Week 4 (carbohydrate metabolism)

Question 1

How much ATP per hour is used when sleeping?

Answer 1

2-3kg

Question 2

How much ATP is stored in the muscle?

Answer 2

~95g

Question 3

How much ATP is used per second during exercise?

Answer 3

53g

Question 4

How many times is an ATP molecule recycled per day?

Answer 4

1000-1500

Question 5

Describe substrate-level phosphorylation

Answer 5

Does not require oxygen
Small contribution to total ATP

Question 6

Describe oxidative phosphorylation

Answer 6

Requires oxygen
Involves respiratory chain (electron transfer)
Main contribution to total ATP.

Question 7

Name and describe the two coupled processes in oxidative phosphorylation

Answer 7

Electron transport
- transport of electrons through the respiratory chain
- achieved by redox reactions
- formation of water
Phosphorylation
- formation of ATP by ATP synthase
- achieved by proton gradients across membrane

Question 8

Where does oxidative phosphorylation take place?

Answer 8

Cristae of mitochondria

Question 9

Each electron transport train contains multiple redox centres; what do these redox centres consist of?

Answer 9

Flavin mononucleotide
Cytochromes (a, b or c)
Iron sulphur cluster

Question 10

What is flavin mononucleotide?

Answer 10

The initial electron acceptors for complex I and complex II.
It can carry two electrons by transferring one at a time.

Question 11

What are cytochromes?

Answer 11

One electron carriers.
Iron coordinating porphyrin ring derivatives.
a, b or c differ by ring additions.,

Question 12

What is coenzyme Q/ubiquinone?

Answer 12

A lipid soluble compound that readily accepts electrons.
A mobile electron carrier transporting electrons from complexes I and II to complex III.
Upon accepting two electrons, it picks up two protons to give an alcohol, ubiquinol.
Ubiquinol can freely diffuse in the membrane, carrying electrons with protons.

Question 13

What delivers electrons to the electron transport chain?

Answer 13

NADH
FADH

Question 14

What is the electron transport chain?

Answer 14

A chain of redox reactions that combine electrons and protons with oxygen to form water.

Question 15

What is required to maintain a proton gradient?

Answer 15

An intact inner mitochondrial membrane.

Question 16

What is ATP synthase?

Answer 16

Acts as a point of re-entry for hydrogen ions across proton gradient.
Convert osmotic energy to chemical energy.

Question 17

How many protons (H+) are needed for the synthesis of 1 ATP?

Answer 17

4

Question 18

What happens as a result of uncoupling of respiration?

Answer 18

Allows the passage of protons across the membrane.
Decreases proton concentration gradient.

Question 19

What are the three main roles of uncoupling proteins (UCP)?

Answer 19

Cold acclimatisation (heat generation)
Facultative diet induced thermogenesis.
Energy homeostasis.

Question 20

Name the uncoupling proteins

Answer 20

UCP1 (found in brown adipose tissue)
UCP2 and UCP3 (more widely distributed e.g. muscle)

Question 21

What do cyanide and carbon monoxide inhibit?

Answer 21

Electron transfer between complex III and IV.

Question 22

What does the ETC generate?

Answer 22

A proton gradient across the inner mitochondrial membrane (i.e. a charge)

Question 23

What is potential energy converted into?

Answer 23

Chemical energy (ATP)

Question 24

What does ATP synthase allow protons to do?

Answer 24

Move back through the inner mitochondrial membrane.

Question 25

Describe uncoupling proteins

Answer 25

Sit on the inner mitochondrial membrane.
Allow free passage of protons.

Question 26

Name the order of carbohydrate metabolism

Answer 26

1. glycolysis
2. pyruvate dehydrogenase
3. TCA cycle
4. Oxidative phosphorylation

Question 27

Describe the malate/aspartate shuttle

Answer 27

Enables the NADH produced in the cytosol to enter the matrix of the mitochondria.
Involves the movement of a proton back into the matrix.
There is 1 less proton for ATP synthase for every NADH carried.

Question 28

Describe the phosphate carriage.

Answer 28

Enables the conversion of GTP to ATP.
GTP produced via the TCA cycle in the mitochondrial matrix leads to ADP phosphorylation to ATP in the cytosol.