PRACTICE QUIZ CHAP. 7

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found? 1) on the outside (external) surface of the membrane 2) in the interior of the membrane 3) on the inside (cytoplasmic) surface of the membrane 4) on both hydrophilic surfaces of the membrane but not in the hydrophobic interior 5) Carbohydrates are rarely associated with plasma membranes.

1

Imagine two solutions separated by a selectively permeable membrane that allows water to pass, but not sucrose or glucose. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change? 1) Nothing happens because the two solutions are isotonic to one another. 2) Water enters the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose. 3) Water leaves the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose. 4) The sucrose solution is hypertonic and will gain water because the total mass of sucrose is greater than that of glucose. 5) After the sucrose dissociates to two monosaccharides, water will be osmotically drawn to that side of the membrane.

1

The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? 1) a hypertonic sucrose solution 2) a hypotonic sucrose solution 3) a hypertonic urea solution 4) a hypotonic urea solution 5) pure water

1

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? 1) a large polar molecule 2) a large nonpolar molecule 3) dissolved gases such as oxygen or carbon dioxide 4) a small nonpolar molecule 5) Any of the above would easily diffuse through the membrane.

1

Which one of the following cell structures exhibits selective permeability between a cell and its external environment? 1) the plasma membrane 2) mitochondria 3) chloroplasts 4) endoplasmic reticulum 5) lysosomes

1

Which one of the following molecules is most likely to diffuse freely across the lipid bilayer of the plasma membrane without the involvement of a transport protein? 1) carbon dioxide 2) glucose 3) sodium ion 4) DNA 5) hemoglobin

1

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found? 1) on the outside (external) surface of the membrane 2) in the interior of the membrane 3) on the inside (cytoplasmic) surface 4) in the interior and on the inside surface, but not on the outside surface 5) on either surface of the membrane, but not in the interior of the membrane

2

If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? 1) The red blood cell would burst, and the plant cell would shrink. 2) Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. 3) Seawater is isotonic to both cells. There will be no change in water content of the cells. 4) Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure. 5) The red blood cell would shrink, and the plant cell would gain water.

2

Which of the following correctly describes a general property of all electrogenic pumps? 1) pumps sodium out of the cell and potassium into the cell 2) creates a voltage difference across the membrane 3) can pump a large variety of solutes across a membrane against their concentration gradient 4) a cell with an interior that is positively charged relative to the outside of the cell 5) a cell with a high internal concentration of protons

2

Which of the following structures is most consistent with the selective permeability property of biological membranes? 1) proteins sandwiched between two layers of phospholipid 2) proteins embedded in two layers of phospholipid 3) a layer of protein coating a layer of phospholipid 4) phospholipids sandwiched between two layers of protein 5) a phospholipid bilayer with proteins scattered on the surfaces of the membranes

2

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? 1) The added salt would enter the cell, causing the cell to take up water and swell. 2) Water would enter the cell by osmosis, and the cell would swell. 3) Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. 4) There would be no osmotic movement of water in response to the added salt. 5) The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis.

3

Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____. 1) A; the diffusion gradient there is shallower 2) A; its membrane transport proteins will not be saturated 3) B; the diffusion gradient in cell B is steeper 4) B; the oxygen molecules inside cell B have a higher kinetic energy 5) B; the gradient of oxygen is oriented in the opposite direction compared to cell A

3

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, don't protons move back into the cell through the sucrose-proton cotransport protein? 1) Protons cannot move through membrane transport proteins. 2) Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. 3) The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time. 4) In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient. 5) Protons, unlike other substances, do not diffuse down their concentration gradient.

3

Glucose is a six-carbon sugar that diffuses slowly through artificial membranes. The cells lining the small intestine, however, rapidly move glucose from the gut into their cytoplasm. This occurs whether the gut concentrations of glucose are higher or lower than the glucose concentrations in intestinal cell cytoplasm. Using this information, which transport mechanism is most likely responsible for the glucose transport in intestinal cells? 1) simple diffusion 2) phagocytosis 3) active transport 4) exocytosis 5) facilitated diffusion

3

Which of the following statements about cotransport of solutes across a membrane is correct? 1) Cotransport involves the hydrolysis of ATP by the transporting protein. 2) A cotransport protein is most commonly an ion channel. 3) Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. 4) The sodium-potassium pump is an example of a cotransport protein. 5) In cotransport, both solutes that are being transported are moving down their chemical gradients.

3

Which of the following types of information is (are) most likely to be derived from freeze-fracture of biological samples? 1) the coded information in DNA 2) thin sections (slices) of fixed and embedded cells 3) proteins embedded in membrane bilayers 4) patterns of movement in living cells 5) all of the above

3

Which one of the following pairs correctly matches a membrane transport process to its primary function? 1) phagocytosis; secretion of large particles from the cell by fusion of vesicles with the plasma membrane 2) exocytosis; the movement of water and solutes out of the cell by vesicle fusion with the plasma membrane 3) pinocytosis; the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane. 4) osmosis; passive diffusion of water and small solutes across a membrane 5) none of the above

3

Which one of the following statements about diffusion is true? 1) It is very rapid over long distances. 2) It requires expenditure of energy by the cell. 3) It is a passive process. 4) It occurs when molecules move from a region of lower concentration to a region of higher concentration. 5) It always requires integral proteins of the cell membrane.

3

Which one of the following statements about the sodium-potassium pump is correct? 1) The sodium-potassium pump transports Na+ and K+ ions across the plasma membrane in the same direction at the expense of ATP hydrolysis. 2) The sodium-potassium pump creates a hydrogen gradient. 3) The sodium-potassium pump is electrogenic. 4) The sodium-potassium pump causes a pH gradient across the plasma membrane. 5) The sodium-potassium pump creates concentration gradients of O+ and Cl- across the plasma membrane.

