15.E: Exercises
- Page ID
- 306708
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The melting point of elaidic acid is 52°C.
- What trend is observed when comparing the melting points of elaidic acid, oleic acid, and stearic acid? Explain.
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Would you expect the melting point of palmitelaidic acid to be lower or higher than that of elaidic acid? Explain.
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Examine the labels on two brands of margarine and two brands of shortening and list the oils used in the various brands.
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Draw a typical lecithin molecule that incorporates glycerol, palmitic acid, oleic acid, phosphoric acid, and choline. Circle all the ester bonds.
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In cerebrosides, is the linkage between the fatty acid and sphingosine an amide bond or an ester bond? Justify your answer.
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Serine is an amino acid that has the following structure. Draw the structure for a phosphatidylserine that contains a palmitic acid and a palmitoleic acid unit.
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Explain whether each compound would be expected to diffuse through the lipid bilayer of a cell membrane.
- potassium chloride
- CH3CH2CH2CH2CH2CH3
- fructose
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Identify the role of each steroid hormone in the body.
- progesterone
- aldosterone
- testosterone
- cortisol
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How does the structure of cholic acid differ from that of cholesterol? Which compound would you expect to be more polar? Why?
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- What fatty acid is the precursor for the prostaglandins?
- Identify three biological effects of prostaglandins.
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Why is it important to determine the ratio of LDLs to HDLs, rather than just the concentration of serum cholesterol?
Answers
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- Stearic acid has the highest melting point, followed by elaidic acid, and then oleic acid with the lowest melting point. Elaidic acid is a trans fatty acid, and the carbon chains can pack together almost as tightly as those of the saturated stearic acid. Oleic acid is a cis fatty acid, and the bend in the hydrocarbon chain keeps these carbon chains from packing as closely together; fewer interactions lead to a much lower melting point.
- The melting point of palmitelaidic acid should be lower than that of elaidic acid because it has a shorter carbon chain (16, as compared to 18 for elaidic acid). The shorter the carbon chain, the lower the melting point due to a decrease in intermolecular interactions.
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- regulates the menstrual cycle and maintains pregnancy
- regulates salt metabolism by stimulating the kidneys to retain sodium and excrete potassium
- stimulates and maintains male sex characteristics
- stimulates the conversion of proteins to carbohydrates
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- arachidonic acid
- induce smooth muscle contraction, lower blood pressure, and contribute to the inflammatory response