Slide 88
Slide 89
Essential knowledge 2.B.1: Cell membranes are selectively
permeable due to their structure. a.Cell membranes separate the
internal environment of the cell from the external environment. b.
Selective permeability is a direct consequence of membrane
structure, as described by the fluid mosaic model. [See also 4.A.1]
1. Cell membranes consist of a structural framework of phospholipid
molecules, embedded proteins, cholesterol, glycoproteins and
glycolipids. 2. Phospholipids give the membrane both hydrophilic
and hydrophobic properties. The hydrophilic phosphate portions of
the phospholipids are oriented toward the aqueous external or
internal environments, while the hydrophobic fatty acid portions
face each other within the interior of the membrane itself. 3.
Embedded proteins can be hydrophilic, with charged and polar side
groups, or hydrophobic, with nonpolar side groups. 4. Small,
uncharged polar molecules and small nonpolar molecules, such as N2,
freely pass across the membrane. Hydrophilic substances such as
large polar molecules and ions move across the membrane through
embedded channel and transport proteins. Water moves across
membranes and through channel proteins called aquaporins.
Slide 90
c. Cell walls provide a structural boundary, as well as a
permeability barrier for some substances to the internal
environments. 1. Plant cell walls are made of cellulose and are
external to the cell membrane. 2. Other examples are cells walls of
prokaryotes and fungi. Learning Objectives: LO 2.10 The student is
able to use representations and models to pose scientific questions
about the properties of cell membranes and selective permeability
based on molecular structure. [See SP 1.4, 3.1] LO 2.11 The student
is able to construct models that connect the movement of molecules
across membranes with membrane structure and function. [See SP 1.1,
7.1, 7.2]
Slide 91
Essential knowledge 2.B.2: Growth and dynamic homeostasis are
maintained by the constant movement of molecules across membranes.
a. Passive transport does not require the input of metabolic
energy; the net movement of molecules is from high concentration to
low concentration. 1. Passive transport plays a primary role in the
import of resources and the export of wastes. 2. Membrane proteins
play a role in facilitated diffusion of charged and polar molecules
through a membrane. Glucose transport Na+/K+ transport 3. External
environments can be hypotonic, hypertonic or isotonic to internal
environments of cells. b. Active transport requires free energy to
move molecules from regions of low concentration to regions of high
concentration. 1. Active transport is a process where free energy
(often provided by ATP) is used by proteins embedded in the
membrane to move molecules and/or ions across the membrane and to
establish and maintain concentration gradients. 2. Membrane
proteins are necessary for active transport.
Slide 92
c. The processes of endocytosis and exocytosis move large
molecules from the external environment to the internal environment
and vice versa, respectively. 1. In exocytosis, internal vesicles
fuse with the plasma membrane to secrete large macromolecules out
of the cell. 2. In endocytosis, the cell takes in macromolecules
and particulate matter by forming new vesicles derived from the
plasma membrane. Learning Objective LO 2.12 The student is able to
use representations and models to analyze situations or solve
problems qualitatively and quantitatively to investigate whether
dynamic homeostasis is maintained by the active movement of
molecules across membranes. [See SP1.4]
Slide 93
Concept 7.1: Cellular membranes are fluid mosaics of lipids and
proteins Phospholipids are the most abundant lipid in the plasma
membrane Phospholipids are amphipathic molecules, containing
hydrophobic and hydrophilic regions The fluid mosaic model states
that a membrane is a fluid structure with a mosaic of various
proteins embedded in it 2011 Pearson Education, Inc.
Slide 94
Figure 7.2 Hydrophilic head Hydrophobic tail WATER
Slide 95
Figure 7.3 Phospholipid bilayer Hydrophobic regions of protein
Hydrophilic regions of protein
Slide 96
Figure 7.5 Glyco- protein Carbohydrate Glycolipid
Microfilaments of cytoskeleton EXTRACELLULAR SIDE OF MEMBRANE
CYTOPLASMIC SIDE OF MEMBRANE Integral protein Peripheral proteins
Cholesterol Fibers of extra- cellular matrix (ECM)
Slide 97
Figure 7.6 Lateral movement occurs 10 7 times per second.
Flip-flopping across the membrane is rare ( once per month).
