Presentation on theme: "LIPIDS. Hydrophobic, non-polar molecules Used for energy storage, building membranes and chemical signalling Four main types: fats, waxes, steroids and."— Presentation transcript:
Hydrophobic, non-polar molecules Used for energy storage, building membranes and chemical signalling Four main types: fats, waxes, steroids and phospholipids
1) FATS Energy storage: Store more energy per gram than carbohydrates, BUT energy is not as easily accessible. Insulation, cushioning internal organs...
Triglycerides Most common fats in plants and animals are the triacylglycerols (aka triglycerides) which consist of a glycerol backbone and 3 fatty acids. Glycerol is an alcohol, while the fatty acids are an acidic carboxyl group combined with a long hydrocarbon chain (usually 16C to 18C long). 1+3=
Esterification When glycerol combines with each fatty acid a condensation reaction (dehydration synthesis) occurs. An acid reacting with an alcohol produces an ester linkage, hence this process is called esterification.
Types of Fatty Acids Saturated fatty acids have no double bonds in the hydrocarbon chain and are solid at room temperature (animal fats, butter, lard). Unsaturated fatty acids have double bonds in the hydrocarbon chain and are liquid at room temperature, known as oils (plant fats). A saturated fat has 3 saturated fatty acids A unsaturated fat has at least one unsaturated fatty acid (mono = 1, poly = 2 or 3).
Hydrogenation is the process of adding hydrogen molecules to plant oil in order to make it saturated and therefore solid. The process is done using an enzyme and hydrogen gas. Can lead to TRANS fatty acids and therefore trans fats.
Trans Fats ‘Trans’ refers to the configuration of the double bond – a trans bond is too hard for our body to breakdown. Found in fried foods, hard margarines, commercial baked goods, processed foods that are made with shortening, margarine or oils containing partially hydrogenated oils and fats.
Good Fats vs. Bad Fats In general terms, polyunsaturated and monounsaturated fatty acids tend to lower your risk of heart disease. They are the healthier fats, and they should be included in your diet. Saturated and trans fatty acids are unhealthy fats because they tend to raise your risk of heart disease.
Canada's Food Guide to Healthy Eating Choose lower fat dairy products, leaner meats and foods prepared with little or no fat. Read the labels on pre-packaged food products.. look for the amount of trans fat in the product also the phrase "partially hydrogenated oil." If you see this phrase in the list of ingredients on the label, it means the product contains trans fat. Choose soft margarines that are labelled as being free of trans fat or made with non-hydrogenated fat. Fry foods less often. When you do fry foods, use healthier oils that contain a higher proportion of monounsaturated fats. Do not re-use the oils more than two or three times. When you eat out, ask about the trans fat content of foods on the menu.
2) PHOSPHOLIPIDS Make up the majority of the cell membrane. Contain a glycerol molecule combined with two fatty acids and a highly polar phosphate group. Phosphate head is hydrophilic while the fatty acid tail is hydrophobic.
In a cell membrane the phospholipid bilayer makes it impossible for polar molecules and charged molecules to pass due to the hydrophobic center. That is why there are protein channels in the cell membrane to allow these types of molecules to pass through.
3) STEROLS (Steroids) Highly hydrophobic Four fused hydrocarbon rings with many different functional groups Cholesterol is a steroid, which is important in cell membranes to maintain their fluidity. It can also be dangerous as ingested cholesterol can lead to blocking of the arteries.
Other steroids Other important steroids include the sex hormones (testosterone, estrogen and progesterone).
4) WAXES Hydrophobic fatty acid chains attached to ring structures or alcohols. Very pliable solids. Used by animals and plants as waterproofing agents (ex. cutin in the cuticle of plants, beeswax, feathers of birds).