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General Physiology > Membranes, Channels, and Transport > Flashcards

Membranes, Channels, and Transport Flashcards

1
Q

separates the cytoplasm from the external environment

A

Cell Membrane

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2
Q

a highly selective permeable barrier that surrounds all living cells

A

Cell Membrane

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3
Q

Cell membrane is very important for ____,____, and___.

A

proper nutrition, maintenance of irritability of the cells, and homeostasis

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4
Q

Cell Membrane functions

A

• define boundaries and serve as permeability barriers
• compartmentalization (for organization and localization of specific functions)
• signal detection
• cell-to-cell communication

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5
Q

Cell Membrane Extraordinary Thin

A

6-23 nm

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6
Q

Iipid-based structure that encloses the cytosol

A

Cell Membrane

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7
Q

sustains different concentrations of certain ions on their two sides, leading to ____.

A

concentration gradient

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8
Q

structures participates in the transport of substances

A

Protein

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9
Q

Describes the organization of cell membranes

A

Fluid Mosaic Model

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10
Q

Fluid Mosaic Model

A

◦ Phospholipids drift and move like a fluid
◦ The bilayer is a mosaic mixture of phospholipids, steroids, proteins, and other molecules

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11
Q

composed____,___ and ____ of arranged in a fluid mosaic structure.

A

phospholipids, proteins, and carbohydrates

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12
Q

composed of lipid and protein molecules kept together by ____ interactions

A

non-covalent

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13
Q

most of their lipid and protein molecules __ in the plane of the bilayer

A

“float”

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14
Q

membranes are ___ __

A

fluid structures

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15
Q

impermeable to the passage of most water-soluble molecules

A

lipid bilayer

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16
Q

fundamental structure of the membrane

A

lipid molecules

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17
Q

usually span from one side of the phospholipid bilayer to the other (integral proteins), but can also sit on one of the surfaces (peripheral proteins)

A

protein

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18
Q

responsible for most of the membrane’s properties

A

protein

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19
Q

embedded in the lipid bilayer provide a mechanism for trans-membrane transport

A

integral protein

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20
Q

passive-transport

A

pores and channels

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21
Q

active-transport

A

pumps and carriers, membrane linked enzymes, and chemical signal receptors and transducers

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22
Q

associated with the surface of the membrane via electrostatic interaction

A

Peripheral proteins

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23
Q

Protein inside surface maintain ____ or ____

A

cell shape or cell motility

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24
Q

catalyzing reactions in the cytoplasm

A

Enzyme

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25
Q

specific binding site where hormones or other chemicals can bind; used for cell signaling and cell recognition

A

receptors

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26
Q

act as receptors

A

protein

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27
Q

proteins in the plasma membrane may provide a variety of major cell functions

A

Transport
Enzymatic Activity
Signal Transduction
Intercellular Joining
Cell-cell recognation
Attchment to the cytoskeleton and EM

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28
Q

Type of protein in a membrane that has a special function

A

◦ Adhesion proteins
◦ Recognition proteins
◦ Receptor proteins
◦ Enzymes
◦ Transport proteins (active and passive)

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29
Q

clotting

A

Agglutination

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30
Q

found on the outer surface and attached to the proteins or sometimes to the phospholipids

A

carbohydrates

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31
Q

Carbohydrates

A

Glycoproteins and glycolipids

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32
Q

protection and cell recognition

A

Glycocalyx

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33
Q

bear oligosaccharide side chains and are vital for cell recognition and communication

A

Glycoproteins

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34
Q

Primary types of lipids

A

Phosphoglycerides
Sphingolipids
Sterols

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35
Q

Phosphoglycerides

A

glycerol backbone

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36
Q

backbone made of sphingosine bases

A

Sphingolipids

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37
Q

cholesterol, nonpolar and only slightly soluble in water

A

sterols

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38
Q

Ampiphatic

A

Phosphoglycerides
Sphingolipids

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39
Q

(one end is hydrophilic –water soluble; other end is hydrophobic – water insoluble)

A

Amphipathic

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40
Q

Phosphoglycerides and Sphingolipids

A

dual nature is crucial to the organization of biological membranes
self-repairing
differences in the lengths of the two fatty acid tails and their composition influence fluidity

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41
Q

Phosphoglycerides and Sphingolipids

A

dual nature is crucial to the organization of biological membranes
self-repairing
differences in the lengths of the two fatty acid tails and their composition influence fluidity

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42
Q

lateral movement of lipids and proteins within a surface of the bilayer.

A

Membrane Fluidity

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43
Q

Membrane Fluidity: depends on its __ and ___ (binds weakly to phospholipids making the membrane less fluid but stronger)

A

composition
cholesterol

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44
Q

membrane molecules are held in place by relatively _____.

A

weak hydrophobic interactions

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45
Q

most lipids and some proteins can drift __ in the plane of the membrane, but rarely ___ from one layer to the other.

