AN SC 260 Ch.5
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What are lipids?
- • Organic compounds
- – Relatively insoluble in water
- – Relatively soluble in organic solvents
- – High content of hydrocarbons
What are fatty acids?
- • Carbon chains
- – 2 – 24+ C atoms long
- – Most animal and plant fats: are Straight (ie. not branched) chains are even number of carbons
- - tend to have a methyl non polar hydrophobic end and a caboxyl end which is polar and hydrophillic
Acetic acid formula?
• Acetic acid – C2H4O2
What does chain lenghth tell you about the lipid?
• Longer chains tend to be more solid
what does a short-chain (< 6 C) fatty acids tell you?
- • Product of microbial fermentation of fibre
- • Volatile (gas)
what does medium-chain (6 to 12 C) fatty acids tell you?
- • MC triglycerides easy to absorb (water-soluble)
- • Product of digestion – palm kernel oil high in MC TG
what does Long-chain (>12 C) fatty acids tell you?
• most feed fats/oils
What does very long-chain (>22 C) fatty acids tell you?
• Specialized feed fats/oils – eg fish oil
What is a saturated fatty acid?
- – No double bonds
- – Straight chain
- – Tend to be solid at room temperature (fats)
What is an unsaturated double bond?
- – At least one double bond
- – Each cis double bond introduces a “kink” into the molecule
- – Tend to be liquid at room temperature (oils)
Monounsaturated vs polyunsaturated. How far do the bonds appear away from each other?
• Double bonds normally appear 3 C apart
Trans vs Cis unsaturated fatty acids
Trans fatty acids both the hydrogens are opposite sides of double bond compared to cis where they are on the same side of the hydrocarbon chain
What is hydrogenation in trans fatty acids? How do they behave after hydrogenation? Who does this process naturally?
- - Catalytic
- - Biohydrogenation
- - removal of the doube bond by addition of hydrogen
- They behave like saturated fats because the double bond has been removed. Has negative effects to human health
- Hydrogenation is preformed by rumen microbes as they dont like unsaturated fats so they change them to saturated
What is CLA?
Is a trans fatty acid (conjugated linolic acid) - but it reduces fat deposition and lowers inflammation.
Nomenclature: 18 carbons 2 double bonds at carbon 9 and 12. Common name?
Systemic name? Standard notation? Omega notation?
- -linoleic acid
- -9, 12 octadecadienoic acid
How does standard notation work? Omega notation?
- STANDARD NOTATION
- • Carbons numbered beginning at the acid (carboxyl or COOH) end
- – Also position of double bonds
- OMEGA NOTATION
- - Carbons numbered beginning at the methyl end
What is better omega or standard notation?
- OMEGA NOTAION
- • Fatty acid chains are lengthened by adding 2 C units at the carboxyl end
- – Also shortened at carboxyl end (β-oxidation)
- • Position of omega bonds remain constant – Metabolic differences
What doe it mean Essential fatty acids? Examples?
– Cannot be synthesized de novo by animals
- • Linoleic acid (C18:26)
- • Linolenic acid (C18:3 3)
- • Arachidonic acid (C20:46)
- – Conditionally essential
- – Can be synthesized by most animals if linoleic acid present
When you have branched and odd numbered fatty acid chains what does this tell you? example?
- – Most are products of microorganisms
- • Presence in ruminant tissues
ex. lactobacillic acid
Simple lipids? Examples
- – Esters of fatty acids with various alcohols
- – Fats and oils – glycerol + fatty acids
- – Waxes – other alcohols + fatty acids
Compound lipids? Examples?
- – Esters of fatty acids containing non-lipid substances
- • CHO, phosphorus, or proteins
What are glycerides?
- – Plant, animal storage of energy
- – Major form of lipid in the body
What are Simple triglycerides? What is their lenghth? Saturation?
– Same fatty acid structure at all 3 positions
- – Chain length (also depends on saturation)
- • <10 C chain – liquid at room temperature
- • >10 C chain – solid at room temperature
- – Chain saturation (also depends on length)
- • State (liquid or solid) depends on degree of saturation
Mixed triglycerides? What is their state at room temperature?
- Considered a mixed tri if fatty acid structures not all the same
- Depends on mixture of fatty acids – Chain length and degree of saturation
Why is there a difference in the melting point between stearic acid and linoleic acid?
- Stearic acid (70 degrees) the chains interact with each other thus it is able to have a high melting point.
- Compared to linoleic acid (-5 degrees) where there is double bonds and thus aren't able to interact as closely and have a low melting point
What are Sterols? Function? Examples
- Multiple ring structure
- – Bile acids
- – Sex hormones
- – Adrenal hormones
- – Vitamin D
- – Cholesterol
• Cholesterol, ergosterol and cholecalciferol
What are Phospholipids? Functions?
- Derivatives of triglycerides
- – 2 fatty acid molecules
- – 1 phosphate group
- • Phospholipid bilayer
- • Cell membranes
- – Allow fat and water to cross membrane
- • Emulsifying properties
- – Lipid transport
- • Keep lipids suspended in blood
- – Fluidity of cell membranes
- • Phospholipids to which a carbohydrate chain is attached
- – Often have markers for cellular recognition
- • A biochemical assembly that contains both proteins and lipids
- – Covalently or non- covalently bound
• Many enzymes, transporters, antigens, toxins
Digestion/ absorption in the mouth?
- – Physical emulsification
- – Secretion of lingual lipase (secreted from the tongue, starts to break down fats)
Digestion/ absorption in the stomach?
- – Physical emulsification
- – Activity of lingual lipase
Digestion/ absorption in the small intestine? 6 things?