Slide 98
Figure 7.7 Membrane proteins Mouse cell Human cell Hybrid cell
Mixed proteins after 1 hour RESULTS
Slide 99
As temperatures cool, membranes switch from a fluid state to a
solid state The temperature at which a membrane solidifies depends
on the types of lipids Membranes rich in unsaturated fatty acids
are more fluid than those rich in saturated fatty acids Membranes
must be fluid to work properly; they are usually about as fluid as
salad oil 2011 Pearson Education, Inc.
Slide 100
The steroid cholesterol has different effects on membrane
fluidity at different temperatures At warm temperatures (such as
37C), cholesterol restrains movement of phospholipids At cool
temperatures, it maintains fluidity by preventing tight packing
2011 Pearson Education, Inc.
Slide 101
Figure 7.8 Fluid Unsaturated hydrocarbon tails Viscous
Saturated hydrocarbon tails (a) Unsaturated versus saturated
hydrocarbon tails (b) Cholesterol within the animal cell membrane
Cholesterol
Slide 102
Evolution of Differences in Membrane Lipid Composition
Variations in lipid composition of cell membranes of many species
appear to be adaptations to specific environmental conditions
Ability to change the lipid compositions in response to temperature
changes has evolved in organisms that live where temperatures vary
2011 Pearson Education, Inc.
Slide 103
Peripheral proteins are bound to the surface of the membrane
Integral proteins penetrate the hydrophobic core Integral proteins
that span the membrane are called transmembrane proteins The
hydrophobic regions of an integral protein consist of one or more
stretches of nonpolar amino acids, often coiled into alpha helices
2011 Pearson Education, Inc.
Slide 104
Figure 7.9 N-terminus helix C-terminus EXTRACELLULAR SIDE
CYTOPLASMIC SIDE
Slide 105
Figure 7.10 Enzymes Signaling molecule Receptor Signal
transduction Glyco- protein ATP (a) Transport (b) Enzymatic
activity (c) Signal transduction (d) Cell-cell recognition (e)
Intercellular joining (f) Attachment to the cytoskeleton and
extracellular matrix (ECM)
Slide 106
The Role of Membrane Carbohydrates in Cell-Cell Recognition
Cells recognize each other by binding to surface molecules, often
containing carbohydrates, on the extracellular surface of the
plasma membrane Membrane carbohydrates may be covalently bonded to
lipids (forming glycolipids) or more commonly to proteins (forming
glycoproteins) Carbohydrates on the external side of the plasma
membrane vary among species, individuals, and even cell types in an
individual 2011 Pearson Education, Inc.
Slide 107
Figure 7.11 Receptor (CD4) Co-receptor (CCR5) HIV Receptor
(CD4) but no CCR5 Plasma membrane HIV can infect a cell that has
CCR5 on its surface, as in most people. HIV cannot infect a cell
lacking CCR5 on its surface, as in resistant individuals.
Slide 108
Concept 7.2: Membrane structure results in selective
permeability A cell must exchange materials with its surroundings,
a process controlled by the plasma membrane Plasma membranes are
selectively permeable, regulating the cells molecular traffic
Hydrophobic (nonpolar) molecules, such as hydrocarbons, can
dissolve in the lipid bilayer and pass through the membrane rapidly
Polar molecules, such as sugars, do not cross the membrane easily
2011 Pearson Education, Inc.
Slide 109
Transport Proteins Transport proteins allow passage of
hydrophilic substances across the membrane Some transport proteins,
called channel proteins, have a hydrophilic channel that certain
molecules or ions can use as a tunnel Channel proteins called
aquaporins facilitate the passage of water Other transport
proteins, called carrier proteins, bind to molecules and change
shape to shuttle them across the membrane A transport protein is
specific for the substance it moves 2011 Pearson Education,
Inc.
Slide 110
Figure 7.17 EXTRACELLULAR FLUID CYTOPLASM Channel protein
Solute Carrier protein (a) A channel protein (b) A carrier
protein
Slide 111
Facilitated Diffusion: Passive Transport Aided by Proteins In
facilitated diffusion, transport proteins speed the passive
movement of molecules across the plasma membrane Channel proteins
provide corridors that allow a specific molecule or ion to cross
the membrane Channel proteins include Aquaporins, for facilitated
diffusion of water Ion channels that open or close in response to a
stimulus (gated channels) 2011 Pearson Education, Inc.