A

laterally
flipflop

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46
Q

influenced by temperature and constituents.

A

Membrane Fluidity

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47
Q

As Temperatures ____, Membranes fluid states transitions to___.

A

Decreases
Solid State

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48
Q

wedged between phospholipid molecules in the plasma membrane of animal cells.

A

Steroid Cholesterol

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49
Q

Steroid Cholesterol: at warm temperatures, it ___ the movement of phospholipids and reduces fluidity

A

restrains

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50
Q

at cool temperatures, it ___ fluidity by preventing tight packing

A

maintains

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51
Q

the existence of distinct lipid and protein domains in specific regions of a membrane

A

Membrane Heterogeneity

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52
Q

splits a membrane along the middle of the phospholid bilayer prior to electron microscopy.

A

Freeze Fracture

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53
Q

shows protein particles interspersed with a smooth matrix, supporting the fluid mosaic model

A

Freeze Fracture

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54
Q

regulates the passage of materials (gases, nutrients, wastes) in and out of the cell

A

Selective permeability

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55
Q

Property of the interior that makes membranes highly impermeable to most polar molecules

A

hydrophobic

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56
Q

The rate at which a substance can passively penetrate a cell membrane

A

membrane permiability

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57
Q

Influenced by inherent properties of both the membrane and the substance

A

Membrane permeability

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58
Q

Transport Systems

A

Passive processes
Active Transport

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59
Q

Passive Processes

A

• no energy expenditure and move down their normal gradient
• simple diffusion/lipid diffusion
• osmosis
• facilitated diffusion/passive Transport

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60
Q

Active Transport

A

• requires metabolic energy and moves substances against their gradients

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61
Q

Three Basic Routes

A

Dissolving in the lipid phase
Diffusion through labile or fixed aqueous channels
Carrier-mediated transport (facilitated or active transport)

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62
Q

no energy expenditure and move down their normal gradient

A

Passive transport

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63
Q

Dissolving in the lipid phase

A

• molecules diffuse through the membrane
• diffusion and osmosis
•leaves the aqueous phase on one side of the membrane
• dissolves directly in the lipid bilayer
•diffuses across the thickness of the lipid or protein layer
•enters the aqueous phase on the opposite side

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64
Q

-solute molecule remains in the aqueous phase
• diffuses through aqueous channels (water-filled pores in the membrane)

A

Diffusion through labile or fixed aqueous channels

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65
Q

• solute molecule combines with a carrier molecule dissolved in a membrane
•carrier “mediates” or “facilitates” the movement of the solute molecule across the membrane

A

Carrier-mediated transport (facilitated or active transport)

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66
Q

dissolves directly in the lipid bilayer

A

Dissolving in the lipid phase

67
Q

random thermal motion of suspended or dissolved molecules causes their dispersion from regions of higher concentration to regions of lower concentrations

A

Diffusion

68
Q

Net movement of particles (atoms, molecules, or ions) along a concentration gradient from an area of higher concentration to an area of lower concentration

A

Diffusion

69
Q

Each substance diffuses down its ______, independent of the concentration gradients of other substances.

A

own concentration gradient

70
Q

diffusion of a substance across a biological membrane is ____

A

passive transport

71
Q

assist molecules with limited permeability to diffuse through the lipid bilayer

A

Transport Protein

72
Q

Introduced by Adolf Fick in 1855.

A

Fick’s law of Diffusion

73
Q

Fick’s Law of Diffusion

A
  1. proportional to the difference in partial pressure
  2. proportional to the area of the membrane, and
  3. inversely proportional to the thickness of the membrane
74
Q

____of a membrane to a substance is the rate at which that substance passively penetrates the membrane under a specified set of conditions.

A

Permeability

75
Q

a few substances can diffuse directly through the lipid bilayer part

A

Simple Diffusion/ Lipid Diffusion

76
Q

lipid-soluble molecules such as steroids, or very small molecules, such as ____,___,and ___.

A

H2O, O2 and CO2

77
Q

Rate of diffusion depends on five factors

A

◦ Size
◦ Temperature
◦ Steepness of the concentration gradient
◦ Charge
◦ Pressure

78
Q

Factors that influence mobility of solute molecule

A

Lipid Solubility
Hydrogen bond with water
Molecular Weight
Molecular Shape
Partition coefficient

79
Q

ratio of the distribution of a substance between two different liquid phases (e.g. oil and water)

A

Partition coefficient

80
Q

Lipid Solubility

A

Increased mobility with increased lipid solubility

81
Q

factors that influence mobility of solute molecule: Hydrogen bond with water

A

Decreased mobility with increased hydrogen bond with water.

82
Q

rate of influx increases in proportion to the concentration of the solute in the extracellular fluid (difference in the number of solute molecules on the two sides of the plasma membrane.

