AP Biology Questions and Answers (Graded A)
A mutation in the gene coding, for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a non-polar R group. When researchers test the catalysis of the no...
AP Biology Questions and Answers (Graded
A)
A mutation in the gene coding, for a single-polypeptide enzyme results in the substitution of the
amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a non-polar
R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they
find that the mutated enzyme has a much lower activity than the normal enzyme does. Which of the
following most likely explains how the amino acid substitution has resulted in decrease catalytic
activity by the mutated enzyme?
A. The substitution decreased the mass of the enzyme so that the mutated enzyme binds more
weakly yo the substrate than the normal enzyme does.
B. The substitution altered the secondary and tertiary structure of the enzyme so that the mutated
enzyme folds into a different shape than the normal enzyme does
C. The substitution caused many copied of the mutated enzyme to cluster together and compete for
substrate to bind.
D. The substitution caused the directionality of the enzyme to change such that the amino terminus of
the normal enzyme has become the carboxyl terminus of the mutated enzyme
B. The substitution altered the secondary and tertiary structure of the enzyme so that the mutated
enzyme folds into a different shape than the normal enzyme does
A typical bag of fertilizer contains high levels of nitrogen, phosphorus, and potassium but trace
amounts of magnesium and calcium. Which of the following best matches the fertilizer component
with the molecule in which it will be incorporated by organisms in the area?
A. Nitrogen will be incorporated into nucleic acids
B. Phosphorus will be incorporated into amino acids
C. Potassium will be incorporated into lipids
D. Magnesium will be incorporated into carbohydrates
A. Nitrogen will be incorporated into nucleic acids
Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one
of the enzymes involved in converting carbohydrate monomers into polymers. Which of the following
best explains the reactions of these enzymes?
A. Amylase acids in the removal of a water molecule to break covalent bonds whereas glycogen
synthase aids in the addition of a water molecule to form a covalent bonds.
B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen
synthase aids in the removal of a water molecule to form covalent bonds.
C. Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen
synthase aids in
the removal of a water molecule to break covalent bonds.
D. Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen
synthase aids in
the addition of a water molecule to break covalent bonds.
B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen
synthase aids in the removal of a water molecule to form covalent bonds.
A researcher measured the temperature at which two different samples of double-stranded denature
(separate into single strands). Sample denatured at a significantly lower temperature than sample did.
Based on the data, the researcher claims that the in sample is composed of a higher percentage of
guanine and cytosine than the in sample is.
Which of the following best supports the researcher's claim?
A. The bonds between guanine and cytosine are covalent bonds, which require more energy to
disrupt than
those between adenine and thymine.
, B. Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds
between
them than adenine-thymine pairs do.
C.Adenine-thymine pairs require less energy to separate because adenine and thymine are both
single-ring
bases.
D. Guanine-cytosine pairs require more energy to separate because one is a purine and one is a
pyrimidine.
B. Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds
between
them than adenine-thymine pairs do.
Which of the following best describes the process by which gas from the atmosphere is obtained by
plants
and used to build lipids?
A. Gas is fixed by plants as part of the sulfur cycle.
B. Gas is fixed by plants as part of the nitrogen cycle.
C. Gas is directly obtained by plants as part of the carbon cycle.
D. Gas is directly obtained by plants as part of the magnesium cycle.
C. Gas is directly obtained by plants as part of the carbon cycle.
Which of the following best explains why a cell's plasma membrane is composed of two layers of
phospholipids rather than just a single layer?
A.Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact
with
water inside and outside of the cell.
B.Having two oppositely oriented layers of phospholipids allows the hydrophilic heads to repel water
both
inside and outside of the cells.
C.Having two identically oriented layers of phospholipids gives cells more protection from the exterior
environment than just a single layer would.
D. Having two identically oriented layers of phospholipids allows for the production of vacuoles while
still
maintaining a protective barrier.
A.Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact
with
water inside and outside of the cell.
If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell
membranes is also inhibited?
A. Movement of oxygen into a cell
B. Movement of water through aquaporins
C. Passage of a solute against its concentration gradient
D. Facilitated diffusion of a permeable substance
C. Passage of a solute against its concentration gradient
Cholesterol is an important component of animal cell membranes. Cholesterol molecules are often
delivered
to body cells by the blood, which transports the molecules in the form of cholesterol-protein
complexes. The
complexes must be moved into the body cells before the cholesterol molecules can be incorporated
into the
phospholipid bilayers of cell membranes.
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