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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
what two forces act on charged atoms or molecules to produce net passive diffusion across a membrane
chemical gradient from difference in solute [ ]s across the membrane difference in electric potential across the membrane
26
electrochemical gradient
the sum of the concentration gradient and electrical gradient
27
equilibrium potential
The voltage when net ion flux is 0
28
what affects the equilibrium potential
ratio of the ion concentrations on opposite sides of the membrane
29
when can an ion passively diffuse against its concentration gradient?
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
30
what is the most concentrated inorganic ion in the cell
potassium K+ 10-30 times higher inside than out
31
is Na+ higher inside or outside cell
outside
32
is Ca2+ higher inside or outside cell
outside
33
why can plant and bacterial cells withstand higher osmotic pressure and turgor pressure
they have rigid cell walls
34
3 types of mechanisms to move things across the membrane
passive diffusion (simple diffusion) passive transport (facilitated diffusion) active transport
35
which two mechanisms of transport across the membrane do not use ATP
passive diffusion and passive transport
36
passive (simple) diffusion
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)
37
passive transport (facilitated diffusion)
protein pores, channels, or carriers move solutes down their concentration gradients into the cell no ATP used
38
carrier protein
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
unitary current
sudden opening of channels that allow thousands of ions/sec to cross membrane
40
nystatin
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
what do we learn from nystatin channels?
very little membrane area is needed to produce significant ion permeability changes through channels
42
aquaporin
channels that specifically permit passive diffusion of water but exclude ions and other substances not permanent hourglass shaped channels controlled by hormone regulation
43
ionophores
small organic compounds that transport ions across the membrane
44
uniporter
carrier protein that transport a single solute
45
coupled transporter
carrier proteins that transport one solute and simultaneously transport a second solute 2 types (symporter and antiporter)
46
symporter
a coupled transporter carrier protein that transfers two solutes in the same direction
47
antiporter
a coupled transporter carrier protein that transports two solutes in opposite directions
48
carrier protein kinetics
a rate plateau is reached b/c michaelis menten rate tapers off when all protein units are saturated
49
how was specificity of transporters discovered
in cystic fibrosis a defect in chloride transport channel protein (CFTR) is responsible for fluid imbalance in lungs
50
why is the distribution of ions across membranes of living cells never at true equilibrium
b/c all living cells continuously expend ATP to maintain a stable differential of transmembrane ion concentrations
51
active transport 2 types
eiher primary active transport or secondary active transport
52
primary active transport
ATP dependent pumps transport substances against their gradients if the energy source is cut off, active transport stops
53
secondary active transport
movement of substance against its electrochemical gradient b/c it is moving down its own concentration gradient doesn't use ATP
54
Na/K pump models primary active transport
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
symporter example
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
block Na/K pump with inhibitor ouabain and effect on alanine transport
inhibitor diminishes extracellular Na [ ] and therefore the gradient this stops transport of alanine into cell
57
antiporter example
Na/Ca antiport system maintains low cytosolic Ca levels Ca expelled from cell in exchange for Na leaking in
58
Na/H cotransport
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
metabolic poisons bring what type of transport to a halt
primary active transport
60
rheogeneic
ionic pumps that produce net charge movement produce a transmembrane electric current
61
electrogenic
describes a pump that produces an electric current with measurable effect on the voltage across the membrane
62
how much energy does the Na/K pump use
25% of total energy 50% in kidneys
63
the energy of ion gradients can be used to drive ...
passive transport or secondary active transport also needed to conduct info along the surface of the membrane
64
when does energy release occur in ion gradients
when the ions are allowed to travel down their concentration gradients
65
3 important cellular processes that utilize the free energy of ion gradients
production of electrical signals chemiosmotic energy transduction uphill transport of other molecules
66
electrochemical energy is stored primarily as...
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
chemiosmotic energy transduction
electron transport chain in mitochondria utilizes H+ gradient to synthesize ATP
68
two important factors producing membrane channel selectivity for ions other than size
ease of dehydration charges within the channel pore
69
ease of dehydration
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
charges within the channel pore
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
channel pore charge example
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
selectivity for nonelectrolytes
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
endocytosis
ingestion of macromolecules by formation and fusion of membrane bound vesicles called pinocytosis if fluid is ingested called phagocytosis if solids are ingested
74
exocytosis
secretion from a cell of macromolecules
75
receptor mediated endocytosis
receptor molecules embedded in external membrane bind ligands that cannot pass through channels receptors can diffuse laterally through membrane
76
coated pit
upon binding ligand, the receptor-ligand complex accumulates within depressions in the membrane this pit invaginates and pinches off, forming a coated vesicle
77
clathrin
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
mechanism of exocytosis
fuse with plasma membrane and release substances into extracelular space
79
membrane recycling
endocytosis recovers extra vesicle material that fuses during exocytosis
80
tissue
cooperative assemblies
81
gap junctions
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
gap junction experiment
used fluorescent dyes to track diffusion into neighboring cells
83
tight junctions
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
zonula occludens
tight junctions in epithelial cells thin band of protein molecules that encircles a cell like a gasket
85
paracellular pathway
path through a membrane between cells
86
transcellular pathway
path through a membrane going through the body of the cell
87
zonula adherens and desmosome
cell junctions that stabilize the structural bonding of neighboring cells
88
epithelia have several features in common
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
salt transport across epithelium experiment
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
major features common to transport epithelium
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
water balance in animals is achieved by the regulation of water transport via _______
epithelial sheets can absorb or secrete aqueous fluids
92
2 hypothesis of uphill transport of water by epithelia
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
osmosis through epithelia
water flows osmotically following Na active transport through portions of membranes facing the intercellular clefts
94
permeability constant equation
P = DmK / x Dm = diffusion coefficient K is partition coefficient x = thickness of the membrane

Animal Physiology (26 decks)

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