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Human physiology > Chapter 5: Membrane Dynamics > Flashcards

Chapter 5: Membrane Dynamics Flashcards

1
Q

What are the two body fluid compartments?

A
  • cells (ICF)

* ECF - fluid that surrounds the cells

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2
Q

the buffer between the cells and outside environment

A

ECF

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3
Q

what makes up the ECF?

A

interstitial fluid

blood plasma

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4
Q

what state are the ICF and ECF in?

A

osmotic equilibrium

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5
Q

brought about by the free movement of water between the ICF and ECF, so the fluid concentrations are balanced on the two sides of the membrane

A

osmotic equilibrium

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6
Q

an uneven distribution of solutes between ICF and ECF

A

chemical disequilibrium

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7
Q

how is disequilibrium maintained?

A

Living cells use energy to maintain this state of disequilibrium

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8
Q
  • the charge difference between the ICF and ECF

* can create electrical signals

A

electrical disequilibrium

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9
Q

osmotic, chemical, and electrical disequilibrium are considered what?

A

dynamic steady states

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10
Q

what is the goal of homeostasis?

A

to maintain the dynamic steady states of the body compartments

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11
Q
  • solvent for all living cells

* can move freely in and out of cells by water-filed ion channels and special water channels

A

water

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12
Q

special water channels

A

aquaporins

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13
Q

why do women have less water/kg of body mass?

A

due to more adipose tissue which occupies most of the cell volume

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14
Q

what is the cell membrane composed of and in what amounts?

A

ICF - 2/3
ECF - 1/3
plasma - minimal

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15
Q

what is extracellular fluid made of and what amounts?

A

plasma -25%

interstitial fluid - 75%

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16
Q

the movement of water across a membrane in response to a solute concentration gradient

A

osmosis

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17
Q

in which direction does water move?

A

Water moves to dilute the more concentrated solution or from areas where it (water) is in higher concentrations to where it (water) is in lower concentrations

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18
Q

when does osmosis stop?

A

when there is no more net movement

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19
Q
  • pressure that opposes the movement of water into a compartment
  • Measured in atmospheres (atm) or (mmHg
A

osmotic pressure

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20
Q

how can osmosis be measured quantitatively?

A
  • osmotic pressure

* concentrations of solutions

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21
Q
  • concentrations are expressed as this

* number of moles of dissolved solute/L of solution

A

molarity

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22
Q

the number of osmotically active particles per liter of solution (osmol/L = OsM, or milliosmoles/L =mOsM)

A

osmolarity

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23
Q

concentration expressed as osmoles of solute per kilogram of water

A

osmolality

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24
Q

why is osmolality used clinically?

A

because it is easy to estimate peoples body water content by weighing them

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25
Q

what does 1 pure L of water weigh?

A

1kg

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26
Q

how do you compare osmolarities of two solutons?

A
  • isosmotic
  • hyperosmotic
  • hypoosmotic
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27
Q

the same number of solute particles per unit volume

A

isoosmotic

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28
Q

contains more particles per unit volume

A

hyperosmotic

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29
Q

contains less particles per unit volume

A

hypoosmotic

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30
Q

the ability of a solution surrounding a cell to cause that cell to gain or lose water

A

tonicity

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31
Q

what does osmolarity compare?

A

two solutions

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32
Q

what does tonicity compare?

A

solution and a cell

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33
Q

will osmolarity or tonicity tell you what happens to a cell placed in a solution?

A

tonicity

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34
Q

what does tonicity depend on?

A

depends on osmolarity and the nature of the solutes in the solution

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35
Q
  • can enter and stay in a cell

* examples: urea & glucose

A

penetrating solutions

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36
Q
  • *cannot cross the cell membrane, and therefore osmosis of water must occur for the solutions to reach equilibrium
  • *tonicity depends on these
  • example: NaCl
A

nonpenetrating solutes

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37
Q

cell higher conc. of nonpenetrating to solution.

A

hypotonic

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38
Q

cell lower conc. of nonpenetrating to solution.

A

hypertonic

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39
Q

cell and solution same nonpenetrating

A

isotonic

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40
Q

what kind of solutions are always hypotonic?

A

hypoosmotic

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41
Q

what does the tonicity of a solution describe?

A

describes the volume change of a cell at equilibrium

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42
Q

how do you determine tonicity?

A

by comparing nonpenetrating solute concentrations in the cell and the solution

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43
Q

where is net water movement?

A

into the compartment with the higher concentration of nonpenetrating solutes

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44
Q
  • is a general form of biological transport

* caused by a pressure gradient where fluids flow from high pressures to low pressures

A

bulk flow

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45
Q

what are specific forms of transport?

