Energy Metabolism

Question 1

What are the monomers of Protein?

Answer 1

Amino Acids

Question 2

What are the monomers of Carbohydrates?

Answer 2

Monosaccharides

Question 3

What are the two components of Fats?

Answer 3

Fatty Acids and Gycerol

Question 4

What are amino acids, monosaccarides and fatty acids converted to before entering the citric acid cycle?

Answer 4

Acetyl CoA

Question 5

What is cellular respiration involve?

Answer 5

The oxidation of food monomers (removal of H+ ions to obtain ATP, CO2 and water)

Question 6

Which two vitamins assist the dehydrogenase enzymes in the oxidation?

Answer 6

Vitamin B2 and Vitamin B3

Question 7

What is the net gain of ATP from anaerobic metabolism of glucose?

Answer 7

2 ATP

Question 8

What is the net gain of ATP from aerobic metabolism of glucose?

Answer 8

32 ATP

Question 9

List the 4 main steps of aerobic metabolism of glucose

Answer 9

1) Glycolysis: glucose → 2 pyruvate in 8 sub steps
2) Pyruvate → Acetyl CoA (by pyruvate dehydrogenase)
3) Acetyl CoA → Citric Acid Cycle in 8 steps producing NADH+, H+, FADH2 and CO2
4) Electric Transport Chain: electrons travel down their concentration gradients in inter-membranous space using ATP synthase

Question 10

Where in the cell does anaerobic metabolism of glucose occur?

Answer 10

The cytosol

Question 11

Which enzyme converts pyruvate to Acetyl CoA?

Answer 11

Pyruvate dehydrogenase

Question 12

What does Acetyl CoA combine with when it enters the citric acid cycle and what does it form

Answer 12

It combines with Oxaloacetate to form Citrate

Question 13

Briefly describe oxidative phosphorylation

Answer 13

H+ ions are pumps into the intramembranous space and flow down their concentration gradient along electron carrier proteins

Energy from this is transferred to bind ADP + Pi to reform ATP using the enzyme complex ATP Synthase

Question 14

How do RBC’s metabolism glucose

Answer 14

Red Blood Cells can do not have a mitochondria so can only metabolise glucose anaerobically

Question 15

What occurs in cells when oxygen is not present?

Answer 15

Pyruvate is converted to lactate instead of Acetyl CoA

Question 16

Explain the Cori Cycle

Answer 16

The Cori Cycle allows the lactate produced in the muscles to move into the liver where it can be reconverted to glucose which is then released into the blood stream

Question 17

What is Lipolysis?

Answer 17

Triglycerides → free fatty acids + glycerol

Question 18

What is Beta Oxidation?

Answer 18

The oxidation of fatty acids in which 2 carbons are cleaved off the beta end, forming Acetyl CoA

Question 19

How many ATP can be generated from one fatty acid?

Answer 19

1 fatty acid = 16 carbons = 106 ATP

Question 20

What is Ketogenesis?

Answer 20

When Acetyl CoA is converted to ketone bodies in a low CHO/ high fat environment

Question 21

What hormone promotes ketogenesis?

Answer 21

Glucagon

Question 22

What is Lipogenesis?

Answer 22

Acetyl CoA → Fatty Acids (which bind with glycerol to be stored as triglycerides)

Question 23

Which hormone is dominant and promotes Lipogenesis?

Answer 23

Insulin

Question 24

What is Ketogenesis?

Answer 24

When ketone bodies are formed in the liver from the break down of fatty acids, where fat is the primary source of energy or in a fasted state.

Question 25

What is Ketosis?

Answer 25

A state in which ketone bodies are able to be measured in the blood

Question 26

What are the 3 types of ketone bodies?

Answer 26

Acetone

Aceto-acetate

Betahydroxybutyrate

Question 27

What is Ketoacidosis?

Answer 27

A state where the concentrations of ketone bodies is so high that the pH of the blood begins to fall

Question 28

What happens to amino acids once they reach the cells?

Answer 28

They undergo deamination, where the amine group is removed leaving behind a carbon skeleton

Question 29

What is the difference between ‘ketogenic amino acids and ‘glucogenic amino acids’?

Answer 29

The carbon skeletons of ketogenic amino acids form Acetyl CoA which can enter the CAC or form ketone bodies

The carbon skeletons of glucogenic amino acids form pyruvate or oxaloacetate (or other intermediates of the CAC) which act as fuels to make ATP

Question 30

What is gluconeogensis?

Answer 30

The formation of new glucose from non-glucose sources (reverse glycolysis)

Question 31

What are the 3 main regulators of energy metabolism?

Answer 31

1) The liver and substrates
- major site of nutrient conversion and storage

2) ATP ‘status’
- High ADP/AMP : ATP ratio activates AMPK to promote nutrient catabolism to increase ATP production

3) Functioning Enzymes, Hormones and Vitamins
- rate limiting
- no calories but essential

Question 32

During a feasted state the enzymes for which pathways are unregulated?

Answer 32

• glycogenesis
• lipogenesis
• protein synthesis
• urea synthesis

Question 33

What is the dominant hormone in a post-prandial state?

Answer 33

Insulin

Question 34

What begins to happen in a fasted state?

Answer 34

1) hepatic glycogen breakdown to maintain BG levels
2) muscle glycogen provides energy for muscles only
3) Protein breakdown as a substrate for gluconeogenesis
4) Fat breakdown becomes main energy source in extended fasting
5) Ketogenesis: ketone bodies become an alternate source for brain/muscles etc. to preserve muscle mass