Week 3

Question 1

What is meant by dual stage regulation of metabolism?

Answer 1

First stage: Calcium acts as a gross controller, regulating processes like muscle contraction and metabolic pathways, by influencing enzymes and activating contractile proteins in muscular contraction

Second stage: The byproducts of ATP hydrolysis (ADP, Pi, and Hydrogen ions) provide a ‘fine-tuning’ mechanism, by indicating energy status in cells and adjusting speed of metabolic enzymes for efficient energy production.

Question 2

What are the main enzymes and their function in intense exercise regulation?

Answer 2

Creatine kinase - Catalyses production of ATP by converting PCr to Creatine and Pi (used to make ATP)

Phosphorylase - Breaks down glycogen into glucose-1-phosphate to enter glycolysis. Activated by adrenaline and AMP

Phosphofructokinase - Regulates glycolysis activated by high levels of ADP and Pi which shows more ATP is needed

Lactate dehydrogenase - Catalyses conversion of pyruvate to lactate when oxygen is limited, enabling further ATP production through anaerobic glycolysis

Hexokinase - catalyses conversion of glucose to glucose-6-phosphate by adding Pi from ATP

Question 3

What regulates enzyme activity?

Answer 3

Product of Muscle Contraction:
AMP: Indicates low energy, stimulates PFK (phosphofructokinase) and GP (glycogen phosphorylase) to promote more ATP production.

Calcium Ions: Activate CK (creatine kinase) and PK (pyruvate kinase), which then activate GP.

Products of ATP Hydrolysis:
ADP, Pi, H+: Low ATP levels trigger activation of CK and GP, enhancing ATP regeneration.

Other Factors:
Lactate: Signals the body to continue glycolysis.

G6P (Glucose-6-phosphate): Produced during glycolysis, inhibits hexokinase to prevent excessive glucose breakdown when glucose levels are sufficient.

Pyruvate: Can be converted to Acetyl CoA for ATP production or to lactate for anaerobic ATP production

Question 4

Fuels needed for endurance exercise?

Answer 4

Carbs and Fats

External: Plasma fatty acids and blood glucose (digestion)

Internal: Intramuscular triglycerides (muscle stored fats) and glycogen (muscle/liver stored glucose)

Question 5

What fuel is used more at higher intensities and why?

Answer 5

Carbohydrates -

Can be broken down faster

Produces ATP faster

Fat requires more oxygen and time to break down

Question 6

What regulations occur during endurance exercise/What is fuel mobilisation regulated by?

Answer 6

Hormonal control -

Increased adrenaline/epinephrine = increased breakdown of stored glycogen and fats

Increased glucagon = stimulates glycogen breakdown and gluconeogenesis (producing glucose from non carb sources)

Decreased insulin = Decreases/prevents glucose storage

Local muscle signals - how much ATP and amount of muscle contraction

Question 7

What main enzymes are involved in endurance exercise regulation?

Answer 7

Pyruvate dehydrogenase (PDH) - converts pyruvate into acetyl-coa = used in krebs

Hormone-sensitive lipase (HSL) - catalyses breakdown of fats, allowing more FFAs to be transported for use during low intensity exercise

B-HAD - Controls fat oxidation by catalysing breakdown of long chain fatty acids to allowing supply of acetyl coa in krebs

Question 8

Factors affecting fat oxidation?

Answer 8

Decreased blood flow to adipose tissue = less fatty acids in blood

Increased acidity =
Inhibition of Hormone sensitive lipase = less fat breakdown

and inhibits CPT1 so less fat transport to mitochondria

Question 9

What transports glucose and fats?

Answer 9

GLUT4
CPT1