Slide 112
Concept 7.4: Active transport uses energy to move solutes
against their gradients Facilitated diffusion is still passive
because the solute moves down its concentration gradient, and the
transport requires no energy Some transport proteins, however, can
move solutes against their concentration gradients 2011 Pearson
Education, Inc.
Slide 113
The Need for Energy in Active Transport Active transport moves
substances against their concentration gradients Active transport
requires energy, usually in the form of ATP Active transport is
performed by specific proteins embedded in the membranes 2011
Pearson Education, Inc.
Slide 114
Animation: Active Transport Right-click slide / select
Play
Slide 115
Active transport allows cells to maintain concentration
gradients that differ from their surroundings The sodium-potassium
pump is one type of active transport system 2011 Pearson Education,
Inc.
Slide 116
Figure 7.18-6 EXTRACELLULAR FLUID [Na ] high [K ] low [Na ] low
[K ] high CYTOPLASM Na 123456 KK KK KK KK KK KK P P P P i ATP
ADP
Slide 117
Figure 7.19 Passive transportActive transport
DiffusionFacilitated diffusion ATP
Slide 118
How Ion Pumps Maintain Membrane Potential Membrane potential is
the voltage difference across a membrane Voltage is created by
differences in the distribution of positive and negative ions
across a membrane 2011 Pearson Education, Inc.
Slide 119
Two combined forces, collectively called the electrochemical
gradient, drive the diffusion of ions across a membrane A chemical
force (the ions concentration gradient) An electrical force (the
effect of the membrane potential on the ions movement) 2011 Pearson
Education, Inc.
Slide 120
An electrogenic pump is a transport protein that generates
voltage across a membrane The sodium-potassium pump is the major
electrogenic pump of animal cells The main electrogenic pump of
plants, fungi, and bacteria is a proton pump Electrogenic pumps
help store energy that can be used for cellular work 2011 Pearson
Education, Inc.
Cotransport: Coupled Transport by a Membrane Protein
Cotransport occurs when active transport of a solute indirectly
drives transport of other solutes Plants commonly use the gradient
of hydrogen ions generated by proton pumps to drive active
transport of nutrients into the cell 2011 Pearson Education,
Inc.
Slide 123
Figure 7.21 ATP HH HH HH HH HH HH HH HH Proton pump Sucrose-H
cotransporter Sucrose Diffusion of H
Slide 124
Concept 7.5: Bulk transport across the plasma membrane occurs
by exocytosis and endocytosis Small molecules and water enter or
leave the cell through the lipid bilayer or via transport proteins
Large molecules, such as polysaccharides and proteins, cross the
membrane in bulk via vesicles Bulk transport requires energy 2011
Pearson Education, Inc.
Slide 125
Animation: Exocytosis and Endocytosis Introduction Right-click
slide / select Play
Slide 126
Exocytosis In exocytosis, transport vesicles migrate to the
membrane, fuse with it, and release their contents Many secretory
cells use exocytosis to export their products 2011 Pearson
Education, Inc.
Slide 127
Animation: Exocytosis Right-click slide / select Play
Slide 128
Endocytosis In endocytosis, the cell takes in macromolecules by
forming vesicles from the plasma membrane Endocytosis is a reversal
of exocytosis, involving different proteins There are three types
of endocytosis Phagocytosis (cellular eating) Pinocytosis (cellular
drinking) Receptor-mediated endocytosis 2011 Pearson Education,
Inc.
Slide 129
Animation: Phagocytosis Right-click slide / select Play In
phagocytosis a cell engulfs a particle in a vacuole The vacuole
fuses with a lysosome to digest the particle
Slide 130
2011 Pearson Education, Inc. Animation: Pinocytosis Right-click
slide / select Play In pinocytosis, molecules are taken up when
extracellular fluid is gulped into tiny vesicles
Slide 131
2011 Pearson Education, Inc. Animation: Receptor-Mediated
Endocytosis Right-click slide / select Play In receptor- mediated
endocytosis, binding of ligands to receptors triggers vesicle
formation A ligand is any molecule that binds specifically to a
receptor site of another molecule
Enduring understanding 2.B: Growth, reproduction and dynamic
homeostasis require that cells create and maintain internal
environments that are different from their external environments.
