5: Biochemistry - Gluconeogenesis

Question 1

Between meals, when dietary carbohydrate is exhausted but there’s still glycogen in the liver, which process supplies the bloodstream with glucose?

Answer 1

Glycogenolysis

Question 2

When hepatic glycogen stores are depleted, i.e glycogenolysis is no longer any good, how does the body supply the bloodstream with glucose?

Answer 2

Gluconeogenesis

Question 3

What is gluconeogenesis?

Answer 3

Synthesis of glucose from NON-CARBOHYDRATE PRECURSORS

Question 4

What’s an emergency situation in which gluconeogenesis would be required?

Answer 4

Prolonged starvation

Question 5

What molecule, produced by skeletal muscle during anaerobic respiration, acts as a precursor for gluconeogenesis?

Answer 5

Lactate

Question 6

Which molecules, usually acting as the building blocks of protein, can be used as precursors for gluconeogenesis?

Answer 6

Amino acids

Question 7

How are amino acids obtained for gluconeogenesis?

Answer 7

Proteolysis of muscle protein

This is why you see muscle wasting during prolonged starvation

Question 8

Which building block of triglycerides can be used by the body as a precursor for gluconeogenesis?

Answer 8

Glycerol

Question 9

How are glycerol molecules obtained for gluconeogenesis?

Answer 9

Lipolysis of triglycerides in adipose (fat) tissue

Question 10

Gluconeogenesis is an anabolic reaction (small molecules ⇒ big molecules) and therefore requires energy. How is this energy obtained?

Answer 10

Oxidation of fatty acids from adipose tissue

This, along with proteolysis of muscle, is why starving people lose weight

Question 11

Where does gluconeogenesis occur?

Answer 11

Liver

Question 12

Gluconeogenesis is essentially the reverse of ___.

Answer 12

glycolysis

Question 13

Which molecule accepts acetyl groups from fat breakdown?

Answer 13

Oxaloacetate

Question 14

Gluconeogenesis is very energetically ___.

Answer 14

expensive

Question 15

How many ATPs worth of energy are required to synthesise one molecule of glucose?

Answer 15

6

Question 16

In the liver, lactate (lactic acid) is converted into ___ which is then converted into glucose.

Answer 16

Pyruvate

remember this is the opposite of glycolysis, where pyruvate is converted to lactic acid

Question 17

What must amino acids be converted to before this molecule can be converted into glucose?

Answer 17

Oxaloacetate

Question 18

Which molecules regulate glycolysis and gluconeogenesis at a systemic level?

Answer 18

Hormones

Question 19

When glucagon levels are high, glycolysis is (stimulated / inhibited) and gluconeogenesis is (stimulated / inhibited).

Answer 19

Glycolysis is inhibited

Gluconeogenesis is stimulated

Question 20

When insulin levels are high, glycolysis is (stimulated / inhibited) and gluconeogenesis is (stimulated / inhibited).

Answer 20

Glycolysis is stimulated

Gluconeogenesis is inhibited

Question 21

Gluconeogenesis is regulated at a systemic level. It is also controlled by individual ___.

Answer 21

cells

Question 22

In an individual cell, if [AMP] or [ADP] were high, what would occur to the rate of gluconeogenesis?

Answer 22

Low energy so gluconeogenesis would be inhibited (as it’s energetically active)

Question 23

In an individual cell, if [ATP] was high, what would happen to the rate of gluconeogenesis?

Answer 23

High energy - so gluconeogenesis would be encouraged

Question 24

High concentrations of molecules associated with the TCA cycle (stimulate / inhibit) glycolysis and (stimulate / inhibit) gluconeogenesis.

Answer 24

Inhibit glycolysis

Stimulate gluconeogenesis