Bio Chapter 3

Which of these is a thiol? * -NH2 * -OH * -COH * -SH * None of the listed responses is correct.

* None of the listed responses is correct. A thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group. The sulfhydryl group (-SH) consists of a sulfur atom bonded to an atom of hydrogen; it resembles a hydroxyl group in shape. None of the selections is correct because a thiol is a full molecule and not a functional group. All of the listed answers belong to a functional group.

The lipids that form the main structural component of cell membranes are * carbohydrates * triacylglycerols * cholesterol * proteins * phospholipids

* phospholipids Correct. Phospholipids have a hydrophilic head and two hydrophobic tails. This permits the phospholipids to be arranged in a bilayer, or double layer, which forms a boundary between the cell and its external environment.

To what does the term polypeptide specifically refer? *None of the listed responses is correct. * A complex carbohydrate * Monomers linked by glycosidic linkages * Amino acids linked by hydrolysis * Carbohydrates with a hydrogen bond holding them together

**None of the listed responses is correct. Diverse as proteins are, they are all unbranched polymers constructed from the same set of 20 amino acids. A polypeptide is a chain of amino acids that have been linked together by dehydration reactions. A protein is a biologically functional molecule that consists of one or more polypeptides, each folded and coiled into a specific three-dimensional structure. Polymers, including polypeptides, are disassembled into monomers through hydrolysis. Complex carbohydrates, or polysaccharides, are polymers of monosaccharides, or simple sugars. Monosaccharides are linked together through dehydration reactions that form glycosidic linkages. Some polysaccharides are held together by hydrogen bonds such as in the case of cellulose microfibrils.

Which of the following functional groups is present in all amino acids? * -OH * -SH * -COH * -OPO3-2 * -NH2

-NH2 Correct. This is the amino group. This group is present in all amino acids.

What do Alzheimer's, Parkinson's, and mad cow disease have in common? * They all cause the misfolding of nucleic acids. * All are associated with the buildup of lipids in brain cells due to faulty lysosome activity. * All have been associated with the buildup of misfolded proteins in cells. * They all associated with plaque buildup in arteries (atherosclerosis). * All are caused by the buildup of misfolded proteins in cells.

All have been associated with the buildup of misfolded proteins in cells.

Which of the following functional groups increases the solubility of organic compounds in water? * -COOH * -COH * -NH2 * -SH * All of the listed responses are correct.

All of the listed responses are correct.

Which of the following hydrocarbons has a double bond in its carbon skeleton? 1) C3H8 2) C2H6 3) CH4 4) C2H4 5) C2H2

C2H4

Which of the following is an organic molecule? a) NaCl b) CH4 c) H2O d) O2 e) Ne

CH4

When a protein is denatured, why does it lose its functionality? * Denaturation destroys the primary structure of the protein, and the protein breaks down to monomers. * Different amino acids are substituted into the sequence, so the protein's properties change. * Denaturation breaks the weak bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function. * Denaturation breaks the covalent bonds that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function. * The protein's pH changes, causing it to lose its functionality.

Denaturation breaks the weak bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.

The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules? * proteins * lipids * amino acids * nucleic acids * carbohydrates

Lipids - Steroids, such as estrogen, progesterone, and testosterone, are lipids based on their insolubility in water. The molecules are characterized by a carbon skeleton consisting of four fused rings of carbon atoms.

Amylase is an enzyme that breaks down starch. Why can't the same enzyme break down cellulose? * The enzyme cannot attack cellulose because of its helical shape. * The monosaccharide monomers in cellulose are bonded together differently than in starch. * Cellulose molecules are much too large. * The bonds between the monosaccharide monomers in cellulose are much stronger. * Starch is made of glucose; cellulose is made of fructose.

The monosaccharide monomers in cellulose are bonded together differently than in starch. Correct. The glucose monomers in cellulose are bonded in a beta glycosidic linkage, whereas those in starch have an alpha glycosidic linkage. The enzyme amylase is specific for the alpha glycosidic linkage.

