Biochem 4 - exercise metabolism

Question 1

Which molecules/hormones result in glycogen mobilisation

Answer 1

Ca2+ in cytoplasm
AMP
Adrenaline

Question 2

At rest, what provides energy for muscle

Answer 2

Oxidative metabolism of fatty acids

Pyruvate into TCA cycle

Question 3

What happens at onset of exercise

Answer 3

Glycogenolysis

Increased O2 consumption and NO/dilation of smooth muscles

Question 4

How does Ca2+ increase glycogen breakdown

Answer 4

By activating glycogen phosphorylase

Also stimulates production of NO -> vasodilation

Question 5

What local regulatory factors affect blood flow

Answer 5

Tissue hypoxia
Adenosine
K+
CO2
H+
NO

Question 6

What metabolic processes does adrenaline stimulate

Answer 6

Glycogen and lipid mobilisation

Question 7

What metabolic processes does increased glucagon and decreased insulin promote

Answer 7

Gluconeogenesis

glycogenolysis

Question 8

What does insulin inhibit

Answer 8

Gluconeogenesis

Question 9

What is phosphocreatine used as

Answer 9

First top up source for muscle ATP

Creatine phosphate + ADP – (creatine kinase) –> ATP + creatine

Question 10

What builds up when there is insufficient oxygen or too much pyruvate

Answer 10

Lactate

Question 11

What happens in the Cori cycle

Answer 11

Lactate transported from muscle to liver, converted into glucose and goes back into blood to muscle as an energy source

Question 12

Does fatty acid oxidation (to produce ATP) need oxygen

Answer 12

Yes, adequate supply needed, as with aerobic metabolism of glucose

Question 13

Accumulation of what in contracting muscle results in a decline of force generated and why?

Answer 13

Accumulation of pyruvate and lactic acid
Due to decrease in muscle pH
-> Glycolysis inhibited by H+ from lactic acid

Question 14

What 2 fuels are used to replenish ATP in short sprints

Answer 14

Phosphocreatine and anaerobic glycogen breakdown to lactate
Phosphocreatine levels become exhausted fairly quickly
Blood vessels are compressed making muscles reliant on anaerobic energy production
Large amounts of lactic acid produced (which liver uses to maintain blood glucose levels)

Question 15

During a marathon, what are muscles reliant on

Answer 15

Oxidative (aerobic) metabolism of glycogen; glucose from liver; fatty acids from adipose tissue

Question 16

Middle distance run metabolism - what contributes?

Answer 16

Aerobic oxidation = 30% of ATP required
Some oxygen may come from oxymyoghobin
Lactate = 65% ATP
Contribution of phosphocreatine decreases - at 800m = 5%, at 1500m = 0%

Question 17

First 10 minutes of a marathon

Answer 17

Glycogen and glucose used
Vasodilation
Glycogen breakdown stimulated by AMO and adrenaline
Fatty acids mobilised (adrenaline) to maintain blood glucose

Question 18

30mins-2 hours of a marathon

Answer 18

Oxidation of glucose and fatty acids for ATP (increased reliance on FAs over time)
Lactate, glycerol and muscle amino acids used to support glucose production by liver

Question 19

2+ hours of marathon

Answer 19

90% liver glycogen used - glucagon levels high

Ketone bodies produced by liver

Question 20

Hitting the wall

Answer 20

Glycogen stores largely depleted after 20 miles
Body switches to fatty acids as main source of energy
-> 50% max power output and pace decreases

Question 21

Can fats supply exercising muscle by themselves

Answer 21

No - absolute requirement for some glucose
The requirement for background level of glucose metabolism increases with exercise intensity
(but fats alone can supply resting muscle)

Question 22

What happens when liver glucose output falls below muscle glucose uptake

Answer 22

Hypoglycaemia

- symptoms: confusion, lactic acidosis, exhaustion