Integration of Metabolism

Question 1

What is the % body weight of muscles and which energy sources do they use?

Answer 1

40% of total body weight
uses carbohydrates and FA

Question 2

What is the % body weight of brain and which energy sources do they use?

Answer 2

2% of total body weight - uses 20% of resting metabolic rate
uses mainly carbohydrates, cannot use FA

Question 3

What is the % body weight of adipose tissue and what do they store?

Answer 3

15% total body weight
Long-term storage of triacyl glycerols

Question 4

What is the % body weight of heart and which energy sources do they use?

Answer 4

1% total body weight - uses 10% of resting metabolic rate
uses carbohydrates and FA

Question 5

What is the % body weight of liver and what does it store?

Answer 5

2.5% of total body weight - uses 20% of resting metabolic rate
glycogen storage and source of blood glucose

Question 6

Which energy source does the brain need continuously?

Answer 6

Glucose

Question 7

What can partially substitute for glucose in the brain?

Answer 7

ketone bodies (e.g. β-hydroxybutyrate)

Question 8

What are the terms called when there is not enough blood glucose or too high blood glucose?

Answer 8

Hypoglycaemia
Hyperglycaemia

Question 9

How is the energy supplied for light contraction of skeletal muscle?

Answer 9

OxPhos

Question 10

How is the energy supplied for vigorous contraction of skeletal muscle?

Answer 10

O2 becomes limiting factor → Glycogen breakdown in muscles → Lactate formation

Question 11

Can heart muscle also rely on anaerobic metabolism?

Answer 11

No, it utilises only aerobic metabolism

Question 12

Which energy sources can the heart use?

Answer 12

TCA cycle substrates (e.g. free fatty acids, ketone bodies)

Question 13

Which organ/tissue can interconvert nutrient types?

Answer 13

Liver

Question 14

What is the normal range for blood glucose?

Answer 14

4.0-5.5 mM

Question 15

What happens to Acetyl CoA during fasting?

Answer 15

Rather than entering TCA cycle, most of it is converted into ketone bodies

Question 16

Which enzyme is used to convert lactate back to pyruvate?

Answer 16

Lactate dehydrogenase (LDH)

Question 17

What is glycerol converted into for gluconeogenesis?

Answer 17

DHAP

Question 18

Which molecules can be derived from amino acids to start gluconeogenesis?

Answer 18

Oxaloacetate and Pyruvate

Question 19

What is lactate converted into for gluconeogenesis?

Answer 19

Pyruvate

Question 20

How is gluconeogenesis not just reverse glycolysis?

Answer 20

Irreversible steps in glycolysis need to be bypassed

Question 21

What is the net change in ATP for gluconeogenesis?

Answer 21

net loss of 6 ATP

Question 22

Gluconeogenesis

How is pyruvate kinase bypassed?

Answer 22

1st step: Pruvate converted into oxaloacetate by pyruvate carboxylase
2nd step: Oxaloacetate converted into phosphoenolpyruvate by phosphoenolpyruvate carboxykinase

Question 23

Gluconeogenesis

Which enzyme bypasses phosphofructokinase?

Answer 23

Fructose 1-6 bisphosphatase

Question 24

Gluconeogenesis

Which enzyme bypasses hexokinase?

Answer 24

Glucose-6-phosphatase

Question 25

What happens to fatty acids during fasting?

Answer 25

Can’t enter gluconeogenesis, converted into ketone bodies

Question 26

How does adrenalin help increase rate of glycolysis in muscles?

Answer 26

Increase gluconeogenesis in liver
Increase release of FA from adipose tissue

Question 27

How is glycogen from liver used in anaerobic respiration of muscles?

Answer 27

Glycogen broken down to glucose in liver → Transported to muscles → Glycolysis and lactate formation → Lactate taken up by liver for gluconeogenesis

Question 28

What does a high Km (Michaelis constant) indicate?

Answer 28

Enzyme active at high concentrations of substrate → Low substrate affinity

Question 29

What does a low Km (Michaelis constant) indicate?

Answer 29

Enzyme active at low concentrations of substrate → High substrate affinity

Question 30

Where is Hexokinase (Hk I) found?

Answer 30

Muscle cells

Question 31

Where is Hk IV or Glucokinase found?

Answer 31

Liver

Question 32

What are the differences between Hk I and Hk IV?

Answer 32

Hk I (Muscle) and Hk IV (Liver)

Question 33

Which glucose metabolism enzyme is present in liver but not muscle?

Answer 33

GLucose-6-phosphatase

Question 34

When is insulin secreted and what does it do?

Answer 34

secreted when glucose levels rise - it stimulates uptake and use of glucose and storage as glycogen and fat

Question 35

When is glucagon secreted and what does it do?

Answer 35

secreted when glucose levels fall - it stimulates production of glucose by gluconeogenesis and breakdown of glycogen and fat

Question 36

When is adrenaline (epinephrine) secreted and what does it do?

Answer 36

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

Question 37

When are glucocorticoids secreted and what do they do?

Answer 37

secreted when glucose is less available - they are steroid hormones which increase the synthesis of metabolic enzymes concerned with glucose availability

Question 38

What are the types of Diabetes Mellitus?

Answer 38

Type I - limited secretion of insulin
Type II - limited response to insulin

Question 39

What are some complications of diabetes?

Answer 39

Hypo/hyperglycaemia - Coma
Cardiovascular (i.e. atherosclerosis)
Ketoacidosis
Retinal damage

Question 40

What is ketoacidosis?

Answer 40

Excess ketone bodies in plasma lowering the pH as they are acidic

Question 41

How can hyperglycaemia result in coma?

Answer 41

The high plasma glucose will disturb solute balance in the brain due to increased osmolarity of body fluids