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phsyiology > ch 5 transport across the plasma membrane > Flashcards

ch 5 transport across the plasma membrane Flashcards

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1
Q

selective permeability

A

the property of a plasma membrane to be permeable to different substances

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2
Q

examples of substances that can cross the lipid bilayer

A

highly permeable to nonpolar molecules: O2, CO2, steroids
moderately permeable to small, uncharged polar molecules: water and urea

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3
Q

impermeable to the lipid bilayer

A

ions and large, uncharged polar molecules, such as glucose

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4
Q

concentration gradient

A

a difference in the concentration of a chemical from one place to another

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5
Q

electrical gradient

A

a difference in electrical charges between two regions

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6
Q

membrane potential

A

the charge difference across the plasma membrane

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7
Q

electrochemical gradient

A

the combined influence of the concentration gradient and the electrical gradient on the movement of a particular ion

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8
Q

passive processes

A

a substance moves across the plasma membrane without any energy input from the cell

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9
Q

active processes

A

cellular energy is used to move a substance across the plasma membrane. the cellular energy is usually in the form of ATP

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10
Q

vesicular transport

A

tiny vesicles (membranous sacs) are used to move substances across the plasma membrane

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11
Q

two main types of vesicular transport

A

endocytosis
exocytosis

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12
Q

passive transport

A

the movement of substances across the plasma membrane down their concentration of electrochemical gradients

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13
Q

diffusion

A

the random mixing of particles from one location to another because of the particles kinetic energy

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14
Q

solutes

A

the dissolved substances

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15
Q

solvent

A

the liquid that does the dissolving

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16
Q

factors that influence diffusion rate

A
  • steepness of the concentration gradient
  • temp
  • mass of the diffusing substance
  • surface area
  • diffusion distance
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17
Q

fick’s law of diffusion

A

mathematically expresses the various factors that determine how quickly a particles diffuses across a membrane from one region to another

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18
Q

three types of diffusion

A
  • simple diffusion
  • facilitated diffusion
  • osmosis
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19
Q

simple diffusion

A

a passive process in which solutes move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins

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20
Q

what crosses the lipid bilayer through simple diffusion

A

nonpolar, hydrophobic molecules and small, uncharged polar molecules
- oxygen, carbon dioxide, nitrogen gases; fatty acids; steroids; and fat-soluble vitamins (A, D, E, and K)
- water, urea, and small alcohols

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21
Q

facilitated diffusion

A

an integral membrane protein assists a specific substance across the membrane

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22
Q

channel-mediated facilitated diffusion

A

a solute moves down its concentration or electrochemical gradient across the lipid bilayer through a membrane channel

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23
Q

ion channels

A

integral transmembrane proteins containing pores that allow passage of small, inorganic ions that are too hydrophilic to penetrate the nonpolar interior of the lipid bilayer

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24
Q

gated

A

a channel is gated when part of the channel protein acts as a “plug” or “gate”, changing shape in one way to open the pore and in another way to close it