A

non-saturation kinetics

83
Q

diffusion of water across a selectively permeable membrane is a special case of passive transport called

A

osmosis

84
Q

Osmosis continues until the solutions are _____.

A

Isotonic

85
Q

water moves from ___ to ____ water potential.

A

higher
lower

86
Q

the movement of water can produce a __________, resulting in a pressure gradient across a semipermeable membrane

A

hydrostatic pressure (a fluid mechanical pressure)

87
Q

pertains to solvent particles; determined by:- osmotic pressure

A

Osmosis

88
Q

the difference in hydraulic pressures of a solution and water (interfacing one another at either side of an SPM) which must be overcome to prevent the entry of water into the solution across the membrane

A

osmotic pressure

89
Q

Osmosis (solution)

A

Isosmotic
Hypoosmotic
Hyperosmotic
Isotonic Solution

90
Q

when two aqueous solutions exert the same osmotic pressure through a membrane permeable only to water.

A

Isosmotic

91
Q

if one solution exerts less osmotic pressure than the other

A

Hypoosmotic

92
Q

if one solution exerts greater osmotic pressure than the other

A

Hyperosmotic

93
Q

The concentration of a solution expressed as the total number of solute particles per liter

A

Osmolarity

94
Q

response of cells or tissues immersed in the solution

A

tonicity

95
Q

–osmotic pressure property of a solution

A

Osmoticity

96
Q

no osmotic pressure difference between the cell and interior and the extracellular solution; no net water gain; cell/tissue neither shrinks nor swell.

A

Isotonic solution

97
Q

•If the tissue swells because it absorbs water, the solution is ___ to the tissue.

A

hypotonic

98
Q

If the tissue shrinks because it loses water, the solution is ____ to the tissue

A

hypertonic

99
Q

cell survival depends on ____ ___ ____ and _____.

A

water uptake
loss

100
Q

more water content

A

Turgid cell

101
Q

Lesser water content

A

Plasmolyzed cells

102
Q

Hydrostatic pressue that puts cell walls in tension

A

Turgor pressure

103
Q

-through transmembrane proteins
-transport proteins tend to be specific for one molecule, so substances can only cross a membrane if it contains the appropriate protein

A

Facilitated Diffusion/Passive Transport

104
Q

Two kinds of transport proteins:

A

channel and carrier

105
Q

water-filled pore or channel in the membrane allows charged substances (usually ions) to diffuse across membranes

A

Diffusion through membrane channel

106
Q

most channels can be _____, allowing the cell to control the entry and exit of ions

A

gated (opened or closed)

107
Q

small organic compounds that specifically transports ions across the plasma membrane.

A

Ionophores

108
Q

some channel proteins, gated channels, open or close depending on _____ or _____ of a physical or chemical stimulus.

A

the presence or absence

109
Q

transports a single solute from one side of the membrane to the other

A

Uniporters

110
Q

transfer one solute and simultaneously or sequentially transfer a second solute

A

Coupled Transporters

111
Q

transfer solutes in the same direction

A

symporters

112
Q

transfer solutes in opposite directions

A

antiporters

113
Q

show saturation kinetics

A

Channel Mediated Transport

114
Q

the rate of influx increases in proportion to the concentration of the solute in the extracellular fluid (difference in the number of solute molecules on the two sides of the plasma membrane

A

Saturation Kinetics

115
Q

Diffusion Through Carrier: binding site for a __ ___ and constantly ___ two states so that the site is alternately open to opposite sides of the membrane

A

specific solute
between

116
Q

substance will bind on the side with ___ concentration and be released at the ___ concentration side

A

higher
lower

117
Q

require metabolic energy and moves substances against their gradients

A

Active Transport

118
Q

supplies the energy for most active transport

A

ATP

119
Q

actively maintains the gradient of sodium (Na+) and potassium ions (K+) across the membrane

A

Sodium-potassium pump

120
Q

Important Features of Active Transport

A
  1. Transport can take place against substantial concentration gradient
  2. Exhibits high degree of selectivity
  3. ATP or other sources of energy are required.
  4. Certain membrane pumps exchange one kind of molecule or ion from one side of the membrane for another kind of molecule or ion from the other side
  5. Some pumps perform electrical work by producing a net flux of charge
  6. Selectively inhibited by specific blocking agents
  7. Energy is released by the hydrolysis of ATP by enzymes (ATPases) present in the membrane
121
Q

_ __ __ ___ pump that transports one solute can indirectly drive the active transport of several other solutes through cotransport via a different protein.

A

A single ATP-powered

122
Q

As the solute that has been actively transported diffuses back passively through a transport protein, its movement can be coupled with the ____ of another substance against its concentration gradient.

A

active transport

123
Q

run on energy stored in ion gradients

A

symporters

124
Q

Small molecules and water enter or leave the cell through the ___ or by ____.

