3. Metabolism and Energies

Question 1

Anabolism vs. Catabolism

Answer 1

Anabolism
- Anabolism: production of macromolecules.
from “building blocks” and energy (ATP). Reducing power is provided by NAD(P)H + H+.
- Catabolism: generation of energy (ATP) and reducing power (NAD(P)H + H+)
from nutrients. By-products of catabolism may be used as precursor molecules for anabolism.

Question 2

Essential elements

Answer 2

C,O,N,H,P,S,Se

Question 3

Defined medium vs. Complex medium

Answer 3

• Defined medium: know exactly what’s in it

- Complex medium: don’t know the proportion inside

Question 4

Fastidious organism

Answer 4

nutritionally demanding, complex nutritional requirement.

because they are lack of some metabolic passkey so there is no production of certain AA, purines or pyrimidines.

Question 5

negative/positive free energy means release/absorb energy?

Answer 5

(-)delta G0’ release E

(+) delta G0’ absorbs E

Question 6

oxidation/reduction

lose/gain e-?

Answer 6

oxidation lose e-

reduction gain e-

Question 7

redox couples(2H+/ H2)
oxidized form/reduced
electron receptor/ electron donar

Answer 7

NAD+ oxidized

NADH reduced

Question 8

three basic catabolic pathways are all that is required to produce all of the precursors needed for anabolism (carbon compounds and energy)?

Answer 8

– Glycolytic pathway (glycolysis, Embden-Meyerhof pathway).
– Pentose phosphate pathway (hexose monophosphate pathway)
– Tricarboxylic acid pathway (TCA; citric acid cycle, Krebs cycle)

Question 9

Fermentation vs. Respiration

Answer 9

– Fermentation: organic compounds are Electron Donors and electron acceptors. ATP is produced by substrate- level phosphorylation.
– Respiration: organic compounds are oxidized to CO2 with O2 (or substitute) as the Electron Acceptor. Most of the ATP is produced by oxidative phosphorylation.

Question 10

In Glycolytic pathway (Glycolysis), 1 molecule of glucose is oxidized to yield how many pyruvates, ATP, NADH?
ATP is produced by?

Answer 10

• 1 mole glucose–>2 moles pyruvates, 2 ATP, and 2NADH + H+

- substrate-level phosphorylation

Question 11

In TCA cycle, pyruvate is oxidized to?

Answer 11

• first oxidized to Acetyl-CoA and CO2 by pyruvate dehydrogenase,
  then enters the cycle to be fully oxidized to CO2 and H2O

Question 12

Succinate dehydrogenase is located at?

Answer 12

in the membrane

Question 13

Why Oxaloacetate must be generated?

Answer 13

products of reaction is the reactants of next reaction, So lack of Oxalacetate—cycle can NOT proceed

Question 14

In 1 turn of TCA cycle, besides the complete oxidation of acetyl group to acetyl-CoA, how many CO2, GTP, NADH, FADH2 is produced?

Answer 14

2 CO2
1 GTP
3NADH
1FADH2

Question 15

before pyruvate enter TCA cycle, it produce?

Answer 15

1 NADH and 1CO2

Question 16

use of NADH+H+ and FADH2

Answer 16

More ATP can be produced from NADH+H+ and FADH2; their oxidation is coupled to the reduction of a terminal electron acceptor – a process called respiration – and the energy released is used to drive the synthesis of ATP.

Question 17

Aerobic respiration vs. Anaerobic respiration

Answer 17

•Aerobic respira0on: O2 is the terminal electron acceptor.
• Anaerobic respira0on: other compounds act as terminal electron acceptors, under anoxic
condi0ons.

Question 18

Respiratory chain

Answer 18

series of hydrogen and electron carriers that can undergo oxida0on-reduc0on.

Question 19

When a reduced substrate is oxidized (NADH+H+), the hydrogens are transferred to…. ?

Answer 19

• hydrogen carrier (FMN).

The hydrogens are then transferred to the next carrier in the sequence.

Question 20

If the next carrier is an electron carrier, what will be accepted?

Answer 20

• only the electrons will be accepted and the protons will be released to the outer phase. Then, if the next carrier is a hydrogen carrier, two protons must be taken from the inner phase.