Manufacturers make vegetable oils solid or semisolid at room temperature by _____. * adding hydrogen atoms to the single bonds of the fatty acid hydrocarbon chains * adding hydrogen atoms to the double bonds in the fatty acid hydrocarbon chains * removing hydrogen atoms and forming additional double bonds in the fatty acid hydrocarbon chains * removing hydrogen atoms and forming additional single bonds in the fatty acid hydrocarbon chains * None of the listed responses is correct.

adding hydrogen atoms to the double bonds in the fatty acid hydrocarbon chains Manufacturers make vegetable oils solid or semisolid at room temperature by adding hydrogen atoms to the fatty acid hydrocarbon chains. The phrase hydrogenated vegetable oils found on food labels means that unsaturated fats have been synthetically converted to saturated fats by the addition of hydrogen. If hydrogen atoms were removed, additional double bonds, not single bonds, could be formed. Removing hydrogen atoms and forming additional double bonds in the fatty acid hydrocarbon chains would increase the liquid nature of the vegetable oil. Additional hydrogen atoms cannot be added if each carbon of the fatty acid hydrocarbon chain is already saturated with hydrogen.

On the basis of the principle of complementary base pairing, you would expect the percentage of _____ to be equal to the percentage of _____. * adenine ... thymine * thymine ... guanine * thymine ... cytosine * adenine ... guanine

adenine ... thymine

Protein molecules are polymers (chains) of _____. * sucrose molecules * DNA molecules * amino acid molecules * purines and pyrimidines * fatty acid molecules

amino acid molecules Correct. Polymers of amino acids are called polypeptides. A protein consists of one or more polypeptides folded into specific conformations.

Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least? * cellulose (in the lettuce) * starch (in the croutons) * protein (in the bacon bits) * sugar (in the dressing) * oil (in the dressing)

cellulose Correct. Cellulose contains glycosidic linkages that cannot be broken by human digestive enzymes.

Which of the following is a polymer? * cellulose, a plant cell wall component * fructose, a component of sucrose * glucose, an energy-rich molecule * triacylglycerol, or fat * testosterone, a steroid hormone

cellulose, a plant cell wall component Correct. The polysaccharide cellulose is a major component of plant cell walls. It is a polymer composed of many glucose monomers joined together by glycosidic linkages.

At a conference, the speaker's grand finale was sautéing mealworms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide _____. * chitin * glycogen * cellulose * collagen * linoleic acid

chitin Correct. Chitin is the structural polysaccharide found in arthropod exoskeletons.

Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by _____ * ester linkages * glycosidic linkages * peptide bonds * ionic bonds * phosphodiester linkages

ester linkages

A nucleotide is made of which of the following chemical components? * a series of nitrogenous bases, a nucleic acid backbone, and a hexose sugar * a nitrogenous base, an amino acid, and a pentose sugar * a nitrogenous base, an amino acid, and a phosphate group * a nitrogenous base, a fatty acid, and an amino acid * a nitrogenous base, a phosphate group, and a pentose sugar

nitrogenous base, a phosphate group, and a pentose sugar Correct. Each nucleotide consists of three parts: an organic molecule, called a nitrogenous base; a 5-carbon sugar, called a pentose; and a phosphate group that serves in the phosphodiester covalent bond that forms a bridge between adjacent nucleotides.

Cellulose is a _____ made of many _____. *protein; amino acids *polymer; glucose molecules *carbohydrate; fatty acids *polypeptide; monomers *lipid; triacylglycerols

polymer ... glucose molecules ; Cellulose is a polysaccharide, constructed from many monosaccharides.

the alpha helix and beta pleated sheet represent which level of protein structure? * secondary structure * pentiary structure * tertiary structure * primary structure * quaternary structure

secondary structure

A straight-chain carbon compound constructed from _____ must contain at least one carbon-carbon double bond. * eight hydrogen, three carbon, three oxygen * six hydrogen, two carbon, one oxygen * 14 hydrogen, 6 carbon * six hydrogen, two carbon * six hydrogen, three carbon

six hydrogen, three carbon No. This is a typical hydrocarbon with single bonds, in which the number of hydrogen atoms is equal to two times the number of carbon atoms plus 2.

In what polysaccharide form do plants store glucose to be available later as an energy source? * protein * starch * glycogen * cellulose * fatty acids

starch

The overall three-dimensional shape of a single polypeptide is called the _____ * secondary structure * primary structure * tertiary structure * double helix * quaternary structure

tertiary structure