Metabolism Flashcards
Classes of Lipids
- Bile Salt
- Eicosanoids
- Steroid hormones
- Triacylglycerol
- Phospholipids
- Vitamins (fat soluble)
- Cholesterol
BEST PVC
What is cholesterol precursor of?
- Bile salt
- Steroid hormones
- Vitamin D
Chemical structure of fatty acid
Which end is alpha-carbon? What is the another end called?
CH3(CH2)nCOO-
Alpha carbon: carboxylic acid end
omega : hydrocarbon end
What is fatty acid transported by in blood? Why does it need a transporter?
Albumin
Fatty acids are insoluble in water
What do glycogen and lipid exist as in cells?
Glycogen granules
Lipid droplets
Name 3 types of lipid-carrying vehicle
Micelle: lipid enclosed by bile salt (bile salt’s hydrophillic side is facing out)
Chylomicron: a type of lipoprotein, transport dietary lipids
VLDL: a type of lipoprotein, transport endogenously synthesized lipids
What is the major lipid in human diet?
Triacylglycerol
Where is triacylglycerol mainly digested in? What is it broken down to?
Intestinal lumen
Triacylglycerol -> free fatty acids + 2-monoacylglycerol
Where will triacylglycerol go after being absorbed by enterocytes?
- Fatty acids + 2-monoacylglycerol get reconverted to traicylglycerol
- Packaged in chylomicrons
- Chylomicrons are secreted into the lymph
- Enter blood circulation
- Digested by LPL (lipoprotein lipase) on capillary wall
- Fatty acids are released and taken up by muscles & other tissues / adipose tissue
What are the 2 hormones secreted by intestine for hydrolysis? What are their functions?
- Cholecystokinin
- gall bladder -> release bile acids
- pancreas -> release digestive enzymes - Secretin
- liver, pancrease -> secrete bicarbonate -> raise pH in intestinal lumen (around 6) -> optimize actions of digestive enzymes
Steps of digestion & absorption for triacylglycerol
- Hydrolysis - by lipases
- Micelle formation - get across water layer next to enterocytes
- Absorption by enterocytes
- Formation of chylomicrons - reassembled into TGA -> incorporated in chylomicrons
- Exocytosis of chylomicrons into body circulation
What kind of fatty acids are hydrolyzed preferentially by lingual lipase & gastric lipase? How does their absorption differ from others?
short & medium length fatty acids (<=12 C)
1. short & medium length: directly absorbed through enterocytes -> go to portal blood while bound to albumin
- longer fatty acids: packaged with micelle to increase solubility -> enter enterocytes -> uptaken by chylomicrons -> enter lymphatic system -> blood circulation
Which part of micelle does not enter enterocyte and which part does? Where does the remaining part go?
Bile salt (outside) doesn't enter enterocyte Lipid-soluble component enter enterocyte membrane
Enterohepatic circulation: Bile salts are reabsorbed and sent back to liver
Where are the major and minor accumulation sites of traicylglycerol?
Major: Adipose tissue
Minor: liver, skeletal muscle
What are the 3 types of monosaccharides? 3 types of common disaccharides?
Monosaccharide: 1. Glucose 2. Galactose 3. Fructose Disaccharide 1. Sucrose: glucose & fructose 2. Maltose: glucose & glucose 3. Lactose: glucose & galactose