Question 21

At complex 4, how many electrons and protons from the inner phase are used to reduce oxygen to water?

Answer 21

2 e- and 2 H+

Oxygen is the final electron acceptor.

Question 22

Complex I

Answer 22

NADH dehydrogenase, FMN (hydrogen carrier), Fe-S center (electron carrier).

Question 23

Q: quinone,

Answer 23

hydrogen carrier.

Question 24

Complex II: succinate dehydrogenase, FAD

Hydrogen carrier

Answer 24

succinate dehydrogenase, FAD

Hydrogen carrier

Question 25

Complex III

Answer 25

cytochrome bc1, Fe-S (electron carriers).

Question 26

Cytochrome c

Answer 26

electron carrier.

Question 27

Complex IV

Answer 27

electron carrier, terminal

oxidase.

Question 28

In E. coli, only__protons per NADH+H+ and __protons per succinate.?

Answer 28

only 8 protons per NADH+H+ and 4 protons per succinate. Because of different cytochromes, 2 protons are pump out at the quinone-level.

Question 29

Proton motive force (pmf)

Answer 29

a transmembrane proton gradient.
- used to drive other energy requiring reactions: flagellum rotation (in bacteria), transport across the membrane, synthesis of ATP.

Question 30

oxidative phosphorylation

Answer 30

• synthesis of ATP using pmf

- 3 - 4 protons are necessary to phosphorylate 1 ADP to ATP.

Question 31

What will affect pmf ?

Answer 31

pH and membrane potential will affect proton motive force

Question 32

products of glycolysis

Answer 32

2 pyruvate
2 ATP (substrate level phophorylation)
2 NADH (oxidative)

Question 33

products of pyruvate dehydrogenase + TCA

Answer 33

3 CO2
4 NADH (oxidative)
1 FADH2 (oxidative)
1 GTP (substrate level)

Question 34

total ATP produced?

Answer 34

34-38 ATP per glucose

Question 35

Cyanide and CO are toxic because ?

Answer 35

no oxygen is brought to the cells, blocks energy transport chain.

Question 36

If no terminal electron acceptor is available, succinate ? respiration? fermentation?

Answer 36

If no terminal electron acceptor is available,
1) succinate cannot be oxidized by succinate dehydrogenase in the respiratory chain.
2) Glycolysis can still function, because NADH+H+ can be oxidized back to NAD+.
3) If there is terminal electron acceptor, cells will do respiration
Without terminal electron acceptor, cells will then go to fermentation to make ATP.

Question 37

What is the electron donor and acceptor in fermentation?

Answer 37

an organic compound serves as the electron donor

an organic degradation product serves as the final acceptor of electrons.

Question 38

net yield of fermentation?

Answer 38

2 ATP per glucose because only glycolysis is functioning

Question 39

In the absence of O2, the yeast popula0on grows very slowly. Why?

Answer 39

because fermentation yields only a fraction of ATP produced by respiration.

Question 40

In most anabolic reactions, the source of reducing power is?

Answer 40

NADPH + H+ is used as the source of reducing power.
use NADH for respiration
use NADPH for anabolic reactions

Question 41

Pentose phosphate pathway require oxygen or not?

Answer 41

Pentose phosphate pathway does NOT require oxygen

Question 42

The pentose phosphate pathway leads to the generation of a diversity of sugars, for example?

Answer 42

Ribose 5-phosphate may be used to produce ribose and later, deoxyribose

Question 43

where does Pentose phosphate pathway take place?

Answer 43

In the cytoplasm (Prokaryotes and Eukaryotes).

Question 44

Anaplerotic pathways

Answer 44

feeds the citric acid cycle with intermediates

e.g. produce malate or oxaloacetate directly from pyruvate

Question 45

respiratory chain are located in___ in eukaryotes vs.prokaryotes?

Answer 45

In eukaryotes:

• Mitochondria: the enzymes of the TCA cycle, respiration and oxidative phosphorylation
• cytoplasm: the enzymes of glycolysis and fermentation.

In prokaryotes:
the respiratory chain is located in the cytoplasmic membrane, while enzymes of glycolysis, TCA cycle and fermenta0on are located in the cytoplasm.