Lipid transport Flashcards
How are free fatty acids formed? [1 mark]
From triacylglycerides in adipose tissue
How are free fatty acids transported? [2 marks]
- Bound to plasma protein (e.g. albumin)
- As Na+ salt
When does saturation of albumin by free fatty acids occur? [1 marks]
At 2mM FA molecules
Types of lipoproteins [5 marks]
- Chylomicrons
- Very low density lipoproteins (VLDL)
- Intermediate density lipoproteins (IDL)
- Low density lipoproteins (LDL)
- High density lipoproteins (HDL)
General structure of lipoproteins [3 marks]
- Single phospholipid layer with cholesterol
- Apolipoprotein
- TGs and cholesterol esters inside
Which lipoprotein has the most TGs? [1 mark]
Chylomicrons
Which lipoprotein has the most apolipoprotein? [1 mark]
HDL
Which lipoprotein has apolipoprotein B48 (shortened version of B100)?
Chylomicrons
Which lipoproteins have apolipoprotein B100? [3 marks]
- VLDL
- IDL
- LDL
Which lipoproteins have apolipoprotein C1? [2 marks]
- VLDL
- HDL
Which lipoproteins have apolipoprotein C2? [2 marks]
- Chylomicrons
- VLDL
Which lipoproteins have apolipoprotein C3? [3 marks]
- Chylomicrons
- VLDL
- HDL
Which lipoproteins have apolipoprotein E? [4 marks]
All except LDL
Which lipoprotein has apolipoproteins A1 and A2? [1 mark]
HDL
What are the functions of apolipoproteins? [4 marks]
- Structural
- Solubilise lipids
- Enzymes or cofactors
- Ligands/agonists
When are apolipoproteins added? [1 mark]
SER
Where are chylomicrons made? [1 mark]
Endothelial cells in blood vessels
What do chylomicrons transport? [1 mark]
Fat soluble vitamins
What is the lifetime of TGs in chylomicrons? [2 marks]
- Very short
- Broken down by lipoprotein lipases
What are lipoprotein lipases in adiocyte activated by? [1 mark]
Insulin
What do VLDLs/LDLs transport? [2 marks]
- Dietary lipids
- Liver lipids
What is VLDL/LDL synthesis enhanced by? [5 marks]
- Dietary carbohydrates
- Circulating FFA
- Alcohol
- Raised insulin
- Decreased glucagon
How are LDLs removed?
- 60% by the liver
- 40% used by non hepatic tissue for steroid biosynthesis
Where are HDLs made? [2 marks]
- Liver
- Intestine
What do HDLs do to cholesterol to remove it from the plasma? [1 mark]
Esterifies it with lecithin cholesterol acyltransferase (LCAT)
Where are LDL and LDL like receptors found? [1 mark]
In the liver
What are LDL and LDL like receptors regulated by? [1 mark]
Cholesterol
What is the affinity for LDL and LDL like receptors to their ligands? [1 mark]
High
Which lipoproteins are LDL receptors on? [2 marks]
- VLDL
- LDL
Which lipoproteins are LDL like receptors on? [3 marks]
- VLDL
- HDL
- Chylomicrons
What is the ligand for LDL receptors? [1 mark]
Apo B100
What is the ligand for LDL like receptors? [1 mark]
Apo E
What does high levels of cholesterol do to HMG-CoA reductase activity? [1 mark]
Inhibits it (inhibits cholesterol production)
What does low levels of cholesterol do to LDL receptor expression? [1 mark]
Increases it
Where are scavenger receptors found? [2 marks]
- Endothelial cells
- Macrophages
What are lipoproteins regulated by? [3 marks]
- Hormones
- Nutritional status (starvation decreases synthesis)
- LDL expression affected by hormones (like oestrogen)
How is lipid transport affected by diabetes?
- Increased FFA mobilisation
- Decreased chylomicron and VLDL utilisation
Where do chylomicrons enter circulation? [1 mark]
Via thoracic duct
How is cholesterol excreted? [1 mark]
As bile salts
