Membrane Transport

Question 1

sides of plasma membrane for epithelial transport

Answer 1

apical (top; where substances enter the cell)

basolateral (bottom; where substances leave the cell)

Question 2

what makes up plasma membranes?

Answer 2

phospholipid bilayer
cholesterol
proteins

Question 3

functions of the plasma membrane

Answer 3

helps maintain the composition of intra- and extracellular fluids
regulates traffic into and out of the cell
forms the framework for protein components
detects chemical messengers arriving at the cell surface
links adjacent cells together

Question 4

desmosome

Answer 4

extension of the plasma membrane that acts as an anchor, preventing cells from falling apart
its environment is very hydrophobic

Question 5

tight junction

Answer 5

allows water or other aqueous molecules to pass through

also holds cells together

Question 6

gap juction

Answer 6

specialized protein complex that creates an aqueous pore between two adjacent cells
typically involves ion movement

Question 7

simple diffusion

Answer 7

movement of molecules from an area of high concentration to an area of low concentration
is gradual, passive, and creates a uniform distribution
does NOT stop when equilibrium is reached (but net flux = 0)
substances diffuses down its own concentration gradient

Question 8

flux

Answer 8

measure of the rate of diffusion

Question 9

factors of net flux

Answer 9

concentration gradient
temperature
surface area
permeability

Question 10

what is the ranking of the relative permeability of molecules (most to least)?

Answer 10

hydrophobic molecules
small, uncharged polar molecules
lage, uncharged polar molecules
ions

Question 11

what is the most hydrophilic molecules?

Answer 11

water

Question 12

what molecules are mediated transport systems needed for?

Answer 12

molecules too large or polar to diffuse

Question 13

types of mediated transport

Answer 13

facilitated diffusion
active transport
bulk transport

Question 14

facilitated diffusion

Answer 14

mode of transport where a protein allows an otherwise impermeable molecule to cross a membrane down its concentration gradient

Question 15

channel

Answer 15

corridor for charged molecules to pass through a plasma membrane
specificity depends on charge and pore size

Question 16

osmosis

Answer 16

net diffusion of water from a region of high concentration to a region of low concentration
its direction is determined by difference of solute concentration, NOT the type of solute

Question 17

osmolarity

Answer 17

total concentration of solutes in a solution

Question 18

conditions of osmolarity

Answer 18

isosmotic
hyposmotic
hyperosmotic

Question 19

isosmotic

Answer 19

cell has an equivalent osmolarity to its extracellular environment
aims to be maintained in physiological conditions

Question 20

hyposmotic

Answer 20

cell has a lower osmolarity than its extracellular environment

Question 21

hyperosmotic

Answer 21

cell has a higher osmolarity than its extracellular environment

Question 22

gated channels

Answer 22

channels that require a certain stimulus to open

Question 23

types of gated channels

Answer 23

ligand-gated, voltage-gated, mechanically gated

Question 24

ligand gated channel

Answer 24

ligand binds to the receptor-channel -> regulates the opening and closing of the gate

Question 25

voltage gated channel

Answer 25

regulated by the electrical state of the cell

Question 26

mechanically gated channel

Answer 26

regulated by physical changes to the cell

Question 27

characteristics of protein carriers

Answer 27

specificity saturation competiton

Question 28

competition

Answer 28

molecules with similar chemical structures compete for carrier binding sites

Question 29

passive mediated transport

Answer 29

no ATP is required | involves permease as the carrier protein

Question 30

active mediated transport

Answer 30

``` requires ATP (directly -> primary; indirectly -> secondary) does NOT depend on the concentration gradient critical for a cell to maintain its internal concentrations of small molecules that would otherwise diffuse across the membrane ```

Question 31

primary active transport

Answer 31

requires ATP moves solutes against their concentration gradients involves specific membrane-bound transport proteins

Question 32

calcium ion pump

Answer 32

ATP hydrolysis is required | causes a higher concentration of calcium ions outside the cell, and a lower concentration inside the cell

Question 33

sodium/potassium pump

Answer 33

requires ATP hydrolysis causes an increase of potassium ions inside the cell, and an increase of sodium ions outside the cell facilitates many biological functions

Question 34

function of a steep gradient

Answer 34

involved in electrochemical impulses increases osmotic flow regulates resting calories expenditure and BMR provides energy for coupled transport of other molecules

Question 35

secondary active transport

Answer 35

no direct input of energy is required | typically involves coupled transport

Question 36

cotransport

Answer 36

transporter moves a molecule or ion in the same direction as another molecule aka symport

Question 37

countertransport

Answer 37

transporter moves a molecule or ion in the opposite direction of another molecule aka antiport

Question 38

bulk transport

Answer 38

movement of large molecules that can't be transported by carriers at the same time types: endocytosis, exocytosis

Question 39

epithelium

Answer 39

boundary of any intestine

Question 40

transcellular transport

Answer 40

molecule is transported through the cell | can involve facilitated diffusion, permease, primary/secondary transport, or osmosis

Question 41

paracellular transport

Answer 41

molecule is transported between cells | ONLY involves simple diffusion

Question 42

absorption

Answer 42

transport of digestion molecules across intestinal epithelium into blood

Question 43

reabsorption

Answer 43

transport of molecules out of the urinary filtrate back into the bloodstream

Question 44

membrane potential

Answer 44

difference in charge between the outside and inside environments measured as mV provides energy for cellular functions

Question 45

depolarization

Answer 45

intracellular environment becomes more positive

Question 46

hyperpolarization

Answer 46

extracellular environment becomes more positive

Question 47

what can changes in membrane potential cause?

Answer 47

the opening or closing of channels