A

diffusion, protein-mediated transport, vesicular transport

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46
Q

what are transport mechanisms across the membrane classified as?

A

active or passive

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47
Q

what is included in active transport?

A
  • vesicular transport (ATP)
    • exocytosis
    • endocytosis
    • phagocytosis
  • protein mediated
    • direct or primary active(ATPases)
    • indirect or secondary active transport
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48
Q

concentration gradient created by ATP

A

indirect or secondary active transport

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49
Q

what is included in passive transport?

A
  • simple diffusion
  • protein mediated
    • facilitated diffusion
    • ionn channel
    • aquaporin channel
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50
Q
  • form of passive transport (kinetic energy inherent

* Molecules move from areas of higher concentration to areas of lower concentration (down a concentration gradient

A

diffusion

51
Q

passive only) occurs with steroids, lipids, and small lipophilic molecules

A

simple diffusion

52
Q

*helps us describe the movement of molecules across the membrane
*Diffusion rate increases when:
surface area, concentration gradient or the membrane permeability increase

A

Fick’s law of diffusion

53
Q
  • describes the flux of a molecule across the membrane

* Diffusion rate/surface area=conc. gradient X mem. Permeability

A

rearranged fick’s law

54
Q

what is the equation for membrane permeability

A

membrane permeabililty = lipid solubility/molecular size

55
Q

what factors affect rate of diffusion through membrane?

A
  • lipid solubility
  • molecular size
  • concentration gradient
  • membrane surface area
  • composition of lipid layer
56
Q

what are membrane proteins classified as?

A

classified based on structure and function

57
Q

what do structural proteins do?

A
  • create cell junctions
  • connect membrane to cytoskeleton
  • connect cell to extracellular matrix
58
Q

what proteins are structural?

A

integral proteins

peripheral proteins

59
Q

which proteins are classified as functional?

A

membrane transport
membrane enzymes
membrane receptors

60
Q

moving molecules across membranes

A

protein-mediated transport

61
Q

what are the two categories of protein-mediated transport?

A

channel proteins

carrier proteins

62
Q
  • (no binding site for ion) = rapid movement (millions of ions/sec) limited to small size molecules.
  • create a water-filled pore
A

channel proteins

63
Q

may be specific or may allow ions of similar charge and size pass

A

ion channels

64
Q

what are the two groups of ion channels?

A 
open channels (leak)
gated channels (chemically gated, voltage gated, mechanically gated)
65
Q
  • (transporters) = slower movement (1000 to 1,000,000 mol/sec) can move larger molecules
  • Open to one side of the membrane or the other, but never both
A

carrier proteins

66
Q

what are the classifications of carrier proteins?

A
  • uniport
  • cotransporters
    • symport
    • antiport
67
Q

transport one kind of molecule

A

uniport

68
Q

transport more than one molecule at a time

A

cotransporters

69
Q

transport more than one molecule at the same time in the same direction

A

symport

70
Q
  • transport more than one molecule at the same time in opposite directions
  • exchangers
A

antiport

71
Q

always down concentration gradient.

A

facilitated diffusion

72
Q
  • against concentration gradient (creates a state of disequilibrium
  • requires energy, ATP
A

active transport

73
Q
  • uses ATP or some other energy source directly to transport substances( ATPases or pumps).
  • example: sodium-potassium pump
A

primary active transport

74
Q
  • powered by a concentration gradient or electrochemical gradient created by primary active transport
  • most driven by sodium
  • energetically efficient way to bring molecules into a cell
A

secondary active transport

75
Q

Na+, K+, ATPase, sodium potassium pump

A

antiport transport

76
Q

Ca^2+, ATPase

A

uniport transport

77
Q

H+, ATPase or proton pump

A

uniport

78
Q

H+, K+, ATPase

A

antiport

79
Q

what do carrier mediated transport (active & passive) demonstrate?

A
  • specificity
  • competition
  • saturation
80
Q

What are the components of specificity?

A
  • GLUT1 (most cells)
  • GLUT2 (liver& kidney)
  • GLUT3 (neurons)
81
Q

(each GLUT transporter has a higher binding affinity for different hexoses sugars)

A

competition

82
Q

(cell can adjust the # of carrier proteins up or down to increase or decrease transport capacity)

A

saturation

83
Q

brings glucose across cell membrane

A

GLUT transporter

84
Q

a competitive
inhibitor that binds to the GLUT transporter but is
not itself carried across the membrane

A

maltose

85
Q

transport can reach a maximum

rate when all the carrier binding sites are filled with substrate

A

saturation

86
Q

is the movement of large macromolecules into and out of the cell

A

vesicular transport

87
Q

what moves materials into and out of the cell in vesicular transport?

