AP cell structure and function

A cell is treated with a drug that prevents the formation of new lysosomes. The cell continues to transcribe the genes that code for the hydrolytic enzymes that are normally found in lysosomes and continues to translate the mRNAs

for those proteins on membrane-bound ribosomes.

The hydrolytic enzymes are most likely to accumulate in which of the following cellular structures?

• Nucleus

• Mitochondrion

• Smooth endoplasmic reticulum

• Golgi complex

Paramecia are unicellular protists that have contractile vacuoles to remove excess intracellular water. In an experimental investigation, paramecia were placed in salt solutions of increasing osmolarity. The rate at which the contractile vacuole contracted to pump out excess water was determined and plotted against osmolarity of the solutions, as shown in the graph. Which of the following is the correct explanation for the data?

• At higher osmolarity, lower rates of contraction are required because more salt diffuses into the paramecia.

• The contraction rate increases as the osmolarity decreases because the amount of water entering the paramecia by osmosis increases.

• The contractile vacuole is less efficient in solutions of high osmolarity because of the reduced amount of ATP produced from cellular respiration.

• In an isosmotic salt solution, there is no diffusion of water into or out of the paramecia, so the contraction rate is zero.

A human kidney filters about 200 liters of blood each day. Approximately two liters of liquid and nutrient waste are excreted as urine. The remaining fluid and dissolved substances are reabsorbed and continue to circulate throughout the body. Antidiuretic hormone (ADH) is secreted in response to reduced plasma volume. ADH targets the collecting ducts in the kidney, stimulating the insertion of aquaporins into their plasma membranes and an increased reabsorption of water.

If ADH secretion is inhibited, which of the following would initially result?

• The number of aquaporins would increase in response to the inhibition of ADH.

• The person would decrease oral water intake to compensate for the inhibition of ADH.

• Blood filtration would increase to compensate for the lack of aquaporins.

• The person would produce greater amounts of dilute urine

Dialysis tubing is permeable to water molecules but not to sucrose. Four dialysis tubes are half filled with 5 percent, 10 percent, 20 percent, and 40 percent sucrose solutions, respectively, and two dialysis tubes are half filled with distilled water. The dialysis tubes are all sealed at both ends, and the initial masses are determined. Five dialysis tubes are placed into beakers containing distilled water, and the sixth dialysis tube, containing distilled water, is placed into a 40 percent sucrose solution. The masses of the dialysis tubes are recorded at 30-minute intervals for 90 minutes, as shown in the table below.

A net movement of water into the beaker occurs in which of the following dialysis tubes?

• 3

• 4

• 5

• 6

A prokaryotic cell has which of the following?

• Centrioles

• Lysosomes

• Plasma membrane

• Mitochondria

All of the following cell components are found in prokaryotic cells EXCEPT

• DNA

• ribosomes

• cell membrane

• nuclear envelope

Contains hydrolytic enzymes associated with the intracellular digestion of macromolecules

• Centriole

• Lysosome

• Nucleolus

• Ribosome

Which structure is thought to have evolved from a photoautotrophic prokaryote?

• A

• B

• C

• D

The following questions refer to an experiment in which a dialysis-tubing bag is filled with a mixture of 3% starch and 3% glucose and placed in a beaker of distilled water, as shown below. After 3 hours, glucose can be detected in the water outside the dialysis-tubing bag, but starch cannot.

From the initial conditions and results described, which of the following is a logical conclusion?

• The initial concentration of glucose in the bag is higher than the initial concentration of starch in the bag.

• The pores of the bag are larger than the glucose molecules but smaller than the starch molecules.

• The bag is not selectively permeable.

• A net movement of water into the beaker has occurred.

If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited?

• Movement of oxygen into a cell

• Movement of water through aquaporins

• Passage of a solute against its concentration gradient

• Facilitated diffusion of a permeable substance