BIOL 380 Lecture Notes - Lecture 4: Bile Acid, Saturated Fat, Adipocyte
26 May 2018
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BIOL 380 – Lecture 4 – Lipids
- Often foods that are low fat are not necessarily low cal
- Lipids: diverse group of molecules that are insoluble in
water (hydrophobic)
- Fats: the lipid content of diets and foods
- Lipids are stored in adipose tissues that protect and
insulate organs, are combined with phosphorous in cell
membranes, and occur as steroids in bile salts, sex
hormones, and other substances
- In food occur as fats and oils
- 3 types of lipids are found in foods and in the body cells and tissues
1. Triglycerides
2. Phospholipids
3. Sterols
Triglycerides
- Triglycerides (also triacylglycerols)
CH3(CH2)nCOOH contain
o 3 fatty acid molecules
o One glycerol molecule
- a sugar attached to a long chain of a hydrocarbon via a dehydration
reaction we remove a hydroxyl group from the glycerol group, and a
hydrogen from the fatty acid
- same form in which most body fat is stored
- triglyceride is a molecule consisting of 3 fatty acids attached to a 3-
carbon glycerol backbone
- fatty acids are long chains of carbon atoms bound to each other as well
as to hydrogen atoms
- glycerol, the backbone of a triglyceride molecule, is an alcohol
composed of 3 carbon atoms
fatty acids are classified by:
1. carbon chain length
2. saturation level (how many dbs you have)
3. shape and geometry*//////////********9/
1. fatty acids carbon chain length
- short (< 6 carbon),
- medium (6-12 carbon)
- long chain (14)
- carbons can be numbered *midterm
o arol ed COOH: α-carbon (alpha = first)
o ethl ed CH3: Ω-carbon (omega = last)
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2
- we absorb short and medium chain fatty acids directly into blood stream
- long chain fatty acids require being carried via the lymphatic system
2. fatty acid saturation level
- saturated fatty acids (SFA) have hydrogen atoms surroudning every
carbon in the chain
- unsaturated fatty acids (UFA) have double bonds
o monounsaturated fatty acids (MUFA) have one db
o polyunsaturated fatty acids (PUFA) have more than one
double bond
SFA and UFA
- saturated fatty acids pack tightly together and are solid at room
temperature
- unsaturated fatty acids do not stack together well and are more liquid at room temperature
sources of SFA, MUFA and PUFA
- SFA: butter and milk (almost 65% total fat
calories); coconut and palm kernel oils (more
than 80%)
- MUFA: beef, salmon and eggs (around 50%);
olive oil (74%) and cashew nuts
- PUFA: cold water marine fish (tuna, salmon);
flaxseed, safflower and corn oils; walnuts (660%
and more), breastmilk (omega-3)
o PUFAs are also EFAs: essential fatty acids
3. Fatty acid shape and geometry
- Determined by the
o Saturation of carbon chains
o Geometry of groups on the double bond
- Hydrogen atoms at the unsaturated part can be arranged in
different positions
o Cis: same side of the carbon chain
o Trans: opposite sides of the chain
Hydrogenation
- Hydrogenation: hydrogen atoms are
added to unsaturated fatty acids
o Solidify oils and makes them more
saturated
o Creates trans fatty acids (undesirable side-effect)
o Reduce rancidity (chemical decomposition) because free
radicals only attack double bonds)
o Increase risk of cardiovascular disease
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3
Trans fatty acids
Smoke point of oils and fats
- Smoke point: is the temperature at
which oil or fat starts to break down
Essential fatty acids
- EFA must be consumed in the diet because they
cannot be made in the body. E.g. linoleic acid
- EFAs are important components of phospholipids in
red blood cells, neurons and myocardiac cells
- Deficiency of fat intake is rare; main deficiency is of
EFA (linoleic and arachidonic acids)
- When synthesizing fatty acids, the body cannot insert
double bonds before the ninth carbon from the ω-
carbon. For this reason, fatty acids with double bonds
loser to the ethl ed at ω-3 ad at ω-6) are
considered essential fatty acids
- Linoleic acid
o Omega-6 fatty acid
o Sunflower, safflower, corn, soy, peanut oil
- Alpha-linoleic acid
o Omega-3 fatty acid
o Flaxseed, fish, soybean
Omega 3 fatty acids
- omega-3 fatty acids are found in fish and fish oil
o eicosapentaenoic acid (EPA)
o docosahexaenoic acid (DHA)
- reduce risk of heart disease
o stimulate prostaglandins and thromboxanes that
reduce inflammatory responses
o reduce blood clotting and plasma triglycerides
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Document Summary
Often foods that are low fat are not necessarily low cal. Lipids: diverse group of molecules that are insoluble in water (hydrophobic) Fats: the lipid content of diets and foods. Lipids are stored in adipose tissues that protect and insulate organs, are combined with phosphorous in cell membranes, and occur as steroids in bile salts, sex hormones, and other substances. 3 types of lipids are found in foods and in the body cells and tissues: triglycerides, phospholipids, sterols. Ch3(ch2)ncooh contain: 3 fatty acid molecules, one glycerol molecule. A sugar attached to a long chain of a hydrocarbon via a dehydration reaction we remove a hydroxyl group from the glycerol group, and a hydrogen from the fatty acid. Same form in which most body fat is stored. Triglyceride is a molecule consisting of 3 fatty acids attached to a 3- carbon glycerol backbone. Fatty acids are long chains of carbon atoms bound to each other as well as to hydrogen atoms.
