lipids 1

Question 1

In what three places do lipids exist?

Answer 1

• cell membranes
• as lipid droplets in adipose tissue
• in blood lipoproteins

Question 2

Name the 6 biological functions of lipids

Answer 2

• stored form of energy
• structural element of membranes
• enzyme cofactors
• hormones
• vitamins A, D, E, K
• signalling molecules

Question 3

What are the classes of lipids?

Answer 3

fatty acids
triacylglycerol
phospholipid
glycolipid
steroids

Question 4

What does ‘18:1’ mean in terms of fatty acid nomenclature?

Answer 4

18 carbons and 1 double bond

Question 5

what are linoleic and linolenic acids examples of?

Answer 5

essential fatty acids in humans

Question 6

Why must some fatty acids be consumed in the diet?

Answer 6

humans cannot introduce double bonds beyond carbon 9

Question 7

what 2 benefits does Omega-3 fatty acid have?

Answer 7

1 - lowers plasma cholesterol and prevents atherosclerosis

2- lowers triacylglycerol and prevents obesity

Question 8

what are triacylglycerols esters of?

Answer 8

fatty acids and glycerol

Question 9

what is phospholipid composed of?

Answer 9

glycerol bonded to two fatty acids and a phosphate group

Question 10

what is the main dietary lipid?

Answer 10

triacylglycerol

Question 11

what is the main site of digestion?

Answer 11

small intestine

Question 12

what role do bile salts play in lipid digestion?

Answer 12

act as biological detergents to form emulsions and mixed micelles

Question 13

what enzyme degrades TAG to monoacylglycerol and two fatty acids in the small intestine?

Answer 13

pancreatic lipase

Question 14

What is the second product of digestion of cholesterol esters as well as free fatty acid?

Answer 14

cholesterol

Question 15

What do phospholipids hydrolyse to?

Answer 15

fatty acid and lysophospholipid

Question 16

what do products of lipid digestion form with bile salts in order to be absorbed?

Answer 16

mixed micelles

Question 17

what is Steatorrhea?

Answer 17

excess fat in faeces

Question 18

which three defects could lead to lipids not being absorbed by cells and potentially steatorrhea?

Answer 18

defects in:

• bile secretion (for secreting bile salts to form mixed micelles and emulsify the fat)
• pancreatic function (for breaking down molecule)
• intestinal cell uptake

Question 19

The intestinal cells resynthesize TAG, PL and CE for export but they are insoluble. How is this problem overcome?

Answer 19

The are packaged with apoB-48 into chylomicrons

Question 20

How are chylomicrons released from intestinal cells and where to?

Answer 20

by exocytosis

into lymph then blood

Question 21

which enzyme hydrolyses TAG in chylomicrons to FA and glycerol?

Answer 21

lipoprotein lipase

Question 22

what are chylomicrons depleted of TAG called and where do they go?

Answer 22

chylomicron remnants

go to liver

Question 23

what two things can happen to fatty acids (those made when TAG is broken down by lipoprotein lipase)

Answer 23

• oxidised as fuel

- re-esterified for storage

Question 24

in what form is TAG stored in adipose cells?

Answer 24

as droplets

Question 25

what releases fatty acid from stored TAG?

Answer 25

hormone sensitive lipase (HSL)

Question 26

hormone sensitive lipase is activated by phosphorylation and inactivated by dephosphorylatiom. What activates and deactivates HSL?

Answer 26

activates - epinephrine

deactivates - high plasma glucose and insulin

Question 27

which protein forms a complex with fatty acids to transport them through the blood?

Answer 27

albumin

Question 28

how are esterified fatty acids carried through the blood?

Answer 28

by lipoproteins

Question 29

name the four lipoproteins in order starting with least dense

Answer 29

chylomicrons
VLDL
LDL
HDL

Question 30

what can too much LDL lead to?

Answer 30

atherosclerosis