Chapter 7

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

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.

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?

1.0 M

Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?

A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis.

Which of the following is a correct difference between active transport and facilitated diffusion? (Concept 7.4) SHOW HINT Active transport requires energy from ATP, and facilitated diffusion does not. Facilitated diffusion involves transport proteins, and active transport does not. Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. Facilitated diffusion requires carrier proteins, but active transport requires channel proteins. Active transport involves transport proteins, and facilitated diffusion does not.

Active transport requires energy from ATP, and facilitated diffusion does not.

Which statements about the sidedness of the plasma membrane is correct? (Concept 7.1) SHOW HINT Every integral membrane protein has a specific orientation in the plasma membrane. The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. 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. The two lipid layers may differ in specific lipid composition. All of the listed responses are correct.

All correct

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B. and cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.

B ... the diffusion gradient in cell B is steeper

Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells. If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?

Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.

Which of the following statements about cotransport of solutes across a membrane is correct? (Concept 7.4) SHOW HINT The sodium-potassium pump is an example of a cotransport protein. Cotransport involves the hydrolysis of ATP by the transporting protein. Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. In cotransport, both solutes that are being transported are moving down their chemical gradients. A cotransport protein is most commonly an ion channel.

Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes.

Which of the following correctly describes a general property of all electrogenic pumps? (Concept 7.4) SHOW HINT Electrogenic pumps result in a cell with an interior that is positively charged relative to the outside of the cell. Electrogenic pumps create a voltage difference across the membrane. Electrogenic pumps can pump a large variety of solutes across a membrane against their concentration gradient. Electrogenic pumps pump sodium out of the cell and potassium into the cell. Electrogenic pumps result in a cell with a high internal concentration of protons.

Electrogenic pumps create a voltage difference across the membrane.

Which of the following is FALSE in regard to facilitated diffusion? Facilitated diffusion requires a concentration gradient. Facilitated diffusion can occur by means of transport proteins. Facilitated diffusion can move ions across membranes. Facilitated diffusion requires the hydrolysis of ATP. Facilitated diffusion can occur through protein channels.

Facilitated diffusion requires the hydrolysis of ATP.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? (Concept 7.1) SHOW HINT Carbohydrates are found associated with the membranes of prokaryotic cells only. The carbohydrate composition of most eukaryotic plasma membranes is quite similar. Membrane carbohydrates function primarily in cell-cell recognition. Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane. Carbohydrates on the plasma membrane are typically long, complex chains of several dozen monosaccharides.

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following functions of membrane proteins is important in tissue formation during embryonic development in animals? (Concept 7.1) SHOW HINT Membrane proteins attach the membrane to the cytoskeleton. Membrane proteins with short sugar chains form identification tags that are recognized by other cells. Membrane proteins possess enzymatic activity. Membrane proteins form channels, which move substances across the membrane. All of the listed responses are correct.

Membrane proteins with short sugar chains form identification tags that are recognized by other cells.

A selectively permeable membrane separates two solutions. Water is able to pass through this membrane; however, sucrose (a disaccharide) and glucose (a monosaccharide) cannot pass. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change?

Nothing will happen, because the two solutions are isotonic to one another.

Which of the following statements about passive transport is correct? (Concept 7.3) SHOW HINT Passive transport does not occur in the human body. In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane. Passive transport operates independently of the concentrations of the moving solute. Passive transport operates independently of diffusion. Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule.

Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct? (Concept 7.1) SHOW HINT Phospholipids are completely unable to interact with water. Phospholipids form a single sheet in water. They are triacylglycerols, which are commonly available in foods. Phospholipids form a selectively permeable structure. Phospholipids form a structure in which the hydrophobic portion faces outward.

Phospholipids form a selectively permeable structure.

