N 207 - fats/lipids

  1. what are the functions of lipids in food?
    • essential fatty acids
    • econcetrated energy
    • carry fat soluble vitamins
    • falvour, texture, aroma
    • satiety
    • emulsification (PLs)
  2. what are the metabolic functions of food?
    • adipose tissue = energy storage
    • cell membranes
    • nerve impulse transmission
    • eicosanoid synthesis
  3. what is a monounsaturated fatty acid (MUFA)?
    • contains 1 double bond between carbons
    • ex. oleic acid C 18:1, n-9
  4. what is a polyunsaturated fatty acid (PUFA)?
    • contains 2 or more double bonds between carbons
    • ex:
    • linoleic acid C18:2, omega 6
    • common food sources = sunflower, safflower, corn and soybean oils

    • alpha linolenic acids C18:3, omega 3
    • common food sources = soybean and canola oils, flaxseed, walnuts
  5. what is hydrogenation?
    • chemical process that adds H to monounsaturated or polyunsaturated fatty acids to reduce the double bonds
    • make sit more saturated and resistant to oxidation
    • more solid
    • protects against rancidity
    • produces trans fatty acids
  6. what is a cis fatty acid?
    • has hydrogens on the same side of the // bond
    • most naturally occurring unsaturated fatty acids in foods are -cis
  7. what is a trans fatty acid?
    • has H on opposite sides of the // bond
    • more linear
    • occur in partially hydrogenated foods when H atoms shift around some // bonds to change from cis to trans
  8. what are the 2 essential fatty acids?
    • linoleic acid = C18:2 n-6
    • alpha linolenic acid = C18:3 n-3
  9. essential fatty acids
    Image Upload 1
  10. what are the functions of eicosanoids?
    • n-6 family (linoleic)
    • ↑ blood clotting
    • ↑ platelet aggregation
    • ↑ blood pressure

    ↑ CVD RISK

    • n-3 family (alpha linolenic) (fish oil)
    • ↓ blood clotting
    • ↓ platelet aggregation
    • ↓ blood pressure

    ↓ CVD RISK
  11. what doe the gall bladder do?
  12. how is fat emulsified by bile?
    • 1. in the stomach, the fat and the water GI juices are separated
    • the enzymes in the GI juices cannot get to the fat
    • 2. when the fat enters the small intestine, the gall bladder secretes bile
    • bile has an affinity for both water and fat so it acts as an emulsifier to bring fat into the water
    • 3. bile converts the large fat globules into small droplets that repel one another
    • 4. after emulsification, more fat is exposed to the enzymes in the GI juices, making fat digestion more efficient
  13. how is a triglyceride digested via hydrolysis?
    • the triglyceride and 2 H2O molecules are split
    • hydrolysis beaks the ester bonds 
    • its leaves 1 monoglycerides and 2 fatty acids
    • the monoglycerides and 2 FAs are what is going to be absorbed in the intestinal cells
    • sometimes the mono glycerol is split to give a 3rd fatty acid + glycerol
    • FAs, mono glycerols and glycerols are absorbed into the intestinal cells
  14. how is fat absorbed?
    • 1. glycerol and small lipids like  short- and medium chain FAs can move directly into the bloodstream
    • 2. large lipids like monoglycerides and long chain FAs combine with bile, forming micelles that are sufficiently water soluble to penetrate the watery solution that bathes the absorptive cells.
    • the lipid content of the micelles diffuse into the cells and the free FAs and monoglycerides re-form "new" triglycerides
  15. what is the composition of a lipoprotein?
    • contains an interior of triglycerides and + cholesterol and an exterior of phospholipids
    • arrangement of hydrophobic molecules on the inside and hydrophilic molecules on the outside allows lipids to travel through the watery fluids of blood
  16. what are the different sizes of lipoprotein?
    • chylomicron = biggest, more triglyceride /less protein, least dense
    • vldl = 1/2 triglycerides
    • ldl = 1/2 cholesterol (bad)
    • hdl = 1/2 protein (good cholesterol)
  17. how doe slipped transport work via lipoproteins?
    • 1. the liver cells can receive the small lipids directly from the intestine 
    • 2. intestinal cells form chylomicrons from dietary lipids
    • 3. chylomicron deliver dietary lipids (triglycerides) to most of the cells in the body
    • 4. cells all over the body (muscle, fat cells) remove triglycerides from the chylomicron as they pass by, so the chylomicrons get smaller and smaller and become chylomicron remnants.
    • 5. liver cells remove chylomicron remnants from the blood
    • 6. liver cells make lipids (cholesterol, fatty acids)
    • 7. liver cells that make lipids with the chylomicron remnants are packaged with proteins that make vldl
    • 8. vldl is shipped to other parts of the body (muscles, fat cells)
    • 9. as vldl travels in the body, cell remove triglycerides causing vldl to shrink into ldl
    • 10. ldl delivers cholesterol to the liver or to body cells (muscle)
    • 11. liver cells make hdl, which pick up cholesterol form the body cells
    • 12. hdl deliver cholesterol for recycling or excretion
  18. how do we get rid of cholesterol?
    • by biliary excretion
    • make more efficient by taking dietary fibre because body cannot break it down
  19. what is an adipose cell?
    • newly imported triglycerides frist form small droplets at the periphery of the cell, then merge with the large, central globule
    • as the central globule enlarges, the fat cell membrane expands to accommodate its swollen contents
  20. what happens in the fed state? (anabolic)
    • ↑ insulin
    • ↑ chylomicrons
    • ↑ fat synthesis = lipogenesis in the liver from glucose and amino acids
    • ↑ VLDL released
    • lipoprotein lipase on adipose cells captures circulating TGs for storage
  21. what happens in the fasted state? (catabolic)
    • ↓ insulin
    • ↑glucagon
    • ↑ hormone sensitive lipase in adipose cells hydrolyses TGs (lipolysis) and releases FAs and glycerol
    • cells oxidize FAs (B-oxidation to acetyl CoA)
  22. what are the steps in arteriosclerosis?
    • Healthy
    • smooth walls
    • elastic with heart beat
    • wide = smooth muscles can expand

    • Inflammation
    • can produce ulcers / blood clots
    • rough
    • rigid
    • narrow
  23. what are some risk factors for arteriosclerosis?
    • gender (premenopausal)
    • age
    • genetics

    • Modifiable risk factors
    • smoking
    • stress
    • sedentary
    • obesity - visceral
    • hypertension
    • high LDL/ low HDL
    • homocysteine (take some vit.B)
    • glucose intolerance
    • chronic inflammation
  24. what are some high risk dietary characteristics?
    • high energy (calories) = promotes obesity
    • high fat = saturated fat
    • high alcohol = ↑ inflammation
    • low complex CHO/fiber
    • low (high) vitamins/minerals = ↑ oxidative stress
  25. how do we monitor cholesterol status?
    • cholesterol synthesis 
    • ↑ by sat. fat
    • ↓ by MUFA and PUFA

    • statins inhibit the enzyme HMG-CoA reductase
    • ezetimibe inhibits the absorption of cholesterol
  26. DRI summary for fat
    • no AI or UL = insufficient date to link level with prevention of chronic disease
    • intake should be 20-35% of energy for adults (up to 40% for toddlers)
    • saturated fat = low as possible
    • trans fat = low as possible
    • N-6 PUFA - 5 to 10% of energy (12-17g)
    • N-3 PUFA - 0.6-1.2% of energy (1.1-1.6g)
Card Set
N 207 - fats/lipids