Lecture 26 - Introduction to Lipids Flashcards
Where do fatty acids come from
Diet – about 30-40% of calories are from fatty acids
Adipose tissue – fat storage cells can release fat when needed
De novo synthesis – made from carbohydrates and some amino acids
Where does digestion of fats begin, and what other organs have an affect
Small Intestine
Liver, pancreas
What is bile
Bile contains a number of slightly different compounds, called bile acids & bile salts, derived from cholesterol
- these act as detergents emulsifying the lipids and forming small droplets of fat
What does the pancreas produce in relation to lipids
produces digestive enzymes and bicarbonate solution
- the enzymes involved in fat digestion are called LIPASES
How are fats digested
Large lipid droplets mixed with bile salts to make it more soluble into smaller droplets, with a larger SA
Pancreatic Lipase acts upon the lipid in the micelles, converting them into monoglyceride and fatty acids
these are then absorbed by intestinal epithelial cells, chylomicrons are created by the ER, which are then exocytosed into the lymphatic vessels
What does triacylglycerol lipase do
Catalyses the hydrolysis of triacylglycerols at their 1 & 3 positions
Triacylglycerol (95% of dietary fat)
1,2 diacylglycerol + fatty acid
2 acylglycerol + fatty
Triacylglycerol lipase info
At the water-lipid interface so surface area for lipase to attach to is important
Fatty acids and 2 acylglycerol are then able to diffuse in to intestinal epithelial cells
i.e. cells lining the intestine
Once inside the cells these components are reconstituted into triacylglycerols
What does phospholipase A2 do
Acts upon phospholipids to aid their digestion by removal of the fatty acid residue from position C2
How are lipids transported
Lipoprotein complexes are used to transport the majority of lipids in the blood stream
The complexes are classified by density but there is overlap in composition from one type to the next
How are free fatty acids solubilised
Essentially, lipid droplets surrounded by proteins and phospholipids that make them soluble in blood
Some free fatty acids can be transported in blood, solubilised by binding to serum albumin
Where is lipoprotein lipase present
Present on capillary surfaces of the tissues that absorb lipid from the blood
i.e. mammary, muscle and adipose tissues
What is lipoprotein lipase activated by
ApocII component of chylomicrons
What does lipoprotein Lipase do
This is able to breakdown the triacylglycerols into fatty acids and monoacylglycerol
These are able to diffuse out of the chylomicrons and in to the cells of the tissue
The chylomicrons shrink and become richer in cholesterol esters
Where are chylomicrons returned to
Return in the blood to the liver where they are processed into VLDL
These also activate lipoprotein lipase and release fatty acids to tissues
Once inside cells fatty acids can be metabolised to give energy
What are the categories of lipoproteins
Chylomicrons
VLDL
LDL
HDL (densest)
(SLIDE 16!!!)
What is Apo short for
Apolipoprotein
