Chapter 6 - Lipids Flashcards
Triglycerides
- the main dietary lipid
- have glycerol backbone with three fatty acids
What are the degree of saturated fatty acids
Saturated = no double bonds
Unsaturated - one (mono) or more (poly) double bonds
What is an example of a polyunsaturated fatty acid
Omega-3 is an example of a polyunsaturated fatty acid. It is named by the position of the double bond from the end of the chain
What are essential fatty acids
Omega 3 - alpha-linoeic acid and Omega 6- linoeic acid. They can be used to form eicosanoids (hormone like molecules)
Describe the relative length of fatty acids and where they would be found
Long chain fatty acids: found in a variety of animal products (14+ carbons)
Medium chain fatty acids: found in tropical oils (6-12 carbons)
Short chain fatty acids are made by bacteria when they ferment indigestible carbs (2-4 carbons)
What is hydrogenation
The artificial production of trans fatty acids
What are sterols
Have a hydrocarbon chain arranged in a ring formation
- can be found in both animal and plant products
Animal derived sterols
- Cholesterol
- Main roles include: cell membrane structure, precursor for vitamin D, precursor for estrogen and testosterone
- Can be synthesized by the liver so is not essential from diet
Plant derived sterols
- Phytosterols
- found in unrefined vegetable oils, buts, seeds, fruits
- may limit absorption of animal sterols
Functions of phospholipids
- Form bilayer
- act as emulsifiers
- carry other lipids around body
Describe lipid digestion
Begins in mouth with the secretion of lingual lipase, which will chemical digest medium and short chain fatty acids, mechanical digestion also separates lipids in the mouth. In the stomach gastric lipase is secreted to digest medium and short chain fatty acids. In the small intestine bile will be secreted by the liver and pancreatic lipase will be secreted by the pancreas to digest the remaining lipids
Describe lipid absorption
Micelle breaks down and the lipid content is absorped into the small intestine cells through passive diffusion.
Lipids get wrapped in phospholipids as they exit the small intestine cell and enter the centre of the villus creating a chylomicron. The chylomicron will then enter the lacteals
What are the different types of lipoproteins
Chylomicron, VLDL, LDL, and HDL
Describe the transport of chylomicron
Delivers triglycerides from the small intestine villus –> lymph –> blood –> body cells –> liver
Describe the transport of VLDL
Delivers triglycerides. Made in liver –> body cells –> becomes LDL as it looses triglycerides
Describe the transport of LDL
Delivers cholesterol. From VLDL –> delivers cholesterol to body cells, returns to the liver, or get deposited into artery walls
Describe the transport of HDL
Mainly removes cholesterol from blood and body cells. Made in liver –> picks up cholesterol from blood cells –> returns it to liver
What are the lipid functions
- Energy provision
- membranes
- transport and storage of fat soluble vitamins
- Synthesis of other key molecules
Describe the function of lipids in energy provision
Lipids provide 9 kcal/g of energy. If carbohydrates are inadequate in the diet, triglycerides are metabolized and their products enter the citric acid cycle
Describe the function of lipids in transport and storage of fat soluble vitamins
Vitamines A, D, E and K are fat soluble vitamins and since they are hydrophobic, they require lipoproteins for transport. They can also be stored in adipose tissue
Describe the function of lipids in the synthesis of other molecules
Cholesterol-derived molecules include: steroid hormones, bile salts, vitamin D, estrogen and testosterone
Essential fatty acid-derived molecules include: eicosanoids, and endocannabinoids
What is atherosclerosis
the build up of fatty materials in artery walls. A type of CVD that causes heart attacks and some strokes
Trans fatty acids and their link with CVD
Known to increase
- Ratio of LDL to HDL
- Risk of CVD
- Risk of CVD morality
Saturated fatty acids and health
Diets high in Saturated fats increase LDL which increases risk of CVD
