ap bio unit 1 2 and 3 exam

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? *Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell. Having two oppositely oriented layers of phospholipids allows the hydrophilic heads to repel water both inside and outside of the cells. Having two identically oriented layers of phospholipids gives cells more protection from the exterior environment than just a single layer would. Having two identically oriented layers of phospholipids allows for the production of vacuoles while still maintaining a protective barrier.

*Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell.

Site of conversion of chemical energy of glucose to ATP *

A

Which of the following was the dependent variable in the researcher's study? AThe concentration of chlorophyll a BThe concentration of total nitrogen and phosphorus CThe slope of the trend line showing the rate of change DThe variance of the data points from the trend line

AThe concentration of chlorophyll a

Which of the following best explains how higher concentrations of nitrogen and phosphorus contribute to eutrophication? AAn increase in the population of algae results in more nitrogen and phosphorus in the water, causing severe eutrophication. BBoth bacteria and algae require nitrogen and phosphorus, so the algae must grow faster to compete with bacteria. CNitrogen and phosphorus stimulate oxidative phosphorylation, which consumes the available oxygen in the water. DAlgae require nitrogen and phosphorus to build macromolecules, so higher concentrations of these nutrients can result in algal blooms.

Algae require nitrogen and phosphorus to build macromolecules, so higher concentrations of these nutrients can result in algal blooms.

Which statement describes how water is pulled up through the xylem to the leaves of the plant? A As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below. B As water exits the leaf, signals are sent to the roots to pump more water up to the leaves through the xylem by adhesion. C Evaporation from the leaf decreases the hydrogen bonds that form between the water molecules in the xylem, which helps the water molecules to be pulled up the xylem. D Evaporation of water from the leaf increases the hydrogen bonds that form between water molecules in the air, providing the energy for transport.

As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below.

A culture of Spirogyra (an autotrophic alga) is maintained in a water solution containing dissolved carbon dioxide and a source of phosphates but lacking nitrogen compounds. A researcher determines the rates of synthesis of several organic compounds found in the Spirogyra before and after several weeks in the water solution. Which of the following graphs best illustrates a likely result of the experiment?

B

Graphs representing enzymes sensitive to changesin pH include which of the foNowing?

b 4 only

Site of modification and packaging of proteins and lipids prior to export from the cell *

C

Site of glucose synthesis *

b. chloroplasts

Which of the following best describes the process by which gas from the atmosphere is obtained by plants and used to build lipids? AGas is fixed by plants as part of the sulfur cycle. BGas is fixed by plants as part of the nitrogen cycle. CGas is directly obtained by plants as part of the carbon cycle. DGas is directly obtained by plants as part of the magnesium cycle.

CGas is directly obtained by plants as part of the carbon cycle.

Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur.Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells? A Simple carbohydrate B Amino acid C DNA D Polypeptide

DNA

The synthesis of protein or carbohydrate polymers always produces which of the following as a byproduct? AATP BOxygen CCarbon dioxide DUrea EWater

EWater

A student analyzed a viral genome and found that the genome had the following nucleotide composition.• 28% adenine• 20% thymine• 35% cytosine• 17% guanine. Which of the following best describes the structure of the viral genome? * Double-stranded DNA Single-stranded DNA Double-stranded RNA Single-stranded RNA

Single-stranded DNA

How might this change affect the structure and function of the protein? A The R-groupR-group of the new amino acid, valine, has different chemical properties than the R-groupR-group of cysteine. This will cause the protein to misfold and not function properly in the cell. B The new amino acid, valine, has replaced cysteine in the new protein. Since the number of amino acids has remained the same, there will be no change in the three-dimensional folding, or function, of the protein. C Since this is a linear section, it does not influence protein folding. Thus, there will be no change in protein structure or function. D Since the new amino acid is bounded on one side by an amino acid with a negatively charged R-groupR-group and by an amino acid on the other side with a positively charged R-groupR-group, the charges will balance and the protein will fold as usual.

The R-groupR-group of the new amino acid, valine, has different chemical properties than the R-groupR-group of cysteine. This will cause the protein to misfold and not function properly in the cell.

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions ( H+ ). Which of the following is the most likely direct effect of adding the chemical to plant cells? * The plant cells will split fewer water molecules into hydrogen ions and oxygen .The plant cells will produce less NADPH . Chlorophyll will require less light energy to excite its electrons. The chloroplasts will generate less ATP .

The chloroplasts will generate less ATP .

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 nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does.Which of the following most likely explains how the amino acid substitution has resulted in decreased catalytic activity by the mutated enzyme? * The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly to the substrate than the normal enzyme does. 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. The substitution caused many copies of the mutated enzyme to cluster together and compete for substrate to bind. The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxy terminus of the mutated enzyme.

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.

The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves? A Water is polar, and the walls of the xylem are nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls. B Water is nonpolar, and the walls of the xylem are polar. Water molecules are able to form hydrogen bonds with the xylem walls, and they are pulled up the xylem. C Water and the xylem are both nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls. D Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

Which of the following is evidence that eukaryotes and prokaryotes share a common ancestor? *all eukaryotes and prokaryotes contain DNA all eukaryotes and prokaryotes contain ribosomes All eukaryotes and prokaryotes use organic molecules as an energy source. All eukaryotes and prokaryotes are capable of mitosis.

all eukaryotes and prokaryotes contain ribosomes

After exposing the samples to light or dark for one hour, the students recorded the pH of the water in each beaker. Carbon dioxide dissolved in water will lower the pH of an aqueous solution. In the experiment, the students used changes in pH to monitor changes in the amount of carbon dioxide in the water. For each treatment group, the students calculated the mean pH and standard error, as documented in the table below.Which of the following graphs is the most appropriate representation of the experimental results documented in the table?

bar graph

Enzymes with their highest activity at an alkaline(basic) pH are represented by which of thefollowing graphs?

c three only

Dialysis tubing was filled with a 25% glucose and 2% starch solution. This was then placed in a beaker filled with water. Glucose is able to pass through the membrane of the dialysis tubing, while starch cannot. Which of the following best predicts what will happen over time? *water and glucose will both leave the dialysis tubing water will enter the dialysis tubing while glucose will leave water will leave the dialysis tubing while glucose will enter water and glucose will both enter the dialysis tubing

water will enter the dialysis tubing while glucose will leave