- – Most digestion, all absorption
- – Secretion of lipase from pancreas
- – Form large droplets in chyme the movement to microvilli impaired
- – Fats are not soluble in water they have a small surface area:volume
Bile salts description?
- – Cholesterol-based
- – Detergent
- • Sterol region and Carboxyl region
What do bile salts do?
- – Emulsify fats, are secreted by the liver
- – Have a Detergent activity
- • create Smaller droplets
- • increase surface area
- • allow more lipase activity
- They are also negatively charged so when they attach on the surfaces of fats they begin to repel each other.
What does intestinal pancreatic lipase do?
- – Work at oil-water interface
- – Cleave TG in 1 and 3 position
- • leaveing 2 fatty acids and 1 monoglyceride and Glycerol
How is cholesterol created?
– Cholesteryl esters cleaved to cholesterol and free fatty acid
What are fat globules made of?
- – Triglycerides
- – Cholesterol
- – Fat-soluble vitamins
When lipid globules are futher reduced in size what is created? What are they made of? Where do they go?
Micelles are formed. They are made of bile salts, monogylerides, fatty acids, phospolipids, and cholesterol. There small size allows them to migrate towards the villi.
How are the micelles absorped?
• Absorbed through intestinal cell membrane thru diffusion
How are micelles formed? Where do they go?
In the precesnce of bile salts, monoglyerides form micelles that are water watery intestine environment. Eventually the monoglycerides leave the micelle to enter the cell. Once the monoglyerides are in the cell they again come back together to form triglyerides.
What happens once the monoglycerides are in the enterocyte?
- – Longer chain (>C12) fatty acids re-formed into TG
- – Shorter chain (<C12) fatty acids absorbed into lymph in most animals
- – Cholesterol re-esterified
lipids are incorporated in chylomicrons? What are chylomicrons?
- They are coated with lipoporteins.
- They contain TG, Phospholipids, Cholesterol esters, Free Cholesterol, and Protein
How do chylomicrons leave the enterocyte in mammals and birds?
By reverse pinocytosis for both. In mamals they leave by the lymph and in birds they leave by portal blood.
Where is cholesterol synthesized? Does how much we ingest have an effect on the amount in the blood?
It is mostly synthesized in the liver. The amount we ingest usually doesnt have an effect on how much is in the blood.
Where do the chylomicrons drain from and what does it look like?
When they drain from the intestine they make the lymphatic vessels appear milky
Where are bile salts recycled? Where are they absorbed? How are they broken down?
They are recycled in the liver, and made available for re-use. They are sometimes absorped by the iliem. If not they will be broken down (deconjugation) and then excreted. This is a good way to get rid of excess bile salts.
What do Chylomicrons, VLDL, LDL, IDL, HDL do?
- - VLDL, LDL, IDL carry cholesterol towards peripheral tissues.
- - High levels of LDL associated with increased atherosclerosis risk "bad"
- - HDL carries cholesterol back to the liver for excretion
- -high levels of HDL associated with decreased atherosclerosis risk "good"
What composition of LDL and HDL are present in red wine?
It has low LDL and high HDL thus it is good for you!
Fat metabolism. Fat that is absorped from the diet?
- - stored as fat (TG)
- -incorportated into cell membranes (PL)
- -oxidized as fuel in B oxidation
What happens when there is excess energy?
When there is excess lipids, carbohydrates, and amino acids they are stored as fat. Fat is a high energy store and is insoluble in water thus easy to sequester
Fatty acid synthesis?
There is four steps required to add a 2 carbon unit (malonyl CoA) to a growing fatty acid chain (elongation).
- - Elongation
- - Acetyl CoA is converted to Malonyl CoA (2 carbons)
- - Malonyl CoA + fatty acid is converted to fatty acid which is 2C longer
- - each 2 C addition requires 2 NADH and energy
What is fatty acid synthase?
- - Multifunctional enzyme
- - Is able to carry out all 4 reactions
Are animals able to saturate and unsaturate their fatty acids?
Yes by either removing or adding hydrogen they can do both. However they can not make their own omega 3s
Beta oxidation? How much ATP does it yield compared to glucose?
- - Removal of 2 acetyl CoA units from a fatty acid to produce energy
- – Turning a water-insoluble storage form into a water soluble TCA precursor
-it is able to yield a huge amount compared to glucose. Fatty acid = 146 aTP and glucose = 38ATP
What are the functions of lipids?
- • Energy
- • Cell membrane structure
- • Carrier of fat-soluble vitamins (absorption)
- • Essential fatty acids
Description of essential fatty acids?
They are a required part of lipid-protein structure of cell membranes. In conjugation with other fatty acids that might not be essential
Essential fatty acids are involved with Eicosanoid metabolism (20 carbons). List some examples and functions.
- – Derivatives of arachidonic acid (or EPA)
- • Thromboxanes
- • Leukotrienes -
- • Prostaglandins
- • Prostacyclins
- - all involved in pain reception and regulation of sleep.
- -show hormone like action such as • Blood pressure • Smooth muscle contraction • Immune regulation • Nervous regulation • Intracellular Ca movement • Reproductive function
Omega 3 fatty acids examples? Health effects?
- Arachidonic acid C20:4(n-6), Eicosapentaenoic acid C20:5(n-3)
- - mainly related to altered eicosanoid function
- -long chain (20 + C) more effective than short chain.
- - has an effeciency of conversion
What is better flax oil or fish oil
It is a greater benefit to get omega 3 fatty acids from fish oil because they will have a greater concentration. Because as time goes on they are continually eating plants/fish that contain omega 3.
are omega 6 fatty acids as good as omega 3.
No it takes more energy from 6 and there is a better response if they come from 3.
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