Chapter 7

internal solute concentration of a plant cell= ~ 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 plasmolyze.

The sodium/potassium pump hydrolyzes ATP and results in a net charge of +1 outside the cell membrane.

Active transport requires an imput of E + can generate voltages across membranes

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 ___

B; the diffusion gradient in cell B is steeper

What can passively diffuse across the plasma membrane?

CO2

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?

Hypertonic sucrose solution

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, both solutions are isotonic

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?

The movement of protons through the cotransport protein can't occur unless sucrose also moves at the same time

increase membrane fluidity

a greater proportion of unsat phospholipids

cotransport of solutes across the membrane

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

sodium-potassium pump

an antiporter that results in a net (-) charge inside the cell

energy, C, and N storage

aren't consequences of protein association within bio membranes

plant + red blood cells in seawater

both cells would lose water; red blood cell would shrivel vs plant plasma membrane would pull away from cell wall

How membranes in a eukaryotic cell vary

certain proteins are unique to each membrane

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?

could block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter.

all electrogenic pumps

create a voltage difference across the membrane

ions diffuse across membranes through specific ion channels

down their electrochemical gradient

fluid mosaic

due to lateral + rotational movement of phospholipids; embedded proteins account for the mosaic part

How is a membrane selectively permeable?

due to proteins embedded in 2 layers of phospholipid

small, hydrophobic molecules

easily pass through a cell membrane

receptor-mediated endocytosis

enables a cell to pick up + concentrate a specific kind of molecule

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

plasma membranes

exhibit selective permeability between a cell + external environment

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?

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

phospholipid function

form a selectively permeable structure

What increases membrane fluidity?

greater proportion of unsat phospholipids

passive transport

includes all others

What can't diffuse through a plasma membrane?

large polar molecules (w/o the help of a transport protein_

phospholipids + proteins

major structural components of cell membrane

facilitated diffusion of solutes

may occur through channel/ transport proteins in the membrane; does NOT require hydrolysis of ATP

carbs association w/ plasma membrane

membrane carbs function primarily in cell-cell recognition

cholesterol in plasma membranes

membrane stays fluid more easily when cell temp drops

water passes quickly through cell membrane

moves through aquaporins within the membrane

pinocytosis vs receptor-mediated endocytosis

nonselective in molecules it brings into cell vs offers more selectivity

location of carbs within a membrane

on the outside (external) surface of the membrane

diffusion

passive process

passive transport

permits the solute to move in either direction, but the net movement of the population of solute occurs down the concentration gradient

white blood cells

phagocytosis

membrane transport process-primary function

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

exocytosis + rough/smooth ER

processes organelle(s) accounts for the replacement of lipids + proteins lost from the plasma membrane

fluid mosaic model structure

proteins are embedded in a lipid bilayer

conclusion of freeze-fracture

proteins are embedded in membrane bilayers

decreasing extracellular pH

rate of sucrose transport in the cell increases

active trasport vs facilitated diffusion

requires E from ATP does NOT

membrane protein structure

short sugar chains from ID tags that are used for cell recognition

transmembrane protein

spans the phospholipid bilayer 1 or more times

membrane potential

voltage across the membrane

A single plant cell is placed in an isotonic solution. Salt is then added to the solution ____

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

location of chlesterol within plasma membranes

within the interior of the membrane