Lipids

Question 1

Which lipids of HMG derivatives?

Answer 1

ketone bodies, cholesterol, bile acids and salts

Question 2

What are the fat soluble vitamins?

Answer 2

A, D, E and K

Question 3

Which molecule can transport fatty acids in the blood?

Answer 3

Albumin

Question 4

When are TAGs utilised?

Answer 4

exercise, starvation and pregnancy

Question 5

Which enzyme mobilises TAG?

Answer 5

Hormone sensitive lipase

Question 6

What does it mean that TAG is stored in a dynamic state?

Answer 6

TAG is constantly being formed and broken down.

Question 7

How are fatty acids activated?

Answer 7

linking to coenzyme A by fatty acyl coA synthase
investment of ATP
in cytoplasm

Question 8

Which membrane is the carnitine shuttle on?

Answer 8

The inner mitochondrial membrane

Question 9

Why is the carnitine shuttle needed?

Answer 9

Because coenzyme A is too big to cross the inner mitochondrial membrane

Question 10

How does the carnitine shuttle work?

Answer 10

Carnitine is combined with acyl and the coA is released. Acyl carnitine is transported across the inner mitochondrial membrane via the shuttle. Acyl carnitine is broken down to reform acyl coA.

Question 11

Which enzyme is required for the carnitine shuttle?

Answer 11

Carnitine acyltransferase

Question 12

Which molecule inhibits the carnitine shuttle?

Answer 12

Malonyl-coA

Question 13

What can defects in the shuttle system cause?

Answer 13

exercise intolerance and lipid droplets in muscle

Question 14

Where does beta oxidation not occur and why?

Answer 14

brain, RBCs and WBCs
Brain = fatty acids cannot cross the blood brain barrier
cells = do not have mitochondria

Question 15

How does beta oxidation work?

Answer 15

The removal of 2 carbons per cycle. Hydrogen is transferred to NAD+ and FAD. There is no ATP synthesis and the process stops in the absence of oxygen.

Question 16

Where is glycerol metabolised?

Answer 16

Liver

Question 17

Which enzyme activates glycerol and what is the product?

Answer 17

enzyme = glycerol kinase
product = glycerol phosphate

Question 18

What can glycerol phosphate be used for?

Answer 18

TAG synthesis or DHAP synthesis

Question 19

Name the 3 ketone bodies

Answer 19

acetoacetate, acetone and beta-hydroxybutyrate

Question 20

Where are ketone bodies synthesised?

Answer 20

Mitochondria in the liver

Question 21

Which enzyme needs to be activated for ketone body synthesis?

Answer 21

HMG-CoA Lyase

Question 22

Which enzyme is inhibited during ketone body synthesis?

Answer 22

HMG-CoA Reductase

Question 23

Which hormone activates HMG-CoA lyase?

Answer 23

Glucagon

Question 24

Are ketone bodies water soluble?

Answer 24

Yes

Question 25

What happens to fatty acids with an odd number of carbon atoms?

Answer 25

beta-oxidation until a 3 carbon molecule is formed carboxylation to methyl malonyl coA rearranged to succinyl coA (vitamin B12 cofactor)

Question 26

Which lipids are fatty acid derivatives?

Answer 26

TAGs and phospholipids

Question 27

How are lipids transported in the blood?

Answer 27

Fatty acids can be bound to albumin. However 98% of lipids are carried as lipoprotein particles.

Question 28

What value should plasma cholesterol be below?

Answer 28

5mmol/L

Question 29

What is the difference between a micelle and a liposome?

