Lipids in health and disease Flashcards
What is the function of cholesterol in the plasma membrane?
It helps maintain structure and fluidity of the cell membrane
How does cholesterol function in the plasma membrane?
The OH group of cholesterol interacts with the polar head groups of the phospholipids, helping to provide a barrier to H+, Na+ and solutes
How does cholesterol help with cell signalling?
Cholesterol helps to form lipid rafts in the plasma membrane
What are the functions of lipid rafts?
They form bridges between receptor proteins and second messengers. They also serve as centres of assembly for signalling molecules
What molecules is cholesterol a precursor for?
Bile acids, vitamin D and steroid hormones
How are lipids carried in the blood?
In a lipoprotein
What molecules form a lipoprotein?
Apolipoproteins
Free cholesterol
Phospholipids
What is the ideal total cholesterol range?
<5 mmol/L
What is the ideal HDL cholesterol range?
0.9-1.6 mmol/L
What is the ideal Total:HDL cholesterol ratio?
<4
What is the ideal triglyceride range?
1.0-2.3 mmol/L
What is a chylomicron?
An ultra-low density lipoprotein that carries absorbed lipids from the intestine
What type of cell produces chylomicrons?
Enterocytes of the small intestine
What enzyme within the capillaries breaks down chylomicrons?
Lipoprotein lipase
Where is lipoprotein lipase synthesised?
In muscle, heart and adipose tissue
What enzyme converts acetyl coenzyme-A into cholesterol?
HMG-CoA-Reductase
What happens to protein content as density of lipoprotein increases?
It increases
What are the 5 different types of lipoproteins?
Chylomicrons
Very Low Density Lipoproteins
Intermediate Density Lipoproteins
Low Density Lipoproteins
High Density Lipoproteins
What is the function of HDL?
It picks up excess cholesterol in the blood stream
What receptors do HDLs bind to in the liver where they are recycled into lower density lipoproteins?
Scavenger receptors
What occurs when more LDL is formed than is broken down into HDL?
LDL builds up and is converted to form oxidised LDL or LDL aggregate
What can damage the endothelium of the blood vessels?
Smoking, hypertension, hyperglycaemia and hypercholesterolaemia
What does damage to the endothelium cause?
It increases permeability of the endothelium, meaning LDLs can enter the tunica intima
What molecule do damaged endothelial cells express?
Adhesion protein molecules
What occurs when adhesion protein molecules are expressed?
Monocytes in the blood bind to the molecules, allowing them to flatten and move between endothelial cells and into the tunica media
What is the process of monocytes flattening and entering the tunica intima known as?
Diapedesis
How do monocytes cause the formation of oxidised LDL?
They release free radicals that can easily oxidise the LDLs in the tunica intima
What cells do oxidised LDLs attract?
White blood cells e.g. more monocytes
How are foam cells produced?
Monocytes engulf an ingest LDL, causing them to release more free radicals. This means that more LDLs are oxidised and engulfed. This cycle continues causing monocytes that are filled with engulfed LDLs to form
What other type of cell engulfs oxidised LDLs?
Smooth muscle cells
What builds up within a plaque?
Oxidised LDL and particles of dead monocytes as foam cells die forming a necrotic core
What forms over a plaque?
A fibrous cap of endothelial cells
What molecule causes the hardening of a plaque?
Calcium salts
What can occur if the endothelial cells of the fibrous cap are damaged?
A blood clot forms in the lumen, known as a thrombus
What forms when a thrombus breaks off from the plaque wall and travels through the blood vessels, potentially blocking smaller vessels?
An embolus
