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© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko
PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Chapter 5Chapter 5The Working Cell
1 Chapter 5 Outline: The Working Cell
• Some Basic Energy Concepts
• ATP and Cellular Work
• Enzymes
• Membrane Function
© 2013 Pearson Education, Inc.
2
Biology and Society:Harnessing Cellular Structures
• Cells control their chemical environment using
– energy,
– enzymes, and
– the plasma membrane.
• Cell-based nanotechnology may be used to power microscopic robots.
© 2013 Pearson Education, Inc.
3 Figure 5.0 4
Chapter 5 Outline: The Working Cell
• Some Basic Energy Concepts
– Conservation of Energy
– Entropy
– Chemical Energy
– Food Calories
• ATP and Cellular Work
• Enzymes
• Membrane Function
© 2013 Pearson Education, Inc.
5 SOME BASIC ENERGY CONCEPTS
• Energy makes the world go around.
• But what is energy?
© 2013 Pearson Education, Inc.
6
Conservation of Energy
• Energy is defined as the capacity to cause change.
– Some forms of energy are used to perform work.
– Energy is the ability to rearrange a collection of matter.
© 2013 Pearson Education, Inc.
7 Conservation of Energy
• Kinetic energy is the energy of motion.
• Potential energy is stored energy. It is energy that an object has because of its
– location or
– structure.
© 2013 Pearson Education, Inc.
8
© 2013 Pearson Education, Inc.
Animation: Energy Concepts
Right click slide / select “Play”
9 Figure 5.1
Climbingconverts kineticenergy topotential energy.
Greatestpotentialenergy
Diving convertspotential energy to kinetic energy.
Leastpotential energy
10
• Machines and organisms can transform kinetic energy to potential energy and vice versa.
• In all such energy transformations, total energy is conserved.
– Energy cannot be created or destroyed.
– Energy can be converted from one form to another.
– This is the principle of conservation of energy.
Conservation of Energy
© 2013 Pearson Education, Inc.
11 Entropy
• Every energy conversion releases some randomized energy in the form of heat.
– In other words, no energy conversion is 100% efficient
• Heat is a
– type of kinetic energy and
– product of all energy conversions.
© 2013 Pearson Education, Inc.
12
Entropy
• Scientists use the term entropy as a measure of disorder, or randomness, in a system.
• All energy conversions increase the entropy of the universe.
© 2013 Pearson Education, Inc.
13 Chemical Energy
• Molecules store varying amounts of potential energy in the arrangement of their atoms.
• Organic compounds are relatively rich in such chemical energy.
© 2013 Pearson Education, Inc.
14
Chemical Energy
• Chemical energy
– arises from the arrangement of atoms and
– can be released by a chemical reaction.
• Living cells and automobile engines use the same basic process to make chemical energy do work.
© 2013 Pearson Education, Inc.
15 Figure 5.2
Fuel rich inchemicalenergy
Energy conversionWaste productspoor in chemicalenergy
Oxygen
Carbon dioxide
Energy conversion in a car
Energy for cellular work
Energy conversion in a cell
Heatenergy
Heatenergy
Carbon dioxide
Oxygen
Combustion
Cellularrespiration
Kinetic energy of movement
ATP
Octane(from gasoline)
Glucose(from food)
Water
Water
16
• Cellular respiration is
– the energy-releasing chemical breakdown of fuel molecules and
– the storage of that energy in a form the cell can use to perform work.
Chemical Energy
© 2013 Pearson Education, Inc.
17
• Humans convert about 34% of the energy in food to useful work, such as the contraction of muscles.
• About 66% of the energy released by the breakdown of fuel molecules generates body heat.
• An average car converts about 25% of the energy in hydrocarbon fuels to move the car forward.
Chemical Energy
© 2013 Pearson Education, Inc.
18
Food Calories
• A calorie is the amount of energy that can raise the temperature of one gram of water by 1 degree Celsius.
• Food Calories are kilocalories, equal to 1,000 calories.
• The energy of calories in food is burned off by many activities.
© 2013 Pearson Education, Inc.
19 Chapter 5 Outline: The Working Cell
• Some Basic Energy Concepts
• ATP and Cellular Work
– The Structure of ATP
– Phosphate Transfer
– The ATP Cycle
• Enzymes
• Membrane Function
© 2013 Pearson Education, Inc.
20
ATP AND CELLULAR WORK
• Chemical energy is
– released by the breakdown of organic molecules during cellular respiration and
– used to generate molecules of ATP.
• ATP
– acts like an energy shuttle,
– stores energy obtained from food, and
– releases it later as needed.
© 2013 Pearson Education, Inc.
