Chapter 7 Bio 1107
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? (eText Concept 7.3)
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? (eText Concept 7.3)
A 30% salt solution is hypertonic to the bacteria, so they lose too much water and plasmolyze.
Which of the following is a correct difference between active transport and facilitated diffusion? (eText Concept 7.4)
Active transport requires energy from ATP, and facilitated diffusion does not.
Which statement(s) about the sidedness of the plasma membrane is/are correct? (eText Concept 7.1)
All of the listed responses are correct. * 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. * 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. * All of the listed responses are correct.
Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell _____ because _____. (eText Concept 7.3)
B ... the diffusion gradient in cell B is steeper
f a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? (eText Concept 7.3) * The red blood cell would burst, and the plant cell would shrink. * 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 isotonic to both cells, therefore, neither cell will change as there will be no movement of water into or out of the cells. * The red blood cell would shrink, and the plant cell would gain water. * Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure.
Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. Correct. Seawater is hypertonic to both cells and will cause the cells to lose wat
Which of the following statements about cotransport of solutes across a membrane is correct? (eText Concept 7.4)
Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. Correct. The electrochemical gradient created by a single ATP-dependent pump can drive the transport of many different solutes using cotransport proteins.
Which of these statements describes some aspect of facilitated diffusion? (eText Concept 7.3)
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. No. Facilitated diffusion occurs through integral membrane transport proteins.
Which of the following is false in regard to facilitated diffusion? (eText Concept 7.3)
Facilitated diffusion requires the hydrolysis of ATP.
The discomfort associated with irritable bowel syndrome can be alleviated with low doses of the class of antidepressants that block the reuptake of serotonin from the synaptic cleft (the space between adjacent neurons). Serotonin is a relatively small polar neurotransmitter used to transmit nerve impulses in the nerve tissue in the gut and central nervous system. Serotonin is transported back into the releasing neuron up its concentration gradient and down a sodium gradient. How might an antidepressant block serotonin reuptake by the releasing neuron? (eText Concept 7.4) * It could promote exocytosis of serotonin. * It could block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter. * It could block receptor-mediated endocytosis. * It could block a cotransporter involved in facilitated diffusion * It could block the passive diffusion of serotonin back into the cell by chemically modifying serotonin.
It could block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter.
Which of the following statements about diffusion is true? (eText Concept 7.3)
It is a passive process.
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? (eText Concept 7.1)
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?
Membrane proteins with short sugar chains form identification tags that are recognized by other cells
Which of the following is a function of membrane proteins and also facilitates tissue formation during embryogenesis? (eText Concept 7.1) * 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 form channels, which move substances across the membrane. * Membrane proteins provide receptors for chemical messengers. * 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? (eText Concept 7.3)
Nothing happens because the two solutions are isotonic to one another. Correct. Osmotic pressure is produced by the concentration of dissolved substances and is not influenced by the relative sizes of the solutes.
Which of the following statements about passive transport is correct? (eText Concept 7.3)
Passive transport permits the solute to move in either direction, but the net movement of the population of solute occurs down the concentration gradient of the molecule. Correct. Passive transport can occur in either direction, but the direction of net diffusion is down the concentration gradient of the solute.
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct? (eText Concept 7.1)
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? (eText Concept 7.1)
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, don't protons move back into the cell through the sucrose-proton cotransport protein? (eText Concept 7.4)
The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time.
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? (eText Concept 7.4)
The sodium/potassium pump hydrolyzes ATP and results in a net charge of +1 outside the cell membrane.
Glucose can be moved into cells via an active transport mechanism can be used 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 most true? (eText Concept 7.4)
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? (eText Concept 7.3)
Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. Correct. The added salt makes the solution hypertonic compared to the cell. Water will leave the cell by osmosis.
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? (eText Concept 7.3)
a hypertonic sucrose solution Correct. When a cell is placed in a hypertonic environment, water will leave the cell, causing it to shrink.
Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? (eText Concept 7.2)
a large polar molecule
Which of the following molecules is most likely to passively diffuse across the plasma membrane? (eText Concept 7.2)
carbon dioxide
Which of the following correctly describes a general property of all electrogenic pumps? (eText Concept 7.4)
create a voltage difference across the membrane Correct. An electrogenic pump creates a net charge difference across a membrane (a membrane potential).
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? (eText Concept 7.5)
endocytosis Correct. Endocytosis is the procedure that cells use to import large molecules across their plasma membrane.
Which of the following functional processes is not a consequence of the association of proteins with biological membranes? (eText Concept 7.1) * cell-cell communication * intercellular joining * enzymatic activity * cell-cell recognition * energy, carbon, and nitrogen storage
energy, carbon, and nitrogen storage
Which of the following is NOT a function of membrane proteins?
energy, carbon, and nitrogen storage
Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane? (eText Concept 7.5)
exocytosis and smooth and rough ER No. Although the Golgi is involved in the shipment of phospholipids to the plasma membrane, endocytosis is a process that removes phospholipids from the plasma membrane by budding off of small vesicles.
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? (eText Concept 7.4)
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? (eText Concept 7.1)
in the interior of the membrane No. Cholesterol is hydrophobic and will be found in the interior of the bilayer membrane.
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found? (eText Concept 7.1)
on the outside (external) surface of the membrane
Which of the following pairs correctly matches a membrane transport process to its primary function? (eText Concept 7.5)
pinocytosis ... the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane No. In phagocytosis (cellular eating), a type of endocytosis, a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane-enclosed sac large enough to be classified as a food vacuole
Which of the following types of information is/are most likely to be derived from freeze-fracture of biological samples? (eText Concept 7.1)
proteins embedded in membrane bilayers No. A freeze-fracture does not sequence DNA nucleotides.
Which of the following structural arrangements of the components in biological membranes is most consistent with membrane's property of selective permeability? (eText Concept 7.2) * proteins embedded in two layers of phospholipid * a layer of protein coating a layer of phospholipid * a phospholipid bilayer with proteins scattered on the surfaces of the membranes * phospholipids sandwiched between two layers of protein * proteins sandwiched between two layers of phospholipid
proteins embedded in two layers of phospholipid
Which of the following enables a cell to pick up and concentrate a specific kind of molecule? (eText Concept 7.5)
receptor-mediated endocytosis Correct. In receptor-mediated endocytosis, only a specific molecule, called a ligand, can bind to the receptor. Without receptor binding occurring first, endocytosis does not proceed.
Which of the following cell structures exhibits selective permeability between a cell and its external environment? (eText Overview)
the plasma membrane
Which of the following statements about the sodium-potassium pump is correct? (eText Concept 7.4) * The sodium-potassium pump is a symporter that results in a net negative charge outside the cell. * 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 uses an existing proton gradient to drive the movement of sodium and potassium ions. * The sodium-potassium pump is an antiporter that results in a net negative charge inside the cell. * 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 is an antiporter that results in a net negative charge inside the cell.
