Bio chapter 7 website

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

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? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) 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 facilitated diffusion of Ca2+ into the cell down its electrochemical gradient movement of Ca2+ into the cell through an ion channel down its concentration gradient cotransport of Ca2+ into the cell with Cl-

endocytosis

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? (see book section: Concept 7.5: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis) endocytosis passive transport osmosis active transport exocytosis

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

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) The sucrose solution is hypertonic and will gain water because the total mass of sucrose is greater than that of glucose. Nothing will happen, because the two solutions are isotonic to one another. After the sucrose dissociates into two monosaccharides, water will move via osmosis to the side of the membrane that contains the dissociated sucrose. Water will enter the sucrose solution because the sucrose molecule is a disaccharide and, thus, larger than the monosaccharide glucose. Water will leave the sucrose solution because the sucrose molecule is a disaccharide and, thus, larger than the monosaccharide glucose.

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

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. 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. 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.

embedded in a lipid bilayer.

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly spread in a continuous layer over the inner and outer surfaces of the membrane. confined to the hydrophobic interior of the membrane. embedded in a lipid bilayer. free to depart from the fluid membrane and dissolve in the surrounding solution. randomly oriented in the membrane, with no fixed inside-outside polarity.

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

Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) 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. The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane. Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell. Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this. Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane.

decreasing extracellular pH

Based on Figure 7.18, which of these experimental treatments would increase the rate of sucrose transport into the cell? decreasing cytoplasmic pH adding a substance that makes the membrane more permeable to hydrogen ions decreasing extracellular pH decreasing extracellular sucrose concentration adding an inhibitor that blocks the regeneration of ATP

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

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 __________. (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) A ... its membrane transport proteins will not be saturated A ... the concentration gradient there is shallower B ... the gradient of oxygen is oriented in the opposite direction compared to cell A B ... the diffusion gradient in cell B is steeper B ... the oxygen molecules inside cell B have a higher kinetic energy

on the outside (external) surface of the membrane

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found? (see book section: Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins) Carbohydrates are rarely associated with plasma membranes. on the outside (external) surface of the membrane on the inside (cytoplasmic) surface of the membrane in the interior of the membrane on both hydrophilic surfaces of the membrane but not in the hydrophobic interior

in the interior of the membrane

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found? (see book section: Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins) on the inside (cytoplasmic) surface on either surface of the membrane, but not in the interior of the membrane in the interior and on the inside surface, but not on the outside surface in the interior of the membrane on the outside (external) surface of the membrane

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

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? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient. Protons cannot move through membrane transport proteins. The movement of protons through the cotransport protein cannot occur unless sucrose moves at the same time. Protons, unlike other substances, do not diffuse down their electrochemical 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.

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? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) Sodium and glucose move together into the cell via facilitated diffusion. To pump glucose up its concentration gradient, sodium moves down its concentration gradient. The distribution of sodium ions across the membrane forms an electrochemical gradient that drives this mechanism. 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.

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

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) High salt concentration raises the pH, thus inhibiting bacterial metabolism. A 30% salt solution is hypertonic to the bacteria, so they lose too much water and undergo plasmolysis. High salt concentration lowers the pH, thus inhibiting bacterial metabolism. A 30% salt solution is hypotonic to the bacteria, so they gain too much water and burst. Bacterial cells shrivel up in high salt solutions, causing the cell to burst.

Certain proteins are unique to each membrane.

In what way do the membranes of a eukaryotic cell vary? Phospholipids are found only in certain membranes. Only certain membranes are constructed from amphipathic molecules. Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm. Only certain membranes of the cell are selectively permeable. Certain proteins are unique to each membrane.

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

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure. The red blood cell would burst, and the plant cell would shrink. Both cells will gain water, but cell walls will prevent both cells from bursting. Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. The red blood cell would shrink, and the plant cell would gain water.

a hypertonic sucrose solution

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) a hypertonic urea solution pure water a hypotonic urea solution a hypertonic sucrose solution a hypotonic sucrose solution

1.0 M

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? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) distilled water 1.0 M 0.8 M 0.4 M 150 mM.

