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Animal Physiology > Exam 1: Ch 4 Book > Flashcards

Exam 1: Ch 4 Book Flashcards

1
Q

fluid mosaic membrane

A

membranes are dynamic and complex

globular proteins are integrated with the membrane

evidence: freeze etch of membrane b4 and after subjecting it to proteolytic enzymes

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2
Q

plasma membrane

A

thin lipid-based structure that encloses the cytoplasm and the cell nucleus

held together by non covalent interactions

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3
Q

integral proteins

A

proteins that span the plasma membrane that include channels, pumps, pores, enzymes, and receptors

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4
Q

peripheral proteins

A

associated with the surface of the plasma membrane by electrostatic interactions

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5
Q

3 primary types of lipids in cell membranes

A

phosphoglycerides: glycerol backbone
sphingolipids: sphingosine base backbones
sterols: cholesterol (nonpolar and slightly soluble in H2O)

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6
Q

which two types of lipid are amphipathic?

A

phosphoglycerides and sphingolipids

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7
Q

fluidity

A

the ability of membrane components to move relative to one another

cholesterol makes membranes less fluid but stronger/stiffer

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8
Q

diffusion

A

random thermal motion of suspended or dissolved molecules causes them to disperse from regions of high concentration to low concentration until equilibrium is reached

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9
Q

Flick diffusion equation

A

rate of diffusion of a solute s

dQs/dt = DsA(dCs/dx)

DQs/dt = rate of diffusion (quantity of s diffusing per unit time)

Ds = diffusion coefficient of s

A = cross sectional area s is diffusing through

dCs/dx = concentration gradient of s (determines rate)

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10
Q

why is a concentration gradient important to diffusion

A

determines the rate at which solute s diffuses down the gradient

higher the gradient fast the diffusion

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11
Q

membrane flux

A

a solute on both sides of a membrane has a unidirectional flux

the flux (J) is the amount of solute that passes through a unit area of membrane every second in one direction

J = dQs/dt

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12
Q

permeability & permeability constant

A

the rate at which the substance passively penetrates the membrane under specified conditions

dQs/dt = P(C1 - C2)

C1 & C2 are concentrations on either side of the membrane

P, the permeability constant has the dimension of velocity (cm per second)

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13
Q

diffusion coefficient

A

how fast a solute diffuses through a membrane

more viscous the membrane the lower the value

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14
Q

partition coefficient

A

how well a solute dissolves in lipids vs water

K = [solute in lipid] / [solute in water]

higher means better lipid solubility

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15
Q

osmosis

A

the movement of water down its concentration gradient from more pure to less pure

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16
Q

hydrostatic pressure

A

a pressure gradient across a semipermeable membrane caused by osmosis

when equal to osmotic pressure, water net flux is 0

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17
Q

osmotic pressure

A

pressure applied by a solution to prevent inward flow of water

proportional to solute concentration and absolute temperature

pi = RTC

higher [solute] = higher osmotic pressure

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18
Q

osmolarity

A

theoretical comparison

osmotic membrane allows water to pass but not solutes

all solutions with the same number of dissolved particles per unit volume are isosmotic

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19
Q

isosmotic, hypoosmotic, hyperosmotic

A

two aqueous solutions that exert the same osmotic pressure

the solution that exerts less osmotic pressure than another solution

the solution that exerts more osmotic pressure than another solution

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20
Q

tonicity

A

the response of cells or tissues immersed in a solution

functional cell based comparison

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21
Q

isotonic

A

a solution is isotonic to a cell or tissue if the cell or tissue neither shrinks or swells when placed in it

there is no osmotic pressure difference and thus no net water gain or loss

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22
Q

hypotonic

A

if the tissue swells because it absorbs water the solution is said to be hypotonic to the tissue

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23
Q

hypertonic

A

if the tissue shrinks because it loses water the solution is said to be hypertonic to the tissue

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24
Q

what does membrane permeability to charged particles depend on

A

membrane permeability constant

electric potential across the membrane

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25
Q

what two forces act on charged atoms or molecules to produce net passive diffusion across a membrane

A

chemical gradient from difference in solute [ ]s across the membrane

difference in electric potential across the membrane

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26
Q

electrochemical gradient

A

the sum of the concentration gradient and electrical gradient

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27
Q

equilibrium potential

A

The voltage when net ion flux is 0

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28
Q

what affects the equilibrium potential

A

ratio of the ion concentrations on opposite sides of the membrane

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29
Q

when can an ion passively diffuse against its concentration gradient?

