Membrane Transport Flashcards

(47 cards)

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
voltage gated channel
regulated by the electrical state of the cell
26
mechanically gated channel
regulated by physical changes to the cell
27
characteristics of protein carriers
specificity saturation competiton
28
competition
molecules with similar chemical structures compete for carrier binding sites
29
passive mediated transport
no ATP is required | involves permease as the carrier protein
30
active mediated transport
``` 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
primary active transport
requires ATP moves solutes against their concentration gradients involves specific membrane-bound transport proteins
32
calcium ion pump
ATP hydrolysis is required | causes a higher concentration of calcium ions outside the cell, and a lower concentration inside the cell
33
sodium/potassium pump
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
function of a steep gradient
involved in electrochemical impulses increases osmotic flow regulates resting calories expenditure and BMR provides energy for coupled transport of other molecules
35
secondary active transport
no direct input of energy is required | typically involves coupled transport
36
cotransport
transporter moves a molecule or ion in the same direction as another molecule aka symport
37
countertransport
transporter moves a molecule or ion in the opposite direction of another molecule aka antiport
38
bulk transport
movement of large molecules that can't be transported by carriers at the same time types: endocytosis, exocytosis
39
epithelium
boundary of any intestine
40
transcellular transport
molecule is transported through the cell | can involve facilitated diffusion, permease, primary/secondary transport, or osmosis
41
paracellular transport
molecule is transported between cells | ONLY involves simple diffusion
42
absorption
transport of digestion molecules across intestinal epithelium into blood
43
reabsorption
transport of molecules out of the urinary filtrate back into the bloodstream
44
membrane potential
difference in charge between the outside and inside environments measured as mV provides energy for cellular functions
45
depolarization
intracellular environment becomes more positive
46
hyperpolarization
extracellular environment becomes more positive
47
what can changes in membrane potential cause?
the opening or closing of channels