Essential knowledge 2.B.3: Eukaryotic cells maintain internal
membranes that partition the cell into specialized regions. a.
Internal membranes facilitate cellular processes by minimizing
competing interactions and by increasing surface area where
reactions can occur. b. Membranes and membrane-bound organelles in
eukaryotic cells localize (compartmentalize) intracellular
metabolic processes and specific enzymatic reactions. [See also
4.A.2] Endoplasmic reticulum Mitochondria Chloroplasts Golgi
Nuclear envelope c. Archaea and Bacteria generally lack internal
membranes and organelles and have a cell wall.
Slide 135
2.B.3 Learning Objectives LO 2.13 The student is able to
explain how internal membranes and organelles contribute to cell
functions. [See SP 6.2] LO 2.14 The student is able to use
representations and models to describe differences in prokaryotic
and eukaryotic cells. [See SP1.4]
Slide 136
Fimbriae Bacterial chromosome A typical rod-shaped bacterium
(a) Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella A
thin section through the bacterium Bacillus coagulans (TEM) (b) 0.5
m Figure 6.5
Slide 137
Eukaryotic cells are characterized by having DNA in a nucleus
that is bounded by a membranous nuclear envelope Membrane-bound
organelles Cytoplasm in the region between the plasma membrane and
nucleus Eukaryotic cells are generally much larger than prokaryotic
cells 2011 Pearson Education, Inc.
Essential knowledge 4.A.2: The structure and function of
subcellular components, and their interactions, provide essential
cellular processes. a. Ribosomes are small, universal structures
comprised of two interacting parts: ribosomal RNA and protein. In a
sequential manner, these cellular components interact to become the
site of protein synthesis where the translation of the genetic
instructions yields specific polypeptides. [See also 2.B.3] b.
Endoplasmic reticulum (ER) occurs in two forms: smooth and rough.
[See also 2.B.3] 1. Rough endoplasmic reticulum functions to
compartmentalize the cell, serves as mechanical support, provides
site-specific protein synthesis with membrane-bound ribosomes and
plays a role in intracellular transport. 2. In most cases, smooth
ER synthesizes lipids.
Slide 141
c. The Golgi complex is a membrane-bound structure that
consists of a series of flattened membrane sacs (cisternae). [See
also 2.B.3] 1. Functions of the Golgi include synthesis and
packaging of materials (small molecules) for transport (in
vesicles), and production of lysosomes. d. Mitochondria specialize
in energy capture and transformation. [See also 2.A.2, 2.B.3] 1.
Mitochondria have a double membrane that allows
compartmentalization within the mitochondria and is important to
its function. 2. The outer membrane is smooth, but the inner
membrane is highly convoluted, forming folds called cristae. 3.
Cristae contain enzymes important to ATP production; cristae also
increase the surface area for ATP production.
Slide 142
e. Lysosomes are membrane-enclosed sacs that contain hydrolytic
enzymes, which are important in intracellular digestion, the
recycling of a cells organic materials and programmed cell death
(apoptosis). Lysosomes carry out intracellular digestion in a
variety of ways. [See also 2.B.3] f. A vacuole is a membrane-bound
sac that plays roles in intracellular digestion and the release of
cellular waste products. In plants, a large vacuole serves many
functions, from storage of pigments orpoisonous substances to a
role in cell growth. In addition, a large central vacuole allows
for a large surface area to volume ratio. [See also 2.A.3, 2.B.3]
g. Chloroplasts are specialized organelles found in algae and
higher plants that capture energy through photosynthesis. [See also
2.A.2, 2 B.3] 1. The structure and function relationship in the
chloroplast allows cells to capture the energy available in
sunlight and convert it to chemical bond energy via photosynthesis.
2. Chloroplasts contain chlorophylls, which are responsible for the
green color of a plant and are the key light-trapping molecules in
photosynthesis. There are several types of chlorophyll, but the
predominant form in plants is chlorophyll a. 3. Chloroplasts have a
double outer membrane that creates a compartmentalized structure,
which supports its function. Within the chloroplasts are
membrane-bound structures called thylakoids. Energy- capturing
reactions housed in the thylakoids are organized in stacks, called
grana, to produce ATP and NADPH2, which fuel carbon-fixing
reactions in the Calvin-Benson cycle. Carbon fixation occurs in the
stroma, where molecules of CO2 are converted to carbohydrates.