3

The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution? 1) distilled water 2) 0.4 M 3) 0.8 M 4) 1.0 M 5) none of the above

4

The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? 1) The fluid component of the membrane is composed of phospholipids, and the mosaic part is composed of carbohydrates. 2) The fluid aspect of the membrane describes its structure at normal temperatures, and the mosaic aspect describes the membrane as the temperature is lowered. 3) The mosaic comprises the carbohydrate chains on the inner surface of the membrane. 4) The fluid component of the membrane is phospholipid, and the mosaic is protein. 5) Only phospholipids are capable of moving in the membrane.

4

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? 1) passive transport 2) facilitated diffusion 3) osmosis 4) receptor-mediated endocytosis 5) channel proteins

4

Which of the following processes, normally associated with membrane transport, must occur to account for an increase in the surface area of a cell? 1) endocytosis 2) active transport 3) receptor-mediated endocytosis 4) exocytosis 5) flip-flop of phospholipids from one side of the plasma membrane to the other

4

Which of the following statements about the role of phospholipids in forming membranes is correct? 1) Phospholipids are completely insoluble in water. 2) Phospholipids form a single sheet in water. 3) Phospholipids form a structure in which the hydrophobic portion faces outward. 4) Phospholipids form a selectively permeable structure. 5) They are triacylglycerols, which are commonly available in foods.

4

Which of these statements describes some aspect of facilitated diffusion? 1) Facilitated diffusion is another name for osmosis. 2) Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. 3) Facilitated diffusion requires energy to drive a concentration gradient. 4) Facilitated diffusion of solutes may occur through protein pores in the membrane. 5) There is only one kind of protein pore for facilitated diffusion.

4

Which one of the following statement concerning carbohydrates associated with the plasma membrane is correct? 1) Carbohydrates are only found associated with the membranes of prokaryotic cells. 2) The carbohydrate composition of most eukaryotic plasma membranes is quite similar. 3) Carbohydrates on the plasma membrane are typically short chains of 2-5 monosaccharides. 4) Membrane carbohydrates function primarily in cell-cell recognition. 5) Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane.

4

A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell? 1) movement of Ca2+ into the cell through an ion channel down its concentration gradient 2) passive diffusion of Ca2+ into the cell down its electrochemical gradient 3) cotransport of Ca2+ into the cell with Cl- ions 4) movement of Ca2+ into the cell through a carrier protein down its electrical gradient 5) facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

5

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process? 1) osmosis 2) passive transport 3) exocytosis 4) active transport 5) endocytosis

5

Active transport requires a cell to expend energy. Which of the following statements is true? 1) Active transport often involves an ATP-powered ion pump and a cotransport protein. 2) Active transport usually uses ATP as its energy source. 3) Active transport moves solutes against the concentration gradient. 4) Active transport requires a protein carrier. 5) all of the above

5

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent contamination by microorganisms? 1) Bacterial cells shrivel up in high salt solutions, causing the cell to burst. 2) High salt concentration lowers the pH, thus inhibiting bacterial metabolism. 3) High salt concentration raises the pH, thus inhibiting bacterial metabolism. 4) A 30% salt solution is hypotonic to the bacteria, so they gain too much water and burst. 5) A 30% salt solution is hypertonic to the bacteria, so they lose too much water and cannot survive.

5

The transmission of nerve impulses between adjacent nerve cells requires the release of a neurotransmitter (a molecule or small peptide) by exocytosis. Which of the following would best reverse the process that resulted in the release of neurotransmitter, returning the cell to its original state? 1) endocytosis 2) pinocytosis 3) active transport of the neurotransmitter back into the cell 4) passive transport (by facilitated diffusion) of the neurotransmitter back into the cell 5) receptor-mediated endocytosis

5

Which of the following functional processes result(s) from the presence of proteins in or on the plasma membrane? 1) enzymatic activity 2) cell-cell recognition 3) intercellular joining 4) cell-cell communication 5) all of the above

5

Which of the following is (are) true about facilitated diffusion? 1) Facilitated diffusion requires a concentration gradient. 2) Facilitated diffusion requires a membrane. 3) Facilitated diffusion involves proteins. 4) Facilitated diffusion does not involve an outside energy source. 5) all of the above

5

Which of the following is a correct difference between active transport and facilitated diffusion? 1) Active transport involves transport proteins, and facilitated diffusion does not. 2) Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. 3) Active transport can move solutes in either direction across a membrane, but facilitated diffusion can only move in one direction. 4) Facilitated diffusion involves transport proteins, and active transport does not. 5) Active transport requires energy from ATP, and facilitated diffusion does not.

5

Which of the following is/are a function of membrane proteins? 1) Membrane proteins attach the membrane to the cytoskeleton. 2) Membrane proteins provide receptors for chemical messengers. 3) Membrane proteins form channels, which move substances across the membrane. 4) Membrane proteins with short sugar chains form identification tags that are recognized by other cells. 5) all of the above

5

Which of the following statements about passive transport is correct? 1) Passive transport operates independently of diffusion. 2) Passive transport operates independently of the concentrations of the substance being transported. 3) In passive transport, all movement of the transported molecule stops when its concentration is the same on both sides of the membrane. 4) Passive transport does not occur in the human body. 5) Passive transport permits the transported molecule to move in either direction, but the majority of transport occurs down the concentration gradient of the molecule.

5

Which statement(s) about the sidedness of the plasma membrane is (are) correct? 1) Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. 2) The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. 3) Every integral membrane protein has a specific orientation in the plasma membrane. 4) The two lipid layers may differ in specific lipid composition. 5) all of the above

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