Nutrition and Energy (Lipid Absorption and Metabolism) Flashcards
What forms of lipid digestion occur in the mouth?
Mechanical digestion: Teeth and jaws
Chemical digestion: Lingual lipase cuts fatty acids from glycerol backbone
What forms of lipid digestion occur in the stomach?
Mechanical digestion: Fat sits on top of stomach acid, peristalsis mixes and pushes fat towards small intestine
Chemical digestion: Gastric lipase stimulated by gastrin and cholecystokinin (limited due to hydrophobic nature of fat)
What forms of lipid digestion occur in the small intestine?
Mechanical digestion: Peristalsis
Chemical digestion: Pancreatic lipase secreted in response to entry of fats into small intestine
Can monoglycerides and large fatty acid chains be absorbed directly into the bloodstream?
No. they must combine with bile to create a micelle to enter enterocytes
Can small fatty acid chains and glycerol backbones be absorbed directly into the bloodstream?
Yes
What happens to monoglycerides and long fatty acid chains when absorbed into enterocytes?
They are reformed into triglycerides
What happens to the triglycerides in enterocytes?
They are packaged with cholesterol and phospholipids to form a chylomicron
Do chylomicrons enter directly into the bloodstream?
No. They are too large so they enter the lymphatic system, entering the thoracic duct to enter the blood stream
How do cells get triglycerides from chylomicrons?
Lipoprotein lipase in capillary walls takes triglycerides from chylomicrons as they flow through the bloodstream
What does a chylomicron become when it has run out of triglycerides? Where does it go?
It becomes a chylomicron remnant which goes to the liver
When a chylomicron remnant reaches the liver, what happens to it?
It is given fatty acids from the liver (from excess glucose) and converted into a VLDL (very low density lipoprotein) particle
As a VLDL (very low density lipoprotein) particle runs out of triglycerides, what happens to it?
It becomes an LDL (low density lipoprotein) particle, which is typically measured in blood tests
How are LDL (low density lipoprotein) particles removed from the blood? What happens if they aren’t removed?
Liver LDL receptors remove them from the blood. If not removed, LDL becomes sticky and can obscure blood vessels
Where are HDL (high density lipoprotein) particles made?
In the liver
What do HDL (high density lipoprotein) particles do?
They remove cholesterol from blood vessel walls and carry it back to the liver for recycling or disposal
