chapter 8 transport

Question 1

semipermeable

Answer 1

Membranes are selectively permeable

Question 2

homeostasis

Answer 2

Cells and cellular compartments accumulate a variety of substances in concentrations that are very different from those of the surroundings.

Question 3

solutes

Answer 3

Most of the substances that move across membranes are dissolved gases, ions, and small organic molecules

Question 4

simple diffusion

Answer 4

the direct unaided movement dictated by differences in concentration of the solute on the two sides of the membrane

Question 5

facilitated diffusion

Answer 5

(or passive transport) uses no energy to move solutes to regions of lower concentration

Question 6

Active Transport

Answer 6

Transport proteins move solutes against the concentration gradient. Requires energy such as that released by the hydrolysis of ATP or by the simultaneous transport of another solute down an energy gradient.

Question 7

The movement of a solute across a membrane is determined by its ____ or ____

Answer 7

concentration gradient or its electrochemical potential

Question 8

Electrochemical Potential

Answer 8

the combined effect of its concentration gradient and the charge gradient across the membrane

Question 9

membrane potential (Vm)

Answer 9

The active transport of ions across a membrane creates a charge gradient across the membrane

Question 10

Osmosis

Answer 10

Is the diffusion of water across a selectively permeable membrane

Question 11

Water will move across membranes in respsonse to differences in ___ concentration because the ___ themselves often do not readily cross the membranes

Answer 11

solute

Question 12

If two solutions are separated by a selectively permeable membrane, permeable to the water but not the solutes, the water will move toward the region of ____ solute concentration.

Answer 12

higher

Question 13

This cell will shrink and shrivel if moved to a

Answer 13

hypertonic solution

Question 14

The same cell will swell and perhaps burst (or lyse) if placed in a very

Answer 14

hypotonic solution

Question 15

For example, an animal cell is happy in an

Answer 15

isotonic solution

Question 16

If the solute concentration is higher outside the cell, the solution is called

Answer 16

hypertonic

Question 17

If the solute concentration is lower outside the cell, the solution is called

Answer 17

hypotonic

Question 18

Carrier protein

Answer 18

(transporters or permeases) bind solute molecules on one side of a membrane, undergo a conformation change, and release the solute on the other side of the membrane.

Question 19

Channel proteins

Answer 19

form hydrophilic channels through the membrane to provide a passage route for solutes.

Question 20

Competitive inhibition of carrier proteins

Answer 20

can occur in the presence of molecules or ions that are structurally related to the correct substrate

Question 21

uniport

Answer 21

When a carrier protein transports a single solute across the membrane

Question 22

symport

Answer 22

If the two solutes are moved across a membrane in the same direction

Question 23

antiport

Answer 23

If the solutes are moved in opposite directions

Question 24

The immediate ___ of glucose upon entry into the cell keeps the internal concentration of glucose low. Once ____, glucose cannot bind the carrier protein any longer and is effectively locked into the cell.

Answer 24

phosphorylation; phosphorylated

Question 25

anion exchange protein

Answer 25

(also called the chloride- bicarbonate exchanger) facilitates reciprocal exchange of Cl– and HCO3– ions only.

Question 26

Voltage-gated channels

Answer 26

open and close in response to changes in membrane potential.

Question 27

Ligand-gated channels

Answer 27

are triggered by the binding of certain substances to the channel protein.

Question 28

Mechanosensitive channels

Answer 28

respond to mechanical forces acting on the membrane.

Question 29

Porins

Answer 29

Transmembrane Proteins That Allow Rapid Passage of Various Solutes

Question 30

The transmembrane segments of porins cross the membrane as ___barrels.

Answer 30

β

Question 31

Aquaporins

Answer 31

Transmembrane Channels That Allow Rapid Passage of Water

Question 32

active transport is used to move solutes ___ a concentration gradient, ___from equilibrium.

Answer 32

up; away

Question 33

direct active transport

Answer 33

(primary active transport), the accumulation of solute molecules on one side of the membrane is coupled directly to an exergonic chemical reaction. (ATP hydrolysis)

Question 34

Indirect active transport

Answer 34

depends on the simultaneous transport of two solutes. * Favorable movement of one solute down its gradient drives the unfavorable movement of the other up its gradient. * This can be a symport or an antiport, depending on whether the two molecules are transported in the same or different directions

Question 35

P-type ATPases

Answer 35

"phosphorylation" a diverse family of ion transporters that use the energy from ATP hydrolysis to move ions and other molecules across cell membranes

Question 36

V-type ATPases

Answer 36

"vacuole" solutes transported: H Kind of membrane: lysosomes, secretory vesticles (animals) vacuolar membrane (plants, fungi) EX: keeps pH of compartment low, which activates hydrolyric enzymes

Question 37

F-type ATPase

Answer 37

"factor" also called ATP synthase solutes transported: H Kind of membrane: inner mitochondrial membrane (eukaryotes), plasma membrane ( bacteria),thylakoid membrane (plants) Ex: Uses H gradient to drive ATP synthesis

Question 38

ABC transporters

Answer 38

"ATP binding cassette" solutes transported: importers (a variety of solutes); exporters (antitumor drugs, toxins, antibiotics, lipids) Kind of membrane: plasma membrane, organellar membranes (bacteria); Plasma membrane (bacteria, archaea, eukaryotes) EX: nutrients, multidrug resistance transporter removes drugs and antibiotics from cell

Question 39

sodium potassium pump

Answer 39

1. Three Na+ ions bind to the E1 conformation. 2. This triggers phosphorylation of the α subunit by ATP. 3. The pump undergoes a shift to the E2 conformation, causing release of the Na+ ions on the outside of the cell. 4. Then, K+ ions bind to the α subunit on the outside of the cell. 5. This triggers dephosphorylation of the α subunit by ATP and a return to the E1 conformation. 6. In the conformational change, K+ ions are carried to the inside of the cell and released

Question 40

The E1 conformation

Answer 40

is open to the inside of the cell and has high affinity for Na+ ions.

Question 41

The E2 conformation

Answer 41

It is open to the outside of the cell and has a high affinity for K+ ions.

Question 42

_____ Drive Indirect Active Transport in Many Organisms

Answer 42

Proton Gradients

Question 43

Bacteriorhodopsin

Answer 43

a light-driven proton pump found in the cell membrane of Halobacteria, particularly Halobacterium salinarum. It functions by absorbing light, initiating a photocycle that causes conformational changes in the protein, ultimately leading to the translocation of protons across the membrane. This proton gradient then drives the production of ATP for energy.

Question 44

Rhodopsin

Answer 44

is a protein in the retina of the eye responsible for detecting light and initiating the visual process, particularly in low-light conditions. It acts as a G-protein coupled receptor (GPCR) and is found in rod cells, which are light-sensitive cells in the retina.