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BIO 225 > Membrane Transport > Flashcards

Membrane Transport Flashcards

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1
Q

sides of plasma membrane for epithelial transport

A

apical (top; where substances enter the cell)

basolateral (bottom; where substances leave the cell)

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2
Q

what makes up plasma membranes?

A

phospholipid bilayer
cholesterol
proteins

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3
Q

functions of the plasma membrane

A

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

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4
Q

desmosome

A

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

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5
Q

tight junction

A

allows water or other aqueous molecules to pass through

also holds cells together

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6
Q

gap juction

A

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

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7
Q

simple diffusion

A

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

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8
Q

flux

A

measure of the rate of diffusion

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9
Q

factors of net flux

A

concentration gradient
temperature
surface area
permeability

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10
Q

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

A

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

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11
Q

what is the most hydrophilic molecules?

A

water

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12
Q

what molecules are mediated transport systems needed for?

A

molecules too large or polar to diffuse

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13
Q

types of mediated transport

A

facilitated diffusion
active transport
bulk transport

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14
Q

facilitated diffusion

A

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

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15
Q

channel

A

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

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16
Q

osmosis

A

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

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17
Q

osmolarity

A

total concentration of solutes in a solution

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18
Q

conditions of osmolarity

A

isosmotic
hyposmotic
hyperosmotic

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19
Q

isosmotic

A

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

20
Q

hyposmotic

A

cell has a lower osmolarity than its extracellular environment

21
Q

hyperosmotic

A

cell has a higher osmolarity than its extracellular environment

22
Q

gated channels

A

channels that require a certain stimulus to open

23
Q

types of gated channels

A

ligand-gated, voltage-gated, mechanically gated

24
Q

ligand gated channel

A

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

25
Q

voltage gated channel

A

regulated by the electrical state of the cell

26
Q

mechanically gated channel

A

regulated by physical changes to the cell

27
Q

characteristics of protein carriers

A

specificity
saturation
competiton

28
Q

competition

A

molecules with similar chemical structures compete for carrier binding sites

29
Q

passive mediated transport

A

no ATP is required

involves permease as the carrier protein

30
Q

active mediated transport

A 
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
31
Q

primary active transport

A

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

32
Q

calcium ion pump

A

ATP hydrolysis is required

causes a higher concentration of calcium ions outside the cell, and a lower concentration inside the cell

33
Q

sodium/potassium pump

A

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

34
Q

function of a steep gradient

A

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

35
Q

secondary active transport

A

no direct input of energy is required

typically involves coupled transport

36
Q

cotransport

A

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

37
Q

countertransport

A

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

38
Q

bulk transport

A

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

39
Q

epithelium

A

boundary of any intestine

40
Q

transcellular transport

A

molecule is transported through the cell

can involve facilitated diffusion, permease, primary/secondary transport, or osmosis

41
Q

paracellular transport

A

molecule is transported between cells

ONLY involves simple diffusion

42
Q

absorption

A

transport of digestion molecules across intestinal epithelium into blood

43
Q

reabsorption

A

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

44
Q

membrane potential

A

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

45
Q

depolarization

A

intracellular environment becomes more positive

46
Q

hyperpolarization

A

extracellular environment becomes more positive

47
Q

what can changes in membrane potential cause?

A

the opening or closing of channels

BIO 225 (5 decks)

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