Answer 29

``` Micelle = one layer of phospholipids Liposome = bilayer of phospholipids ```

Question 30

Where does cholesterol come from?

Answer 30

some in the diet but most synthesised by liver

Question 31

What is cholesterol a precursor to?

Answer 31

steroid hormones and bile acids

Question 32

How is cholesterol transported?

Answer 32

As cholesterol ester. | Cholesterol + fatty acid

Question 33

What are the main carriers of fat?

Answer 33

chylomicrons and VLDLs

Question 34

What are the main carriers of cholesterol esters?

Answer 34

ILDL, LDL and HDL

Question 35

Which lipoprotein particle has the biggest diameter?

Answer 35

Chylomicron

Question 36

Which lipoprotein particle has the smallest diameter?

Answer 36

HDL

Question 37

How many classes of apolipoproteins are there?

Answer 37

6 major classes

Question 38

Name the major classes of apolipoproteins

Answer 38

A, B, C, D, E and H

Question 39

What are the roles of apolipoproteins?

Answer 39

maintain structural integrity, cofactor for enzymes and ligand for receptors

Question 40

Where are chylomicrons loaded?

Answer 40

In the small intestine

Question 41

What is the pathway for chylomicrons?

Answer 41

loaded in small intestine, enter lymphatic system, travel to thoracic duct, enter left subclavian vein, bind to lipoprotein lipase on adipocytes and muscle, release fatty acids, become chylomicron remnant then return to liver to be broken down

Question 42

Which apolipoproteins do chylomicrons gain once they enter the blood?

Answer 42

apoC and apoE

Question 43

Which apolipoprotein of chylomicrons binds to lipoprotein lipase?

Answer 43

apoC

Question 44

When does a chylomicron become a remnant?

Answer 44

When TAG ~ 20% and apoC dissociates

Question 45

What does apoE bind to?

Answer 45

LDL receptor on hepatocytes

Question 46

What is the role of lipoprotein lipase?

Answer 46

Hydrolysis of TAG

Question 47

Where and why is VLDL made?

Answer 47

Liver | Transport TAG

Question 48

Which apolipoproteins does VLDL have and where are they added?

Answer 48

apoB100 - added in liver | apoC and apoE - added in blood

Question 49

When does a VLDL become an IDL?

Answer 49

when the content is ~30%

Question 50

What happens when IDL content is ~10%?

Answer 50

IDL loses apoC and apoE | becomes an LDL particle

Question 51

What is the primary function of LDL?

Answer 51

Transport cholesterol from liver to tissues

Question 52

What is the difference between LDL and IDL/VLDL?

Answer 52

LDL does not have apoC or apoE and therefore is not efficiently cleared by the liver.

Question 53

What is receptor expression for a lipoprotein particle controlled by?

Answer 53

cholesterol content within the cell

Question 54

Which of VLDL, IDL or LDL has the longer half life?

Answer 54

LDL has a longer half life

Question 55

How are atherosclerotic plaques formed?

Answer 55

oxidised LDLs are taken up by macrophages Enter into the tunica intima transform into foam cells form plaques

Question 56

Where is HDL synthesised?

Answer 56

liver and intestine

Question 57

Which lipoprotein particles can HDL bud off?

Answer 57

VLDL and chylomicrons

Question 58

How does HDL fill up?

Answer 58

HDL accumulates phospholipids and cholesterol from cells lining blood vessels hollow core fills ABCA1 protein facilitates transfer of cholesterol to HDL

Question 59

Which enzyme converts cholesterol to cholesterol ester?

Answer 59

LCAT

Question 60

What is the function of chylomicrons?

Answer 60

transport dietary TAG from intestines to tissues

Question 61

What is the function of VLDL?

Answer 61

transport of TAG synthesised in liver to adipose tissue

Question 62

What is the function of IDL?

Answer 62

Precursor of LDL. Transport of cholesterol synthesised in the liver to tissues.

Question 63

What is the function of LDL?

Answer 63

Transport of cholesterol synthesised in the liver to the tissues.

Question 64

What is the function of HDL?

Answer 64

Transport of excess cholesterol from tissues to liver for disposal as bile salts.

Question 65

What is a hyperlipoproteinaemia?

Answer 65

A raised plasma level of one of more lipoprotein class.

Question 66

What causes Type I hyperlipoproteinaemia and how would you spot it?

Answer 66

defective lipoprotein lipase | chylomicrons present in fasting plasma sample

Question 67

What causes Type IIa hyperlipoproteinaemia and what is it also called?

Answer 67

defective LDL receptor | familial hyperlipoproteinaemia

Question 68

What are the clinical signs of hypercholesterolaemia?

Answer 68

high cholesterol in blood and cholesterol depositions

Question 69

Where can cholesterol depositions occur?

Answer 69

eyelids, tendons and eyes

Question 70

Which layer do foam cells build up in?

Answer 70

Tunica intima

Question 71

How do you treat hyperlipoproteinaemias?

Answer 71

change diet: reduce cholesterol, reduce fats, increase fibre increase exercise stop smoking take statins - reduce cholesterol synthesis take bile salt sequestrants - liver must produce more bile salts and therefore use up more cholesterol

Question 72

Why should a patient with hyperlipoproteinaemia increase their fibre intake?

Answer 72

More fibre means that the liver will make more bile salts and therefore more cholesterol is removed from the blood.

Question 73

What is the problem with statins?

Answer 73

They have many side effects because they inhibit cholesterol synthesis early on in the process.

Question 74

Why might a low protein diet affect lipid transport?

Answer 74

The liver cannot synthesise sufficient apolipoproteins to export the TAG it synthesises. Fatty liver may occur.

Question 75

Define emesis

Answer 75

Vomiting

Question 76

Define oedema

Answer 76

Increased net flow of fluid from plasma to tissues because of reduced oncotic pressure.