Week 4 - ATP & Carbohydrate utilisation during exercise

Question 1

What are the 3 uses of ATP during exercise?

Answer 1

Mechanical energy - muscle contraction
Electrical energy - Electrical nerve impulses (Na+ - K+ Pump and Ca2+ pumpP
Heat - Maintenance of body temp

Question 2

What system allows muscles to keep working during maximal exercise?

Answer 2

Phosphocreatine system

Question 3

What enzyme maintains ATP during hard exercise, and how does it do this?

Answer 3

Myokinase - generates ATP by essentially ‘gluing’ together 2 ADP molecules

Question 4

How does Creatine Kinase drive ATP synthesis during hard exercise?

Answer 4

Phosphocreatine + ADP = Creatine + ATP

Question 5

What is the ratio of PCr to Cr in muscle?

Answer 5

2:1 - this favours the conversion to Cr and ATP

Question 6

Where is creatine kinase located to optimally reform ATP during exercise?

Answer 6

Very near myosin heads

Question 7

When are PCr stores regenerated?

Answer 7

During a recovery period, this cannot be done during exercise. The rate of regeneration is much slower than ATP.

Question 8

What are the bonds in glucose that yields energy?

Answer 8

C-H bonds

Question 9

Describe the digestion of carbohydrates

Answer 9

• Starts in the mouth and then small intestine where enzyme a-amylase hydrolyses (1-4) glycosidic bonds in starch to short-chain carbohydrates (oligosaccharides)
• Oligosaccharides are broken down to disaccharides in the villi of the small intestine.
• Specific enzymes such as lactase, maltase and sucrase then breakdown disaccharides to monosaccharides.
• Monosaccharides then absorbed into cytosol of enterocytes and transported into capillaries that empty into venous blood and the portal vein that supplies the liver.

Question 10

Where is glycogen mainly stored?

Answer 10

Liver (3-7%) and muscle (1-1.5%)

Question 11

What 3 enzymes are involved in glycogen synthesis?

Answer 11

Glycogenin, glycogen synthase & branching enzyme

Question 12

What 2 enzymes are involved in glycogen breakdown?

Answer 12

Glycogen phosphorylase & debranching enzyme

Question 13

How is glycogen phosphorylase activated?

Answer 13

When ATP is broken down (ADP+Pi), the phosphate group activates glycogen phosphorylase to phosphorylate glucose. This then feeds directly into metabolic pathways.

Question 14

What 4 factors are glycogen phosphorylase activity in the muscle increased by?

Answer 14

o Increase Pi
o Increase AMP/ATP ratio.
o Increase Adrenaline
o Increase CA2+

Question 15

What 1 factors is glycogenolysis in the liver increased by?

Answer 15

Adrenaline

Question 16

What is the relationship between Pi and glycogen phosphorylase?

Answer 16

Pi is a substrate for glycogen phosphorylase

Question 17

What is the relationship between AMP and glycogen phosphorylase?

Answer 17

When ATP drops, AMP increases. AMP can bind to glycogen phosphorylase and activate it.

Question 18

How does adrenaline (and calcium) indirectly regulate glycogen phosphorylase?

Answer 18

Adrenaline binds to receptors on muscle/liver and triggers a response, indirectly activating glycogen phosphorylase.
When it binds, it alters conformation of adrenaline receptor (inside cell) activating cAMP which diffuses to glyogen phosphorylase and activates it.

Question 19

Why do we measure lactate levels?

Answer 19

• Can be used to give an indication of fuel metabolism (indicator of CHO metabolism).
• Used to define intensity zones during exercise training.
• Blood lactate response to a standardised test can be used to show training adaptations.

Question 20

Why does even a large production of lactate NOT cause a huge drop in pH?

Answer 20

Because of endogenous buffering systems such as bicarbonate.