Nutrition and metabolism of lipids Flashcards
Why do we need lipids?
Membrane structure, fat soluble vitamins (A, D, E, K), energy storage, insulation and protection, building blocks for hormones, flavor and texture.
How much fat does you need?
Fat should be 25-35 (40) E%
Fat = 9 kcal / 37 kJ per gram
What are some main dietary lipids?
Mono-, di- and triglycerides, phospholipids and glycolipids, lipoprotein, fatty acids, sterols and fat soluble vitamins and phytochemicals.
Triglycerides = 3 fatty acids + glycerol
Phospho- and glycolipids = bases for membrane
What is the fatty acid nomenclature?
numbers of carbon : number of double bonds : n-how many carbons from the end.
E.g. 18:2 n-6 (linoleic acid)
What are essential fatty acids?
Human cannot synthesis n-3 or n-6 fatty acids. Therefore, they are needed to be implied into the diet.
n-3 are conditionally indispensable (i.e. necessary as f.)
What are som key sources of lipids in the diet?
Meat: SFA and cholesterol Fish: PUFA Eggs: SFA and phospholipids Dairy: SFA Snacks: SFA, PUFA and trans-fats? Spreads: SFA, PUFA and trans-fats?
SFA = saturated fat PUFA = poly unsaturated fat
What is best, saturated or unsaturated fat?
Unsaturated
What are some food-sources for n-3 and n-6 fatty acids?
n-3: fatty fish, linseed/flax-seed, algae
n-6: corn/maize oil, sunflower oil, soybean oil
Where can you find trans fats?
Mainly from hydrogenation of plant oils to make them soild (margarine) – makes them more stable like butter.
Very low amounts from ruminant digestion (dairy, meat).
Only very low amounts in food allowed currently.
What is phospholipids?
Structural lipids.
Used for membrane that is critical for normal function.
How is triglycerides broke down?
TAG + pancreatic lipids = 2-MAG + 2 FA
Triglycerides are broken down to fatty acids and glycerol in the intestunal lumen by PANCREATIC LIPIDS
! FA is not water soluble
How is lipids absorbed?
aka how is a chylomicron created?
Due to FA not being water soluble something needs to happen for the lipids to be absorbed into the water layer.
Short chain FA can pass to the blood with ATP.
Longer FA as TAG, PL and fatty acid conjugated bile acid forms a simple michelle in the intestinal lumen.
Together with 2-MG and cholesterol esther, a mixed michelle is formed. The mixed ester can pass the unstirred water layer.
This are the stacked close together TG, PL, FFA around a cholesterol ester. This is called CHYLOMICRON.
The chylomicron is then exocytosis (active transport of the cells) and then affect by lacteal in the blood stream.
FA-fatty acids TAG-triglycerides PL-phospholipids 2-MG FFA - fatty free acid
What are the two pathways for lipid absorption?
Exogenous and endogenous pathway
Describe the exogenous pathway.
Consist of 8 steps and is the transport and distribution of dietary lipids.
1: in the intestine a chylomicron is produced.
2: the chylomicron is transported to the capillary
3: In the capillary the chylomicron is degraded by lipoprotein lipase (LPL) to create FFA that is moved to the adipose tissue (i.e. fat tissue)
4: After step 3 there are a chylomicron remnant CM REM) and empty HDL (high-density lipids) left.
5: The empty HDL is transported away. As the HDL is empty it will cruise around in the body to find cholesterol to fill it up.
6: The CM REM will travel to the liver. On the CM REM a apoE is attached.
7: The apoE finds the remnant receptor on the outside of the liver. This makes the CM REM pass into the liver.
8: in the liver the CM REM is dived up into FFA and cholesterol.
Describe the endogenous pathway.
Consist of 10 steps, is the transport and distribution of endogenously synthesized lipids. Lipids can be synthesized from excess carbohydrates.
1: FFA and cholesterol created from excess carbohydrates is transported into the liver. FFA and cholesterol is bound together with apolipoproteins to create VLDL(very low density lipoprotein).
2: VLDL is then transported into the capillary.
3: In the capillary the VLDL is degraded by lipoprotein lipase (LPL) to create FFA that is moved to the adipose tissue (i.e. fat tissue)
4: The reaming from the capillary is called IDL(intermediate-density lipoprotein), by-product HDL.
5: The empty HDL is transported away. As the HDL is empty it will cruise around in the body to find cholesterol to fill it up.
6: The HDL is then passed into the liver.
7: IDL is degraded by hepatic lipase (HPL) to LDL (low density protein)
8: LDL is then transported out of the liver
9: On peripheral tissue (any tissue outside of the gastrointestinal track) a LDL receptor can be found. The LDL is transported to the tissue.
10: The LDL can also be transported back to the liver.
