REVIEW CARB METAB

Question 1

Purpose of NADPH produced in glycolysis

Answer 1

1. Glutathione sustenance
2. Biosynthesis of FA & Cholesterol

Question 2

What is the link between fluoride and glycolysis?

Answer 2

Fluoride blocks Enolase in bacteria
* When enolase is blocked by fluoride, 2-phosphoglycerate accumulates as a result of this inhibition

Question 3

Does heart use muscle?

Answer 3

It doesn’t use but PRODUCE lactate. The lactate will be delivered to the liver to convert it to glucose which can be used by the heart.

Question 4

What cell can use lactate directly?

Answer 4

Brain

Question 5

Key regulating step in gluconeogenesis

Answer 5

Pyruvate carboxylase

Question 6

compare glycolysis PFK1 and Gluconeogenesis Pyruvate carboxylase in a fasted state.

Answer 6

In fasted state, everything is phosphorylated.
- Glycolysis is inactive when phosphorylated
- Gluconeogenesis is active phosphorylated

Question 7

what pathways are activated when its key steps are phosphorylated?

Answer 7

Phosphorylated means fasting.
1. Gluconeogenesis
2. Glycogenolysis
3. Ketogenesis

Question 8

What is the significance of the NADH/NAD ratio, what do high NADH/NAD ratio imply?

Answer 8

• high energy state
• inhibits gluconeogenesis
• can be due to alcoholism (by taking up alcohol)

Question 9

Role of Biotin across the 2 energy state

Answer 9

FFA synthesis (FED state)
Gluconeogenesis (FASTED state)

Question 10

Why is it vital to maintain plasma glucose levels?

Answer 10

Brain

Question 11

Where do gluconeogenesis occur?

Answer 11

• 90% liver (hepatocytes)
• 10% kidney (proximal tubular cells)

Question 12

What are the key substrates for gluconeogenesis?

Answer 12

1. Lactate
2. Glycerol (coming from TAG) - the backbone can be glucose
3. Glucogenic Amino Acids - all AA can be glucose except leucine and lysine

Question 13

Explain this. Aiah was not exercising but still losing weight. What is the explanation behind this?

Answer 13

One potential explanation could indeed be fasting.

During fasting, the body switches to alternative fuel sources to sustain energy needs, such as gluconeogenesis. In this process, triglycerides (TAG) stored in adipose tissue are broken down into glycerol and free fatty acids (FFA). Glycerol can be converted into glucose via gluconeogenesis, providing a source of energy for tissues that rely on glucose, including the brain. Meanwhile, the free fatty acids can be oxidized for energy by the liver and other tissues. The increased metabolic demand on the liver during fasting, especially in maintaining gluconeogenesis and other essential processes, can contribute to energy expenditure and weight loss even in the absence of exercise.
Liver requires lots of ATP to maintain the processes even at fasted state, when there is no much glucose entering the body

Question 14

What is the significance of Fructose-2,6-Bisphosphate?

Answer 14

This is a regulatory molecule for both glycolysis and gluconeogenesis.

When F-2,6-BP is high:
- insulin is high
- glycolysis is upregulated

Question 15

During fasted state, what will happen to OAA and Acetyl CoA?

Answer 15

OAA will proceed to gluconeogenesis

Acetyl CoA will undergo ketogenesis