revision specific topics Flashcards
what are lipoproteins
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
what is the exogenous pathway
dietary cholesterol and fatty acids are absorbed
what are the main stages in the exogenous pathway
- intestine
- chylomicrons
- capillary (LPL- Lipoprotein lipase)
- Free fatty acids adipose tissue
- empty HDL
- chylomicron remnant
what are Apolipoproteins
Apolipoproteins are the main protein that form lipoproteins and are receptors on outer surface on lipoproteins
Gluconeogenesis involves the conversion of
pyruvate to glucose
what are hyperlipidaemias
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
what is the main site of LPL activity
adipose, mammary tissue, skeletal tissue and myocardium
when do chylomicrons disappear from circulation
12 hours after fat rich meal
what are the fatty acids from the LPL used as
muscle for energy and adipose tissue for storage
what are the main stages In the exogenous pathway
- dietary cholesterol and fatty acids are absorbed (triglycerides are formed in the intestinal cells from free fatty acids and glycerol and cholesterol is esterified)
- Trigylcerides and cholesterol combine to form chylomicrons
- Chlomircons enter circulation and travel to peripheral sites
- 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
- VLDL is formed in the liver from triglycerides and cholesterol esters
- These can be hydrolysed by LPL to form VLDL remnants or IDL (Intermediate Density Lipoprotein)
- VLDL remnants are either cleared from the circulation by the liver or metabolised by hepatic lipase into LDL
What is LDL production and clerance regulated by
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
when LDL is taken up by macrophages and other cells what does this lead to
excess accumulation and formation of foam cells that are revenant to atherosclerotic plaque formation
What is HDL Metabolism
- 2 subclasses
- major role of HDL is reverse transport cholesterol from different tissues to the liver for excretion
- anti-atherogenic
- precursor HDL particles are secreted by the liver and small intestine and interact with LCAT to produce mature HDL
What is the link between atherosclerosis and inflammation
inflammation plays an important role in atherosclerosis, which results from an interaction between endothelial cells, blood cells, platelets and smooth muscle cells
what process breaks down fatty acids
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
what happens in trigylerol breakdown
broken down by lipases (releasing FAs to be further degraded) and glycerol further degradation
what happens in fatty acid breakdown (beta-oxidation)
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
what are the products from the beta oxidation pathway
FADH2 + NADH + acetyl CoA and/or propionyl CoA
What is the key difference between short and long chain fatty acids in terms of their activation
short/medium chain fatty acids are activated in the mitochondria, whereas long chain FAs in the outer mitochondrial membrane
what are the essential lipids
alpha-linolenic acid (n-3) and linoleic acid (n-6)
what are the 2 kinds of body fat
subcutaneous fat - under the skin
visceral fat - around the internal organs
where does the biosynthesis of FA occur
cytosol
what is the role of biosynthesis
to generate lipids for storage, cell membrane structure or for energy.
what is the starting and end point of biosynthesis of FAs
start- acetyl CoA
end - Palmitol-ACP
