Ketogenesis

Question 1

What are the sources of energy in the body

Answer 1

Carbohydrates
Fats
Lipids

Question 2

How long can glycogen stores sustain energy levels

Answer 2

12 hours

Question 3

How long can lipid energy reserves provide energy

Answer 3

up to 12 weeks

Question 4

When is protein stores used

Answer 4

Used when muscle glycogen stores fail

Question 5

What do fatty acids contain

Answer 5

Carboxylic head with aliphatic group

Saturated or unsaturated

Question 6

What are most fatty acids derived from

Answer 6

Triglycerides and phospholipids

Question 7

Where does fatty acid oxidation occur

Answer 7

Cytoplasm

Question 8

Describe Acyl-CoA

Answer 8

12 carbons

Can be diffuse into the mitochondrial membrane

Question 9

What is the order of fatty acid activation

Answer 9

Fatty acid

Acyl adenylate

Acyl-CoA

Question 10

What does fatty acid use and produce

Answer 10

Use - ATP, CoA-SH

Produce - PPi, AMP

Question 11

What are the features of most dietary acids

Answer 11

> 14 carbons

Taken through mitochondrial membrane using carnitine shuttle

Question 12

What happens to most acetyl-CoA under normal metabolic conditions

Answer 12

Utilised via the TCA acid cycle to produce glucose

Question 13

What happens to a small amount of acetyl-CoA under normal metabolic conditions

Answer 13

Converted into ketones

Question 14

What are ketones produced

Answer 14

By liver from acetyl-CoA

Question 15

3 examples of ketones

Answer 15

Acetone

Acetoacetate

Beta-hydroxybutyrate

Question 16

What happens during high rate of fatty acid oxidation

Answer 16

Large amounts of acetyl-CoA are generated

Question 17

Why does ketogenesis occur

Answer 17

When large amounts of acetyl-CoA are produced

Exceeds capacity of the TCA cycle

Question 18

In ketogenesis what can acetoacetate undergo

Answer 18

Spontaneous decarboxylation to acetone

OR

Enzymatically converted to beta-hydroxybutyrate

Question 19

Where can acetoacetate:succinyl-CoA be found

Answer 19

All tissues but hepatic tissue

Question 20

What are ketone bodies utilised by

Answer 20

Extrahepatic tissues through conversion of beta-hydroxybutyrate and acetoacetate to acetoacetyl-CoA

Required acetoacetate:succinyl-CoA

Question 21

What is ketogenesis regulated by

Answer 21

1. Release of free fatty acids from adipose tissue
2. High concentration of glycerol-3-phospahte in the liver results in triglyceride production, whilst low level results in increased ketone body production
3. Demand for ATP is high, acetyl-CoA is likely to be further oxidised via the TCA cycle to carbon dioxide
4. Fat oxidation is dependant upon the amount of glucagon (activation) or insulin (inhibition) present

Question 22

Describe ketoacidosis

Answer 22

Occurs in insulin-dependent diabetics when dose is inadequate or because of increased insulin requirement (infection, trauma, acute illness)

Often presenting feature in newly diagnosed type 1 diabetics

Occurs in chronic abuse

Patient presents with hyperventilation and vomiting

Question 23

Diabetic ketoacidosis

What are the three things that can occur in insulin deficiency

Answer 23

Inhibition of glycolysis and stimulation of gluconeogenesis

Glycogen breakdown and inhibition of glycogen synthesis

Increased lipolysis (increased fatty acids)

Question 24

What does Inhibition of glycolysis and stimulation of gluconeogenesis lead to

Answer 24

Hyperglycaemia

Question 25

What does Glycogen breakdown and inhibition of glycogen synthesis lead to

Answer 25

Hyperglycaemia

Question 26

What does increased lipolysis (increased free fatty acids) lead to

Answer 26

Increased acetoacetate and beta-hydroxybutyrate

Question 27

What are the consequences of ketoacidosis

Answer 27

Excessive ketones lower pH in the blood - impairs the ability of haemoglobin to bind to oxygen

pH - low
pO2 - high
pCO2 - low
HCO3 - low

Question 28

What are ketones

Answer 28

Relatively strong acids (pKa approx. 3.5)