Lipids in health and disease

Question 1

What is the function of cholesterol in the plasma membrane?

Answer 1

It helps maintain structure and fluidity of the cell membrane

Question 2

How does cholesterol function in the plasma membrane?

Answer 2

The OH group of cholesterol interacts with the polar head groups of the phospholipids, helping to provide a barrier to H+, Na+ and solutes

Question 3

How does cholesterol help with cell signalling?

Answer 3

Cholesterol helps to form lipid rafts in the plasma membrane

Question 4

What are the functions of lipid rafts?

Answer 4

They form bridges between receptor proteins and second messengers. They also serve as centres of assembly for signalling molecules

Question 5

What molecules is cholesterol a precursor for?

Answer 5

Bile acids, vitamin D and steroid hormones

Question 6

How are lipids carried in the blood?

Answer 6

In a lipoprotein

Question 7

What molecules form a lipoprotein?

Answer 7

Apolipoproteins
Free cholesterol
Phospholipids

Question 8

What is the ideal total cholesterol range?

Answer 8

<5 mmol/L

Question 9

What is the ideal HDL cholesterol range?

Answer 9

0.9-1.6 mmol/L

Question 10

What is the ideal Total:HDL cholesterol ratio?

Answer 10

<4

Question 11

What is the ideal triglyceride range?

Answer 11

1.0-2.3 mmol/L

Question 12

What is a chylomicron?

Answer 12

An ultra-low density lipoprotein that carries absorbed lipids from the intestine

Question 13

What type of cell produces chylomicrons?

Answer 13

Enterocytes of the small intestine

Question 14

What enzyme within the capillaries breaks down chylomicrons?

Answer 14

Lipoprotein lipase

Question 15

Where is lipoprotein lipase synthesised?

Answer 15

In muscle, heart and adipose tissue

Question 16

What enzyme converts acetyl coenzyme-A into cholesterol?

Answer 16

HMG-CoA-Reductase

Question 17

What happens to protein content as density of lipoprotein increases?

Answer 17

It increases

Question 18

What are the 5 different types of lipoproteins?

Answer 18

Chylomicrons
Very Low Density Lipoproteins
Intermediate Density Lipoproteins
Low Density Lipoproteins
High Density Lipoproteins

Question 19

What is the function of HDL?

Answer 19

It picks up excess cholesterol in the blood stream

Question 20

What receptors do HDLs bind to in the liver where they are recycled into lower density lipoproteins?

Answer 20

Scavenger receptors

Question 21

What occurs when more LDL is formed than is broken down into HDL?

Answer 21

LDL builds up and is converted to form oxidised LDL or LDL aggregate

Question 22

What can damage the endothelium of the blood vessels?

Answer 22

Smoking, hypertension, hyperglycaemia and hypercholesterolaemia

Question 23

What does damage to the endothelium cause?

Answer 23

It increases permeability of the endothelium, meaning LDLs can enter the tunica intima

Question 24

What molecule do damaged endothelial cells express?

Answer 24

Adhesion protein molecules

Question 25

What occurs when adhesion protein molecules are expressed?

Answer 25

Monocytes in the blood bind to the molecules, allowing them to flatten and move between endothelial cells and into the tunica media

Question 26

What is the process of monocytes flattening and entering the tunica intima known as?

Answer 26

Diapedesis

Question 27

How do monocytes cause the formation of oxidised LDL?

Answer 27

They release free radicals that can easily oxidise the LDLs in the tunica intima

Question 28

What cells do oxidised LDLs attract?

Answer 28

White blood cells e.g. more monocytes

Question 29

How are foam cells produced?

Answer 29

Monocytes engulf an ingest LDL, causing them to release more free radicals. This means that more LDLs are oxidised and engulfed. This cycle continues causing monocytes that are filled with engulfed LDLs to form

Question 30

What other type of cell engulfs oxidised LDLs?

Answer 30

Smooth muscle cells

Question 31

What builds up within a plaque?

Answer 31

Oxidised LDL and particles of dead monocytes as foam cells die forming a necrotic core

Question 32

What forms over a plaque?

Answer 32

A fibrous cap of endothelial cells

Question 33

What molecule causes the hardening of a plaque?

Answer 33

Calcium salts

Question 34

What can occur if the endothelial cells of the fibrous cap are damaged?

Answer 34

A blood clot forms in the lumen, known as a thrombus

Question 35

What forms when a thrombus breaks off from the plaque wall and travels through the blood vessels, potentially blocking smaller vessels?

Answer 35

An embolus