Upload
nightdaze
View
220
Download
0
Embed Size (px)
Citation preview
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 1/56
Chapter 5:
THE WORKING CELL
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 2/56
Chapter 5: THE WORKING CELL
•Some organisms use energy-convertingreactions to produce light
–Examples are organisms that live in the oceanand use light to hide themselves from predators
•Energy conversion involves not only energy
but also membranes and enzymes
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 3/56
Bioluminescent
anglerfish
Cookiecutter shark
Firefly squid
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 4/56
MEMBRANE STRUCTURE ANDFUNCTION
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 5/56
Phospholipidbilayer
Hydrophobic regionsof protein
Hydrophilicregions of protein
•Membranes are composed of phospholipids and proteins
–Membranes are commonly described as afluid mosaic
5.1 Membranes are a fluid mosaic of phospholipids and proteins
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 6/56
Cholesterol
Glycoprotein
Glycolipid
Carbohydrate of glycoprotein
Phospholipid
Microfilamentsof cytoskeleton
Integrin
Integrins give themembrane a
strongerframework-attach to theextracellular matrixon the outside of the
cell-Glycoproteins
serve asidentification tagsspecificallyrecognized bymembrane proteinsof other cells
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 7/56
•Many membrane proteins function asenzymes,others insignal transduction, while others areimportant intransport
–Because membranes allow some substances to cross
or be transported more easily than others, they exhibitselectively permeability
–Nonpolar molecules (carbon dioxide and oxygen) cross easily
–Polar molecules (glucose and other sugars) do not cross easily
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 8/56
Enzymes
Enzyme Actiity
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 9/56
Messenger molecule
Actiatedmolecule
!eceptor
"ignal #ransduction
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 10/56
#ransport
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 11/56
5.2EVOLUTION CONNECTION: Membranesform spontaneously, a critical step in the
origin of life
•Phospholipids, the key component of biologicalmembranes, spontaneously assemble into simplemembranes
Copyright © 2009 Pearson Education, Inc.
$ater%filledbubble made of
phospholipids
$ater
$ater
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 12/56
5.3 Passive transport is diffusion across amembrane with no energy investment
•Diffusion is a process in which particles spreadout evenly in an available space
–Particles move from an area of more concentratedparticles to an area where they are less concentrated
–This means that particles diffuse down theirconcentration gradient
Copyright © 2009 Pearson Education, Inc.
Diffusion across a cell membrane does notrequire energy, so it is calledpassivetransport
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 13/56
Molecules of dye Membrane E&uilibrium
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 14/56
#'o differentsubstances
Membrane E&uilibrium
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 15/56
5.4 Osmosis is the diffusion of wateracross a membrane
•It is crucial for cells thatwater moves across theirmembrane
–Water moves across membranes in response tosolute concentration inside and outside of the cell by a process
calledosmosis–Osmosis will move water across a membrane down itsconcentration gradient until theconcentration of solute is equal on both sides of the membrane
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 16/56
"electielypermeablemembrane
"olutemolecule
(o'er concentration
of solute
H)*
"olute molecule 'ithcluster of 'ater molecules
+et flo' of 'ater
$ater molecule
E&ualconcentration
of solute
Higher concentration
of solute
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 17/56
5.5 Water balance between cells and theirsurroundings is crucial to organisms
•Tonicity is a term that describes the ability of asolution to cause a cell to gain or lose water
–Tonicity is dependent on the concentration of anonpenetrating solute on both sides of the membrane
–Isotonic indicates that the concentration of a solute is the sameon both sides
–Hypertonic indicates that the concentration of solute is higheroutside the cell
–Hypotonic indicates a higher concentration of solute inside the
cell
Copyright © 2009 Pearson Education, Inc.
