copyright © 2005 pearson education, inc. publishing as benjamin cummings happy friday! 5/7/2010...
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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Happy Friday! 5/7/2010Outline how monosaccharides are converted into polysaccharides. 2 marks
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
condensation;involves the removal of water to join monosaccharides together / equation to show this;catalysed by enzymes;consists of many monosaccharides linked (glycosidic) to make polysaccharide;
[2]
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Chapter 5Chapter 5
The Working Cell
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HOW ENZYMES FUNCTION
5.5 Enzymes speed up the cell’s chemical reactions by lowering energy barriers
http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&06&04&5D%20How%20Enzymes%20Function
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• For a chemical reaction to begin
– Reactants must absorb some energy, called the energy of activation
Figure 5.5A
EA barrier
Reactants
Products1 2E
nzym
e
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• protein catalyst = enzyme
– Can decrease activation energy needed to begin reaction
Figure 5.5B
Reactants
EA withoutenzyme
EA withenzyme
Net changein energy
Products
Ene
rgy
Progress of the reaction
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5.6 A specific enzyme catalyzes each cellular reaction
• Enzymes have unique 3-D shapes
– determine which chem reactions occur in a cell
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Figure 5.6
Enzyme(sucrase)Glucose
Fructose
Active site Substrate(sucrose)
H2O
1 Enzyme availablewith empty activesite
2 Substrate binds to enzyme with induced fit
4 Products arereleased
3 Substrate is converted to products
• The catalytic cycle of an enzyme
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5.7 The cellular environment affects enzyme activity
• Temperature, salt concentration, and pH influence enzyme activity
• Some enzymes require nonprotein cofactors
– Such as metal ions or organic molecules called coenzymes
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5.8 Enzyme inhibitors block enzyme action
• Inhibitors interfere with an enzyme’s activity
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• A competitive inhibitor
– Takes the place of a substrate in the active site
• A noncompetitive inhibitor
– Alters an enzyme’s function by changing its shape
Figure 5.8
Substrate
Enzyme
Active site
Normal binding of substrate
Enzyme inhibition
Noncompetitiveinhibitor
Competitiveinhibitor
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CONNECTION
5.9 Many poisons, pesticides, and drugs are enzyme inhibitors
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Cool “Fires” Attract Mates and Meals
• Fireflies use light to send signals to potential mates
– Instead of using chemical signals like most other insects
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• light comes from a set of chemical reactions
– occur in light-producing organs at rear of insect
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• Females of some species
– Produce a light pattern that attracts males of other species, which are then eaten by the female
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ENERGY AND THE CELL
5.1 Energy is the capacity to perform work
• All organisms require energy
– Which is defined as the capacity to do work
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• Kinetic energy is the energy of motion
• Potential energy is stored energy
– And can be converted to kinetic energy
Figure 5.1A–C
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5.2 Two laws govern energy transformations
• Thermodynamics
– Is the study of energy transformations
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The First Law of Thermodynamics
• According to the first law of thermodynamics
– Energy can be changed from one form to another
– Energy cannot be created or destroyed
Figure 5.2A
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The Second Law of Thermodynamics
• The second law of thermodynamics
– States that energy transformations increase disorder or entropy, and some energy is lost as heat
Figure 5.2B
Heat
Chemical reactions
ATP ATP
Glucose
+
Oxygen
water
Carbon dioxide
+
Energy for cellular work
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5.3 Chemical reactions either store or release energy
• Endergonic reactions
– Absorb energy and yield products rich in potential energy
Figure 5.3A
Pot
entia
l ene
rgy
of m
olec
ules
Reactants
Energy required
Products
Amount of energy
required
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• Exergonic reactions
– Release energy and yield products that contain less potential energy than their reactants
Figure 5.3B
Reactants
Energy released
Products
Amount of energy
released
Po
ten
tial e
ne
rgy
of
mo
lecu
les
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• Cells carry out thousands of chemical reactions
– The sum of which constitutes cellular metabolism
• Energy coupling
– Uses exergonic reactions to fuel endergonic reactions
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5.4 ATP shuttles chemical energy and drives cellular work
• ATP powers nearly all forms of cellular work
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• The energy in an ATP molecule
– Lies in the bonds between its phosphate groups
Phosphategroups
ATP
EnergyP P PP P PHydrolysis
Adenine
Ribose
H2O
Adenosine diphosphateAdenosine Triphosphate
++
ADP
Figure 5.4A
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• ATP drives endergonic reactions by phosphorylation
– Transferring a phosphate group to make molecules more reactive
Figure 5.4B
ATP
Chemical work Mechanical work Transport work
P
P
P
P
P
P
P
Molecule formed Protein moved Solute transported
ADP+
Product
Reactants
Motorprotein
Membraneprotein Solute
+
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ATP
ADP + P
Energy forendergonicreactions
Energy fromexergonicreactions
Pho
spho
ryla
tion
Hydrolysis
