Chapter 7
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
which statement(s) about the wideness of the plasma membrane is/are correct?
ALL. every integral membrane protein has specific orientation, proteins exposed on both ER & cytoplasmic side, distribution determined during membrane construction, & 2 lipid layers may differ in specific lipid composition.
cells A & B are the same size, shape, & temp, 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 _____ b/c _______.
B.....the diffusion gradient in cell B is steeper
green olives may be preserved in brine, which is 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 & plasmolyze
which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein?
a large polar molecule
which of the following is a correct difference between active transport and facilitated diffusion?
active transport requires energy from ATP, and facilitated diffusion doesn't
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 loose water; rbc would shrivel and plant plasma membrane would pull away from the cell wall
in what way do the membrane of a eukaryotic cell vary?
certain proteins are unique to each membrane
based on figure 7.21, which of the experimental treatments would increase the rate of sucrose transport into the cell?
decreasing extracellular pH
according to the fluid mosaic model of membrane structure, proteins of the membrane are mostly...
embedded in lipid bilayer
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 functional process is not a consequence of the association of proteins with biological membranes?
energy, carbon, and nitrogen storage
which of the following processes and organelle(s) accounts for replacement of lipids and proteins lost from the plasma membrane?
exocytosis and smooth and rough ER
which of these statements describes some aspect of facilitated diffusion?
facilitated diffusion of solutes may occur through channel or transport proteins in the membrane
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 & urea can. osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?
hypertonic sucrose solution
which of the following statements concerning carbs associated with the plasma membrane is correct?
membrane carbohydrates function primarily in cell-cell recognition
which of the following is a function of membrane proteins and also facilitates tissue formation during embryogenesis?
membrane proteins with short sugar chains from identification tags that are recognized by other cells
which of the following processes includes all the others?
passive transport
which of the following statements about passive transport is correct?
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.
which of the following cell structures exhibits selective permeability between a cell and its external environment?
plasma membrane
which of the following is false in regard to facilitated diffusion?
requires hydrolysis of ATP
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 sucrose-proton con transport protein?
the movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time.
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 salt addition?
water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.
which of the following molecules is most likely to passively diffuse across the plasma membrane?
carbon dioxide
the discomfort associated w/IBS can be alleviated with low doses of the class of antidepressants that block the reuptake of serotonin from the synaptic cleft. Serotonin is a relatively small polar neurotransmitter used to transmit nerve impulses in the nerve tissue in the gut & CNS. 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?
block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter
which of the following statements about cotransport of solutes across a membrane is correct?
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?
create a voltage difference across the membrane
a cell has a membrane potential of -100 mV (more - inside than outside) & has 1,000X more calcium ions outside the cell than inside. which of the following best describes a mechanism by which Ca2+ enters the cell?
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?
interior of membrane
which of the following statements about diffusion is true?
it is a passive process
a selectively permeable membrane separates two solutions. water is able to pass through this membrane, however, sucrose (disaccharide) and glucose (mono) 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
consider the currently accepted fluid mosaic model of the plasma membrane. where in the membrane would carbs 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?
phinocytosis: uptake of water and small solutes into the cell by formation of vesicles at plasma membrane
which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
phospholipids form a selectively permeable structure
which of the following types of information is/are most likely to be derived from freeze-fracture of biological samples?
proteins embedded in membrane bilayers
which of the following structural arrangements of the components in biological membranes is most consistent with membrane's property of selective permeability?
proteins embedded in two layers of phospholipid
which of the following enables a cell to pick up and concentrate a specific kind of molecule?
receptor-mediated endocytosis
which of the following statements about the sodium-potassium pump is correct?
the sodium-potassium pump is an anti porter that results in a net negative charge inside the cell
active transport requires an input of energy and can also generate voltages across the membrane. based on this info, which of the following statements is true?
the sodium/potassium pump hydrolyzes ATP and results in a net charge of +1 outside cell membrane
