Biology Ch. 5 Assessment

24) Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

A) CO2

10) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

6) According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

A) They can move laterally along the plane of the membrane.

28) Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

A) Water will leave the cells, causing them to shrivel and collapse.

13) A protein that spans the phospholipid bilayer one or more times is

A) a transmembrane protein.

53) In general, a signal transmitted via phosphorylation of a series of proteins

A) brings a conformational change to each protein.

7) Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

A) by increasing the percentage of unsaturated phospholipids in the membrane

42) Familial hypercholesterolemia is characterized by which of the following?

A) defective LDL receptors on the cell membranes

21) The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an example of

A) diffusion across the lipid bilayer.

5) The presence of cholesterol in the plasma membranes of some animals

A) enables the membrane to stay fluid more easily when cell temperature drops.

54) Which of the following most likely would be an immediate result of a growth factor binding to its receptor?

A) protein kinase activity

23) Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

B) It exhibits a specificity for a particular type of molecule.

16) The formulation of a model for a structure or for a process serves which of the following purposes?

B) It functions as a testable hypothesis.

49) In which of the following ways do plant hormones differ from hormones in animals?

B) Plant hormones may travel in air or through vascular systems.

40) Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?

B) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.

46) Which of the following is true of steroid receptors?

B) The receptor may be inside the nuclear membrane.

58) In which of the following ways could signal transduction most probably be explored in research to treat cancer?

B) alteration of protein kinases in cell cycle regulation in order to slow cancer growth

1) Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At high temperatures, these regions

B) are less fluid than the surrounding membrane.

51) Testosterone functions inside a cell by

B) binding with a receptor protein that enters the nucleus and activates specific genes.

41) A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

B) lysosomes.

22) What kinds of molecules pass through a cell membrane most easily?

B) small and hydrophobic

56) Which of the following is a correct association?

C) GTPase activity and hydrolysis of GTP to GDP

59) Which of the following is the greatest advantage of having multiple steps in a transduction pathway?

C) Having multiple steps provides for greater possible amplification of a signal.

25) Which of the following statements is correct about diffusion?

C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

19) Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

C) The two sides of a cell membrane face different environments and carry out different functions.

11) Which of the following is true of integral membrane proteins?

C) They are usually transmembrane proteins.

15) The cell membranes of Antarctic ice fish might have which of the following adaptations?

C) a high percentage of polyunsaturated fatty acids

39) Which of the following would increase the electrochemical gradient across a membrane?

C) a proton pump

8) In order for a protein to be an integral membrane protein it would have to be

C) amphipathic, with at least one hydrophobic region.

37) The movement of potassium into an animal cell requires

C) an energy source such as ATP.

36) The sodium-potassium pump is called an electrogenic pump because it

C) contributes to the membrane potential.

60) GTPase activity is important in the regulation of signal transduction because it

C) hydrolyzes GTP to GDP, thus shutting down the pathway.

35) What is the voltage across a membrane called?

C) membrane potential

32) Which of the following membrane activities requires energy from ATP hydrolysis?

C) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

44) In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?

C) on the inside surface of the vesicle

48) Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

C) paracrine signaling

14) Which of these are not embedded in the hydrophobic portion of the lipid bilayer?

C) peripheral proteins

3) Which of the following types of molecules are the major structural components of the cell membrane?

C) phospholipids and proteins

43) The difference between pinocytosis and receptor-mediated endocytosis is that

C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

27) Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that

C) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.

20) Which of the following is true for the evolution of cell membranes?

D) All components of membranes evolve as a result of natural selection.

29) Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.

18) Over the years, the fluid mosaic model has been refined based on recent experimental findings. In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?

D) The concentration of protein molecules appears to be much higher.

17) Why are lipids and proteins free to move laterally in membranes?

D) There are only weak hydrophobic interactions in the interior of the membrane.

52) Which of the following is true of transcription factors?

D) They control gene expression.

B) The receptor may be inside the nuclear membrane.

D) They might not be able to multiply in response to growth factors from nearby cells.

2) Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes

D) consist of protein molecules embedded in a fluid bilayer of phospholipids.

38) Ions diffuse across membranes through specific ion channels

D) down their electrochemical gradients.

9) When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are

D) integral proteins.

50) When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

D) signal molecule

33) Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

E) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

55) Which of the following statements is true of signal molecules?

E) Protein kinase A activation is one possible result of signal molecules binding to G-protein-coupled receptors.

30) When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?

E) The cell will become turgid.

45) When protein membrane receptors are activated, what usually happens?

E) The receptor changes conformation after binding with signal polypeptides.

34) The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of

E) cotransport.

31) Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

E) facilitated diffusion

57) The function of phosphatases in signal transduction is best described as to

E) inactivate protein kinases and turn off the signal transduction.

26) Water passes quickly through cell membranes because

E) it moves through aquaporins in the membrane.

4) When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

E) the hydrophobic interactions that hold the membrane together are weakest at this point.

12) The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

E) to mediate cell-to-cell recognition.