• Cellular work can be sustained
– Because ATP is a renewable resource that cells regenerate
Figure 5.4C
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MEMBRANE STRUCTURE AND FUNCTION
5.10 Membranes organize the chemical activities of cells
• Membranes
– Provide structural order for metabolism
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• The plasma membrane of the cell is selectively permeable
– Controlling the flow of substances into or out of the cell
Figure 5.10
Cytoplasm
Outside of cell
TE
M 2
00,0
00
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5.11 Membrane phospholipids form a bilayer
• Phospholipids
– Have a hydrophilic head and two hydrophobic tails
– Are the main structural components of membranes
Figure 5.11A
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH3
CH3
CH3N+
O
O O–P
O
CH2CHCH2
C O C O
O O
Phosphategroup
Symbol
Hydrophilic head
Hydrophobic tails
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• Phospholipids form a two-layer sheet
– Called a phospholipid bilayer, with the heads facing outward and the tails facing inward
Figure 5.11B
Water
Water
Hydrophilicheads
Hydrophobictails
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5.12 The membrane is a fluid mosaic of phospholipids and proteins
• A membrane is a fluid mosaic
– With proteins and other molecules embedded in a phospholipid bilayer
Figure 5.12
Fibers of the extracellular matrix Carbohydrate
(of glycoprotein)
Glycoprotein
Microfilamentsof cytoskeleton
Phospholipid
CholesterolProteins
Plasmamembrane
Glycolipid
Cytoplasm
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5.13 Proteins make the membrane a mosaic of function
• Many membrane proteins
– Function as enzymes
Figure 5.13A
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• Other membrane proteins
– Function as receptors for chemical messages from other cells
Figure 5.13B
Messenger molecule
Receptor
Activatedmolecule
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• Membrane proteins also function in transport
– Moving substances across the membrane
Figure 5.13C
ATP
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5.14 Passive transport is diffusion across a membrane
• In passive transport, substances diffuse through membranes without work by the cell
– Spreading from areas of high concentration to areas of low concentration
EquilibriumMembraneMolecules of dye
Equilibrium
Figure 5.14B
Figure 5.14A
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• Small nonpolar molecules such as O2 and CO2
– Diffuse easily across the phospholipid bilayer of a membrane
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5.15 Transport proteins may facilitate diffusion across membranes
• Many kinds of molecules
– Do not diffuse freely across membranes
• For these molecules, transport proteins
– Provide passage across membranes through a process called facilitated diffusion
Figure 5.15
Solutemolecule
Transportprotein
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5.16 Osmosis is the diffusion of water across a membrane
• In osmosis
– Water travels from a solution of lower solute concentration to one of higher solute concentration
Figure 5.16
Lowerconcentration
of solute
Higherconcentration
of solute
Equalconcentration
of solute
H2OSolutemolecule
Selectivelypermeablemembrane
Watermolecule
Solute molecule withcluster of water molecules
Net flow of water
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5.17 Water balance between cells and their surroundings is crucial to organisms
• Osmosis causes cells to shrink in hypertonic solutions
– And swell in hypotonic solutions
• In isotonic solutions
– Animal cells are normal, but plant cells are limp
Figure 5.17
Plantcell
H2O
H2O H2O
H2O
H2O
H2O
H2O
H2OPlasma
membrane
(1) Normal (2) Lysed (3) Shriveled
(4) Flaccid (5) Turgid(6) Shriveled (plasmolyzed)
Isotonic solution Hypotonic solution Hypertonic solution
Animalcell
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• The control of water balance
– Is called osmoregulation
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PP PProtein
changes shapePhosphatedetaches
ATPADPSolute
Transportprotein
Solute binding1 Phosphorylation2 Transport3 Protein reversion4
5.18 Cells expend energy for active transport
• Transport proteins can move solutes against a concentration gradient
– Through active transport, which requires ATP
Figure 5.18
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Fluid outside cell
Cytoplasm
Protein
Vesicle
5.19 Exocytosis and endocytosis transport large molecules
• To move large molecules or particles through a membrane
– A vesicle may fuse with the membrane and expel its contents (exocytosis)
Figure 5.19A
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• Membranes may fold inward
– Enclosing material from the outside (endocytosis)
Figure 5.19B
Vesicle forming
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• Endocytosis can occur in three ways
– Phagocytosis
– Pinocytosis
– Receptor-mediated endocytosis
Pseudopodium of amoeba Food being ingested
Phagocytosis Pinocytosis Receptor-mediated endocytosis
Material bound to receptor proteins
PIT
Cytoplasm
Plasma membrane
TE
M 5
4,00
0
TE
M 9
6,50
0
LM 2
30
Figure 5.19C
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CONNECTION
5.20 Faulty membranes can overload the blood with cholesterol
• Harmful levels of cholesterol
– Can accumulate in the blood if membranes lack cholesterol receptors
LDL particle
Protein
Phospholipid outer layer
CytoplasmReceptorprotein
Plasmamembrane
Vesicle
Cholesterol
Figure 5.20
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5.21 Chloroplasts and mitochondria make energy available for cellular work
• Enzymes are central to the processes that make energy available to the cell
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• Chloroplasts carry out photosynthesis
– Using solar energy to produce glucose and oxygen from carbon dioxide and water
• Mitochondria consume oxygen in cellular respiration
– Using the energy stored in glucose to make ATP
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