21 The Structure of ATP
• ATP (adenosine triphosphate)
– consists of an organic molecule called adenosine plus a tail of three phosphate groups and
– Each phosphate group is negatively charged
– The negative charges repel each other
– Potential energy stored in that last covalent bond
– Energy is released when the 3rd phosphate is repelled by the negative charges causing it to move away (now kinetic energy)
– ATP + H2O → ADP + Pi ∆G˚ = −7.3 kcal/mol
– ATP + H2O → AMP + PPi ∆G˚ = −10.9 kcal/mol
– is broken down to ADP and a phosphate group, releasing energy
© 2013 Pearson Education, Inc.
22
© 2013 Pearson Education, Inc.
Blast Animation: Structure of ATP
23 Figure 5.4
Triphosphate Diphosphate
Adenosine Adenosine
Energy
ATP ADP
P P P P P P
Phosphate(transferred to another molecule)
24
Phosphate Transfer
• ATP energizes other molecules by transferring phosphate groups.
• This energy helps cells perform
– mechanical work,
– transport work, and
– chemical work.
© 2013 Pearson Education, Inc.
25 Figure 5.5
ATP
ATP
ATP
ADP
ADP
ADP
P
P
P
ADP P
P P
P
PX X Y
Y
(a) Motor protein performing mechanical work (moving a muscle fiber)
(b) Transport protein performing transport work (importing a solute)
(c) Chemical reactants performing chemical work (promoting a chemical reaction)
Solute
Solute transported
Protein moved
Product madeReactants
Transportprotein
Motor protein 26
The ATP Cycle
• Cellular work spends ATP continuously.
• ATP is recycled from ADP and a phosphate group through cellular respiration.
• A working muscle cell spends and recycles up to 10 million ATP molecules per second.
© 2013 Pearson Education, Inc.
27
© 2013 Pearson Education, Inc.
Blast Animation: ATP/ADP Cycle
Select “Play”
28
Figure 5.6
Cellular respiration:chemical energyharvested fromfuel molecules
Energy forcellular work
ATP
ADP P
29 Figure 5.UN01
Energy for cellular work
Adenosine
Adenosine
diphosphateEnergy from
organic fuel
Phosphate
(can be transferred
to another molecule)
ATP
cycle
ATP ADP
P P P P P PAdenosine
Adenosine
triphosphate
96
Chapter 5 Outline: The Working Cell
• Some Basic Energy Concepts
• ATP and Cellular Work
• Enzymes
– Activation Energy
– Induced Fit
– Enzyme Inhibitors
• Membrane Function
© 2013 Pearson Education, Inc.
30 ENZYMES
• Metabolism is the total of all chemical reactions in an organism.
• Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions.
– Enzymes are catalysts which means they speed chemical reactions without being used up themselves
• All living cells contain thousands of different enzymes, each promoting a different chemical reaction.
© 2013 Pearson Education, Inc.
31
Activation Energy
• Activation energy
– activates the reactants and
– triggers a chemical reaction.
• Enzymes reduce the amount of activation energy required to break bonds of reactant molecules.
© 2013 Pearson Education, Inc.
32 Figure 5.7
(a) Without enzyme (b) With enzyme
Reactant Reactant
Products Products
Activationenergy barrier Activation
energy barrierreduced byenzyme
Enzyme
En
erg
y
En
erg
y
33
The Process of Science:
Can Enzymes Be Engineered?
• Observation: Genetic sequences suggest that many of our genes were formed through a type of molecular evolution.
• Question: Can laboratory methods mimic this process through artificial selection?
• Hypothesis: An artificial process could be used to modify the gene that codes for lactase into a new gene coding for an enzyme with a new function.
© 2013 Pearson Education, Inc.
34 Induced Fit
• An enzyme is very selective in the reaction it catalyzes.
• Each enzyme recognizes a substrate, a specific reactant molecule.
– The active site fits to the substrate, and the enzyme changes shape slightly.
– This interaction is called induced fit because the entry of the substrate induces the enzyme to change shape slightly.
© 2013 Pearson Education, Inc.
40
• Enzymes can function over and over again, a key characteristic of enzymes (i.e. they are catalysts)
• Many enzymes are named for their substrates, but with an –ase ending.
Induced Fit
© 2013 Pearson Education, Inc.
41 Figure 5.9-1
Active site
Enzyme(sucrase)
Ready forsubstrate
1
42
Figure 5.9-2
Active site
Enzyme(sucrase)
Ready forsubstrate
Substrate (sucrose)
Substrate binding
1
2
43 Figure 5.9-3
Active site
Enzyme(sucrase)
Ready forsubstrate
Substrate (sucrose)
Substrate binding
Catalysis
H2O
1
2
3
44
Figure 5.9-4
Active site
Enzyme(sucrase)
Ready forsubstrate
Substrate (sucrose)
Substrate binding
Catalysis
H2O
Fructose
Glucose
Productreleased
4
1
2
3
45 Enzyme Inhibitors
• Enzyme inhibitors can prevent metabolic reactions by binding
– to the active site or
– near the active site, resulting in changes to the enzyme’s shape so that the active site no longer accepts the substrate.
