Plasma Membrane Flashcards

(56 cards)

1
Q

plasma membrane

A

a thin, flexible, lipid bilayer that separates the contents of the cell from its surrounding

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2
Q

molecular gradients

A

ECF: Na+, Ca++ and Cl-
(positive outside)
ICF: proteins -, phosphate -, K+
(negative inside)

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3
Q

membrane potential

A

slight negative charge on the inside of the cell and slight positive charge on the outside of the cell

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4
Q

phospholipid molecule

A
  • head: negatively charged, polar, hydrophilic

- tail: uncharged, nonpolar, hydrophobic

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5
Q

membrane protein functions

A
  • channels for passage of small ions
  • carriers for transport of substances
  • docking-marker acceptors for secretory vesicles
  • membrane bound enzymes
  • receptors for responding to chemical messengers (endocrine system)
  • cell adhesion molecules that hold cells together
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6
Q

myasthenia gravis

A
  • muscle weakness
  • channel proteins issue
  • binding to receptors and openings of the channels are missing in MG
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7
Q

receptor proteins- insulin insensitivity

A
  • DMII
  • have insulin but can’t go into the cell
  • receptors don’t recognize insulin
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8
Q

hereditary spherocytosis

A
  • anchor proteins

- RBC are spherical

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9
Q

fluid mosaic model

A

-relates to the membrane fluidity and the mosaic pattern of free floating proteins in the bilayer

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10
Q

cell to cell adhesions

A
  • the extracellular matric binds cells together
  • three types of proteins: collagen, elastin (elastic), fibronectin (reticular)
  • also held together by desmosomes, tight junctions, and gap junctions
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11
Q

collagen

A
  • flexible nonelastic fibers or sheets that provide tensile strength(resistance to being stretch lengthwise)
  • most abundant protein in the body
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12
Q

elastin

A
  • allows tissues to stretch and recoil

- found in the lungs

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13
Q

fibronectin

A

-promotes cell adhesion and holds cells in position

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14
Q

desmosomes

A
  • act like “Velcro” and anchor two adjacent non-touching cells
  • most abundant in tissues that are subject to stretching
  • pair of dense, buttonlike, cytoplasmic thickenings called plaques
  • has strong filaments containing cadherins that extend across the plaques
  • they bind adjacent plasma membrane together so they resist being pulled apart
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15
Q

tight junctions

A
  • firmly bond adjacent cells together
  • seal off passageway between the two cells
  • found in primarily in sheets of epithelial tissue
  • prevents leaks within epithelial sheets
  • lines the internal cavities
  • kiss sites are strands of proteins known as claudins that fuse the outer surfaces
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16
Q

gap junctions

A
  • between adjacent cells linked by small connecting tunnels formed by connexons
  • extend through the thickness of the membranes
  • communicating junctions
  • permits unrestricted passage of small nutrient molecules between cells, and water soluble molecules
  • abundant in cardiac and smooth muscle, can transmit electrical activity throughout an entire muscle mass and allows synchronized contraction of a whole muscle mass
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17
Q

membrane transport-permeability

A
  • if a substance can cross the membrane it is permeable to that substance
  • can’t pass through membrane, it is impermeable
  • plasma membrane is selectively permeable: allows some particles to pass while preventing others
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18
Q

particle solubility and size

A
  • the two properties of particles that influence whether they can permeate cell membrane without assistance
  • lipid solubility and particle size
  • highly lipid-soluble particles dissolve in the lipid bilayer and pass through the membrane
  • non-lipid particles require assisted transport to move across the membrane (charged particles and polar molecules)
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19
Q

simple diffusion kinds

A
  • diffusion through lipid bilayer, diffusion through protein channel, osmosis
  • passive
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20
Q

carrier-mediated transport

A

-facilitated diffusion, primary active transport, secondary active transport (symport or antiport)

