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15: Homework Solutions

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    (01) Saturated fats are primarily composed of triglycerides with saturated hydrocarbon tails. Unsaturated fats are primarily composed of triglycerides with unsaturated hydrocarbon tails. This unsaturation occurs as cis-carbon to carbon double bonds. A monounsaturated fat contains only one cis-double bond. A polyunsaturated fat contains more than one cis-double bond. In nature, triglycerides only contain cis-double bonds.

    (02) omega-6 or delta-5,8,11, 14

    (03) omega-6 or delta-9,12

    (04) The fatty acids with the lower melting points have multiple cid-C=C double bonds. The fatty acids with the higher melting points are saturated. arachidonic (4 C=C) < linoleic (3 C=C) < oleic (1 C=C) < stearic (saturated / 18 carbons) , myrisitc (saturated / 14 carbons)

    (05) All triglycerides are composed of one molecule of glycerine and three molecules of fatty acids. These compounds are bonded together by three ester bonds to form the triglyceride. Fatty acids are carboxylic acids with long hydrocarbon tails.

    (06) The high percentage of saturated hydrocarbon tails from the fatty acids result in tight packing of the triglycerides resulting in a higher melting point and the solid phase at room temperature.

    (07) 89% saturation results in a solid at room temperature. 13% saturation results in a liquid at room temperature.

    (08)

    ch15q8answer.png

    (09) canola < corn < olive < lard < butter < coconut

    (10) The tetrahedral geometry of the carbons in a saturated hydrocarbon tail create a saw-tooth shape that allows for tight packing of these triglycerides which increases the surface area for interactions resulting in stronger IMFs and increased melting points.

    The trigonal planar geometry of the cis-double bonds creates bends and folds in the hydrocarbon tails which decrease the surface area available for interactions resulting in weaker IMFs and decreased melting points.

    (11)

    ch15q11answer.png

    (12) The polar heads point out toward the aqueous body fluids and in toward the aqueous cytosol. The non-polar tails are pointed into the center of the cell member creating a hydrophobic barrier between the inside and outside of the cell. Cell membranes regulate the substances that enter and leave a cell.

    (13) Glycerophospholipids have a glycerine backbone and two fatty acids form the hydrocarbon tails.

    Sphingophospholipids have a sphingosine backbone that forms one of the hydrocarbon tails. The other hydrocarbon tails is formed from a fatty acid.

    (14) a. phospholipid because it contains a phosphoester group

    b. glycerophospholipid because it has a glycerine backbone

    c. lauric acid; saturated; ester bonds connect the fatty acids to the glycerine

    (15) The outer regions of the lipid bilayer are highly polar or ionic and interact via ion-dipole and H-bonding. The interior portion of the lipid bilayer is non-polar and interact through London Dispersion forces.

    (16)

    ch15q16answer.jpg

    (17) Small non-polar molecules such as oxygen and carbon dioxide can pass through cell membranes without assistance or special passages. Note: other compounds from the text may also be listed.

    (18) Cholesterol is a precursor f or bile salts, vitamin D, and hormones.

    (19) Triglycerides and steroids are both hydrophobic and lipophilic. Triglycerides have long hydrocarbon tails while steroids have four fused rings.

    (20) Emulsification: very small drops of organic molecules such as triglycerides suspended in water. Emulsification is needed for fat digestion because it brings the water-insoluble fats into contact with water-soluble digestive enzymes (lipase). Bile salts help emulsify fats and oils. Bile salts are stored in the gall bladder and are released into the small intestine during digestion.

    (21) Many answers possible - refer to the relevant section of the text.

    Glucocorticoids regulate glucose metabolism. Mineralcorticoids regulate electrolytes balances. Progestins, androgens, and estrogens regulates sexual development.

    (22) a. estradiol

    b. prednisone

    c. cholate

    (23) Eicosanoids are derived from arachidonic acid. Eicosanoids are signaling molecules that initiate the inflammatory responses.

    (24) Inflammation is one of the body's immune responses to trauma. Symptoms of inflammation include redness, swelling, pain, and warmth.

    (25) Lipoxyganase inhibitors block the formation of leukotrienes from arachidonic acid. Cyclooxygenase inhibitors block the formation of prostaglandins from arachidonic acid.

    (26) NSAIDs are non-steroidal anit-inflammatory drugs. NSAIDs are cyclooxygenase inhibtiors.


    15: Homework Solutions is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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