Slide 143
4.A.2 Learning Objectives LO 4.4 The student is able to make a
prediction about the interactions of subcellular organelles. [See
SP 6.4] LO 4.5 The student is able to construct explanations based
on scientific evidence as to how interactions of subcellular
structures provide essential functions. [See SP 6.2] LO 4.6 The
student is able to use representations and models to analyze
situations qualitatively to describe how interactions of
subcellular structures, which possess specialized functions,
provide essential functions. [See SP 1.4]
Slide 144
Concept 6.4: The endomembrane system regulates protein traffic
and performs metabolic functions in the cell Components of the
endomembrane system Nuclear envelope Endoplasmic reticulum Golgi
apparatus Lysosomes Vacuoles Plasma membrane These components are
either continuous or connected via transfer by vesicles 2011
Pearson Education, Inc. X
Slide 145
The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic
reticulum (ER) accounts for more than half of the total membrane in
many eukaryotic cells The ER membrane is continuous with the
nuclear envelope There are two distinct regions of ER Smooth ER,
which lacks ribosomes Rough ER, surface is studded with ribosomes
2011 Pearson Education, Inc.
Slide 146
Figure 6.11 Smooth ER Rough ER ER lumen Cisternae Ribosomes
Smooth ER Transport vesicle Transitional ER Rough ER 200 nm Nuclear
envelope X
Slide 147
Functions of Smooth ER The smooth ER Synthesizes lipids
Metabolizes carbohydrates Detoxifies drugs and poisons Stores
calcium ions 2011 Pearson Education, Inc.
Slide 148
Functions of Rough ER The rough ER Has bound ribosomes, which
secrete glycoproteins (proteins covalently bonded to carbohydrates)
Distributes transport vesicles, proteins surrounded by membranes Is
a membrane factory for the cell 2011 Pearson Education, Inc.
Slide 149
The Golgi apparatus consists of flattened membranous sacs
called cisternae Functions of the Golgi apparatus Modifies products
of the ER Manufactures certain macromolecules Sorts and packages
materials into transport vesicles The Golgi Apparatus: Shipping and
Receiving Center 2011 Pearson Education, Inc.
Slide 150
Figure 6.12 cis face (receiving side of Golgi apparatus) trans
face (shipping side of Golgi apparatus) 0.1 m TEM of Golgi
apparatus Cisternae
Slide 151
Lysosomes: Digestive Compartments A lysosome is a membranous
sac of hydrolytic enzymes that can digest macromolecules Lysosomal
enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic
acids Lysosomal enzymes work best in the acidic environment inside
the lysosome 2011 Pearson Education, Inc. X
Slide 152
Animation: Lysosome Formation Right-click slide / select Play
X
Slide 153
Some types of cell can engulf another cell by phagocytosis;
this forms a food vacuole A lysosome fuses with the food vacuole
and digests the molecules Lysosomes also use enzymes to recycle the
cells own organelles and macromolecules, a process called autophagy
2011 Pearson Education, Inc.
Slide 154
Figure 6.13 Nucleus Lysosome 1 m Digestive enzymes Digestion
Food vacuole Lysosome Plasma membrane (a) Phagocytosis Vesicle
containing two damaged organelles 1 m Mitochondrion fragment
Peroxisome fragment (b) Autophagy Peroxisome Vesicle Mitochondrion
Lysosome Digestion X
Slide 155
Vacuoles: Diverse Maintenance Compartments A plant cell or
fungal cell may have one or several vacuoles, derived from
endoplasmic reticulum and Golgi apparatus 2011 Pearson Education,
Inc. Food vacuoles are formed by phagocytosis Contractile vacuoles,
found in many freshwater protists, pump excess water out of cells
Central vacuoles, found in many mature plant cells, hold organic
compounds and water
Slide 156
Figure 6.15-1 Smooth ER Nucleus Rough ER Plasma membrane X
ENDOMEMBRANE SYSTEM MUST KNOW!
