NHM 101 Lecture 6: Ch 5 - Lipids
2 May 2018
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Chapter 5- Lipids
Lipid Structures
Lipids have carbon, hydrogen, and oxygen, similar to carbohydrates.
- Lipids have more calories because they have more carbons and hydrogens.
- Lipids are characterized by their insolubility
- Most are not ringed (except for sterols)
All fatty acids have the same basic structure:
- Methyl group (CH3) & acid group
- Chain of carbons and hydrogens in the middle of the two groups
Differences among fatty acids:
- Length of chain
- Saturation (double bonds)
- Location of double bonds
Saturated Fatty Acids
● Fully loaded with all hydrogen
● NO double bonds
Unsaturated Fatty Acids
● At least 1 double bond
Monounsaturated Fatty Acid
● 1 double bond
● Ex. Oleic acid in olive and canola oil
Polyunsaturated Fatty Acid
● 2+ double bonds
● Ex. Linoleic acid in vegetable oils
Location of Double Bonds
- Name fatty acids by location of double bond
- Omega number- position of the double bond closest to the methyl group (CH3)
Omega-3 Fatty Acid
● Closest double bond is 3 carbons from methyl group
Omega-6 Fatty Acid
● Closest double bond is 6 carbons from methyl group
Essential Fatty Acids
● Cannot be made by the body
Linoleic Acid (Omega-6 Fatty Acid)
- Supplied by vegetable oils and meats
- Makes arachidonic acid (in Omega-6 family); if you don’t get enough of linoleic
acid, then your body cannot make this. Arachidonic acid thus becomes medicinally
essential (only essential in some cases)
Linolenic Acid (Omega-3 Fatty Acid)
- Supplied by dark green vegetables, vegetable oils, and flaxseed
- Makes eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)- but only in
small amounts
- Food sources include fatty, cold
water fish, shellfish, and human
milk
Triglycerides
● Fats and oils
● Most common type of lipid
-Contain 1 glycerol and 3 fatty acids.
-Condensation forms a triglyceride
-Hydrolysis breaks it down
Characteristics of Fat and Oils
Firmness
● Degree of unsaturation determines firmness
● Polyunsaturated fats are liquid at room temperature
● Animal or saturated fats are solid at room temperature
Stability
● Polyunsaturated fats spoil (rancid) more easily than saturated fats
Hydrogenation - Some or all points of unsaturation (double bonds) are saturated by
adding hydrogen molecules
● Prolongs shelf life for food products by preventing oxidation
● The number of double bonds is reduced to make it more similar to saturated fats
and increase stability
● Alters texture (makes liquids more solid)
●
Partially-Hydrogenated Oil
(often in ingredients list): undergoes hydrogenation to
help food products stay fresh longer
○ Most fats are partially hydrogenated, and not 100%.
● Hydrogenation can cause
trans-
fatty acids
○ Products with partially-hydrogenated oil DO have trans-fat, even if it is
labeled “trans-fat free.” It just has less than 0.5 grams. This can be sneaky
especially if someone eats multiple of these products in a day.
Fatty Acid Composition
Saturated Fatty Acids
Monounsaturated Fatty
Acids
Omega-6
Polyunsaturated Fatty
Acids
Omega-3
Polyunsaturated Fatty
Acids
- Coconut oil
- Butter
- Beef fat
- Palm oil
- Lard (pork fat)
- Chicken fat
- Olive oil
- Canola oil
- Peanut oil
- Safflower oil
- Sunflower oil
- Corn oil
- Soybean oil
- Walnut oil
- Cottonseed oil
- Flaxseed oil
- Fish oil
(salmon)
Document Summary
Lipids have carbon, hydrogen, and oxygen, similar to carbohydrates. Lipids have more calories because they have more carbons and hydrogens. Most are not ringed (except for sterols) All fatty acids have the same basic structure: Chain of carbons and hydrogens in the middle of the two groups. Name fatty acids by location of double bond. Omega number- position of the double bond closest to the methyl group (ch3) Closest double bond is 3 carbons from methyl group. Closest double bond is 6 carbons from methyl group. Makes arachidonic acid (in omega-6 family); if you don"t get enough of linoleic acid, then your body cannot make this. Arachidonic acid thus becomes medicinally essential (only essential in some cases) Supplied by dark green vegetables, vegetable oils, and flaxseed. Makes eicosapentaenoic acid (epa) and docosahexaenoic acid (dha)- but only in cold human small amounts. Food sources include fatty, water fish, shellfish, and milk. Polyunsaturated fats are liquid at room temperature.
