Energy metabolism 2

Question 1

What does Pyruvate dehydrogenase (PDH) do?

Answer 1

Enzyme that convers pyruvate to Acetyl-CoA

Question 2

PDH is rate-limiting for.. A
And the B step in mito’s
Makes up the balance between C and D metabolism and is E

Answer 2

A- Rate limiting for CHO oxidation
B- Key enzyme
C- First step in mito’s
D- Balance between aerobic (ox phos) and anaerobic metabolism (substrate phosphorylation)
E- Irreversible

Question 3

PDH is controlled by two enzymes, namely..

Answer 3

1. PDK (pyruvate dehydrogenase kinase): inactivates PDH when there is plenty of energy
2. PDP (Pyruvate dehydrogenase phosphatase): activates PDH bc of Calcium

Question 4

What is a crucial difference in the oxidation of fat vs CH?

Answer 4

FA can be present inside muscle cells, but majority in adipose tissue.
> Can enter muscle cell: fatty acyl-CoA enters mito.

> oxidation/utilization fat ALWAYS takes place in mito, it is ALWAYS aerobic.
= crucial difference CH and Fat

Question 5

What is the rate-limiting step for entrance in mito’s?

Answer 5

 CPT-1

Question 6

What is a key hormone that activates lipolysis?

Answer 6

Andrenaline

Question 7

What determines the dominant pathway (CH vs fat)?

Answer 7

being fasted or not
Nutrient sensing and signalling regulate substrate selection during fasting and feeding

Question 8

What happens in more detail during fasting/feeding with the CH/fat pathways?

Answer 8

During fasting: lot of FA available. High rate of beta-oxidation, lot of acetyl-CoA (or: acyl-CoA?).
Accumulates: feed-back inhibition. PDH shuts down it activity. High fat oxidation will limit/reduce activity of glycolytic system.

During feeding: Lots of Ch, acetyl-CoA. Can be converted to mal-CoA: inhibitor CPT1. Lot of Ch metabolism, inhibition of fat oxidation.

Question 9

CPT-1: rate-limiting enzyme, C stands for X

Answer 9

Carnitine

Question 10

What can cause an increase in FFA due to increased lipolysis, besides adrenaline?

Answer 10

Elevation glucagon, GH, cortisol

Question 11

What can inhibit lipolysis?

Answer 11

• lactate accumulation
• increase insulin after CH intake

Question 12

AMPK: activated as soon as the ratio between X is going up (stress/exercise).

Answer 12

AMP/ATP

Question 13

When AMPK is activated, it inhibits X. This is involved in …. and it means that …. is no longer ….

Answer 13

Inhibits ACC1 = involved conversion acetyl-CoA to malonyl-CoA. Means that fat oxidation is no longer inhibited.

Question 14

What are factors that influence substrate utilization?

Answer 14

> Substrate availability
Activity of rate-limiting enzymes
Local factors, such as..

o Oxygen availability; Muscle fiber composition
o Previous exercise and diet
o Type, intensity and duration of exercise
o Drugs; Exercise training
o Levels of plasma hormone

Question 15

What happens when the endurance athlete ‘hits a wall’?

Answer 15

• Muscle glycogen depletion (fat oxidation can only meet energy 50-60% VO2max)
• hepatic glycogen depletion (hypoglycaemia)

Switch to only fat oxidation

Question 16

With intermittent HI exercise (such as soccer), X contribution will decrease and glycogen stores will be depleted more and more but PCR and aerobic stays roughly the same (with enough rest)

Answer 16

anaerobic glycolysis

 With repeated sprint: mainly PCr and aerobic contributions: anaerobic glycolysis rapidly decreases