9. Integration of metabolism

Question 1

Describe specialised metabolic features of skeletal muscle

Answer 1

Capable of using a lot of ATP during exercise
Light: ATP consumption met by oxidative phosphorylation (glucose and fatty acids)
Vigorous: ATP consumption faster than supply by oxidative phosphorylation so muscle stores of glycogen broken down

Question 2

Describe specialised metabolic features of the brain

Answer 2

Requires continuous supply of glucose
Can’t metabolise fatty acids
Ketone bodies can partially substitute for glucose

Question 3

Describe specialised metabolic features of the heart

Answer 3

Must beat constantly- designed for completely aerobic metabolism, rich in mitochondria
Utilises TCA cycle substrates e.g. free fatty acids, ketone bodies

Question 4

Describe specialised metabolic features of the liver

Answer 4

Immediate recipient of nutrients absorbed by intestines
Undertakes many metabolic processes (e.g. glycolysis, gluconeogenesis, transamination)
Highly metabolically active
Can interconvert nutrient types

Question 5

What are the key roles of the liver?

Answer 5

Maintain blood glucose at 4.0-5.5mM
Glucose storage (glycogen)
Lipoprotein metabolism (transport of triglycerides and cholesterol)

Question 6

What is excess glucose-6-phosphate used to generate?

Answer 6

Glycogen in liver and muscle

Question 7

What is excess Acetyl CoA used to generate?

Answer 7

Fatty acids

Stored as triglycerides in adipose tissue

Question 8

During extreme exercise what occurs?

Answer 8

ATP demands of muscle > oxygen supply needed for aerobic respiration
Lactate is produced

Question 9

During fasting what occurs?

Answer 9

Rather than enter TCA cycle, most of acetyl CoA produced results in ketone body formation

Question 10

What occurs if fasting and plasma glucose falls below 3mM?

Answer 10

Hypoglycaemic coma

Question 11

List 3 short term solutions to avoiding hypoglycaemia

Answer 11

Breakdown liver glycogen stores
Release free fatty acids from adipose tissue
Convert Acetyl CoA to Ketone bodies via Liver

Question 12

Why is it useful for muscle to use fatty acids and ketone bodies?

Answer 12

Makes more plasma glucose available for brain

Question 13

Describe gluconeogenesis

Answer 13

Occurs 12-18 hours through fasting as glycogen stores exhausted
Produces glucose from non-carbohydrate sources e.g.. lactate, AAs and glycerol

Question 14

Where does gluconeogenesis occur and what does it require?

Answer 14

Liver

Requires investment of ATP

Question 15

What is the overall aim of gluconeogenesis?

Answer 15

Generate glucose from pyruvate

Question 16

When and where is lactate produced?

Answer 16

By skeletal muscle during intense exercise when rate of glycolysis > rate of TCA cycle and ETC

Question 17

Where is lactate taken up and what is it used for?

Answer 17

Taken up by liver

Utilised to regenerate pyruvate by lactate dehydrogenase (LDH)

Question 18

When are amino acids delivered and how can they be utilised?

Answer 18

From diet/ during times of starvation

Converted to pyruvate or oxaloacetate

Question 19

What does hydrolysis of triglycerides produce and why is this useful?

Answer 19

fatty acids and glycerol.

Glycerol backbone used to generate dihydroxyacetone phosphate (DHAP)