Week 4 - Energy production from lipids

Question 1

Storage of fatty acids and glycerol under hormonal control: Name what hormones storage is promoted by and reduced by.

Answer 1

Promoted by:
Insulin

Reduced by: 
Glucagon
Adrenaline
Cortisol
Growth hormone
Thyroxine

Question 2

Way in which fatty acids are transported to tissues from adipose tissue:

Answer 2

Fatty acids are carried to tissues via the blood stream non-covalently bound to albumin
Albumin bound fatty acids are called: non-esterified fatty acids/free fatty acids;

Question 3

Which tissues can use fatty acids as a source of energy?

Answer 3

1. Liver
2. Heart muscle
3. Skeletal muscle

Question 4

B-oxidation

Answer 4

Process by which fatty acids are oxidised to release energy; occurs in mitochondria

Question 5

Which cells cannot carry out B-oxidation?

Answer 5

1. Cells that do not contain mitochondria: e.g. red blood cells
2. Cells of the central nervous system (spinal cord, brain): fatty acids do not readily cross the blood-brain barrier

Question 6

Classes of lipids

Answer 6

1. Fatty acid derivatives:
   Phospholipids: components of cell membrane and plasma lipoproteins
   Fatty acids - fuel molecules
   Triacylglycerols- fuel storage and insulation
   Eicosanoids - local mediators
2. Hydroxy-methyl-glutaric acid derivatives (C6 compound):
   Ketone bodies (C4)- water-soluble fuel molecules
   Cholesterol (C27): membrane and steroid hormone synthesis
   Cholesterol esters: cholesterol storage
   Bile salts and acids: lipid digestion
3. Vitamins: A, D, E and K

Question 7

Process of fatty acid activation

Answer 7

• Fatty acids are linked to coenzyme A
• coenzyme A is a complex molecule that contains the vitamin pantothenic acid and a free -SH group
• Fatty acids are linked to the coenzyme via the -S atom forming a high energy of hydrolysis bond

Question 8

What is the transport of activated fatty acids into mitochondria inhibited by?

Answer 8

1. Malonyl coA; an intermediate in fatty acid synthesis
2. This inhibition is important as it prevents newly synthesised fatty acids (in cytoplasm) from being directly transported into the mitochondria and oxidised.

Question 9

What happens to patients who have a defective mitochondrial fatty acid transport system?

Answer 9

They suffer from poor exercise tolerance and have unusually large amounts of triacylglycerols in muscle cells.

Question 10

What is the major site of lipid synthesis in the body?

Answer 10

Liver (some in adipose tissue)

Question 11

Three ketone bodies produced in the body:

Answer 11

1. Acetoacetate: CH3COCH2COO-
2. Acetone: CH3COCH3
3. B-hydroxybutyrate: CH3CHOHCH2COO-

Question 12

How are acetoacetate and B-hydroxybutyrate (ketone bodies) made?

Answer 12

They are synthesised in the liver from acetyl coA.

Question 13

How is acetone produced?

Answer 13

Acetone arises from the spontaneous (non-enzymatic) decarboxylation of acetoacetate.

Question 14

Range of ketone bodies in the following circumstances:

1. Normal
2. Starvation
3. Diabetes

Answer 14

1. Normal: 10 mmol/L (pathological ketosis)