© 2013 Pearson Education, Inc.
46
Figure 5.10
(a) Enzyme and substratebinding normally
(b) Enzyme inhibition bya substrate imposter
(c) Inhibition of an enzyme by a molecule that causesthe active site to changeshape
Substrate
Substrate
Substrate
Active site
Active site
Active site
Inhibitor
Inhibitor
Enzyme
Enzyme
Enzyme
48 Figure 5.10a
(a) Enzyme and substrate binding normally
Substrate
Enzyme
Active site
49
Figure 5.10b
(b) Enzyme inhibition by a substrate imposter
Substrate
Active site
Inhibitor
Enzyme
50 Figure 5.10c
(c) Inhibition of an enzyme by a moleculethat causes the active site to change shape
SubstrateActive site
Inhibitor
Enzyme
51
• Some products of a reaction may inhibit the enzyme required for its production.
– This is called feedback regulation.
– It prevents the cell from wasting resources.
• Many beneficial drugs work by inhibiting enzymes.
– Penicillin blocks the active site of an enzyme that bacteria use in making cell walls.
– Ibuprofen inhibits an enzyme involved in sending pain signals.
– Many cancer drugs inhibit enzymes that promote cell division.
Enzyme Inhibitors
© 2013 Pearson Education, Inc.
52 Chapter 5 Outline: The Working Cell
• Some Basic Energy Concepts
• ATP and Cellular Work
• Enzymes
• Membrane Function
– Passive Transport
– Osmosis and Water Balance
– Active Transport
– Exocytosis and Endocytosis
– The Role of Membranes in Cell Signaling
© 2013 Pearson Education, Inc.
53
MEMBRANE FUNCTION
• Cells must control the flow of materials to and from the environment.
• Membrane proteins perform many functions.
• Transport proteins
– are located in membranes and
– help move substances across a cell membrane.
© 2013 Pearson Education, Inc.
54
© 2013 Pearson Education, Inc.
Animation: Membrane Selectivity
Right click slide / select “Play”
55
© 2013 Pearson Education, Inc.
BioFlix Animation: Membrane Transport
56 Figure 5.11Cell signaling
Attachment to the cytoskeletonand extracellular matrix
Enzymatic activity
Cytoskeleton
Cytoplasm
Cytoplasm
Transport
Fibers ofextracellularmatrix
Intercellularjoining
Cell-cellrecognition
57
Passive Transport: Diffusion across Membranes
• Molecules contain heat energy that causes them to vibrate and wander randomly.
• Diffusion is the movement of molecules so that they spread out evenly into the available space.
© 2013 Pearson Education, Inc.
58
• Passive transport is the diffusion of a substance across a membrane without the input of energy.
• Cell membranes are selectively permeable, allowing only certain substances to pass.
• Substances diffuse down their concentration gradient, a region in which the substance’s density changes
• “Down the concentration gradient” means going from higher concentration to lower concentration
• Concentration is equivalent to density of a particular substance in a liquid. Thus it is the amount of one substance in a particular volume
Passive Transport: Diffusion across Membranes
© 2013 Pearson Education, Inc.
59
© 2013 Pearson Education, Inc.
Blast Animation: Diffusion
Right click slide / select “Play”
60
© 2013 Pearson Education, Inc.
Blast Animation: Passive Diffusion Across a Membrane
61
Figure 5.12Molecules of dye Membrane
(a) Passive transport of one type of molecule
(b) Passive transport of two types of molecules
Net diffusion Net diffusion Equilibrium
Net diffusion Net diffusion Equilibrium
Net diffusion Net diffusion Equilibrium
62
• Some substances do not cross membranes spontaneously or cross slowly.
– These substances can be transported via facilitated diffusion.
– Specific transport proteins act as selective corridors.
– No energy input is needed.
Passive Transport: Diffusion across Membranes
© 2013 Pearson Education, Inc.
63
Osmosis and Water Balance
• The diffusion of water across a selectively permeable membrane is osmosis.
© 2013 Pearson Education, Inc.
64 Figure 5.13-1
Hypotonic solution
Hypertonic solution
Sugarmolecule
Selectivelypermeablemembrane Osmosis
65
Figure 5.13-2
Hypotonic solution
Hypertonic solution
Sugarmolecule
Selectivelypermeablemembrane Osmosis
Isotonic solutions
Osmosis
66
• Compared to another solution,
– a hypertonic solution has a higher concentration of solute,
– a hypotonic solution has a lower concentration of solute, and
– an isotonic solution has an equal concentration of solute.