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 plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? (see book section: Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins) Only phospholipids are capable of moving in the membrane. 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 mosaic aspect of the membrane is due to the glycosylation of phospholipids on the cytoplasmic side of 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 is due to the behavior of phospholipids, and the mosaic aspect is due to the presence of carbohydrates.

the plasma membrane

Which of the following cell structures exhibits selective permeability between a cell and its external environment? (see book section: Overview: Life at the Edge) the plasma membrane lysosomes mitochondria chloroplasts endoplasmic reticulum

Electrogenic pumps create a voltage difference across the membrane.

Which of the following correctly describes a general property of all electrogenic pumps? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) Electrogenic pumps result in a cell with a high internal concentration of protons. Electrogenic pumps can pump a large variety of solutes across a membrane against their concentration gradient. 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 pump sodium out of the cell and potassium into the cell.

receptor-mediated endocytosis

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? (see book section: Concept 7.5: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis) channel proteins passive transport osmosis receptor-mediated endocytosis facilitated diffusion

a greater proportion of unsaturated phospholipids

Which of the following factors would tend to increase membrane fluidity? a lower temperature a relatively high protein content in the membrane a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses a greater proportion of saturated phospholipids a greater proportion of unsaturated phospholipids

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

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

Facilitated diffusion requires the hydrolysis of ATP.

Which of the following is FALSE in regard to facilitated diffusion? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) Facilitated diffusion can move ions across membranes. Facilitated diffusion requires the hydrolysis of ATP. Facilitated diffusion requires a concentration gradient. Facilitated diffusion can occur by means of transport proteins. Facilitated diffusion can occur through protein channels.

energy, carbon, and nitrogen storage

Which of the following is NOT a function of membrane proteins? (see book section: Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins) intercellular joining enzymatic activity transport cell-cell recognition energy, carbon, and nitrogen storage

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

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

carbon dioxide

Which of the following molecules is most likely to passively diffuse across the plasma membrane? (see book section: Concept 7.2: Membrane structure results in selective permeability) carbon dioxide glucose sodium ion hemoglobin DNA

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

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

exocytosis and smooth ER and rough ER

Which of the following processes and organelles account for the replacement of lipids and proteins lost from the plasma membrane? (see book section: Concept 7.5: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis) endocytosis and Golgi exocytosis and smooth ER and rough ER flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi receptor-mediated endocytosis and smooth ER and Golgi active transport and the rough ER

passive transport

Which of the following processes includes all others? facilitated diffusion osmosis transport of an ion down its electrochemical gradient diffusion of a solute across a membrane passive transport

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

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

It is a passive process.

Which of the following statements about diffusion is true? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) It always requires integral proteins of the cell membrane. It is a passive process. It requires expenditure of energy by the cell. It involves only the movement of water molecules. It occurs when molecules move from a region of lower concentration to a region of higher concentration.

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 passive transport is correct? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane. 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 does not occur in the human body. Passive transport operates independently of the concentrations of the moving solute.

Phospholipids form a selectively permeable structure.

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

The sodium-potassium pump moves Na+ and K+ in opposite directions, resulting in a net negative charge inside the cell.

Which of the following statements about the sodium-potassium pump is correct? (see book section: Concept 7.4: Active transport uses energy to move solutes against their gradients) The sodium-potassium pump transports Na+ and K+ across the plasma membrane in the same direction at the expense of ATP hydrolysis. The sodium-potassium pump moves Na+ and K+ in opposite directions, resulting in a net negative charge inside the cell. The sodium-potassium pump uses an existing proton gradient to drive the movement of sodium and potassium ions. The sodium-potassium pump moves sodium out of the cell and co-transports protons into the cell, which is the source of energy for the movement of the potassium into the cell. The sodium-potassium pump moves Na+ and K+ in the same direction, resulting in a net negative charge outside the cell.

Membrane carbohydrates function primarily in cell-cell recognition.

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

a large, polar molecule

Which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein? (see book section: Concept 7.2: Membrane structure results in selective permeability) dissolved gases such as oxygen or carbon dioxide a large, nonpolar molecule a large, polar molecule a small, nonpolar molecule Any of the listed molecules would easily diffuse through the membrane.

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

Which of these statements describes some aspect of facilitated diffusion? (see book section: Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment) Facilitated diffusion requires energy to drive a concentration gradient. 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. Facilitated diffusion is another name for osmosis. There is only one kind of protein pore for facilitated diffusion.

All of the listed responses are correct.

Which statements about the sidedness of the plasma membrane is correct? (see book section: Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins) 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.