bio: ch 2

submerging a plant cell in distilled water will result in... a) plasmyolysis of the cell b) the cell becoming flaccid c) lysis of the cell membrane d) the cell becoming turgid e) bursting of the cell

d

what kinds of molecules pass through a cell membrane most easily? a) large and hydrophilic b) large polar c) large hydrophobic d) small ionic e) small hydrophobic

e

which of the following statements about diffusion is correct? a) requires an expenditure of energy by the cell b) very rapid over long distances c) passive process in which molecules move from region of lower concentration to a region of higher concentration d) active process in which molecules move from a region of lower concentration to one of higher concentration e) passive process in which molecules move from a region of higher concentration to a region of lower concentration

e

water potential

the physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure

______ proteins allow passage of hydrophilic substances across the membrane

transport

saturated fats/fatty acids

- fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms attached to the carbon skeleton - straight - saturated tails pack together -> more solid - ex; solid butter

unsaturated fats/fatty acids

- fatty acid that has one or more double bonds between carbons in the hydrocarbon tail. such bonding reduces the number of hydrogen atoms attached to the carbon skeleton - has bend - unsaturated fats prevent packing -> more fluid - ex; olive oil

plasma membrane

- selectively-permeable phospholipid bilayer forming the boundary of the cells - separates the cells' internal and external environments

hypertonic solution

- solute concentration is greater outside than inside the cell - cell loses water - cell lyses

hypotonic solution

- solute concentration is less than inside the cell - cell gains water - animal cells burst; plant cells expand

isotonic solution

- solute concentration is the same as inside the cell - no net water movement across the plasma membrane - cell remains the same

co-transport

- the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient - movement of one solute down its gradient provides the energy to pump another solute against its gradient - passive process causes active process

osmosis

- the diffusion of free water molecules across a selectively permeable membrane

active transport

- the movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy - uses energy to move solutes against their gradient - allows cells to maintain their concentration gradients that differ from their surroundings

receptor-mediated endocytosis

- the movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances - allows for intake of specific substances that bind to the receptor - ex; cholesterol, LDL receptor

membrane protein functions

- transport - enzymatic activity - signal transduction

the mechanism by which testosterone (a steroid hormone) alters cell function is by... a) binding to a cytoplasmic receptor that enters the nucleus and activates specific genes b) binding a g protein which leads to production of cAMP c) serving as a second messenger in transduction d) binding to a plasma membrane receptor and initiating a phosphorylation cascade

a

which of the following factors would tend to increase membrane fluidity? a) a greater proportion of unsaturated phospholipids b) a greater proportion of saturated phospholipids c) a relatively high protein content in the membrane d) a lower temperature

a

which of the following molecules would you expect to diffuse through the lipid bilayer of a plasma membrane most rapidly? a) o2 b) glucose c) amino acid d) na+ e) starch

a

which of the following processes could result in the net movement of a substance into a cell if the substance is more concentrated in the cell than in the surroundings? a) active transport b) facilitated diffusion c) diffusion d) osmosis

a

pressure potential

a component of water potential that consists of the physical pressure on a solution, which can be positive, zero, or negative

solute potential

a component of water potential that is proportional to the molarity of a solution and that measures the effect of solutes on the direction of water movement; also called osmotic potential, it can be either zero or negative

selective permeability

a property of biological membranes that allows them to regulate the passage of substances across them

large molecules are moved out of the cell by which of the following processes? a) endocytosis b) exocytosis c) translocation d) passive diffusion

b

active transport uses energy to move solutes ________ their gradient

against

a patient has had a serious accident and lost a lot of blood. in an attempt to replenish bodily fluids, distilled water- equal to the volume of blood lost- is transferred directly into one of his veins. what will be the most probable result of this transfusion? a) patient's red blood cells will shrivel up because the fluid surrounding the blood cells has become hypertonic compared to the cells b) the patient's red blood cells will swell because the fluid surrounding the blood cells has become hypotonic compared to the cells c) the patient's red blood cells will swell because the fluid surrounding the blood cells has become hypertonic compared to the cells d) the patient's red blood cells will shrivel up because the fluid surrounding the blood cells has become hypotonic compared to the cells

b

the cell membranes of antarctic ice fish living in very cold waters might have which of the following adaptations to maintain membrane fluidity? a) a high percentage of saturated fatty acids b) a high percentage of unsaturated fatty acids c) a low percentage of unsaturated fatty acids d) none of the above

b

mammalian blood contains the equivalent of 0.15 M NaCl. seawater contains the equivalent of 0.45 M NaCl. what will happen if red blood cells are transferred to seawater? a) NaCl will passively diffuse into the red blood cells b) NaCl will be exported from the red blood cells by facilitated diffusion c) water will leave the cells, causing them to shrivel and collapse d) the blood cells will take up water, swell, and eventually burst

c

the phosphate transport system in bacteria imports phosphate into the cell against the phosphate concentration gradient. the energy for phosphate import is provided by a pH gradient across the membrane (lower pH outside the cell than inside the cell), rather than by atp hydrolysis. the bacterial phosphate transport system is an example of... a) facilitated diffusion b) passive diffusion c) co-transport d) active transport e) receptor-mediated endocytosis

c

endocytosis

cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane

fluid mosaic model

currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids

glucose diffuses slowly through artificial phospholipid bilayers. the cells lining the small intestine, however, rapidly moves large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. based on this information, which transport mechanism is most likely responsible for glucose transport in the intestinal cells? a) active transport pumps b) simple diffusion c) sodium potassium pump d) facilitated diffusion

d

which of the following uses passive transport, without protein channels, to move materials across the membrane? a) depolarization of a muscle cell b) uptake of glucose by the microvilli of cells lining the stomach c) movement of insulin across the cell membrane d) movement of carbon dioxide across the cell membrane

d

the fluid mosaic model describes the plasma membrane as consisting of...

diverse proteins embedded in a phospholipid bilayer

thinking about the environments where plant and animal cells typically exist, which of the following statements is correct? a) animal cells are generally in an isotonic solution, and plant cells are generally in a hypertonic solution b) animal cells are generally in a hypotonic solution, and plant cells are generally in an isotonic solution c) animal cells are generally in a hypertonic solution, and plant cells are generally in a hypotonic solution d) animal cells are generally in a hypertonic solution, and plant cells are generally in an isotonic solution e) animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution

e

small, nonpolar, hydrophobic molecules such as fatty acids...

easily pass through a membrane's lipid bilayer

bulk transport across the plasma membrane occurs by...

endocytosis/exocytosis

bulk transport requires...

energy (ATP)

amphipathic

having both a hydrophilic region and a hydrophobic region

lower pH

higher concentration of H+ (acidic)

water flows from regions of _______ water potential to regions of _______ water potential

higher, lower

______ molecules, such as ______, can dissolve in the lipid bilayer of the cell and cross it easily

hydrophobic, hydrocarbons

high pH

lower concentration of H+ (basic)

______ molecules, such as sugars, do not cross the membrane easily

polar

example of active transport system

sodium potassium pump

exocytosis

the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane

direction of water flow is determined by...

water potential (a quantity that includes the effects of solute concentration and pressure)

constant volume means...

water potential must be the same within the cell as outside of the cell to remain constant

open container means...

zero pressure potential

water potential equation

Ψ = Ψs + Ψp

solute potential equation

Ψs = -iCRT