117 lines
6.0 KiB
Markdown
117 lines
6.0 KiB
Markdown
- **Lipids** are a class of nutrients that do not dissolve in water.
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- They will dissolve in organic solvents
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- Oil is less dense than water, so it will rise to the top of a solution
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- Major functions of lipids in the body include
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- Providing and storing energy
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- forming and maintaining cell membranes
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- producing steroid hormones
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- insulating the body
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- cushioning the body against bumps and blows
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- forming body contours
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- **absorbing fat soluble vitamins and phytochemicals**
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## Fatty Acids
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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:
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- The number of carbon atoms
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- 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
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- **Monounsaturated** (MUFA)
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- Has **one** double bond within the carbon chain
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- Sources include:
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- **Canola oil**
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- **Olive oil**
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- **Avocados**
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- Nuts
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- Seeds
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- Peanut butter
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- **Polyunsaturated** (PUFA)
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- Fatty acid that has **two or more bonds** within the carbon chain
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- Sources include:
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- **Soybean oil**
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- **Fatty fish**
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- **Flax seed**
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- **Walnuts**
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- Corn oil
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- Sunflower oil
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- Most naturally occurring fatty acids are cis fatty acids
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- 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.
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- Hydrogen atoms of the double bonded carbons are on the opposite side of the hydrocarbon chain
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- **Hydrogenation** is the food manufacturing process that adds hydrogen atoms to liquid vegetable oil, forming trans fats.
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- Can be stored for longer periods because they are less likely to undergo oxidation
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- Raise "bad" cholesterol levels in the blood
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- Increases risk of heart disease
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- **Essential fatty acids** are fatty acids that must be supplied by the diet
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- **Linoleic acid** - 18 carbon omega-6 fatty acid found in vegetable oils
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- **Alpha-linolenic acid** - 18 carbon omega-3 unsaturated fatty acid, found in flaxseed, walnuts
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- Precursor for
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- Eicosapentaonoic acid (EPA) - 20 carbons
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- Docosahexaenoic acid (DHA): 22 carbons
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- Both acids are found mainly in fatty fish
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- Essential fatty acids are needed for growth and healthy cell membranes, especially in the brain.
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- Infants that have an essential fatty acid deficiency can experience developmental and nerve system issues.
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- Signs of essential fatty acid deficiency include:
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- Scaly skin
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- Hair loss
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- Poor wound healing
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# Triglycerides
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A lipid that has three fatty acids attached to a three-carbon compound called glycerol
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- Comprises 95% of lipids in food and body
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- **Glycerol** is a three carbon alcohol that forms the backbone of fatty acids
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# Phospholipids
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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.
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- Partially water soluble
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- Hydrophilic
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- Part that attracts water
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- Hydrophobic
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- Part that repels water and attracts fat
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- Can serve as an emulsifier
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- Helps water soluble and water insoluble compounds mix with each other
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# Sterols
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Sterols are lipids that have a more chemically complex structure than a triglyceride or fatty acid
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- -ol suffix: Attached to an alcohol
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**Cholesterol** is a lipid found in animal foods: precursor for steroid hormones, **bile**, and vitamin D.
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- Found in:
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- Egg yolk
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- Liver
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- Meat
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- Poultry
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- Dairy products
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| Cholesterol (mg/dl) | Classification |
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| --------------------------- | -------------------------- |
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| <200 | Desireable |
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| 200-239 | Borderline high |
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| >= 240 | High |
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| **LDL Cholesterol (mg/dl)** | **Classification** |
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| < 100 | Optimal |
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| 100 - 129 | Near optimal/above optimal |
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| 130-159 | Borderline high |
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| 160-189 | High |
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| >= 190 | Very high |
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| **HDL Cholesterol (mg/dl)** | **Triglycerides (mg/dl)** |
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| < 150 | Normal |
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| 150-199 | Borderline high |
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| >= 200 | High |
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# Lipases
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Lipases are enzymes that break down lipids
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- **Cholecystokinin** is a hormone that stimulates the gallbladder to release bile and the pancreas to secrete digestive juices
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- Bile helps with the emulsification of and digestion of fat.
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- Secretin is a hormone that stimulates the liver to produce bile and the pancreas to secrete bicarbonate rich pancreatic juice
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# Lipoproteins
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Lipoproteins are water-soluble structures that transport lipids through the bloodstream. Lipoproteins are needed because fat is hydrophobic.
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- **Chylomicron** mostly carries triglycerides
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- **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
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- **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
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- **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
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- **Oxidized LDL** is formed when chemically unstable substances damage LDL, transports cholesterol into the arterial lining |