Exam 2 Study Guide--Chapters 3 (partial)-5

Exam 2 Study Guide--Chapters 3 (partial)-5 - EXAM 2...

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EXAM 2 MATERIAL Chapter 3—Biological Molecules Lipids —mostly nonpolar hydrophobic molecules composed mainly of carbon and hydrogen o Diverse group of organic molecules that are insoluble in water, but will dissolve in nonpolar solvents. o 3 types: o Fats, oils, and waxes Composed of carbon, hydrogen, and oxygen Contain 1 or more fatty acids Usually no ring structure Fats and oils are macromolecules constructed from fatty acids and glycerol. Triglyceride —a fat composed of three fatty acids bonded to one glycerol by ester linkages. o The higher your triglyceride level, the more fat you have in your blood, and the more at risk you are for a heart attack. Functions of fats and oils: Energy Storage: o One gram of fat stores twice as much energy in its chemical bonds as one gram of polysaccharide. o Because of the higher energy per gram, energy storage is more compact with fats and oils than with carbohydrates. Why do we crave fats ? Fats store enormous amounts of energy, and because of this, humans have actually evolved an extremely strong taste preference for foods that are high in fats. Olestra “Fake Fat”—designed to be similar to fats in taste and texture. o Can’t be digested by humans. o Instead of being a triglyceride with 3 fatty acids linked to a glycerol, it has 8 fatty acids attached to a molecule of sucrose. o It simulates the taste buds on your tongue that tell your brain that you are eating fat. But because it is so complex in shape, it prevents your body’s digestive chemicals from grabbing onto it and breaking it down. Fats Humans store fat in adipose tissue cells, which swell and shrink as fat is added to, or taken from them. Fat also insulates the body and protects vital organs. 2 types: o Saturated No double bonds between carbons. Maximum number of hydrogen atoms bonded to the carbon of the skeleton (saturated). Usually solid at room temperature. Most animals store fats. o Unsaturated One or more double bonds between carbons.
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Chain kinks at each double bond, so individual chains can’t pack close enough together to solidify easily. Usually liquid at room temperature. Most plants store oils. o Phospholipids Compounds with molecular building blocks of glycerol, two fatty acids, a phosphate group, and usually a small chemical group attached to the phosphate group. Differs from a fat in the third carbon of the glycerol; is attached to a negatively charged phosphate. Phosphate group with a small chemical group attached is hydrophilic. Forms cell membranes naturally. Phospholipids have 2 ends that behave completely differently in water. Heads: hydrophilic
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Exam 2 Study Guide--Chapters 3 (partial)-5 - EXAM 2...

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