Session 2-Energy Production: Carbs

Question 1

What is another name for the tricarboxylic acid cycle?

Answer 1

Krebs cycle

Question 2

Where is pyruvate dehydrogenase (PDH) located?

Answer 2

Mitochondrial matrix

Question 3

How many enzymes is PDH made up of?

Answer 3

5 enzymes

Question 4

What does PDH deficiency lead to?

Answer 4

Lactic acidosis

Question 5

What is PDH activated by? (5)

Answer 5

Pyruvate
CoASH
NAD+
ADP
Insulin

Question 6

What is PDH inhibited by? (4)

Answer 6

Acetyl-CoA
NADH
ATP
Citrate

Question 7

True or false: PDH activators work by phosphorylation

Answer 7

FALSE - dephosphorylation

Question 8

Which two reactions in the TCA cycle are irreversible?

Answer 8

1) isocitrate (C6) -> alpha-ketoglutarate (C5)

2) alpha-ketoglutarate (C5) -> succinyl-CoA (C4)

Question 9

How many TCA cycles occur per glucose molecule?

Answer 9

2

Question 10

How is the TCA cycle regulated?

Answer 10

Energy availability ie ATP/ADP ratio and NADH/NAD+ ratio

Question 11

Which two enzymes are allosterically regulated by NADH and ATP in the TCA cycle?

Answer 11

1) isocitrate dehydrogenase

2) alpha-ketoglutarate dehydrogenase

Question 12

True or false: TCA supplies biosynthetic processes

Answer 12

TRUE

Question 13

True or false: TCA cycle is only catabolic

Answer 13

FALSE - also anabolic

Question 14

TCA cycle is the central pathway in the catabolism of which substances? (5)

Answer 14

Sugars
Fatty acids
Ketone bodies
AA
Alcohol

Question 15

How is ATP produced in the TCA cycle?

Answer 15

Substrate level phosphorylation

Question 16

True or false: TCA cycle can function in the absence of O2

Answer 16

FALSE

Question 17

Where does electron transport and ATP synthesis occur?

Answer 17

Inner membrane of the mitochondria

Question 18

Which coenzymes are re-oxidised in stage 4 of catabolism?

Answer 18

NADH

FADH2

Question 19

What is O2 reduced to in stage 4 of catabolism?

Answer 19

Water

Question 20

Why does stage 4 of catabolism occur in small steps?

Answer 20

To retain energy

Question 21

Which two processes use reducing power to synthesise ATP?

Answer 21

1) Electron transport

2) Oxidative phosphorylation

Question 22

What happens in electron transport?

Answer 22

Electrons on NADH and FADH2 are transferred through a series of carrier molecules to oxygen

Question 23

What happens in oxidative phosphorylation?

Answer 23

Free energy released is used to drive ATP synthesis

Question 24

True or false: the inner membrane of a mitochondrion is impermeable

Answer 24

TRUE

Question 25

What happens to electrons as they are passed from proton translocating complex (PTC) 1 to PTC3?

Answer 25

Lose energy

Question 26

In the electron transport chain, why do protons want to reenter the matrix and what prevents them from doing so?

Answer 26

- Concentration gradient and electrical gradient | - Membrane is impermeable so can only enter through ATP synthase

Question 27

Approximately what % of energy is used to move H+ across the membrane in the electron transport chain?

Answer 27

~30%

Question 28

What is the H+ gradient across the inner mitochondrial membrane called?

Answer 28

Proton motive force (pmf)

Question 29

Where are electrons transferred to from NADH and FADH2?

Answer 29

Molecular oxygen

Question 30

Complete the sentence: Energy from the dissipation of the pmf is coupled to the synthesis of ___ from ___

Answer 30

ATP | ADP

Question 31

True or false: electrons in FADH2 have more energy than in NADH

Answer 31

FALSE - other way round

Question 32

How many PTCs does NADH use?

Answer 32

3

Question 33

How many PTCs does FADH2 use?

Answer 33

2

Question 34

True or false: the greater the pmf, the _______ ATP is synthesised

Answer 34

More

Question 35

How is oxidative phosphorylation regulated?

Answer 35

When [ATP] is high ([ADP] is low), no substrate for ATP synthase so the inward flow of H+ stops. The concentration of H+ in the intermitochondrial space increases, preventing further H+ pumping. Electron transport is therefore stopped

Question 36

Complete the sentence: Inhibitors ______ electron transport, preventing the acceptance of electrons by _________

Answer 36

Block | Oxygen

Question 37

Give examples of an inhibitor of oxidative phosphorylation

Answer 37

Cyanide | Carbon monoxide

Question 38

What do uncouplers of oxidative phosphorylation do?

Answer 38

Increase permeability of the inner mitochondrial membrane to protons. This dissipates the proton gradient, thereby reducing the pmf so there is no drive for ATP synthesis

Question 39

Give an example of uncouplers

Answer 39

Fatty acids

Question 40

What does the efficiency of coupling of oxidative phosphorylation depend on?

Answer 40

Tightness of coupling

Question 41

What controls the degree of coupling in brown adipose tissue and what does this allow?

Answer 41

Fatty acids | Allows extra heat generation

Question 42

What does brown adipose tissue contain that is usually inactive?

Answer 42

Thermogenin (UCP1) = naturally-occurring uncoupling protein

Question 43

What is activated in UCP1's response to cold and noradrenaline? (2)

Answer 43

1) lipase which releases fatty acids from triacylglycerol | 2) fatty acid oxidation -> NADH/FADH2 -> electron transport

Question 44

Apart from cold and noradrenaline, what else activates UCP1 and what effect does this have?

Answer 44

- Fatty acids - UCP1 transports H+ back into mitochondria so electron transport is uncoupled from ATP synthesis and the energy of pmf is released as extra heat.

Question 45

In which organisms can brown adipose tissue be found in?

Answer 45

Newborn infants | Hibernating animals

Question 46

In what way are the enzymes used in oxidative phosphorylation different to those used in substrate level phosphorylation?

Answer 46

In oxidative, enzymes are membrane-associated whereas in substrate level, enzymes are soluble

Question 47

True or false: energy coupling occurs indirectly through the generation and subsequent utilisation of a proton gradient in substrate level phosphorylation

Answer 47

FALSE - ^ in oxidative

Question 48

How does energy coupling occur in substrate level phosphorylation?

Answer 48

Directly through formation of high energy hydrolysis bond

Question 49

True or false: oxidative phosphorylation can occur to a limited extent in the absence of O2

Answer 49

FALSE - ^ is substrate level

Question 50

Which is the major process for ATP synthesis?

Answer 50

Oxidative phosphorylation

Question 51

How many moles of ATP are produced per mole of glucose?

Answer 51

32

Question 52

The reaction catalysed by PDH is sensitive to the deficiency of which vitamin?

Answer 52

B1

Question 53

Which reaction does PDH catalyse?

Answer 53

Pyruvate -> acetyl-CoA + CO2