5.7 KiB
- Lipids are a class of nutrients that do not dissolve in water.
- They will dissolve in organic solvents
- Oil is less dense than water, so it will rise to the top of a solution
- Major functions of lipids in the body include
- Providing and storing energy
- forming and maintaining cell membranes
- producing steroid hormones
- insulating the body
- cushioning the body against bumps and blows
- forming body contours
- absorbing fat soluble vitamins and phytochemicals
Fatty Acids
A fatty acid is a hydrocarbon chain found in lipids; one end of the chain forms a carboxylic acid, and one end forms a methyl group.
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Short chain fatty acids have 2 to 4 carbons
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Medium chain fatty acids have 6 to 12 acids
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Long chan acids have 14 to 24 carbons
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Fatty acids are identified by:
- The number of carbon atoms
- The type of bond between carbon atoms
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An omega-3 fatty acid is a polyunsaturated fatty acid with its first double bond at the third carbon from the omega end of the chain.
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Saturated fatty acid (SFA) Every single carbon atom is filled with hydrogen atoms
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Unsaturated fatty acid is a fatty acid that is missing hydrogen atoms and has one or more double bonds within the carbon chain
- Monounsaturated (MUFA)
- Has one double bond within the carbon chain
- Sources include:
- Canola oil
- Olive oil
- Avocados
- Nuts
- Seeds
- Peanut butter
- Polyunsaturated (PUFA)
- Fatty acid that has two or more bonds within the carbon chain
- Sources include:
- Soybean oil
- Fatty fish
- Flax seed
- Walnuts
- Corn oil
- Sunflower oil
- Monounsaturated (MUFA)
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Most naturally occurring fatty acids are cis fatty acids
- Hydrogen atoms of the double bonded carbon are on the same side of the hydrocarbon atom
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Trans fats are unsaturated fatty acids that have a trans double bond.
- Hydrogen atoms of the double bonded carbons are on the opposite side of the hydrocarbon chain
- Hydrogenation is the food manufacturing process that adds hydrogen atoms to liquid vegetable oil, forming trans fats.
- Can be stored for longer periods because they are less likely to undergo oxidation
- Raise "bad" cholesterol levels in the blood
- Increases risk of heart disease
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Essential fatty acids are fatty acids that must be supplied by the diet
- Linoleic acid - 18 carbon omega-6 fatty acid found in vegetable oils
- Alpha-linolenic acid - 18 carbon omega-3 unsaturated fatty acid, found in flaxseed, walnuts
- Precursor for
- Eicosapentaonoic acid (EPA) - 20 carbons
- Docosahexaenoic acid (DHA): 22 carbons
- Both acids are found mainly in fatty fish
- Essential fatty acids are needed for growth and healthy cell membranes, especially in the brain.
- Infants that have an essential fatty acid deficiency can experience developmental and nerve system issues.
- Signs of essential fatty acid deficiency include:
- Scaly skin
- Hair loss
- Poor wound healing
Triglycerides
A lipid that has three fatty acids attached to a three-carbon compound called glycerol
- Comprises 95% of lipids in food and body
- Glycerol is a three carbon alcohol that forms the backbone of fatty acids
Phospholipids
A phospholipid is a type of lipid needed for the flexibility, structure, and makeup of the cell membranes and for proper functioning of nerve cells.
- Partially water soluble
- Hydrophilic
- Part that attracts water
- Hydrophobic
- Part that repels water and attracts fat
- Hydrophilic
- Can serve as an emulsifier
- Helps water soluble and water insoluble compounds mix with each other
Sterols
Sterols are lipids that have a more chemically complex structure than a triglyceride or fatty acid
- -ol suffix: Attached to an alcohol Cholesterol is a lipid found in animal foods: precursor for steroid hormones, bile, and vitamin D.
- Found in:
- Egg yolk
- Liver
- Meat
- Poultry
- Dairy products
| Cholesterol (mg/dl) | Classification |
|---|---|
| <200 | Desireable |
| 200-239 | Borderline high |
| >= 240 | High |
| LDL Cholesterol (mg/dl) | Classification |
| < 100 | Optimal |
| 100 - 129 | Near optimal/above optimal |
| 130-159 | Borderline high |
| 160-1 |
Lipases
Lipases are enzymes that break down lipids
- Cholecystokinin is a hormone that stimulates the gallbladder to release bile and the pancreas to secrete digestive juices
- Bile helps with the emulsification of and digestion of fat.
- Secretin is a hormone that stimulates the liver to produce bile and the pancreas to secrete bicarbonate rich pancreatic juice
Lipoproteins
Lipoproteins are water-soluble structures that transport lipids through the bloodstream. Lipoproteins are needed because fat is hydrophobic.
- Chylomicron mostly carries triglycerides
- High density lipoprotein (HDL) carries the most protein (45-50%), and roughly 30% phospholipids. HDL carries lipids away from tissues and to the liver, where they can be processed and eliminated. It's considered "good" cholesterol
- Low density lipoprotein (LDL) carries the most cholesterol, and it carries lipids from the liver out to other tissues in the body. It's considered "bad" cholesterol
- Very low density lipoprotein (VLDL) carries triglycerides from the liver into the bloodstream, where cells that line capillaries break down the triglycerides into fatty acids and glycerol
- Oxidized LDL is formed when chemically unstable substances damage LDL, transports cholesterol into the arterial lining