• While not entirely correct, you can think of tonicity as “saltiness”
Osmosis and Water Balance
© 2013 Pearson Education, Inc.
67
• Osmoregulation is the control of water balance within a cell or organism.
Water Balance in Animal Cells
© 2013 Pearson Education, Inc.
68
• Plants have rigid cell walls.
• Plant cells are healthiest in a hypotonic environment, which keeps their walled cells turgid.
Water Balance in Plant Cells
© 2013 Pearson Education, Inc.
69
Figure 5.14
Animal cell
Plant cell
Normal
Flaccid (wilts)
Lysing
Turgid (normal)
Shriveled
Shriveled
Plasmamembrane
H2OH2O H2O H2O
H2OH2OH2O H2O
(a) Isotonicsolution
(b) Hypotonicsolution
(c) Hypertonicsolution
70
• As a plant cell loses water,
– it shrivels and
– its plasma membrane may pull away from the cell wall in the process of plasmolysis, which usually kills the cell.
Water Balance in Plant Cells
© 2013 Pearson Education, Inc.
71
© 2013 Pearson Education, Inc.
Video: Turgid Elodea
72 Figure 5.15 73
Active Transport: The Pumping of Molecules across Membranes
• Active transport requires that a cell expend energy to move molecules across a membrane.
– Where does this energy come from?
© 2013 Pearson Education, Inc.
74
© 2013 Pearson Education, Inc.
Blast Animation: Active Transport: Sodium-Potassium Pump
75
© 2013 Pearson Education, Inc.
Animation: Active Transport
Right click slide / select “Play”
76 Figure 5.16-1
Lower solute concentration
Higher solute concentration
ATP
Solute
Active transport
77
Figure 5.16-2
Lower solute concentration
Higher solute concentration
ATP
Solute
Active transport
78 Figure 5.UN03
Passive Transport(requires no energy)
Active Transport(requires energy)
Diffusion Facilitated diffusion Osmosis
Higher solute concentration
Lower solute concentration
Higher water concentration(lower solute concentration)
Lower water concentration(higher solute concentration)
Solute
Higher soluteconcentration
Lower soluteconcentration
ATP
So
lute
So
lute
Wa
ter
So
lute
MEMBRANE TRANSPORT
98
Exocytosis and Endocytosis:
Traffic of Large Molecules
• Exocytosis is the secretion of large molecules within transport vesicles.
© 2013 Pearson Education, Inc.
79 Figure 5.17
Outside of cell
Cytoplasm
Plasmamembrane
Exocytosis
83
• Endocytosis takes material in via vesicles that bud inward from the plasma membrane.
Exocytosis and Endocytosis:
Traffic of Large Molecules
© 2013 Pearson Education, Inc.
84 Figure 5.18
Endocytosis
88
Figure 5.UN04
Exocytosis Endocytosis
99
© 2013 Pearson Education, Inc.
Blast Animation: Endocytosis and Exocytosis
80
© 2013 Pearson Education, Inc.
Animation: Exocytosis and Endocytosis Introduction
Right click slide / select “Play”
81
© 2013 Pearson Education, Inc.
Animation: Exocytosis
Right click slide / select “Play”
82
© 2013 Pearson Education, Inc.
Animation: Receptor-Mediated Endocytosis
Right click slide / select “Play”
87
• In the process of phagocytosis (“cellular eating”), a cell engulfs a particle and packages it within a food vacuole.
Exocytosis and Endocytosis:
Traffic of Large Molecules
© 2013 Pearson Education, Inc.
89
© 2013 Pearson Education, Inc.
Animation: Phagocytosis
Right click slide / select “Play”
85
• The plasma membrane helps convey signals
– between cells and
– between cells and their environment.
• Receptors on a cell surface trigger signal transduction pathways that
– relay the signal and
– convert it to chemical forms that can function within the cell.
The Role of Membranes in Cell Signaling
© 2013 Pearson Education, Inc.
90
© 2013 Pearson Education, Inc.
Animation: Overview of Cell Signaling
Right click slide / select “Play”
91
© 2013 Pearson Education, Inc.
Animation: Signal Transduction Pathways
Right click slide / select “Play”
92
Figure 5.19
Outside of cell Cytoplasm
ReceptionTransduction Response
Receptorprotein
Epinephrine(adrenaline)from adrenalglands
Plasma membrane
Proteins of signal transduction pathway
Hydrolysisof glycogenreleasesglucose forenergy
93Evolution Connection:
The Origin of Membranes
• Phospholipids
– are key ingredients of membranes,
– were probably among the first organic compounds that formed from chemical reactions on early Earth, and
– self-assemble into simple membranes.
© 2013 Pearson Education, Inc.
94
Figure 5.20
Water-filledbubble made ofphospholipids
95