Integration Of Metabolism

Question 1

Muscle

Answer 1

Relies upon carbohydrate and fatty acid oxidation

Have periods of very high ATP requirement

Question 2

Brain and nervous system

Answer 2

Cannot utilise fatty acids as a fuel source

Uses 20% of resting metabolic rate —> has continuous high ATP requirement

Question 3

Adipose tissue

Answer 3

Long term storage site for triglycerides

Question 4

Heart

Answer 4

Can oxidise fatty acids and carbohydrates

10% of resting metabolic rate

Question 5

Liver

Answer 5

Main carbohydrate store

Source of blood glucose

20% resting metabolic rate

Source of ketone bodies (from fatty acids)

Question 6

What does the brain require a continuous supply of?

Answer 6

Glucose

(Ketone bodies can partially substitute for glucose)

Question 7

What can the brain not metabolise?

Answer 7

Fatty acids

Question 8

In the brain what does too little and too much glucose cause?

Answer 8

Too little = hypoglycaemia —> fairness and coma

Too much = hyperglycaemia —> irreversible damage

Question 9

In the muscle how are requirements met during light contraction?

Answer 9

OxPhos
—> O2 and blood borne glucose and fatty acids used as fuel

Question 10

In the muscles how are requirements met during vigorous contraction?

Answer 10

Glycogen breakdown

Lactate formation

When ATP consumption > than ATP supply rate by OxPhos
—> O2 becomes a limiting factor

Question 11

Metabolic features of the heart

Answer 11

Completely aerobic metabolism —> rich in mitochondria

Utilises TCA substrates —> free fatty acids, ketone bodies e.g.

Loss of O2 —> cell death —> myocardial infarction

Question 12

What happens during extreme exercise?

Answer 12

ATP demand > ATP production
—> lactate produced

Question 13

What happens during fasting?

Answer 13

Instead of entering TCA cycle —> acetyl CoA results in ketone body production

Question 14

What happens if glucose levels fall below 3 mM?

Answer 14

Body enters a hypoglycaemic coma

Question 15

How is hypoglycaemia avoided?

Answer 15

Breakdown of liver glycogen stores —> maintain plasma glucose levels

Release free fatty acids from adipose tissue

Convert acetyl CoA into ketone bodies via the liver

Question 16

What reaction can directly enter pathway to increase oxaloacetate for gluconeogenisis?

Answer 16

Transamination of amino acids
—> carbon skeleton enters the cycle

Question 17

Why must some redactions on gluconeogenisis be bypassed?

Answer 17

The forward reactions are essentially irreversible under cellular conditions

Question 18

Why can’t the muscle produce glucose via gluconeogenisis?

Answer 18

It doesn’t have the enzyme (glucose-6-phosphatase) to bypass the reaction

Question 19

Why is it important that the muscle doesn’t have glucose-6-phosphatase?

Answer 19

It ill reverse the reaction —> set up a futile cycle

Question 20

What are glucogenic amino acids used for?

Answer 20

Generate glucose via gluconeogenisis

Question 21

What are ketogenic amino acids used for?

Answer 21

Synthesis fatty acids and ketone bodies

Question 22

Fats as a fuel source

Answer 22

Triglycerides —> fatty acids and glycerol

Fatty acid —> ketone bodies

Glycerol —> DHAP —> enter gluconeogenisis

Question 23

Energy stores and consumption - Aerobic respiration

Answer 23

Contractions increase ATP demand

Contractions increase glucose transport

Muscle glycolysis increases (adrenalin)

Gluconeogenisis increases (adrenalin)

Fatty acids increase (adrenalin)

Question 24

Energy stores and consumptions - Anaerobic respiration

Answer 24

ATP demand not matched by O22 delivery

Transport cannot keep up with the demand for glucose

Muscle glycogen breakdown increases

Lactate increases

Liver uses lactate to form glucose (recovery) —> replenishes NAD+ levels

Question 25

Hormonal control of blood - what does insulin do?

Answer 25

Secreted by islets of pancreas when glucose levels rise

Stimulate uptake and use of glucose and storage of glycogen and fat

Suppresses glucagon release

Question 26

Hormonal control of blood — what does glucagon do?

Answer 26

Secreted by islet of pancreas when glucose levels fall

Stimulates production of glucose by gluconeogenisis and breakdown of glycogen and fat

Question 27

Hormonal control of blood - what does adrenalin do?

Answer 27

Strong and fast metabolic effects to mobilise glucose for ‘fight or flight’

Question 28

Hormonal control of blood - what do glucocorticoids do?

Answer 28

Steroid hormones —> increases synthesis of metabolic enzymes concerned with g;leucose availability

Question 29

Hormonal control of blood - right after a meal

Answer 29

Blood glucose levels rise —> controlled by increased secretion of insulin and reduced glucagon

Increased glucose uptake by liver

Increased glucose uptake and glycogen synthesis in muscle

Increased triglyceride synthesis in adipose tissue

Increased usage of metabolic intermediates

Question 30

Hormonal control of blood - some time after a meal

Answer 30

Blood glucose levels start to fall and are controlled by:

Increased glucagon secretion + reduced insulin

Glucose production in liver from glycogen breakdown and gluconeogenisis

Fatty acid breakdown as alternative substrate for ATP production

Adrenalin stimulera glycogen breakdown, glycolysis + lipolyses

Question 31

Hormonal control of blood - after prolonged fasting

Answer 31

Glucagon/insulin ratio increases further

Adipose tissue hydrolyses triglycerides to provide fatty acids

TCA cycle intermediates reduced in amount to provide substrates for gluconeogenisis

Protein breakdown provides amino acid substrates for gluconeogenisis

Ketone bodies produced from fatty acids and amino acids in liver

Question 32

Type 1 diabetes

Answer 32

Failure to secret enough insulin (beta cell dysfunction)

Question 33

Type 2 diabetes

Answer 33

Failure to respond appropriately to insulin levels (insulin resistance)

Question 34

What are some complications of diabetes?

Answer 34

Hyper and hypoglycaemia

Cardiovascular complications

Ketoacidosis