Integration of metabolism

Question 1

What are the three fuel storages of the heart?

Answer 1

Fatty Acids

Lactate

Ketone Bodies

Question 2

Where in the body can excess G6P be used to generate glycogen?

Answer 2

Liver and muscle

Question 3

What can excess acetyl CoA be used to generate?

Answer 3

Fatty acids

Question 4

List 3 ways the body can avoid hypoglycaemia?

Answer 4

1. Breakdown of liver glycogen stores occurs to maintain plasma glucose levels
2. Release free FAs from adipose tissue
3. Convert acetyl CoA into ketone bodies via the liver

Question 5

What is the Cori cycle?

Answer 5

When lactate is taken up by the liver and utilised to regenerate pyruvate by Lactate Dehydrogenase

Question 6

What are the three non-carbohydrate precursors for energy through gluconeogeneis and what process occurs from?

Answer 6

Glycerol from fatty acid hydrolysis used to make DHAP then G3P
Amino acids from diet or breakdown of skeletal muscle during starvation and form oxaloacetate or pyruvate
lactate through the cori cycle

Question 7

Which enzymes catalyse the irreversible reactions of glycolysis and which enzymes are used to bypass this in gluconeogenesis?

Answer 7

pyruvate > oxaloacetate via pyruvate carboxylase
then
pyruvate kinase bypassed by phosphoenalpyruvate carboxykinase
phosphofructokinase bypassed by fructose-1,6-bisphosphatase
Hexokinase bypassed by Glucose-6-phosphatase

Question 8

What is the Michaelis constant (KM)?

Answer 8

The concentration of substrate at which an enzyme functions at a half-maximal rate (Vmax).

Question 9

What causes type 1 diabetes?

Answer 9

Beta-cell dysfunction (failure to secrete enough insulin)

Question 10

What causes type 2 diabetes?

Answer 10

Individual fails to respond appropriately to insulin levels

Question 11

During moderate exercise (when oxygen is not a limiting factor), how are the increased demands of skeletal muscle for ATP met?

Answer 11

Increased numbers of glucose transporters on the surface of muscle cells to aid glucose uptake for glycolysis.
There is also an increased rate of gluconeogensis induced by adrenalin (epinephrine) and increased lipolysis in the adipose tissue to release free fatty acids.

Question 12

During strenuous exercise, (when oxygen becomes a limiting factor) how are the increased demands of skeletal muscle for ATP met?

Answer 12

Glycogenolysis in the liver, provides a source of glucose, as does gluconeogenesis.
To replenish NAD+ levels and maintain glycolysis, pyruvate is converted to lactate by the liver.
Increased lipolysis also provides free fatty acids for β-oxidation.
.

Question 13

What can lead to hyperglycaemia?

Answer 13

Insulin deficiency and relative excess of glucagon can lead to increased hepatic output of glucose and thus hyperglycaemia

Question 14

What are some complications of diabetes?

Answer 14

Hyperglycaemia with progressive tissue damage (retina, kidney, peripheral nerves)
Increase in plasma fatty acids and lipoprotein levels
Increased ketone bodies and risk of acidosis

Question 15

What is the hormonal response to blood glucose levels falling?

Answer 15

Glucose levels fall > increased glucagon secretion > breaks down glycogen and fat and stimulates production of glucose by gluconeogenesis

Question 16

What is the hormonal response to blood glucose levels rising?

Answer 16

Glucose levels rise > Insulin secreted > stimulates the uptake and use of glucose and storage as glycogen and fat

Question 17

What effect does adrenaline/epinephrine have on metabolism?

Answer 17

strong and fast metabolic effects to mobilise glucose for fight or flight

Question 18

What effect do glucocorticoids have on metabolism?

Answer 18

Steroid hormones which increase synthesis of metabolic enzymes concerned with glucose availability

Question 19

What fuel sources can the brain use?

Answer 19

only glucose and partially ketone bodies ( b-hydroxybutarate)

Question 20

What are the metabolic functions of the liver?

Answer 20

Highly active 
can interconvert nutrient types 
plays a role in maintaining glucose at 4-5.5mM
Glucose storage organ
Role in lipoprotein metabolism

Question 21

What occurs during prolonged fasting?

Answer 21

Glucagon/insuline ratio increases further
Adipose tissue begins to break down to provide fatty acids for metabolism
TCA cycle intermediates reduced in amount to provide substrate for gluconeogenesis
Ketone bodies produced from fatty acids and amino acids in liver to substitute partially the brains requirement for glucose

Question 22

In a fed state why does insulin stimulate an increase in the number of glucose transporters on the adipocyte surface?

Answer 22

To facilitate glucose uptake to make triglycerides