A

when there is a greater electrical potential than chemical concentration gradient

ex. if the interior of a cell has a negative charge greater than the equilibrium potential, K+ ions will diffuse into the cell even though its intracellular [ ] is higher than extracellular

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30
Q

what is the most concentrated inorganic ion in the cell

A

potassium K+

10-30 times higher inside than out

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31
Q

is Na+ higher inside or outside cell

A

outside

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32
Q

is Ca2+ higher inside or outside cell

A

outside

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33
Q

why can plant and bacterial cells withstand higher osmotic pressure and turgor pressure

A

they have rigid cell walls

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34
Q

3 types of mechanisms to move things across the membrane

A

passive diffusion (simple diffusion)

passive transport (facilitated diffusion)

active transport

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35
Q

which two mechanisms of transport across the membrane do not use ATP

A

passive diffusion and passive transport

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36
Q

passive (simple) diffusion

A

solute molecule comes in contact with membrane and passes through if thermal energy is high enough

breaks H-bonds with extracellular water to diffuse

rate of influx is determined by concentration gradient (high to low)

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37
Q

passive transport (facilitated diffusion)

A

protein pores, channels, or carriers move solutes down their concentration gradients into the cell

no ATP used

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38
Q

carrier protein

A

an integral protein that mediates the movement of solute across a membrane down its concentration gradient

this mechanism is called carrier-mediated passive transport

39
Q

unitary current

A

sudden opening of channels that allow thousands of ions/sec to cross membrane

40
Q

nystatin

A

a rod-shaped antibiotic that forms channels that allow water, urea, and chloride to diffuse

produces a 100,000 fold increase in membrane permeability to chloride

doesn’t allow large molecules or cations to diffuse

41
Q

what do we learn from nystatin channels?

A

very little membrane area is needed to produce significant ion permeability changes through channels

42
Q

aquaporin

A

channels that specifically permit passive diffusion of water but exclude ions and other substances

not permanent hourglass shaped channels controlled by hormone regulation

43
Q

ionophores

A

small organic compounds that transport ions across the membrane

44
Q

uniporter

A

carrier protein that transport a single solute

45
Q

coupled transporter

A

carrier proteins that transport one solute and simultaneously transport a second solute

2 types (symporter and antiporter)

46
Q

symporter

A

a coupled transporter carrier protein that transfers two solutes in the same direction

47
Q

antiporter

A

a coupled transporter carrier protein that transports two solutes in opposite directions

48
Q

carrier protein kinetics

A

a rate plateau is reached b/c michaelis menten

rate tapers off when all protein units are saturated

49
Q

how was specificity of transporters discovered

A

in cystic fibrosis a defect in chloride transport channel protein (CFTR) is responsible for fluid imbalance in lungs

50
Q

why is the distribution of ions across membranes of living cells never at true equilibrium

A

b/c all living cells continuously expend ATP to maintain a stable differential of transmembrane ion concentrations

51
Q

active transport 2 types

A

eiher primary active transport or secondary active transport

52
Q

primary active transport

A

ATP dependent pumps transport substances against their gradients

if the energy source is cut off, active transport stops

53
Q

secondary active transport

A

movement of substance against its electrochemical gradient b/c it is moving down its own concentration gradient

doesn’t use ATP

54
Q

Na/K pump models primary active transport

A

enzyme called an ATPase with binding sites for Na and ATP on cytoplasmic side, and K+ on extracellular side

pumps 3 Na out and cleaves ATP –> ADP to induce a conformational change, and pumps 2 K in to maintain higher extracellular Na

55
Q

symporter example

A

transport of alanine is coupled to the transport of Na+

when Na+ is present, alanine is taken up by the cell until the cytosolic [ ] is 7-10 times higher than extracellular

56
Q

block Na/K pump with inhibitor ouabain and effect on alanine transport

A

inhibitor diminishes extracellular Na [ ] and therefore the gradient

this stops transport of alanine into cell

57
Q

antiporter example

A

Na/Ca antiport system maintains low cytosolic Ca levels

Ca expelled from cell in exchange for Na leaking in

58
Q

Na/H cotransport

A

antiporter in proximal tubule of the kidneys

extrusion of H+ from inside cells into urine couples with Na uptake into cell in 1:1 ratio

avoids expending ATP to perform electrical work of exchanging two ions of the same charge

allows kidney to reclaim Na from urine and excrete excess H+

59
Q

metabolic poisons bring what type of transport to a halt

A

primary active transport

60
Q

rheogeneic

A

ionic pumps that produce net charge movement

produce a transmembrane electric current

61
Q

electrogenic

A

describes a pump that produces an electric current with measurable effect on the voltage across the membrane

