Acetoacetate, beta hydroxy butyrate and acetone are collectively known as ketone bodies. All these are water soluble energy producing substances. Acetone is a volatile substance which is excreted from the body through breathing.

ketogenesis:- Generation of ketone bodies from acetyl-CoA is called ketogenesis. Liver cell is the only site for ketogenesis.

Location: Mitochondrial matrix of liver cells

Pathway of Ketogenesis

Utilization of ketone bodies

Though ketone bodies are formed in the liver cell but the hepatic cell can not utilize the ketone body. This is because liver cell does not have CoA transferase enzyme, that’s why they cannot utilize it. These ketone bodies are transfer from liver cell to the extra hepatic cells and tissues through blood supply.

Metabolism of acetone is not happened because of its volatile nature. So it is exhaled by the lungs to the outer environment. Acetone has a fruity smell

Significance of Ketogenesis

1. It allows the liver to metabolize excess quantity of acetyl-CoA.
2. During low supply of carbohydrate that is during starvation or diabetes mellitus, ketone bodies serves as alternate source of energy.
3. During long starvation, brain cells receives maximum energy from ketone bodies.

Regulation of ketogenesis

• The overproduction of ketone bodies is due to the un-availability of carbohydrates. 
• This is the outcome of excessive utilization of fatty acids to meet the energy requirements
• Glucagon stimulates ketogenesis while on the other hand, insulin inhibits ketogenesis.
• Diabetes Mellitus also promotes ketogenesis Due to the disturbances caused in carbohydrate and lipid metabolism.
• Low concentration of oxaloacetate (an intermediate of TCA cycle) favors the ketogenesis. 

Multiple choice questions (MCQs)

1. what is ketogenesis?
A. Generation of acetyl-CoA from ketone bodies
B. Generation of ketone bodies from acetyl-CoA
C. Generation of acyl-CoA from ketone bodies
D. Generation of ketone bodies from acyl-CoA

2. Which structure is included in ketone bodies?
A. Acetone

B. Acetoacetate

C. Beta hydroxyl butyrate

D. All of the above

3. What Is the location of ketogenesis?
A. Cytosol

B. Plasma membrane

C. Mitochondria

D. Ribosomes

4. In which cell, ketogenesis takes place?
A. Brain cells

B. Liver cell

C. Nerve cell

D. None of the above

5. Match the following-
A. Hepatic cell 1. Utilize ketone bodies
b. Non-hepatic cell 2. Generate ketone bodies
c. Insulin 3. Stimulate lypolysis
d. Glucagon 4. Inhibits lypolysis

6. Which of the following is a volatile substance?
A. Acetone B. Phenol
C. Hydroxyl butyrate D. Acetoacetate

7. Why is ketone bodies not utilized by hepatic cells?
A. Absence of acetone

B. Absence of CoA transferase

C. Absence of CoA dehydrogenase

D. Both A and B

8. Which of the following statement is not true?
A. Metabolism of acetone does not occur
B. Acetone has sour taste
C. Starvation stimulate ketogenesis
D. Oxaloacetate stimulate ketogenesis

9. Which of the following is not the significance of ketogenesis?
A. Supply energy to brain cells
B. Metabolize excess of acetyl-CoA
C. Supply energy in absence of carbohydrate
D. None of the above

10. What is the reason for low concentration of oxaloacetate?
A. Well fed condition

B. Bronchitis

C. Starvation

D. Improper metabolism of lipid

11. Which hormone stimulates the lypolysis?
A. Insulin

B. Glucagon

C. Adrenaline

D. Non-epinephrine

12. Fill in the blanks- ketogenesis is generation of ketone bodies from ——?
A. Acyl-CoA

B. Acetyl-CoA

C. Aryl-CoA

D. Alkyl-CoA

13. How is acetone removed from the body?
A. Through urine

B. Vomiting

C. Cough

D. Exhalation

14. High concentration of oxaloacetate favors which pathway?
A. Glycolysis

B. TCA cycle

C. HMP shunt

D. Glycogenolysis

15. all the compounds of ketone bodies are soluble in which liquid?
A. Water

B. Chloroform

C. Ester

D. None of the above

ANSWERS:

1. Generation of ketone bodies from acetyl-CoA

2. All of the above

3. Mitochondria

4. Liver cell

5. a – 2 b – 1 c – 4 d – 3

6. Acetone

7. Absence of CoA-transferase

8. Acetone has sour taste

9. None of the above

10. Starvation

11. Glucagon

12. Acetyl-CoA

13. Exhalation

14. TCA cycle

15. Water

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REFERENCE:- 1. Pankaja Naik- Biochemistry; 4^th edition; page no:- 219-222

2. U Satyanarayana, U chakrapani- Biochemistry; 4th edition; page no- 293-296.