•Osmoregulation:maintain water balance
–prevents excessive uptake or excessive loss of water
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 18/56
Isotonic solution
,B- (ysed ,C- "hrieled
,.- /laccid ,E- #urgid ,/- "hrieled
Hypertonic solutionHypotonic solution
Plant
cell
Animalcell
,A- +ormal
Plasmamembrane
,plasmolyzed-
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 19/56
5.6 Transport proteins may facilitatediffusion across membranes
•Many substances do not freely diffuseacross the membrane
–Specific transport proteins (aquaporins)
–These proteins assist infacilitated diffusion, atype of passive transport that does not requireenergy
–the protein is specific for the substrate, which
can be sugars, amino acids, ions, and evenwater
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 20/56
"olute
molecule
#ransportprotein
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 21/56
#ransportprotein
"olute
"olute binding0 Phosphorylation) #ransport1
Proteinchanges shape
Protein reersion2
Phosphatedetaches
•Cells have a mechanism for moving a solute against itsconcentration gradient
–It requires energy in the form of ATP
–The mechanism alters the shape of the membrane protein through
phosphorylation using ATP
5.8 Cells expend energy in the active transport of a solute against its concentration gradient
9E i d d i
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 22/56
5.9 Exocytosis and endocytosis transportlarge molecules across membranes
•A cell uses two mechanisms for movinglarge molecules across membranes
–Exocytosis is used to export bulky molecules,
such as proteins or polysaccharides–Endocytosis is used to import substancesuseful to the livelihood of the cell
•In both cases, material to be transported is
packaged within a vesicle that fuses with themembrane
Copyright © 2009 Pearson Education, Inc.
Th th kid f d ti
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 23/56
PhagocytosisE3#!ACE((4(A!/(4I.
Pseudopodium
C5#*P(A"M
/ood
acuole
6/ood7 or other particle
/oodbeingingested
•There are three kinds of endocytosis
–Phagocytosis is engulfment of a particle by wrapping
cell membrane around it, forming a vacuole
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 24/56
Pinocytosis
Plasmamembrane
8esicle
Plasma membrane
Pinocytosis is the same thing except that fluidsare taken into small vesicles
R di d d i h
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 25/56
Coatedesicle
Coatedpit
"pecificmolecule
!eceptor%mediated endocytosisCoat protein
!eceptor
Coatedpit
Material boundto receptor proteins
Plasma membrane
Receptor-mediated endocytosis is where receptors in areceptor-coated pit interact with a specific protein,
initiating formation of a vesicle
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 26/56
ENERGY AND THE CELL
Copyright © 2009 Pearson Education, Inc.
510Cllt f
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 27/56
5.10 Cells transform energy asthey perform work
•Energy is the capacity to do work andcause change
–Work is accomplished when an object is movedagainst an opposing force, such as friction
–There are two kinds of energy
–Kinetic energy is the energy of motion
–Potential energy is energy that an object possessesas a result of its location
Copyright © 2009 Pearson Education, Inc.
Cells are small units, a chemical factory, housing thousands of chemical reactions
510Cllt f
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 28/56
5.10 Cells transform energy asthey perform work
•Kinetic energy performs work by transferringmotion to other matter
–For example, water moving through a turbinegenerates electricity
Copyright © 2009 Pearson Education, Inc.
510Cll f
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 29/56
5.10 Cells transform energyas they perform work
•An example of potential energy is water behind adam
Copyright © 2009 Pearson Education, Inc.
–Chemical energy is potential energy because of its energy
available for release in a chemical reaction
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 30/56
5.11 Two laws govern energytransformations
•Thermodynamics: the study of Energytransformations–Biologists study thermodynamics because an organism exchangesboth energy and matter with its surroundings
Copyright © 2009 Pearson Education, Inc.