62
Q

how much energy does the Na/K pump use

A

25% of total energy

50% in kidneys

63
Q

the energy of ion gradients can be used to drive …

A

passive transport or secondary active transport

also needed to conduct info along the surface of the membrane

64
Q

when does energy release occur in ion gradients

A

when the ions are allowed to travel down their concentration gradients

65
Q

3 important cellular processes that utilize the free energy of ion gradients

A

production of electrical signals

chemiosmotic energy transduction

uphill transport of other molecules

66
Q

electrochemical energy is stored primarily as…

A

Na and Ca gradients

release of this energy controlled by gated ion channels that are normally closed, but open in response to chemical or electrical signals

this is the basis of the nervous system

67
Q

chemiosmotic energy transduction

A

electron transport chain in mitochondria utilizes H+ gradient to synthesize ATP

68
Q

two important factors producing membrane channel selectivity for ions other than size

A

ease of dehydration

charges within the channel pore

69
Q

ease of dehydration

A

for an ion to enter a channel pore it must dissociate from water molecules

large ions dehydrate more easily than smaller ones so a pore with weak polar sites will admit large ions preferentially over smaller ones

70
Q

charges within the channel pore

A

charged amino acids repel ions with the same charges

smaller ions can approach the polar sites more easily and interact with them more strongly than large ions

71
Q

channel pore charge example

A

K channels in bacterium streptomyces have 4 identical protein subunits

K+ passes through in single file aided by negative aas (K is larger than Na)

Na cannot pass through b/c it is too small to interact with protein subunits

72
Q

selectivity for nonelectrolytes

A

determined by molecular properties responsible for the partition coefficient

mechanisms for restricting nonelectrolyte flow through membranes haveq not evolved

drugs like a nicotine patch take advantage of this

73
Q

endocytosis

A

ingestion of macromolecules by formation and fusion of membrane bound vesicles

called pinocytosis if fluid is ingested

called phagocytosis if solids are ingested

74
Q

exocytosis

A

secretion from a cell of macromolecules

75
Q

receptor mediated endocytosis

A

receptor molecules embedded in external membrane bind ligands that cannot pass through channels

receptors can diffuse laterally through membrane

76
Q

coated pit

A

upon binding ligand, the receptor-ligand complex accumulates within depressions in the membrane

this pit invaginates and pinches off, forming a coated vesicle

77
Q

clathrin

A

coats coated vesicles and covers the cytoplasmic surface of the vesicle membrane

directs budding off of vesicle from membrane

recycled to the plasma membrane after contents delivered

78
Q

mechanism of exocytosis

A

fuse with plasma membrane and release substances into extracelular space

79
Q

membrane recycling

A

endocytosis recovers extra vesicle material that fuses during exocytosis

80
Q

tissue

A

cooperative assemblies

81
Q

gap junctions

A

provide a means of communication between cells by allowing inorganic ions and small water-soluble molecules to pass directly from the cytosol of one cell to another

couple cells electrically and metabolically

clusters of hexagonal channels with 6 subunits

82
Q

gap junction experiment

A

used fluorescent dyes to track diffusion into neighboring cells

83
Q

tight junctions

A

seal cells together into an epithelial sheet but do not provide a channel

stops leakage of substances across the membrane from gaps inbetween cells (paracellular)

substances must cross the membrane transcellularly

84
Q

zonula occludens

A

tight junctions in epithelial cells

thin band of protein molecules that encircles a cell like a gasket

85
Q

paracellular pathway

A

path through a membrane between cells

86
Q

transcellular pathway

A

path through a membrane going through the body of the cell

87
Q

zonula adherens and desmosome

A

cell junctions that stabilize the structural bonding of neighboring cells

88
Q

epithelia have several features in common

A

occur at surfaces that separate the internal space of an organism from the environment

cells of outermost layer are sealed by tight junctions

have a serosal (internal) and mucosal (external) side

89
Q

salt transport across epithelium experiment

A

uses frog skin to demonstrate that active transport is needed to move salt across an epithelium

Na/K pump in serosal side creates normal net neg resting potential inside cell

mucosal side is impermeable to K and has channels or carriers that let Na in

90
Q

major features common to transport epithelium

A

tight junctions disallow paracellular pathways so transport through transcellular pathways is used

mucosal and serosal portions exhibit functional differences; they are asymmetric in pumping and permeability

active transport of cations is accompanied by transport (active or passive) of anions in same direction to minimize buildup of electrical potentials

transport not limited to pumping of Na, other ions too

91
Q

water balance in animals is achieved by the regulation of water transport via _______

A

epithelial sheets

can absorb or secrete aqueous fluids

92
Q

2 hypothesis of uphill transport of water by epithelia

A

transported by a specific carrier mechanism driven by ATP (unlikely b/c no pump or carrier has been found)

transported by osmosis as a consequence of solute transport (validated as the Standing-Gradient Hypothesis)

93
Q

osmosis through epithelia

A

water flows osmotically following Na active transport through portions of membranes facing the intercellular clefts

94
Q

permeability constant equation

A

P = DmK / x

Dm = diffusion coefficient

K is partition coefficient

x = thickness of the membrane

Animal Physiology (26 decks)

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