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Metabolism: Fueling Cell Growth

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Title: Metabolism: Fueling Cell Growth


1
MetabolismFueling Cell Growth
  • Chapter 6

2
Preview
  • Principles of metabolism
  • Metabolism, catabolism, anabolism, energy, redox
    reaction.
  • Central metabolic pathway
  • Glycolysis, TCA
  • Respiration
  • Electron transport chain
  • Fermentation

3
Metabolism
  • Chemical reactions to keep an organism alive.
  • Basic needs

4
Principles of Metabolism
  • Metabolism is broken down into two components
  • Anabolism
  • Catabolism
  • Catabolism
  • Degradative reactions
  • Reactions produce energy from the break down of
    larger molecules
  • Anabolism
  • Reactions involved in the synthesis of cell
    components
  • Anabolic reactions require energy
  • Anabolic reactions utilize the energy produced
    from catabolic reactions

5
Metabolic Pathways
6
Principles of Metabolism
Glycolysis
7
Energy
  • Definition
  • Free energy-energy released by breaking chemical
    bonds
  • reactants have more free energy
  • Exergonic reaction
  • products have more energy
  • Endergonic reaction
  • Energy source
  • Compound broken down to release energy
  • Common energy sources

8
Energy
  • Oxidizing energy source to release energy

Gas O2
CO2H2Oenergy
GlucoseO2
CO2 H2O energy
Oxidization gain of oxygen, loss of hydrogen,
loss of electron
9
Harvesting Energy
  • Oxidation/reduction reactions (redox reactions)

electron acceptor
electron donor
LEO - Lose electrons oxidized GER - Gain
electrons reduced
  • Protons often follow electrons (i.e. a hydrogen
    atom is extracted/added e- H H )
  • General rules
  • If a compound gains oxygen or loses hydrogen, the
    reaction is an oxidation
  • If a compound loses oxygen or gains hydrogen, the
    reaction is a reduction

10
Harvesting Energy
The role of electron carriers
In redox reactions, protons often follow
electrons
11
Harvesting Energy
The role of ATP
energy currency
Adenosine triphosphate
12
Harvesting Energy
The role of ATP
energy currency
13
Harvesting Energy
Synthesizing ATP
  • Substrate-level phosphorylation

14
Harvesting Energy
Synthesizing ATP
  • Substrate-level phosphorylation
  • Oxidative phosphorylation
  • Photophosphorylation
  • Other methods involve an electron transport chain
    and redox reaction

15
Principles of Metabolism
Synthesizing ATP
  • Substrate-level phosphorylation
  • Oxidative phosphorylation - chemical energy is
    used to create the proton motive force (involves
    an electron transport chain) the energy of
    proton motive force is harvested by making ATP
  • Photophosphorylation - radiant energy is used to
    create the proton motive force (involves an
    electron transport chain) the energy of proton
    motive force is harvested by making ATP

16
Central metabolic pathway
  • Central pathways are catabolic and provide
  • Energy
  • Reducing power
  • Precursor metabolites
  • Central metabolic pathways
  • Glycolysis
  • Pentose phosphate pathway
  • Tricarboxcylic acid cycle

17
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff pathway,
glycolytic pathway)
glucose? 2 pyruvate
18
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff pathway,
glycolytic pathway)
glucose? 2 pyruvate
  • 2 ATP (net gain)
  • 2 spent 4 made
  • 2 NADH
  • 6 precursor metabolites

19
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff pathway,
glycolytic pathway)
glucose? 2 pyruvate
  • 2 ATP (net gain)
  • 2 spent 4 made
  • 2 NADH
  • 6 precursor metabolites

20
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff pathway,
glycolytic pathway)
glucose? 2 pyruvate
  • 2 ATP (net gain)
  • 2 spent 4 made
  • 2 NADH
  • 6 precursor metabolites