The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? (Concept 7.1) SHOW HINT The mosaic aspect of the membrane is due to the glycosylation of phospholipids on the cytoplasmic side of the membrane. Only phospholipids are capable of moving in the membrane. The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect. The fluid aspect of the membrane describes its structure at normal temperatures, and the mosaic aspect describes the behavior of the membrane as the temperature is lowered. The fluid aspect of the membrane is due to the behavior of phospholipids, and the mosaic aspect is due to the presence of carbohydrates.

The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.

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, do protons not move back into the cell through the sucrose-proton cotransport protein?

The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time.

ctive transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true? (Concept 7.4) SHOW HINT Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane. The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane. The source of energy for active transport of a solute up its gradient can be ATP or a concentration gradient of a second solute. This second gradient of solutes maintains no net difference in voltage across the membrane. Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this. Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell.

The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane.

Glucose can be moved into cells via an active transport mechanism when the concentration of glucose inside the cell is higher than the concentration of glucose outside of the cell. This active transport mechanism moves glucose and sodium into the cell at the same time. The glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is accurate? (Concept 7.4) SHOW HINT Sodium and glucose move together into the cell via facilitated diffusion. The distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. To pump glucose up its concentration gradient, sodium moves down its concentration gradient. Sodium and glucose move together into the cell via facilitated diffusion, and to pump glucose up its concentration gradient, sodium moves down its concentration gradient. To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism.

To pump glucose up its concentration gradient, sodium moves down its concentration gradient, and the distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism.

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? There would be no osmotic movement of water in response to the added salt. The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis. Water would enter the cell by osmosis, and the cell would swell. The added salt would enter the cell, causing the cell to take up water and swell. Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

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? a hypertonic urea solution a hypertonic sucrose solution pure water a hypotonic urea solution a hypotonic sucrose solution

a hypertonic sucrose solution

Which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein? (Concept 7.2) SHOW HINT dissolved gases such as oxygen or carbon dioxide a small, nonpolar molecule a large, polar molecule a large, nonpolar molecule Any of the listed molecules would easily diffuse through the membrane.

a large polar molecule

Which of the following molecules is most likely to passively diffuse across the plasma membrane? (Concept 7.2) SHOW HINT sodium ion carbon dioxide glucose hemoglobin DNA

carbon Dioxide

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?

endocytosis

Which of the following is NOT a function of membrane proteins? enzymatic activity transport cell-cell recognition intercellular joining energy, carbon, and nitrogen storage

energy, carbon, and nitrogen storage

Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane? (Concept 7.5) SHOW HINT receptor-mediated endocytosis and smooth ER and Golgi active transport and the rough ER exocytosis and smooth ER and rough ER flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi endocytosis and Golgi

exocytosis and smooth ER and rough ER

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? (Concept 7.4) SHOW HINT movement of Ca2+ into the cell through a carrier protein down its electrical gradient passive diffusion of Ca2+ into the cell down its electrochemical gradient movement of Ca2+ into the cell through an ion channel down its concentration gradient facilitated diffusion of Ca2+ into the cell down its electrochemical gradient cotransport of Ca2+ into the cell with Cl-

facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

in the interior of the membrane

Which of the following statements about diffusion is true? (Concept 7.3) SHOW HINT It always requires integral proteins of the cell membrane. It requires expenditure of energy by the cell. It is a passive process. It occurs when molecules move from a region of lower concentration to a region of higher concentration. It involves only the movement of water molecules.

it is a passive process

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?

on the outside (external) surface of the membrane

Which of the following pairs correctly matches a membrane transport process to its primary function? (Concept 7.5) SHOW HINT phagocytosis: secretion of large particles from the cell by fusion of vesicles with the plasma membrane osmosis: passive diffusion of water and small solutes across a membrane pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane exocytosis: the movement of water and solutes out of the cell by vesicle fusion with the plasma membrane None of the listed responses is correct.

pinocytosis: the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? (Concept 7.5) SHOW HINT facilitated diffusion osmosis channel proteins passive transport receptor-mediated endocytosis

receptor-mediated endocytosis