A

lipid bilayer
transport proteins

125
Q

Large molecules, such as polysaccharides and proteins, cross the membrane via ___

A

vesicles

126
Q

bilayers come into close apposition and then they fuse

A

Fusion of separate regions of the lipid bilayer

127
Q

Movement Across Membranes

A

Endocytosis
Exocytosis
Receptor-Mediated endocytosis

128
Q

cell brings in macromolecules and particulate matter by forming new vesicles from the plasma membrane.

A

Endocytosis

129
Q

cell creates a vesicle around a droplet of extracellular fluid

A

Pinocytosis (cellular drinking)

130
Q

Pinocytosis (cellular drinking)

A

non-specific process

131
Q

Cellular eating

A

Phagocytosis

132
Q

Depends on the presence of receptor molecules embedded in the cell membrane .

A

Receptor-mediated endocytosis

133
Q

Receptor-mediated endocytosis:triggered when extracellular substances bind to special receptors, ____ , on the membrane surface, especially near coated pits

A

ligands

134
Q

Upon binding of ligand, receptor

A

ligand complex accumulate within coated pits (internalizes the ligand)

135
Q

•transport vesicle that budded from the Golgi apparatus is moved by the cytoskeleton to the plasma membrane
•when the two membranes come in contact, the bilayers
fuse and spill the contents to the outside.

A

Exocytosis

136
Q

Membrane-Crossing Mechanisms

A

Junction between cells

137
Q

Three main types of intercellular links:

A

tight junctions,
adhering junctions (zonula adherens, desmosomes),
and gap junctions

138
Q

membranes of adjacent cells are fused, forming continuous belts around cells

A

Tight Junctions

139
Q

prevent leakage of extracellular fluid across a layer of epithelial cells

A

Tight Junctions

140
Q

fasten cells together into strong sheets, much like rivets

A

Desmosome (anchoring junctions)

141
Q

reinforced by intermediate filaments of keratin

A

Desmosome (anchoring junctions)

142
Q

attach muscle cells to each other in a muscle

A

Desmosome (anchoring junctions)

143
Q

provide cytoplasmic channels between adjacent cells

A

Gap junction (communicating junctions)

144
Q

salt ions, sugar, amino acids, and other small molecules can pass

A

Gap Junctions

145
Q

every cell maintains concentrations of inorganic solutes inside the cell that are different from those outside the cell

A

Ionic steady state

146
Q

Osmotic properties of Cells

A

Ionic Steady State
Cell volume

147
Q

cells will change size when placed in different concentrations of impermeable substances dissolved in water

A

Cell Volume

148
Q

shrinkage or swelling – osmotic movement of water

A

Cell Volume

149
Q

Two ways to prevent osmotic swelling

A

a. pump water out as fast as it leaks in
b. pump out solutes that leak into the cell – major mechanism for regulation of cell volume

150
Q

major mechanism for regulation of cell volume

A

pump out solutes that leak into the cell

151
Q

membrane permeability to charged particles depends both on the ___ and on the _____.

A

membrane permeability constant
electrical signal

152
Q

Two Forces can act on charged atoms and molecules to produce a net __ ___ of each species across a membrane

A

passive diffusion

153
Q

arising from differences in the concentration of the substance on the two sides of the membrane.

A

Chemical Gradient

154
Q

difference in electric potential across the membrane

A

electric field

155
Q

ion will move away from regions of ____ ___, and it that ion is ___ charged it will also move toward increasing negative potential

A

high concentration, positively

156
Q

determined by the sum of the combined forces of the concentration gradient and electrical gradient

A

Electrochemical gradient

157
Q

potential at which an ion is in electrochemical equilibrium

A

Equilibrium potential

158
Q

influence the value of the equilibrium potential

A

ratio ions on opposite sides of the membrane

159
Q

an ion species can passively diffuse ___ its chemical concentration gradient if the electrical gradient (potential difference) across the membrane is in the opposite direction to and exceeds the concentration gradient

A

against

160
Q

will not be affected by electrical forces but by the concentration gradient

A

uncharged molecules (sugar)

161
Q

____ of cell has a greater negative charge than the equilibrium potential for K+

A

interior

162
Q

will diffuse into the cell even if the intracellular concentration of K+ is much higher than the extracellular concentration

A

K+

163
Q

if diffusible solutes are separated by a membrane that is freely permeable to water and electrolytes but totally impermeable to one species of ion, the diffusible solutes become unequally distributed between the two compartments

A

Donnan Equilibrium

164
Q

At equilibrium, the diffusible cation, K+ , is ___ concentrated in the compartment in which the nondiffusible anion, A+ , is confined than in the other, whereas the diffusible anion, Cl- , becomes ___ concentrated in that compartment than in the other.

A

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General Physiology (5 decks)

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