Slide 157
Figure 6.15-2 Smooth ER Nucleus Rough ER Plasma membrane cis
Golgi trans Golgi X
Slide 158
Figure 6.15-3 Smooth ER Nucleus Rough ER Plasma membrane cis
Golgi trans Golgi X
Slide 159
Peroxisomes: Oxidation Peroxisomes are specialized metabolic
compartments bounded by a single membrane Peroxisomes produce
hydrogen peroxide and convert it to water Peroxisomes perform
reactions with many different functions How peroxisomes are related
to other organelles is still unknown 2011 Pearson Education,
Inc.
Slide 160
Figure 6.UN01 Nucleus (ER) (Nuclear envelope)
Slide 161
Roles of the Cytoskeleton: Support and Motility The
cytoskeleton helps to support the cell and maintain its shape It
interacts with motor proteins to produce motility Inside the cell,
vesicles can travel along monorails provided by the cytoskeleton
Recent evidence suggests that the cytoskeleton may help regulate
biochemical activities 2011 Pearson Education, Inc. X
Slide 162
Figure 6.21 ATP Vesicle (a) Motor protein (ATP powered)
Microtubule of cytoskeleton Receptor for motor protein 0.25 m
Vesicles Microtubule (b) X
Slide 163
Enduring understanding 4.B: Competition and cooperation are
important aspects of biological systems. Essential knowledge 4.B.1:
Interactions between molecules affect their structure and function.
a. Change in the structure of a molecular system may result in a
change of the function of the system. [See also 3.D.3] b. The shape
of enzymes, active sites and interaction with specific molecules
are essential for basic functioning of the enzyme 1. For an
enzyme-mediated chemical reaction to occur, the substrate must be
complementary to the surface properties (shape and charge) of the
active site. In other words, the substrate must fit into the
enzymes active site. 2. Cofactors and coenzymes affect enzyme
function; this interaction relates to a structural change that
alters the activity rate of the enzyme. The enzyme may only become
active when all the appropriate cofactors or coenzymes are present
and bind to the appropriate sites on the enzyme.
Slide 164
c. Other molecules and the environment in which the enzyme acts
can enhance or inhibit enzyme activity. Molecules can bind
reversibly or irreversibly to the active or allosteric sites,
changing the activity of the enzyme. d. The change in function of
an enzyme can be interpreted from data regarding the concentrations
of product or substrate as a function of time. These
representations demonstrate the relationship between an enzymes
activity, the disappearance of substrate, and/or presence of a
competitive inhibitor. Learning Objective: LO 4.17 The student is
able to analyze data to identify how molecular interactions affect
structure and function. [See SP 5.1]
Slide 165
Concept 8.4: Enzymes speed up metabolic reactions by lowering
energy barriers A catalyst is a chemical agent that speeds up a
reaction without being consumed by the reaction An enzyme is a
catalytic protein Hydrolysis of sucrose by the enzyme sucrase is an
example of an enzyme-catalyzed reaction 2011 Pearson Education,
Inc. Sucrase Sucrose (C 12 H 22 O 11 ) Glucose (C 6 H 12 O 6 )
Fructose (C 6 H 12 O 6 )
Slide 166
Enzyme speed reactions by lowering E A. The transition state
can then be reached even at moderate temperatures. Enzymes do not
change delta G. It hastens reactions that would occur eventually.
Because enzymes are so selective, they determine which chemical
processes will occur at any time. Fig. 6.13
Slide 167
A substrate is a reactant which binds to an enzyme. When a
substrate or substrates binds to an enzyme, the enzyme catalyzes
the conversion of the substrate to the product. Sucrase is an
enzyme that binds to sucrose and breaks the disaccharide into
fructose and glucose. 2. Enzymes are substrate specific
Slide 168
The active site of an enzymes is typically a pocket or groove
on the surface of the protein into which the substrate fits. The
specificity of an enzyme is due to the fit between the active site
and that of the substrate. As the substrate binds, the enzyme
changes shape leading to a tighter induced fit, bringing chemical
groups in position to catalyze the reaction. Fig. 6.14
Slide 169
In most cases substrates are held in the active site by weak
interactions, such as hydrogen bonds and ionic bonds. R groups of a
few amino acids on the active site catalyze the conversion of
substrate to product. 3. The active site is an enzymes catalytic
center
Slide 170
Fig. 6.15
Slide 171
1) Enzymes are unaffected by the reaction and are reusable in
fact, a single enzyme molecule can catalyze thousands or more
reactions a second. 2)Very specific only bind one substrate 3)Dont
change the reaction equilibrium 4) Metabolic enzymes can catalyze a
reaction in both the forward and reverse direction. The actual
direction depends on the relative concentrations of products and
reactants. Enzymes catalyze reactions in the direction of
equilibrium. Characteristics of Enzymes
Slide 172
Enzymes use a variety of mechanisms to lower activation energy
and speed a reaction. The active site orients substrates in the
correct orientation for the reaction. As the active site binds the
substrate, it may put stress on bonds that must be broken, making
it easier to reach the transition state. R groups at the active
site may create a conducive microenvironment for a specific
reaction. Enzymes may even bind covalently to substrates in an
intermediate step before returning to normal. How Enzymes Lower
Activation Energy
Slide 173
The three-dimensional structures of enzymes (almost all
proteins) depend on environmental conditions. Changes in shape
influence the reaction rate. Some conditions lead to the most
active conformation and lead to optimal rate of reaction. A cells
physical and chemical environment affects enzyme activity
Slide 174
1 ) The rate that a specific number of enzymes converts
substrates to products depends in part on substrate concentrations.
