Biochemistry 2280A Study Guide - Midterm Guide: Stereochemistry, Acetaldehyde, Pyruvate Dehydrogenase Complex

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Describe and distinguish between different classes of lipids, explain their biological roles. Fatty acid molecule has two distinct regions: a hydrocarbon chain (hydrophobic, not chemically reactive), and a carboxyl group behaving as an acid. In aqueous solution, carboxyl group is ionized, hydrophilic, and chemically reactive: more often, the carboxyl group is linked to other groups to form esters or amides. Fatty acids are covalently linked to other molecules by their carboxylic acid group. Amphipathic: molecules with both hydrophobic and hydrophilic regions. Some fatty acids have saturated/unsaturated hydrocarbon tails: palmitic acid has a saturated tail: no double bonds, contains max. possible number of hydrogens, oleic acid has unsaturated tail, with one/more double bonds. Double bonds create kinks in hydrocarbon tails, interfering with their ability to pack together: first c=c double bond added to fatty acids is usually between c9 and c10, from the cooh end. Almost always cis, forming a kink in the chain.

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64. Which of these statements about fatty acids are false? A. The physical state of a triglyceride with three unsaturated fatty acid tails would be a clear liquid. B. Complex lipids that contain mainly unsaturated fatty acids are liquids (oils) at room temperature C. Its best to use fats with high melting points in our diet. D. A disadvantage of the ability of saturated fats to pack tightly is that tightly packed, saturated fats clog arteries as atherosclerosis 65. Trans fatty acids A. are formed when vegetable oil is hydrogenated (for solidification). B. are found in fried foods C. have an atypical shape that affects their chemical activity D. are not flexible and can adhere to surfaces E. should be avoided because they are composed of partially hydrogenated (partially hardened) oils F. are all of the above 66 Which of these statements about fatty acids are false? A. When plants and animals build fatty acids they make the trans forms. B. Food manufacturers found that foods like chips with the trans form have a longer "shelf life" C Natural cis fatty acids tend to turn rancid and spoil D Although natural cis fatty acids turn rancid and spoil, it is the cis form that is used by the body. E.The process of hydrogenation, in which hydrogens are added to unsaturated fats, produces a mixture of saturated fatty acids and standard and trans forms of unsaturated fatty acids 67. Good tips for reducing dietary fats are to A. use non-fat or low-fat dairy products and other products B use low-fat cooking methods C bake, roast, steam, broil, stir fry, microwave D. seldom have fried foods E choose lean cuts of meat, trim fat F. do all the above 68. Which of these statements about the properties of fatty acids are true? A. Melting point of all fatty acids increases with increasing hydrocarbon chain length (i.e increasing size) B cis double bonds prevent good alignment of molecules in unsaturated fatty acids leading to C Melting point of unsaturated fatty acid are lower than that of a saturated fatty acid with the D. The melting point of a saturated fatty acid is greater than that of an unsaturated fatty acid of poor packing same number of carbon atoms due to the presence of their double bonds the same chain length, because saturated fatty acid chains tend to be fully extended and to stack in a regular structure, thereby causing increased intermolecular attraction. E. all of the above 69. Freebie 70 Freebie

Question 1 (2.5 points) Question 1 Saved Liquid vegetable oils can be converted to solid fats such as margarine by Question 1 options: 1) hydrogenation. 2) hydrolysis. 3) hydration. 4) oxidation. 5) saponification. Save Question 2 (2.5 points) Question 2 Saved A triacylglycerol that is solid at room temperature is called a(n) Question 2 options: 1) terpene. 2) lecithin. 3) oil. 4) wax. 5) fat. Save Question 3 (2.5 points) Question 3 Saved Unsaturated fatty acids have lower melting points than saturated fatty acids because Question 3 options: 1) they have fewer hydrogen atoms. 2) they have more hydrogen atoms. 3) their molecules fit closely together. 4) the cis double bonds produce a shape that reduces contact between molecules. Save Question 4 (2.5 points) Question 4 Unsaved Cholesterol is a member of the ________ group of lipids. Question 4 options: 1) glycerophospholipid 2) steroid 3) prostaglandin 4) triacylglycerol 5) wax Save Question 5 (2.5 points) Question 5 Unsaved Which of the following is an example of an emulsion? Question 5 options: Paint Milk Jelly Pitch Asphalt Save Question 6 (2.5 points) Question 6 Unsaved _____ are lipids with four fused ring structures. Question 6 options: Sphingolipids Phospholipids Steroids Enzymes Gangliosides Save Question 7 (2.5 points) Question 7 Unsaved The ionic part of a lipid is hydrophobic and the nonpolar part is hydrophilic. Question 7 options: True False Save Question 8 (2.5 points) Question 8 Unsaved The most abundant saturated fatty acid contains 16 carbons and is known as: Question 8 options: lauric acid. myristic acid. palmitic acid. stearic acid. butyric acid. Save Question 9 (2.5 points) Question 9 Unsaved What type of lipid is shown below? lipid Question 9 options: steroid wax fatty acid tryacylgliceride Save Question 10 (2.5 points) Question 10 Unsaved What type of lipid is shown below? lipid Question 10 options: steroid wax fatty acid tryacylgliceride Save

Biochemistry 2280A Study Guide - Midterm Guide: Stereochemistry, Acetaldehyde, Pyruvate Dehydrogenase Complex

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