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Physiology > Plasma Membrane > Flashcards

Plasma Membrane Flashcards

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
Q

molecules using simple diffusion

A
  • 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
Q

ions and channels

A
  • ions can across the membrane through protein channels
  • channels are specific to one ion
  • can be opened or closed
27
Q

ions move through channels:

A
  • down their concentration gradient

- down the electrical gradient

28
Q

water transport

A
  • water can easily pass through membrane
  • through the tails of the phospholipids
  • aquaporins
29
Q

aquaporins

A
  • channels specific for the passage of water
  • the driving force is the concentration gradient
  • different cells have different density
30
Q

osmosis

A
  • water moves passively down concentration gradient
  • semi-permeable membrane
  • area of high concentration of non-penetrating solutes to low concentration
31
Q

osmolarity

A

-of a solution is measured by total solute particles per liter

32
Q

osmotic pressure

A
  • 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
Q

tonicity

A
  • of a solution refers to the effect the solution has on cell volume
  • if the cell stays the same size, shrinks or swells
34
Q

isotonic

A

-same concentration of nonpenetrating solutes as normal body cells do

35
Q

hypotonic solution

A
  • below-normal concentration of nonpenetrating solutes
  • water diffuses in
  • cell swells
36
Q

hypertonic solution

A
  • above normal concentration of nonpenetrating solutes
  • water leaves cell
  • cell shrinks
37
Q

assisted membrane transport

A
  • 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
Q

facilitated diffusion

A

-carrier moves the particle down its concentration gradient

39
Q

active transport

A

-carrier moves particle against its concentration gradient

40
Q

facilitated diffusion: passive

A
  • 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
Q

facilitated diffusion: active transport

A
  • 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
Q

symport

A
  • cotransport

- the transported solute moves in the same direction as the gradient of the driving ion

43
Q

antiport

A
  • counter transport or exchange

- the transported solute moves in the direction opposite from the gradient of the driving ion

44
Q

carrier-mediated transport characteristics

A
  • specificity
  • saturation
  • transport maximum (Tm)
  • competition
45
Q

specificity

A

-each carrier transports a specific substance or a few closely related compounds

46
Q

saturation

A

-a limited number of carrier binding sites are available

47
Q

transport maximum

A

-the amount of a substance transported in a given time

48
Q

competition

A

-several closely related compounds may compete for transport on the same carrier

49
Q

resting membrane potential

A

-70mV

50
Q

Na+ and K+ pump

A
  • 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
Q

equilibrium potentials

A

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
Q

contributions of K+ and Na+

A
  • 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
Q

excitable cells

A
  • 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
Q

transport pathophysiology

A

-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
Q

familial hypercholestrolemia

A
  • mutations in LDL receptor protein
  • LDL particles not taken up by cells
  • more in blood
  • ??
56
Q

chronic granulomatous disease

A
  • inability of phagocytes to kill microbes
  • normal functioning is mediated by: nicotinamide adenine dinucleotide phosphate (NADPH) oxidase
  • oxidative burst kills the phagocyte

Physiology (13 decks)

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