21
Central Metabolic Pathways
Pentose phosphate pathway
glucose? intermediate of glycolysis
  • NADPH (amount varies)
  • 2 precursor metabolites

22
Central Metabolic Pathways
Pentose phosphate pathway
glucose? intermediate of glycolysis
  • NADPH (amount varies)
  • 2 precursor metabolites

Primary role is biosynthesis ignored in
energy-yield calculations
23
Central Metabolic Pathways
Pentose phosphate pathway
glucose? intermediate of glycolysis
  • NADPH (amount varies)
  • 2 precursor metabolites

Primary role is biosynthesis ignored in
energy-yield calculations
24
Central Metabolic Pathways
pyruvate (3 C) ? acetyl CoA (2 C) CO2 (twice
per glucose)
Transition step
25
Central Metabolic Pathways
Transition step
pyruvate (3 C) ? acetyl CoA (2 C) CO2 (twice
per glucose)
  • NADH
  • precursor metabolite

26
Central Metabolic Pathways
TCA cycle (aka Krebs cycle, citric acid cycle)
acetyl CoA (2 C) ? 2 CO2 (twice per glucose)
27
Central Metabolic Pathways
TCA cycle (aka Krebs cycle, citric acid cycle)
acetyl CoA (2 C) ? 2 CO2 (twice per glucose)
  • ATP
  • 3 NADH
  • FADH2
  • 2 precursor metabolites

28
Central Metabolic Pathways
TCA cycle (aka Krebs cycle, citric acid cycle)
acetyl CoA (2 C) ? 2 CO2 (twice per glucose)
  • ATP
  • 3 NADH
  • FADH2
  • 2 precursor metabolites

29
Central Metabolic Pathways
TCA cycle (aka Krebs cycle, citric acid cycle)
acetyl CoA (2 C) ? 2 CO2 (twice per glucose)
  • ATP
  • 3 NADH
  • FADH2
  • 2 precursor metabolites

30
Review of central metabolic pathway
Precursor metabolites
ATP (substrate-level phosphorylation)
- carried by NADH, FADH2, NADPH
Biosynthesis Electron transport chain ATP
(oxidative phosphorylation)
Glycolysis Pentose phosphate pathway Krebs cycle
( transition step)
Oxidation of glucose Dehydrogenation to CO2
reducing power (H)
31
Precursor Metabolites
Intermediates of catabolism also used in
biosynthesis
32
Review
33
Respiration
34
Electron Transport Chainof mitochondria
TCA cycle Electron carrier get recycled Electron
transport chain Oxidative phosphorylation
Part of figure 3.53
35
Electron Transport Chainof mitochondria
Inside of mitochondria
36
Electron Transport Chainof mitochondria
37
Electron Transport Chainof mitochondria
38
Electron Transport Chain
The Mechanics
39
Electron Transport Chain
Hydrogen carrier
Electron carrier
Hydrogen carrier
Electron carrier
2H
Hydrogen carrier
2H
Electron carrier
40
Electron Transport Chain
Hydrogen carrier
NAD
Regenerates NAD
Electron carrier
Hydrogen carrier
Electron carrier
2H
Hydrogen carrier
2H
Electron carrier
41
Electron Transport Chain
Hydrogen carrier
NAD
2H
Electron carrier
2e-
Hydrogen carrier
Electron carrier
2H
Hydrogen carrier
2H
Electron carrier
42
Electron Transport Chain
Hydrogen carrier
NAD
2H
Electron carrier
Hydrogen carrier
2e-
2H
Electron carrier
Hydrogen carrier
2H
Electron carrier
43
Electron Transport Chain
Hydrogen carrier
NAD
2H
Electron carrier
Hydrogen carrier
2H
Electron carrier
2e-
Hydrogen carrier
2H
Electron carrier
44
Electron Transport Chain
Hydrogen carrier
NAD
2H
Electron carrier
Hydrogen carrier
2H
Electron carrier
Hydrogen carrier
2e-
2H
Electron carrier
45
Electron Transport Chain
Hydrogen carrier
NAD
2H
Electron carrier
Hydrogen carrier
2H
Electron carrier
Hydrogen carrier
2H
Terminal electron acceptor
Electron carrier
2e-
46
Electron Transport Chainof mitochondria
47
Electron Transport Chainof E. coli
  • Aerobic respiration (shown)
  • Anaerobic respiration
  • NO3 as a TEA (different ubiquinol oxidase)
  • Quinone used provides humans with vitamin K

