Biochem- Gluconeogenesis And Glycolysis

Question 1

What is gluconeogenesis?

Answer 1

The process by which the body maintains blood sugar levels by producing glucose from non- carbohydrate sources.

Question 2

Where does gluconeogenesis takes place?

Answer 2

Liver, kidney, cytosol and mitochondria

Question 3

List the enzymes that are responsible for the irreversible steps of glycolysis.

Answer 3

Hexokinase
Phosphofructokinase (PFK1)
Pyruvate kinase

Question 4

Why is gluconeogenesis important to the human body?

Answer 4

The continuous supply of glucose is required as a source of energy for the brain, CNS, RBC and skeletal muscles for during starvation

Question 5

List the key enzymes of gluconeogenesis.

Answer 5

Pyruvate carboxylase
Phospoenolpyruvate carboxykinase (PEPCK)
Fructose 1,6- bis-phosphatase
Glucose 6-phosphatase

Question 6

Explain Cori’s cycle

Answer 6

Glucose/ glycogen —> lactate in the muscle and this lactate is converted back to glucose in the liver.

Question 7

What regulates, promotes and inhibits gluconeogenesis?

Answer 7

Regulate- The glucagon and the availability of substrates
Stimulate/ promote - glucagon and Acetyl coA, citrate
Inhibit- insulin, AMP, PFK-2

Question 8

What is the rate limiting step of gluconeogenesis?

Answer 8

Fructose 1,6- bisphosphatase

Question 9

Which enzyme in gluconeogensis requires GTP?

Answer 9

PEPCK

Question 10

Why is the glycolysis pathway important?

Answer 10

It takes places in all cells of the body.
It provides energy to erythrocytes.
Anaerobic glycolysis proves a major source of energy to muscles during exercise.
Provides carbon skeletons for synthesis to non essential amino acids
It is the major pathway for ATP synthesis in tissues lacking mitochondria.
Pre-requisite for aerobic oxidation of carbohydrates.

Question 11

What is the main goal of glycolysis?

Answer 11

The break down/ degradation of glucose into pyruvate.

Question 12

Describe the glycolysis pathway.

Answer 12

Glucose — Glucose 6-P — Fructose 6- P— Fructose 1,6-P — Phosphoenolpryruvate — Pyruvate.

Question 13

Why is hexokinase the main enzyme that breaks down the glucose into glucose 6-P in glycolysis?

Answer 13

Hexokinase is available in all tissues and it has an high affinity to glucose, therefore it will catalyze glucose into G-6-P. It operates the basal glucose metabolism.

Glucokinase only comes in when there is a large concentration of Glu and Hexokinase needs help to breakdown the glucose.

Question 14

What is the rate limiting enzyme of glycolysis?

Answer 14

Phosphofructokinase- 1 (PFK-1)
Converts Fructose -6P into fructose 1,6- BisP

Question 15

What inhibits and promote PFK-1 in the glycolysis pathway?

Answer 15

ATP citrate, glucagon - inhibit
AMP, PFK2 - promotes.

Iodioacetate
Arsenite - glycerifinal dehyrdpovse.

Question 16

What is the name of the enzyme that makes Fructose 2,6- BisP?

Answer 16

PFK-2.

Question 17

State the role of PFK-2 in glycolysis and its effect on the rate limiting enzyme, PFK-1?

Answer 17

PFK-2 increases glycolysis by promoting PFK-1.
It is inhibited by glucagon and promoted by insulin, therefore, insulin will also favor PFK-1 and pyruvate kinase (located at the end of the cycle).

Question 18

How does insulin favor glycolysis?

Answer 18

It activates the enzymes within glycolyses, PFK-1, PFK-2, Pyruvate and glucokinase.

Question 19

What happens to pyruvate after glycolysis?

Answer 19

It is transferred to the mitochondria via pyruvate transporter.

Question 20

What are the steps of gluconeogenesis?

Answer 20

Pyruvate — pyruvate carboxylase — oxaacetate — PEPCK — phospoenolpyruvate — fructose 1,6 Bisphosphate — FBPhosphatase — fructose 6 - phosphate - glucose 6 phosphate - G-6-phosphatase - glucose.