As add substrate, speeds up until a certain point = enzyme
saturation. At low substrate concentrations, an increase in
substrate speeds binding to available active sites. However, there
is a limit to how fast a reaction can occur. At some substrate
concentrations, the active sites on all enzymes are engaged, called
enzyme saturation. 2) Enzyme concentration Things that Influence
Reaction Rates
Slide 175
3) Temperature has a major impact on reaction rate. As
temperature increases, collisions between substrates and active
sites occur more frequently as molecules move faster. However, at
some point thermal agitation begins to disrupt the weak bonds that
stabilize the proteins active conformation and the protein
denatures. Each enzyme has an optimal temperature. Fig. 6.16a
Slide 176
4) Because pH also influences shape and therefore reaction
rate, each enzyme has an optimal pH too. This falls between pH 6 -
8 for most enzymes. However, digestive enzymes in the stomach are
designed to work best at pH 2 while those in the intestine are
optimal at pH 8, both matching their working environments. Fig.
6.16b
Slide 177
5) Ion concentration salts and other ions their charges may
disrupt charged R-groups that determine shape of proteins active
site 6) Many enzymes require nonprotein helpers, cofactors, for
catalytic activity. They bind permanently to the enzyme or
reversibly. Some inorganic cofactors include zinc, iron, and
copper. Organic cofactors, coenzymes, include vitamins or molecules
derived from vitamins. The manners by which cofactors assist
catalysis are diverse.
Slide 178
7) Binding by some molecules, inhibitors, prevent enzymes from
catalyzing reactions. If binding involves covalent bonds, then
inhibition is often irreversible. If binding is weak, inhibition
may be reversible. If the inhibitor binds to the same site as the
substrate, then it blocks substrate binding via competitive
inhibition. Fig. 6.17a, b
Slide 179
If the inhibitor binds somewhere other than the active site, it
blocks substrate binding via noncompetitive inhibition. Binding by
the inhibitor causes the enzyme to change shape, rendering the
active site unreceptive at worst or less effective at catalyzing
the reaction. Reversible inhibition of enzymes is a natural part of
the regulation of metabolism. Fig. 6.17c
Slide 180
Lets look at a model enzyme-catalyzed reaction
http://www.kscience.co.uk/animations/model.swf Setup each and then
record trend: 1) control E(5), S(20), T(40), pH(7) vol(300) 2)
increase enzyme (15) 3) increase substrate (40) 4) non-optimal temp
(0 and 60) 5) non-optimal pH (10) Note: this particular model uses
an enzyme that favors acid pH Then try E(10), S(60) and rest as for
control notice how rate of reaction slows
Slide 181
In general More enzyme = faster reaction rate More substrate up
to a certain point = faster reaction rate Too high/too low temp =
slower reaction rate Too high/too low pH = slower reaction rate
With inhibitors= slower reaction rate
Slide 182
Regulation of enzyme activity helps control metabolism Chemical
chaos would result if a cells metabolic pathways were not tightly
regulated A cell does this by switching on or off the genes that
encode specific enzymes or by regulating the activity of enzymes
2011 Pearson Education, Inc.
Slide 183
Allosteric Regulation of Enzymes Allosteric regulation may
either inhibit or stimulate an enzymes activity Allosteric
regulation occurs when a regulatory molecule binds to a protein at
one site and affects the proteins function at another site 2011
Pearson Education, Inc.