A
  • into the cell
    • phagocytosis
    • endocytosis
  • out of the cell
    • exocytosis
88
Q

engulfs bacterium and other large particles by pushing out membrane surface

A

phagocytosis

89
Q

occurs more frequently, membrane surface indents, and vesicles formed are much smaller than phagocytosis

A

endocytosis

90
Q

nonselective endocytosis

A

pinocytosis

91
Q

highly selective endocytosis

A

receptor-mediated endocytosis

92
Q
  • a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane
  • energetically expensive
A

exocytosis

93
Q
  • absorb (lumen to ECF) or secrete (ECF to lumen) materials must transport substances inward across the membrane on one side of the cell and outward across the membrane on the opposite side
  • each side must possess different transport systems
A

epithelial cells

94
Q

what is the structure of epithelial cells?

A
  • polarized
  • apical membrane (muscosal)
  • basolateral membrane (serosal)
95
Q

how does movement across epithelium occur?

A
  • paracellular transport

* transcellular transport

96
Q

can change tightness, ex. claudins

A

paracellular transport

97
Q

can alter their permeability by inserting or withdrawing membrane proteins

A

transcellular transport

98
Q

what are the steps of transepithelial absorption of glucose?

A
  1. Na+ glucose symporter brings glucose into cell against its gradient using energy stored
  2. GLUT transporter transfers glucose to ECF by facilitated diffusion
  3. Na+, K+, ATPase pumpes Na+ out of the cell, keeping ICF Na+ concentration low
99
Q

uses vesicular transport to move large molecules across the membrane

A

transcytosis

100
Q

what is an example of transcytosis?

A

infants absorb maternal antibodies from breast milk, infant intestinal epithelium to ECF)

101
Q

How does transcytosis occur across the capillary endothelium?

A
  1. Plasma proteins are concentrated in caveolae, which undergo endocytosis and form vesicles
  2. vesicles cross the cell with help from the cytoskeleton
  3. vesicle contents are released into interstitial fluid by exocytosis
102
Q

arise due to membrane potential

A

electrical driving forces

103
Q

the difference in electrical potential (form of potential energy) or voltage that exists across the membranes cells

A

membrane potential

104
Q

how is a membrane potential built?

A

The concentration gradient creates an electrical gradient, so in combination the electrical and concentration gradients create the electrochemical gradient

105
Q

what is the cell membrane potential like at the start?

A

When we begin, the cell has no membrane potential:
The ECF (composed of Na+ and Cl– ions) and the ICF
(K+ and large anions, A-) are electrically neutral

106
Q

How is the membrane potential started?

A
  1. insert a leak channel for K+
  2. K+ starts to move out of the cell down its concentration gradient
  3. The A- can’t follow K+ out of the cell cause the cell is not permeable to A-
  4. additional K+ leaves the cell
  5. the negative charge inside the cell begins to attract ECF K+ back into the cell: an electrical gradient in the opposite direction from the concentration gradient
107
Q

For any ion, the membrane potential that exactly opposes a given concentration gradient is…

A

equilibrium potential

108
Q

how do you calculate equilibrium potential?

A

Nernst equation

Eion=61/zlog([ion]out/[ion]in) where z is the charge of the ion

109
Q

when is the nernst equation used?

A

used for a cell that is freely permeable

to only one ion at a time

110
Q

electrical gradient seen in all living cells

A

resting

111
Q

a form of stored energy

A

potential

112
Q

determined by the combined contributions of the concentration gradient and the membrane permeability for each ion (Goldman equations)

A

resting membrane potential

113
Q

what are important ions in resting membrane potential?

A

potassium
sodium
sodium-potassium pump

114
Q

more permeable to the cell than sodium. (30 ICF to 1 ECF)

A

potassium

115
Q

less permeable to the cell. (1 ICF to 15 ECF)

A

sodium

116
Q

(3 sodium out, 2 potassium in) maintains resting membrane potential

A

sodium-potassium pump

117
Q

what happens if the membrane potential becomes less negative that the resting potential?

A

the cell depolarizes

118
Q

what happens if the membrane potential becomes more negative than the resting potential?

A

the cell hyperpolarizes

119
Q

when the cell becomes less negative.

A

depolarization

120
Q

when the cell becomes more negative.

A

hyperpolarization

121
Q

what happens when a beta cell is at rest?

A

. The KATP channel is open, and

the cell is at its resting membrane potential

122
Q

what happens when a beta cell secretes insulin?

A

Closure of KATP channel

depolarizes cell, triggering exocytosis of insulin

123
Q

resting cell membranes are most permeable to what?

A

K+

124
Q

what happens to the membrane potential of a cell that suddenly becomes more permeable to Na+?

A

it becomes more positive

Human physiology (17 decks)

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