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21
Q

net diffusion

A

refers to the difference between two opposing movements

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22
Q

unassisted membrane transport

A
  • particles that can penetrate the plasma membrane on their own
  • passively driven across the membrane
  • diffusion down a concentration gradient
  • movement along an electrical gradient
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23
Q

simple diffusion

A
  • unassisted, passive membrane transport
  • uniform spreading out due to random intermingling
  • move from high to low concentrations
  • occurs until equilibrium is reached
  • crucial to survival of every cell
24
Q

fick’s law of diffusion

A
  • directly proportional: concentration gradient of substance, surface area of membrane, lipid solubility
  • inversely proportional: molecular weight, distance (thickness)
25
molecules using simple diffusion
- nonpolar molecules dissolve through down their concentration gradients - small ions can move down electrochemical gradients through open protein channels - cations move towards area more negatively charged and vise versa with anions
26
ions and channels
- ions can across the membrane through protein channels - channels are specific to one ion - can be opened or closed
27
ions move through channels:
- down their concentration gradient | - down the electrical gradient
28
water transport
- water can easily pass through membrane - through the tails of the phospholipids - aquaporins
29
aquaporins
- channels specific for the passage of water - the driving force is the concentration gradient - different cells have different density
30
osmosis
- water moves passively down concentration gradient - semi-permeable membrane - area of high concentration of non-penetrating solutes to low concentration
31
osmolarity
-of a solution is measured by total solute particles per liter
32
osmotic pressure
- of a solution is the pressure that must be applied to the solution to completely stop osmosis - the magnitude of the osmotic pressure is equal to the magnitude of the opposing hydrostatic pressure
33
tonicity
- of a solution refers to the effect the solution has on cell volume - if the cell stays the same size, shrinks or swells
34
isotonic
-same concentration of nonpenetrating solutes as normal body cells do
35
hypotonic solution
- below-normal concentration of nonpenetrating solutes - water diffuses in - cell swells
36
hypertonic solution
- above normal concentration of nonpenetrating solutes - water leaves cell - cell shrinks
37
assisted membrane transport
- small particles are transported across the membrane by their carrier proteins - protein flips to move particle from side to side - facilitated and active transport
38
facilitated diffusion
-carrier moves the particle down its concentration gradient
39
active transport
-carrier moves particle against its concentration gradient
40
facilitated diffusion: passive
- substances move from a higher concentration to a lower concentration - requires a carrier molecule - does not require energy - how glucose is transported into cells
41
facilitated diffusion: active transport
- substance against concentration gradient - primary: direct use of ATP - secondary: driven by ion concentration gradient, established by primary active transport, has symport and antiport
42
symport
- cotransport | - the transported solute moves in the same direction as the gradient of the driving ion
43
antiport
- counter transport or exchange | - the transported solute moves in the direction opposite from the gradient of the driving ion
44
carrier-mediated transport characteristics
- specificity - saturation - transport maximum (Tm) - competition
45
specificity
-each carrier transports a specific substance or a few closely related compounds
46
saturation
-a limited number of carrier binding sites are available
47
transport maximum
-the amount of a substance transported in a given time
48
competition
-several closely related compounds may compete for transport on the same carrier
49
resting membrane potential
-70mV
50
Na+ and K+ pump
- small contribution to the resting membrane potential - 3 Na+ out for every 2 K+ in - loses more positive charges than it gains - inside becomes more negative - actively maintain the Na+ and K+ concentration gradients
51
equilibrium potentials
K+: -90mV Na+: +60 mV -resting membrane is 25 to 30 times more permeable to K+ than Na+ -closer to K+'s equilibrium potential
52
contributions of K+ and Na+
- more K+ diffuses out the cell - excessive of positive charge outside of cell - when -70mV is reached no net movement of K+ and Na+ occurs
53
excitable cells
- nerve and muscle cells can rapidly alter their membrane permeability - fluctuates membrane potential - fluctuations are responsible for producing electrical impulses in nerve and muscle cells
54
transport pathophysiology
-diffusion: pneumonia -facilitated diffusion: GLUT4 in DM voltage gated Na channel inhibited by tetrodotoxin (puffer fish) and saxitoxin (shell fish) -CHF: Na+ and K+ pump inhibited by digitalis -H+-K+ pump inhibited by omeprazole -Na-glucose co-transporter - in GI mucosa and PCT, oral rehydration
55
familial hypercholestrolemia
- mutations in LDL receptor protein - LDL particles not taken up by cells - more in blood - ??
56
chronic granulomatous disease
- inability of phagocytes to kill microbes - normal functioning is mediated by: nicotinamide adenine dinucleotide phosphate (NADPH) oxidase - oxidative burst kills the phagocyte