–Thefirst law of thermodynamics—energy in the universe is
constant: can be transferred or transformed but can’t be
created or destroyed
–Thesecond law of thermodynamics—energy conversionsincrease the disorder of the universe
–Entropy is the measure of disorder, or randomness
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 31/56
/uel
Gasoline
Energy conersion in a cell
Energy for cellular 'ork
Cellular respiration
$aste productsEnergy conersion
Combustion
Energy conersion in a car
*9ygen
Heat
Glucose
*9ygen $ater
Carbon dio9ide
$ater
Carbon dio9ide
:inetic energyof moement
Heatenergy
512Chemicalreactionseitherreleaseor
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 32/56
5.12 Chemical reactions either release orstore energy
•Anexergonic reaction is a chemicalreaction that releases energy
–Burning wood releases the energy in glucose,
producing heat, light, carbon dioxide, and water–Cellular respiration also releases energy andheat and produces products but is able to usethe released energy to perform work
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 33/56
!eactants
Amount of
energyreleased
P o t e n t
i a l e n e r g y o
f m o l e c u l e s
Energy released
Products
512Chemicalreactionseitherreleaseor
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 34/56
5.12 Chemical reactions either release orstore energy
•Anendergonic reaction requires an input ofenergy and yields products rich in potential energy
–The reactants contain little energy in the beginning, but
energy is absorbed from the surroundings and stored incovalent bonds of the products
–Photosynthesis makes energy-rich sugar moleculesusing energy in sunlight
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 35/56
!eactants
P o t e n t i a l e n e r g y o
f m o l e c u l e s
Energy re&uired
Products
Amount of energy
re&uired
512Chemicalreactionseitherreleaseor
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 36/56
5.12 Chemical reactions either release orstore energy
•A living organism produces thousands ofendergonic and exergonic chemical reactions
–All of these combined is calledmetabolism
–Ametabolic pathway is a series of chemical reactionsthat either break down a complex molecule or build up acomplex molecule
Copyright © 2009 Pearson Education, Inc.
512Chemicalreactionseitherreleaseor
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 37/56
5.12 Chemical reactions either release orstore energy
•A cell does three main types of cellular work–Chemical work—driving endergonic reactions
–Transport work—pumping substances acrossmembranes
–Mechanical work—beating of cilia
•To accomplish work, a cell must manage itsenergy resources, and it does so byenergy coupling—the use of exergonic processesto drive an endergonic one
Copyright © 2009 Pearson Education, Inc.
513ATPshuttleschemicalenergyand
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 38/56
•ATP, adenosine triphosphate, is the energycurrency of cells.
–ATP is the immediate source of energy that powersmost forms of cellular work.
–It is composed of adenine (a nitrogenous base), ribose(a five-carbon sugar), and three phosphate groups.
Copyright © 2009 Pearson Education, Inc.
5.13 ATP shuttles chemical energy anddrives cellular work
•Hydrolysis of ATP releases energy by transferring its thirdphosphate from ATP to some other molecule
–The transfer is calledphosphorylation
–In the process, ATP energizes molecules
#riphosphate ,A#P-Adenosine
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 39/56
!ibose
Adenine
#riphosphate ,A#P-Adenosine
Phosphategroup
#riphosphate ,A#P-Adenosine
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 40/56
!ibose
Adenine
#riphosphate ,A#P-Adenosine
Phosphategroup
Hydrolysis
.iphosphate ,A.P-Adenosine
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 41/56
Chemical 'ork
"olute transportedMolecule formed
Product
!eactants
Motor protein
Membraneprotein
"olute
#ransport 'orkMechanical 'ork
Protein moed
•ATPisarenewablesourceofenergyforthecell
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 42/56
Energy frome9ergonic
reactions
Energy for endergonic
reactions
ATP is a renewable source of energy for the cell
–When energy is released in an exergonic reaction, such as
breakdown of glucose, the energy is used in an endergonic
reaction to generate ATP
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 43/56
HOW ENZYMES FUNCTION
Copyright © 2009 Pearson Education, Inc.
514Enzymesspeedupthecell’schemical
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 44/56
5.14 Enzymes speed up the cells chemicalreactions by lowering energy barriers
•Although there is a lot ofpotential energy in
biological molecules, such as carbohydratesand others, it is not released spontaneously
–Energy must be available to break bonds andform new ones
–This energy is calledenergy of activation (EA)
Copyright © 2009 Pearson Education, Inc.
