Lecture 25

Question 1

What is the chemical nature of lipids?

Answer 1

Hydrophobic or amphiphilic organic molecules

Question 2

What are the three forms of lipid in the diet?

Answer 2

Phospholipid, sterols, triacylglycerol

Question 3

What is an example of a sterol?

Answer 3

Cholesterol

Question 4

What is the role of cholesterol in the body?

Answer 4

A range including membranes, signalling (hormones) and forming bile salts

Question 5

What is the chemical structure of cholesterol?

Answer 5

A hydrophobic ring structure

Question 6

What is an example of a triacylglycerol (TAGs)?

Answer 6

Fatty acids

Question 7

What is a fatty acid?

Answer 7

Carbon chain attached to a carboxylic acid

Question 8

What is a free fatty acid (FFA)?

Answer 8

A fatty acid not bound to any other molecule

Question 9

What is the chemical nature of the carbon chain in fatty acids?

Answer 9

Hydrophobic

Question 10

What is the chemical nature of the carboxylic acid in fatty acids?

Answer 10

Hydrophilic

Question 11

What is the structure of a triagylglycerol?

Answer 11

1x Glycerol (3C) with 3x fatty acids (acyl groups) attached

Question 12

What component of the TAG is polar?

Answer 12

Glycerol

Question 13

What component of the TAG is non-polar?

Answer 13

fatty acid (acyl group)

Question 14

What type of enzyme breaks down TAGs?

Answer 14

Lipase

Question 15

What does lipase do to TAGs?

Answer 15

Hydrolyses it to release the free fatty acids (FFAs)

Question 16

What are bile acids?

Answer 16

Salts synthesised from cholesterol in the liver

Question 17

How are bile acids synthesised?

Answer 17

By adding hydroxyl and/or carboxyl groups to create a hydrophilic face

Question 18

What do bile acids form?

Answer 18

Micelles, multiple bile acids come together to form a hydrophobic core of TAGs inside to be absorbed into epithelial cells

Question 19

What are exogenous fatty acids?

Answer 19

Fatty acids ingested from the diet

Question 20

What is the path of exogenous fatty acid transport to the blood stream?

Answer 20

Consumed in diet fats exist as TAGs, pancreatic lipase breaks these down into MAG and 2FFAs which are then rearranged to form a micelle (with bile salts on the outside) for transportation to SI lining for absorption. Once absorbed MAG and 2FFAs are rearranged back into a TAG which are packaged into chylomicrons along with apoproteins to enter capillaries.

Question 21

What is a chylomicron?

Answer 21

A type of large lipoprotein involved in TAG transport with low protein:lipid (~1:50)

Question 22

What is a lipoprotein?

Answer 22

A type of ‘delivery system’ for lipid transportation, to help solubilise them

Question 23

What are the components of a lipoprotein?

Answer 23

Phospholipids, unesterified cholesterol, esterified cholesterol, TAGs and apoproteins

Question 24

What is unesterified and esterified cholesterol

Answer 24

Cholesterol without and with FFAs attached (respectively)

Question 25

What is an apoprotein?

Answer 25

The protein component of the lipoprotein that can have several roles including; structural, ligand for receptors and enzyme co-factors

Question 26

What are the classes of lipoprotein?

Answer 26

Chylomicron, VLDL, LDL, HDL

Question 27

What is a VLDL?

Answer 27

Very low-density lipoprotein involved in TAG transport with medium lipid:protein (~1:9)

Question 28

What is a LDL?

Answer 28

Low-density lipoprotein involved in cholesterol transport

Question 29

What is a HDL?

Answer 29

High-density lipoprotein involved in cholesterol regulation

Question 30

What happens to the chylomicron once it enters the blood stream?

Answer 30

Lipoprotein lipase hydrolyses the TAG into monoacylglycerol and fatty acids to enter the tissue

Question 31

What is lipoprotein lipase activated by?

Answer 31

ApoCll

Question 32

What remains in the blood after TAG hydrolysis in the chylomicron?

Answer 32

A chylomicron remnant

Question 33

What do defects by mutation is ApoCll or lipoprotein lipase cause?

Answer 33

Elevated levels on chylomicrons in the blood and plasma triacylglycerol

Question 34

Where is the LPL found?

Answer 34

On the endothelial surface of capillaries

Question 35

What type of muscle cell prefers to use fat at fuel?

Answer 35

Red muscle cells

Question 36

Why are fats the primary energy stored in mammals?

Answer 36

Because less space is required to store the same amount of fuel as fats are more reduced than carbohydrates

Question 37

How is excess glucose stored as fat in the body?

Answer 37

Glucose → Pyruvate (via glycolysis) Pyruvate → Acetyl-CoA (in mitochondria) Acetyl-CoA → Fatty acids (if energy needs are met) Fatty acids + glycerol → Triacylglycerol (TAG) TAG stored in fat cells for future energy use

Question 38

What happens to the chylomicron remnants in the liver?

Answer 38

Liver recycles the remnants to make VLDL to be released into the blood and bile salts + cholesterol to break down exogenous lipids

Question 39

What happens to VLDL in the blood?

Answer 39

LPL breaks down further to send FFAs into the tissue and releases the remaining as a VLDL remnant

Question 40

What happens to the VLDL remnant?

Answer 40

50% is absorbed back into the liver to be recycled and 50% is converted to an LDL to be used by peripheral tissues and also recycled by the liver