Slide 184
Figure 8.19 Regulatory site (one of four) (a) Allosteric
activators and inhibitors Allosteric enzyme with four subunits
Active site (one of four) Active form Activator Stabilized active
form Oscillation Non- functional active site Inactive form
Inhibitor Stabilized inactive form Inactive form Substrate
Stabilized active form (b) Cooperativity: another type of
allosteric activation
Slide 185
Cooperativity is a form of allosteric regulation that can
amplify enzyme activity One substrate molecule primes an enzyme to
act on additional substrate molecules more readily Cooperativity is
allosteric because binding by a substrate to one active site
affects catalysis in a different active site 2011 Pearson
Education, Inc.
Slide 186
Identification of Allosteric Regulators Allosteric regulators
are attractive drug candidates for enzyme regulation because of
their specificity Inhibition of proteolytic enzymes called caspases
may help management of inappropriate inflammatory responses 2011
Pearson Education, Inc.
Slide 187
Figure 8.20 Caspase 1 Active site Substrate SH Known active
form Active form can bind substrate Allosteric binding site
Allosteric inhibitor Hypothesis: allosteric inhibitor locks enzyme
in inactive form Caspase 1 Active formAllosterically inhibited form
Inhibitor Inactive form EXPERIMENT RESULTS Known inactive form
Slide 188
Feedback Inhibition In feedback inhibition, the end product of
a metabolic pathway shuts down the pathway Feedback inhibition
prevents a cell from wasting chemical resources by synthesizing
more product than is needed 2011 Pearson Education, Inc.
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Figure 8.21 Active site available Isoleucine used up by cell
Feedback inhibition Active site of enzyme 1 is no longer able to
catalyze the conversion of threonine to intermediate A; pathway is
switched off. Isoleucine binds to allosteric site. Initial
substrate (threonine) Threonine in active site Enzyme 1 (threonine
deaminase) Intermediate A Intermediate B Intermediate C
Intermediate D Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 End product
(isoleucine)
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L.O. 4.17
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Essential knowledge 4.B.2: Cooperative interactions within
organisms promote efficiency in the use of energy and matter. a.
Organisms have areas or compartments that perform a subset of
functions related to energy and matter, and these parts contribute
to the whole. [See also 2.A.2, 4.A.2] 1. At the cellular level, the
plasma membrane, cytoplasm and,for eukaryotes, the organelles
contribute to the overall specialization and functioning of the
cell. 2. Within multicellular organisms, specialization of organs
contributes to the overall functioning of the organism. Exchange of
gases Circulation of fluids Digestion of food Excretion of wastes
3. Interactions among cells of a population of unicellular
organisms can be similar to those of multicellular organisms, and
these interactions lead to increased efficiency and utilization of
energy and matter. Learning Objective: LO 4.18 The student is able
to use representations and models to analyze how cooperative
interactions within organisms promote efficiency in the use of
energy and matter. [See SP 1.4]
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Enduring understanding 4.C: Naturally occurring diversity among
and between components within biological systems affects
interactions with the environment. Essential knowledge 4.C.1:
Variation in molecular units provides cells with a wider range of
functions. a. Variations within molecular classes provide cells and
organisms with a wider range of functions. [See also 2.B.1, 3.A.1,
4.A.1, 4.A.2] Different types of phospholipids in cell membranes
Different types of hemoglobin MHC proteins Chlorophylls Molecular
diversity of antibodies in response to an antigen b. Multiple
copies of alleles or genes (gene duplication) may provide new
phenotypes. [See also 3.A.4, 3.C.1] 1. A heterozygote may be a more
advantageous genotype than a homozygote under particular
conditions, since with two different alleles, the organism has two
forms of proteins that may provide functional resilience in
response to environmental stresses.
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2. Gene duplication creates a situation in which one copy of
the gene maintains its original function, while the duplicate may
evolve a new function. The antifreeze gene in fish Learning
Objective: LO 4.22 The student is able to construct explanations
based on evidence of how variation in molecular units provides
cells with a wider range of functions. [See SP 6.2]