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25
carrier-mediated facilitated diffusion
a carrier (transporter) is used to move a solute down its concentration or electrochemical gradient across the plasma membrane
26
four characteristics of ligand-protein binding of carrier-mediated facilitated diffusion
- specificity - affinity - saturation - competition
27
transport maximum (Tm)
upper limit on the rate at which a solute is transported by facilitated diffusion
28
steps of glucose transport by carrier-mediated facilitated diffusion
1. glucose binds to a specific type of carrier protein called the glucose transporter (GLUT). the binding site initially faces the outside surface of the membrane 2. the transporter undergoes a conformational change, which causes the binding site to face the inside of the cell 3. glucose dissociated from the transporter and enters the cytosol
29
osmosis
a type of diffusion in which there is net movement of a solvent through a selectively permeable membrane
30
aquaporins
integral membrane proteins that function as water channels
31
hydrostatic pressure
the pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity
32
osmotic pressure
the minimum pressure which needs to be applied to a solution to prevent inward flow of its pure solvent across a semipermeable membrane - is proportional to the concentration of solutes that cannot cross the membrane
33
osmolarity
a measure of the total number of dissolved particles per liter of solution = molarity x number of particles per kilogram
34
osmolality
the number of solute particles per kilogram of water
35
isoosmotic
when two solution have the same osmolarity (same number of solute particles per unit volume)
36
hyperosmotic
a solution with a higher osmolarity (more solute particles per unit volume) than another solution
37
hypoosmotic
a solution with a lower osmolarity (fewer solute particles per unit volume) than another solution
38
penetrating solutes
able to pass through a membrane - ex. urea
39
nonpenetrating solutes
unable to pass through a membrane - ex. Na+ ions and Cl- ions
40
tonicity
a measure of a solution's ability to change to volume of cells by altering their water content determined by the concentration of nonpenetrating solutes in the solution
41
isotonic solution
any solution in which a cell maintains its normal shape and volume the concentration of nonpenetrating solutes are the same on both sides of the membrane
42
hypotonic solution
a solution that has a lower concentration of nonpenetrating solutes than the cytosol inside - water molecules enter the cells faster than they leave, causing the cell to swell and eventually burst
43
hemolysis
the rupture of erythrocytes due to placement in a hypotonic solution
44
lysis
the rupture of other types of cells due to placement in a hypotonic solution
45
hypertonic solution
has a higher concentration of nonpenetrating solutes that the cytosol inside - water molecules move out of the cell faster than they enter, causing the cells to shrink
46
crenation
shrinkage of cells due to placement in a hypertonic solution
47
active transport
an active process to move solutes across a membrane
48
primary active transport
energy derived from hydrolysis of ATP changes the shape of a carrier protein, which pumps a solute across a plasma membrane against its concentration or electrochemical gradient
49
pumps
carrier proteins that mediate primary active transport
50
sodium-potassium pump (Na+/K+ ATPase)
most prevalent primary active transport mechanism that expels sodium ions from cells and brings potassium ions into cells
51
secondary active transport
energy stored in an ionic electrochemical gradient is used to drive other solutes across the membrane against their own concentration of electrochemical gradients - indirectly uses energy obtained from the hydrolysis of ATP
52
symporters
when transporters move two solutes in the same direction
53
antiporters
when transporters move two solutes in the opposite direction
54
receptor-mediated endocytosis
highly selective type of endocytosis by which cells take up specific ligands a vesicle forms after receptor proteins in the plasma membrane are bound by particular ligands in the extracellular fluid
55
low-density lipoproteins (LDLs)
a type of lipoprotein that carries cholesterol in the blood
56
steps of receptor mediated endocytosis of LDLs
1. binding 2. vesicle formation 3. uncoating 4. fusion with endosome 5. recycling of receptors to plasma membrane 6. degradation in lysosomes
57
phagocytosis
a form of endocytosis in which the cell engulfs large solid particles
58
phagocytes
cells that carry out phagocytosis
59
pseudopods
projections of its plasma membrane and cytoplasm. surround the particles outside the cell, and the membranes fuse to form a phagosome which enters the cytoplasm
60
residual body
vesicle of any undigested materials in the phagosome
61
bulk-phase endocytosis (pinocytosis)
a form of endocytosis in which tiny droplets of extracellular fluid are taken up
62
exocytosis is especially important in two types of cells
- secretory cells that liberate digestive enzymes, hormones, mucus, or other secretions - neurons that release neurotransmitters
63
transepithelial transport
the movement of solutes across epithelial cells through the use of membrane transport mechanisms
64
tight junctions
cell junctions that retard the passage of substances between cells and prevent contents of these organs from leaking into the blood or surrounding tissues
65
apical membrane
the surface of the epithelial cell that faces the lumen (interior space) of the organ. may contain microvilli to increase surface area
66
basolateral membrane
other surfaces of the epithelial cells which an in contact with interstitial fluid and nearby blood vessels in underlying connective tissue
67
polarized
intrinsic asymmetry observed in cells, either in shape, structure, or organization of cellular components in epithelial cells callows solutes to be transported in one direction across epithelial cell
68
absorption
solute moves from the lumen of an organ into the bloodstream
69
reabosrption
kidney function that transports solutes from the lumen into the bloodstream
70
secretion
movement of a solute from the bloodstream into the lumen of an organ
71
transcytosis
vesicle undergo endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side

phsyiology (7 decks)

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