Lipids

Question 1

What is Xanthelasma ?

Answer 1

• a yellow deposit of cholesterol under the skin usually around the eyelids

Question 2

What causes xanthelasma ?

Answer 2

High levels of cholesterol in the bloodstream

Question 3

Why is cholesterol insoluble in water?

Answer 3

Contains very few polar groups

Question 4

What chemical group does cholesterol belong to?

Answer 4

Steroids

Question 5

Where is cholesterol synthesised?

Answer 5

Liver

Question 6

What is the process of cholesterol synthesis?

Answer 6

• Acetic acid gets activated to acetyl coA
  Combines using multiple enzymes to form mevalonic acid which gets converted to cholesterol

Question 7

How do statins lower cholesterol ?

Answer 7

• Inhibit HMG-CoA (HMGCR) reductase, which is involved in mevalonic acid path way - lowers cholesterol

Question 8

What is the structure of fatty acids?

Answer 8

• carboxylic acids with an aliphatic chain
• either saturated or unsaturated (double bond )

Question 9

What is a property of saturated fatty acids that unsaturated do not fatty acids have?

Answer 9

• Saturated fatty acids can stack + no double bond

Question 10

What is a property of saturated fatty acids that unsaturated fatty acids do not have ?

Answer 10

• Saturated fatty acids can stack and do not have a double bond

Question 11

Are liquid or solid fats healthier (butter /olive oil) ?

Answer 11

Liquid fats -solid fats form clots in blood more readily
Olive oil has cis double bond which prevents stacking

Question 12

What are properties of cis fatty acid isomers?

Answer 12

• Contains a double bond
• does not stack
• healthier

Question 13

What is the structure of a triglyceride?

Answer 13

Glycerol + three fattyi acids

Question 14

What is fat hydrogenation?

Answer 14

Unsaturated cis oils, converted into solid fats via hydrogenation (adding H2)

Question 15

What are lipoproteins?

Answer 15

• Central core contains cholesterol, esters + triglycerides
• sphere shaped
• contains phospholipids and apolipoproteins on outside

Question 16

What are apolipoproteins ?

Answer 16

• Proteins that binds lipids

Question 17

What are the 5 classes of lipoproteins?

Answer 17

1.chylomicrons
2. Very low-density lipoproteins (VLDL)
3. Low -density lipoproteins (LDL
4. Intermediate density lipoproteins(IDL)
5. High density lipoproteins (HDL)

Question 18

What is the composition of HDL ?

Answer 18

Equal mix of proteins and lipids = good

Question 19

What is the composition of LDL?

Answer 19

• 80 % unhealthy

Question 20

What is the composition of IDL?

Answer 20

85% = lipids also bad/ unhealthy

Question 21

What is composition of VLDL?

Answer 21

92% of lipids

Question 22

How do fats form an emulsion in the intestine?

Answer 22

• by bile secretions

Question 23

Describe the process of fat absorption?

Answer 23

• Fats form an emulsion in the intestine by bile secretions
• bile emulsifies lipids = breaks them into small droplets which increases surface area for lipases to work
• emulsion forms micelles
• micelles go to cells of intestine wall + collapse
• fats and triglycerides are absorbed into epithelial cells

Question 24

What are bile salts and how are they made?

Answer 24

• Help produce an emulsion from fats + intestinal aqueous juices in the intestine
• made from cholesterol in the liver

Question 25

How are lipoproteins made + where are they transported?

Answer 25

• Fatty acids and triglycerides get incorporated into chylomicrons (largest lipoproteins ) in the Golgi apparatus
• pass into lymph system and then blood- stream

Question 26

How do lipoproteins contribute to heart disease?

Answer 26

• lipids are transported through blood
• low density lipoproteins begin to stick to blood vessel walls