revision specific topics

Question 1

what are lipoproteins

Answer 1

allow lipids to be circulated and to pass through cells. They are complex particles with a central hydrophobic core of non-polar lipids, held together by hydrophilic membrane of phospholipids and apolipoproteins

Question 2

what is the exogenous pathway

Answer 2

dietary cholesterol and fatty acids are absorbed

Question 3

what are the main stages in the exogenous pathway

Answer 3

1. intestine
2. chylomicrons
3. capillary (LPL- Lipoprotein lipase)
4. Free fatty acids adipose tissue
5. empty HDL
6. chylomicron remnant

Question 4

what are Apolipoproteins

Answer 4

Apolipoproteins are the main protein that form lipoproteins and are receptors on outer surface on lipoproteins

Question 5

Gluconeogenesis involves the conversion of

Answer 5

pyruvate to glucose

Question 6

what are hyperlipidaemias

Answer 6

abnormally elevated levels of lipids or lipoproteins in the blood. Primary- is due to genetic and inherited and secondary is an acquired condition due to underlying causes like diabetes or obesity

Question 7

what is the main site of LPL activity

Answer 7

adipose, mammary tissue, skeletal tissue and myocardium

Question 8

when do chylomicrons disappear from circulation

Answer 8

12 hours after fat rich meal

Question 9

what are the fatty acids from the LPL used as

Answer 9

muscle for energy and adipose tissue for storage

Question 10

what are the main stages In the exogenous pathway

Answer 10

1. dietary cholesterol and fatty acids are absorbed (triglycerides are formed in the intestinal cells from free fatty acids and glycerol and cholesterol is esterified)
2. Trigylcerides and cholesterol combine to form chylomicrons
3. Chlomircons enter circulation and travel to peripheral sites
4. In peripheral tissues, free fatty acids are release from the chylomicrons to be used as energy, converted to triglyceride or stored in adipose and remnant are used in the formation of HDL
5. VLDL is formed in the liver from triglycerides and cholesterol esters
6. These can be hydrolysed by LPL to form VLDL remnants or IDL (Intermediate Density Lipoprotein)
7. VLDL remnants are either cleared from the circulation by the liver or metabolised by hepatic lipase into LDL

Question 11

What is LDL production and clerance regulated by

Answer 11

hepatic LDL receptor activity. Around 70% of LDL is cleared by the liver and the remainder is taken up by non-hepatic tissues, where LDL is used in hormone production, cell membrane synthesis or stored

Question 12

when LDL is taken up by macrophages and other cells what does this lead to

Answer 12

excess accumulation and formation of foam cells that are revenant to atherosclerotic plaque formation

Question 13

What is HDL Metabolism

Answer 13

1. 2 subclasses
2. major role of HDL is reverse transport cholesterol from different tissues to the liver for excretion
3. anti-atherogenic
4. precursor HDL particles are secreted by the liver and small intestine and interact with LCAT to produce mature HDL

Question 14

What is the link between atherosclerosis and inflammation

Answer 14

inflammation plays an important role in atherosclerosis, which results from an interaction between endothelial cells, blood cells, platelets and smooth muscle cells

Question 15

what process breaks down fatty acids

Answer 15

beta oxidation and it occurs in the mitochondria and in some cases the peroxisomes and is a recurring cycle involving 4 key steps. It produces FADH2 and NADH

Question 16

what happens in trigylerol breakdown

Answer 16

broken down by lipases (releasing FAs to be further degraded) and glycerol further degradation

Question 17

what happens in fatty acid breakdown (beta-oxidation)

Answer 17

occurs in the mitochondria or peroxisomes. In the activation step fatty acids are converted to acyl CoA derivatives and has 4 key steps and the outcome is the yield energy

Question 18

what are the products from the beta oxidation pathway

Answer 18

FADH2 + NADH + acetyl CoA and/or propionyl CoA

Question 19

What is the key difference between short and long chain fatty acids in terms of their activation

Answer 19

short/medium chain fatty acids are activated in the mitochondria, whereas long chain FAs in the outer mitochondrial membrane

Question 20

what are the essential lipids

Answer 20

alpha-linolenic acid (n-3) and linoleic acid (n-6)

Question 21

what are the 2 kinds of body fat

Answer 21

subcutaneous fat - under the skin
visceral fat - around the internal organs

Question 22

where does the biosynthesis of FA occur

Answer 22

cytosol

Question 23

what is the role of biosynthesis

Answer 23

to generate lipids for storage, cell membrane structure or for energy.

Question 24

what is the starting and end point of biosynthesis of FAs

Answer 24

start- acetyl CoA
end - Palmitol-ACP