What are the main types of lipids found in food
What are the functions of lipids?
Main types of Lipids: Fatty acids, phospholipids and sterols
Functions of Lipids:
- energy storage and production
- insulation and padding
- cell signalling
- structural support
- inflammatory response
- hormonal production
What are Fatty Acids
Simplest of lipids which contain methyl (non polar) and carboxyl (polar) ends
- most abundant and identified through the length of the chain
What is the difference between MUFA and PUFA
How do you indicate nomenculture
MUFA: monounsaturated which are fatty acids with one double bond
Ex: oleic and palmitoleic acid
PUFA: polyunsaturated which have two or more double bonds
Ex: linoleic and arachidonic acids
- first number indicate the number of carbons and the second number of the double bonds found within the hydrocarbon
What is the effect of regular consumption of omega 3 and omega 6 fatty acids
Omega 3: decrease blood pressure, blood clots, reduce risk of heart disease and stroke and defence against inflammatory disease
Omega 6: pro inflammatory as the repair system
What is the difference between Cis-Fatty Acids and Trans-Fatty Acids
Cis fatty acids: hydrogens located next to the double bond on the same side of the carbon chain found in seed fats, leaves, milk and meat products
- more prone to oxidation since double bonds are not as stable)
Trans fatty acids: fat is partially hydrogenated and double bonds with some trans configuration to protect from oxidation to prolong self life
- intake of trans fatty acids increase LDL levels and decrease HDL = resulting increase heart disease, weight gain , fat accumulation and inflammation
What are Triglycerides (TG)
What is the structure of Triglycerides
Make up largest proportion of lipids humans consume composed of three fatty acids esterified to a glycerol molecule
- found in adipocytes as a form of energy storage and an insulator
Sources: butter, margarine, cooking oil, nuts, dairy, bacon, beef, chicken skin and salad dressing
Structure: 1 glycerol molecule and 3 fatty acids (components must be separated before used for energy)
What are NEFAs?
Non esterified fatty acids which are released into the circulation as free fatty acids
- low solubility in aqueous solutions which bind to protein albumin to be transported into the circulation
- skeletal muscles, heart and liver take NEFA rom circulation and divert to B-oxidation for energy production
Explain how breakdown of TG (catabolism)
What is the difference between transporting SCFA and LCFA
- TG catabolize through lipolysis which occur in the adipose tissue to breakdown into Glycerol and Three Fatty Acids
- activated by Acetyl-CoA to allow fatty acids to undergo oxidation for energy production
SCFA: directly pass through mitochondrial matrix and fatty acids is activated to form fatty acyl-CoA
LCFA: require special transport from carnitine
- Carnitine Palmitoyltransferase I (CPT I): located on outer mitochondrial membrane to transfer fatty acyl group from CoA to Carnitine to form fatty acyl carnitine
- Carnitine Acycarnitine Translocase: transporter of inner mitochondrial membrane which move fatty acyl carnitine into the mitochondrial matrix
- Carnitine Palmitoyltransferase II (CPT II): located on inner mitochondrial membrane and convert fatty acyl carnitine back to Fatty acyl CoA
- carnitine is transported back to the cytosol to repeat the process
- once inside the mitochondrial matrix the fatty acyl-CoA undergo B-oxidation to produce Acetyl-CoA, NADH and FADH2
What are phospholipids composed of
Composed of glycerol, two fatty acids and a phosphate group (PO4) which attract water and fa solvable substances
-carbon 1: alpha carbon of glycerol backbone is esterified to saturated fatty acids
-carbon 2: beta carbon is esterified to unsaturated fatty acids
- carbon 3: attached to a phosphate group
-phospholipids attract water because they are more polar than TG and sterols since they are positioned on the surface of chylomicrons to stabilize the particle in aqueous solutions
- contain hydrophilic (water loving) phosphate head and two hydrophobic (water repelling) fatty acids tails in order to interact with water and lipids
What are Sterols and what are the sources?
Four ring core structure with a hydroxyl group attached to the ring and a hydrocarbon side chain
- mainly hydrophobic (fat soluble) but a amphipathic due to the hydroxyl group
Function: which is the precursor for hormone production (cortisol, aldosterone, estrogen and testosterone)
Sources: meats, egg yolk, poultry and dairy products
What is cholesterol and its function
Type of sterol found in the body with the four ring structure that is fat soluble (does not dissolve in water)
- abundant in brain and nerve tissues for daily function but does not produce energy and eliminate through the biliary system
- cholesterol is produced mainly in the liver but obtained through animal based foods and transported by lipoproteins = HDL and LDL
What are phytosterols
Plant based sterols with a four ring steroid structure but different side chains in which they are able to compete with cholesterol during digestion and absorption in the intestine
- exert cholesterol lowering effect
Sources: vegetable oils, nuts and seeds, whole grains, legumes, fruits and vegetables
Explain the process of endogenous synthesis
What is the precursor
Where does this process occur
Precursor: Acetyl-CoA
Formation of HMG-CoA is the rate limiting enzyme which control the influx of the production of cholesterol
- HMG-CoA reductive converts Acetyl-CoA to Mevalonate
- Mevalonate convert to Squalene
- Squalene convert to Cholesterol
Occur mainly in the liver to use Acetyl-CoA, ATP and NADPH controlled by HMG-CoA
Explain the process of digestion and absorption of lipids
- lipids are not soluble in water and enzymes that digest them are secreted in aqueous solutions
1. Lingual lipase to start the process of TG hydrolysis to cleave Fatty Acid esterified (release from glands in tongue to breakdown TG)
2. Gastric lipase promotes lipid digestion (breakdown TG into small fat droplets)
3. Emulsification in small intestine (most digestion occur in duodenum) as gallbladder releases bile produced in the liver - bile salts emulsify fat to breakdown large fat to small droplets
Explain the process of absorption of fatty acids
Where does absorption occur
- occur in the distal duodenum and jejenum
- Protein independent through diffusion
- Protein dependent mediated by fatty acid transport proteins, FATP 1-4. And FAT/CD36
- both processes do not require energy