48
Harvesting Energy
The role of electron carriers
C6H12O6 6 O2 ? 6 CO2 6 H2O
  • Passed to the electron transport chain (used to
    create the proton motive force) ultimately
    passed to a terminal electron acceptor (such as
    O2, making H2O)
  • Used in biosynthesis (to reduce compounds)

49
Principles of Metabolism
Synthesizing ATP
  • Substrate-level phosphorylation
  • Oxidative phosphorylation - the energy of proton
    motive force is harvested chemical energy is
    used to create the proton motive force (involves
    an electron transport chain)

ADP Pi ? ATP
50
Harvesting Energy
Energy source versus terminal electron acceptor
Glucose 6 O2 ? 6 CO2 12 H2O
51
Overall Maximum Energy Yield
Overall maximum energy yield of aerobic
respiration (ignoring the pentose phosphate
pathway)
Complete oxidation of glucose 4 ATP
  • 3 ATP/NADH
  • 2 ATP/FADH2

10 NADH 2 FADH2
Electron transport chain (oxidative
phosphorylation)
52
Overall Maximum Energy Yield
Overall maximum energy yield of aerobic
respiration (ignoring the pentose phosphate
pathway)
Complete oxidation of glucose 4 ATP
  • 3 ATP/NADH
  • 2 ATP/FADH2

10 NADH 2 FADH2
Electron transport chain (oxidative
phosphorylation)
38 ATP (maximum theoretical)
53
Respiration
54
Fermentation
  • Used when respiration is not an option
  • Lack of TEA
  • No electron transport chain
  • Oxidation of glucose stops at pyruvate
  • Passes electrons from NADH to pyruvate or a
    derivative

The logic
  • Oxidizes NADH, generating NAD for use in further
    rounds of glucose breakdown
  • Stops short of the transition step and the TCA
    cycle, which together generate 5X more reducing
    power

55
Fermentation
56
Fermentation
57
Review
58
Catabolism of Organic Compounds Other than
Glucose (The Elegance of Metabolism)
59
Anabolic Pathways
  • Synthesis of subunits from precursor metabolites
  • Pathways consume ATP, reducing power and
    precursor metabolites
  • Macromolecules produces once subunits are
    synthesized

60
Principles of Metabolism
  • Role of enzymes
  • Enzymes facilitate each step of metabolic pathway
  • They are proteins acting as chemical catalysts
  • Accelerate conversion of substrate to product
  • Catalyze reactions by lowering activation energy
  • Energy required to initiate a chemical reaction

61
Enzymes
  • A specific, unique, enzyme catalyzes each
    biochemical reaction
  • Enzyme activity can be controlled by a cell
  • Enzymes can be exploited medically, industrially
  • Enzyme names usually reflect the function and end
    in -ase

62
Enzymes
63
Enzymes
Allosteric regulation
reversible
64
Enzymes
Enzyme inhibition
Competitive inhibition
- Inhibitor/substrate act at the same site
Ex. ? PABA ? ? folic acid ? coenzyme
65
Enzymes
Enzyme inhibition
Non-competitive inhibition
- Inhibitor/substrate act at different sites
  • Regulation (allosteric)
  • Enzyme poisons (example mercury)

66
Enzymes
Environmental factors influence enzyme
activity temperature, pH
67
Enzymes
Cofactors act in conjunction with certain enzymes
Coenzymes are organic cofactors
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