Protein control: (leyland) lipid metabolism 1 Flashcards
General properties of lipids
Hydrophobic
Most only contain C, H, O (phospholipids contain P, N)
More reduced than carbs
-> release more energy when oxidised
How are lipids transported in the body?
Lipoprotein particles
Structure of a lipoprotein particle? molecules involved?
Neutral core of Triacylglycerols (TAGs) and Cholesteryl esters (CEs)
Outer shell of phospholipids, free cholesterol and apolipoproteins
What is a chylomicron? What do they do?
Type of lipoprotein particle composed of mostly TAGS
Role: transport of dietry lipids to tissues
contains apoCII
role of apoCII lipoprotein?
activates lipoprotein lipase (LPL) that lines luminal wall of tissues to hydrolyse TAGs
What are very low density lipoproteins (VLDLs)? What do they do?
Type of lipoprotein particle composed of mostly TAGs and some CEs+cholesterols.
Role: Transport of endogenous (synthesised) lipids to adipose and muscle
What are low density lipoproteins (LDLs)? What do they do?
Type of lipoprotein composed of mainly CEs
Role: cholesterol transport
contains apoB100 -> aids with initiating endocytosis of cholesterol by cells
Example of a disease causing defects in lipoprotein metabolism + risks involved
Familial hypercholesterolemia
-> caused by mutations in LDL receptor
-> LDL accumulates in blood
= increased risk of heart attack
What are high density lipoproteins (HDLs) what do they do?
Type of lipoprotein composed of mainly CEs
Role: reverse cholesterol transport (transports cholesterol and CE back to liver)
contains apoA, (activates LCAT),
LCAT (esterifies cholesterol)
4 types of lipoprotein and their proportion of TAGS/cholesterol? Order largest to smallest
Largest
Chylomicrons: high TAG, lowest cholesterol
VLDLs: high TAG, lower cholesterol
LDLs: low TAG, highest cholesterol
HDLs: lowest TAG, high cholesterol
Smallest
Step by step process of dietry lipid metabolism upon ingestion?
1) bile salts emulsify dietry fats in small intestine -> form mixed micelles
2) Intestinal lipases degrade TAGs
3) FA’s and other breakdown products taken up by intestinal mucosa and converted back to TAGs
4) TAGs incorporated with cholesterols and apolipoproteins into chylomicrons
5) chylomicrons move through bloodstream and lymphatic system to tissues
6) Lipoprotein lipase activated by apoC-II converts TAGs to FAs and glycerols
7) FAs enter cells and used for fuel or reesterified for storage
How is lipid digestion regulated in the small intestine?
Secretion of cholecystokinin
- slows release of gastric contents from stomach
- stimulates release of bile
Release of secretin
- stimulates pancreatic secretion
Describe the formation process of chylomicrons
Begins in ER of intestinal epithelial cells
-> nascent chylomicrons
apoE and apoCII added from HDL within lymph and blood
-> mature chylomicrons