514Enzymesspeedupthecell’schemical
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 45/56
5.14 Enzymes speed up the cells chemicalreactions by lowering energy barriers
•The cell uses catalysis to drive (speed up)biological reactions
–Catalysis is accomplished byenzymes,
–Enzymes speed up the rate of the reaction bylowering the EA, and they are not used up in the
process
–Each enzyme has a particular target molecule
called thesubstrate
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 46/56
!eaction'ithoutenzyme
EA 'ith
enzyme
E n e r g y !eactants
!eaction 'ithenzyme
EA 'ithout
enzyme
+etchangein energy,the same-
Products
Progress of the reaction
515Aspecificenzymecatalyzeseach
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 47/56
5.15 A specific enzyme catalyzes eachcellular reaction
•Enzymes have unique three-dimensional shapes
–The shape is critical to their role as biological catalysts
–As a result of its shape, the enzyme has anactive site where the enzyme interacts with the enzyme’s substrate
–Consequently, the substrate’s chemistry is altered toform the product of the enzyme reaction
Copyright © 2009 Pearson Education, Inc.
Enzyme aailable0
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 48/56
Enzyme aailable'ith empty actiesite
Actie site
0
Enzyme
,sucrase-
"ubstrate bindsto enzyme 'ithinduced fit
)
"ubstrate
,sucrose-
"ubstrate isconerted toproducts
1
Products arereleased
2
/ructose
Glucose
5.15Aspecificenzymecatalyzeseach
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 49/56
5.15 A specific enzyme catalyzes eachcellular reaction
•For optimum activity, enzymes requirecertain environmental conditions
–Temperature is very important, and optimally,human enzymes function best at 37ºC, or body
temperature–High temperature will denature human enzymes
–Enzymes in animals also require a pH around neutralityfor best results
Copyright © 2009 Pearson Education, Inc.
•Some enzymes require nonprotein helpers
–Cofactors are inorganic, such as zinc, iron, or copper
–Coenzymes are organic molecules and are often vitamins
516Enzymeinhibitorsblockenzymeactionand
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 50/56
5.16 Enzyme inhibitors block enzyme action andcan regulate enzyme activity in a cell
•Inhibitors are chemicals that inhibit anenzyme’s activity
–competitive inhibitors:
compete for the enzyme’s active site and thusblock substrates from entering the active site
Copyright © 2009 Pearson Education, Inc.
-noncompetitive inhibitors:
bind somewhere else and change the shape
of the enzyme so that the substrate will no longer
fit the active site
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 51/56
"ubstrate
Enzyme
Actie site
+ormal binding of substrate
Competitieinhibitor
Enzyme inhibition
+oncompetitieinhibitor
516Enzymeinhibitorsblockenzymeactionand
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 52/56
5.16 Enzyme inhibitors block enzyme action andcan regulate enzyme activity in a cell
•Enzyme inhibitors are important in regulating cellmetabolism
–Often the product of a metabolic pathway can serve as
an inhibitor of one enzyme in the pathway, a mechanismcalledfeedback inhibition
–The more product formed, the greater the inhibition, andin this way, regulation of the pathway is accomplished
Copyright © 2009 Pearson Education, Inc.
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 53/56
Youshouldnowbeableto
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 54/56
5.Explain how an imbalance in water between thecell and its environment affects the cell
6.Describe membrane proteins that facilitatetransport of materials across the cell membrane
without expenditure of energy
7.Discuss how energy-requiring transport proteinsmove substances across the cell membrane
8.Distinguish between exocytosis and endocytosisand list similarities between the two
Copyright © 2009 Pearson Education, Inc.
You should now be able to
Youshouldnowbeableto
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 55/56
9.Explain how energy is transformed during lifeprocesses
10.Define the two laws of thermodynamics andexplain how they relate to biological systems
11.Explain how a chemical reaction can eitherrelease energy or store energy
12.Describe ATP and explain why it is considered to
be the energy currency of a cell
Copyright © 2009 Pearson Education, Inc.
You should now be able to
Youshouldnowbeableto
7/25/2019 05 Lecture Presentation
http://slidepdf.com/reader/full/05-lecture-presentation 56/56
You should now be able to
13.Define enzyme and explain how enzymescause a chemical reaction to speed up
14.Discuss the specificity of enzymes
15.Distinguish between competitive inhibitorsand noncompetitive inhibitors