Fig. 2.15 Fats (lipids)

FUNCTIONS Fats are mostly for storing energy long term in an organism. Fats also serve to: Insulate the body Pad and protect organs Store fat-soluble vitamins (ADEK) Form steroid hormones (testosterone, estrogen etc.) Structurally form cell membranes.

Various Fats Neutral Fats Phospholipids Sterol Lipids Although there are a variety of types of fats/lipids, and structurally they may look very different and functionally they may serve very different purposes; one thing they have in common is that they are all HYDROPHOBIC – don’t mix with water.

Fig. 2.22 NEUTRAL Fats Formed when a Glycerol Molecule undergoes a dehydration synthesis reaction with Fatty Acid Chains. If only one chain joins on = Monoglyceride If two chains join on = Diglyceride If three chains join on = Triglyceride These molecules are used to store energy, as the fatty acids can be burned as fuel by the organism.

Fig. 2.23ab PHOSPHOLIPIDS Formed when a Glycerol combines with two hydrophobic fatty acid chains, but on the third site on the glycerol a polar (hydrophilic) phosphate group binds on. So part of the phospholipid love water while the rest of the molecule avoids water.

Fig. 2.23c When two layers of Phospholipids form, they take up the following orientation. This “Phospholipid Bilayer” forms the main portion of a cell’s membrane.

Cell membrane model

STEROL LIPIDS Fig. 2.24 Recognized by having four carbon rings (yellow in molecules below) fused together in the pattern below.

Sterol Lipid Functions Cholesterol is used to structurally firm up the cell membrane Cholesterol Most Sterol Lipids form Hormone messengers in the body, while other sterol lipids are used as structural building molecules