Membranes, Channels, and Transport Flashcards
1
Q
separates the cytoplasm from the external environment
A
Cell Membrane
2
Q
a highly selective permeable barrier that surrounds all living cells
A
Cell Membrane
3
Q
Cell membrane is very important for ____,____, and___.
A
proper nutrition, maintenance of irritability of the cells, and homeostasis
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
5
Q
Cell Membrane Extraordinary Thin
A
6-23 nm
6
Q
Iipid-based structure that encloses the cytosol
A
Cell Membrane
7
Q
sustains different concentrations of certain ions on their two sides, leading to ____.
A
concentration gradient
8
Q
structures participates in the transport of substances
A
Protein
9
Q
Describes the organization of cell membranes
A
Fluid Mosaic Model
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
11
Q
composed____,___ and ____ of arranged in a fluid mosaic structure.
A
phospholipids, proteins, and carbohydrates
12
Q
composed of lipid and protein molecules kept together by ____ interactions
A
non-covalent
13
Q
most of their lipid and protein molecules __ in the plane of the bilayer
A
“float”
14
Q
membranes are ___ __
A
fluid structures
15
Q
impermeable to the passage of most water-soluble molecules
A
lipid bilayer
16
Q
fundamental structure of the membrane
A
lipid molecules
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
18
Q
responsible for most of the membrane’s properties
A
protein
19
Q
embedded in the lipid bilayer provide a mechanism for trans-membrane transport
A
integral protein
20
Q
passive-transport
A
pores and channels
21
Q
active-transport
A
pumps and carriers, membrane linked enzymes, and chemical signal receptors and transducers
22
Q
associated with the surface of the membrane via electrostatic interaction
A
Peripheral proteins
23
Q
Protein inside surface maintain ____ or ____
A
cell shape or cell motility
24
Q
catalyzing reactions in the cytoplasm
A
Enzyme
25
specific binding site where hormones or other chemicals can bind; used for cell signaling and cell recognition
receptors
26
act as receptors
protein
27
proteins in the plasma membrane may provide a variety of major cell functions
Transport
Enzymatic Activity
Signal Transduction
Intercellular Joining
Cell-cell recognation
Attchment to the cytoskeleton and EM
28
Type of protein in a membrane that has a special function
◦ Adhesion proteins
◦ Recognition proteins
◦ Receptor proteins
◦ Enzymes
◦ Transport proteins (active and passive)
29
clotting
Agglutination
30
found on the outer surface and attached to the proteins or sometimes to the phospholipids
carbohydrates
31
Carbohydrates
Glycoproteins and glycolipids
32
protection and cell recognition
Glycocalyx
33
bear oligosaccharide side chains and are vital for cell recognition and communication
Glycoproteins
34
Primary types of lipids
Phosphoglycerides
Sphingolipids
Sterols
35
Phosphoglycerides
glycerol backbone
36
backbone made of sphingosine bases
Sphingolipids
37
cholesterol, nonpolar and only slightly soluble in water
sterols
38
Ampiphatic
Phosphoglycerides
Sphingolipids
39
(one end is hydrophilic –water soluble; other end is hydrophobic – water insoluble)
Amphipathic
40
Phosphoglycerides and Sphingolipids
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
41
Phosphoglycerides and Sphingolipids
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
42
lateral movement of lipids and proteins within a surface of the bilayer.
Membrane Fluidity
43
Membrane Fluidity: depends on its __ and ___ (binds weakly to phospholipids making the membrane less fluid but stronger)
composition
cholesterol
44
membrane molecules are held in place by relatively _____.
weak hydrophobic interactions
45
most lipids and some proteins can drift __ in the plane of the membrane, but rarely ___ from one layer to the other.
laterally
flipflop
46
influenced by temperature and constituents.
Membrane Fluidity
47
As Temperatures ____, Membranes fluid states transitions to___.
Decreases
Solid State
48
wedged between phospholipid molecules in the plasma membrane of animal cells.
Steroid Cholesterol
49
Steroid Cholesterol: at warm temperatures, it ___ the movement of phospholipids and reduces fluidity
restrains
50
at cool temperatures, it ___ fluidity by preventing tight packing
maintains
51
the existence of distinct lipid and protein domains in specific regions of a membrane
Membrane Heterogeneity
52
splits a membrane along the middle of the phospholid bilayer prior to electron microscopy.
Freeze Fracture
53
shows protein particles interspersed with a smooth matrix, supporting the fluid mosaic model
Freeze Fracture
54
regulates the passage of materials (gases, nutrients, wastes) in and out of the cell
Selective permeability
55
Property of the interior that makes membranes highly impermeable to most polar molecules
hydrophobic
56
The rate at which a substance can passively penetrate a cell membrane
membrane permiability
57
Influenced by inherent properties of both the membrane and the substance
Membrane permeability
58
Transport Systems
Passive processes
Active Transport
59
Passive Processes
• no energy expenditure and move down their normal gradient
• simple diffusion/lipid diffusion
• osmosis
• facilitated diffusion/passive Transport
60
Active Transport
• requires metabolic energy and moves substances against their gradients
61
Three Basic Routes
Dissolving in the lipid phase
Diffusion through labile or fixed aqueous channels
Carrier-mediated transport (facilitated or active transport)
62
no energy expenditure and move down their normal gradient
Passive transport
63
Dissolving in the lipid phase
• 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
64
-solute molecule remains in the aqueous phase
• diffuses through aqueous channels (water-filled pores in the membrane)
Diffusion through labile or fixed aqueous channels
65
• solute molecule combines with a carrier molecule dissolved in a membrane
•carrier “mediates” or “facilitates” the movement of the solute molecule across the membrane
Carrier-mediated transport (facilitated or active transport)
66
dissolves directly in the lipid bilayer
Dissolving in the lipid phase
67
random thermal motion of suspended or dissolved molecules causes their dispersion from regions of higher concentration to regions of lower concentrations
Diffusion
68
Net movement of particles (atoms, molecules, or ions) along a concentration gradient from an area of higher concentration to an area of lower concentration
Diffusion
69
Each substance diffuses down its ______, independent of the concentration gradients of other substances.
own concentration gradient
70
diffusion of a substance across a biological membrane is ____
passive transport
71
assist molecules with limited permeability to diffuse through the lipid bilayer
Transport Protein
72
Introduced by Adolf Fick in 1855.
Fick's law of Diffusion
73
Fick's Law of Diffusion
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
____of a membrane to a substance is the rate at which that substance passively penetrates the membrane under a specified set of conditions.
Permeability
75
a few substances can diffuse directly through the lipid bilayer part
Simple Diffusion/ Lipid Diffusion
76
lipid-soluble molecules such as steroids, or very small molecules, such as ____,___,and ___.
H2O, O2 and CO2
77
Rate of diffusion depends on five factors
◦ Size
◦ Temperature
◦ Steepness of the concentration gradient
◦ Charge
◦ Pressure
78
Factors that influence mobility of solute molecule
Lipid Solubility
Hydrogen bond with water
Molecular Weight
Molecular Shape
Partition coefficient
79
ratio of the distribution of a substance between two different liquid phases (e.g. oil and water)
Partition coefficient
80
Lipid Solubility
Increased mobility with increased lipid solubility
81
factors that influence mobility of solute molecule: Hydrogen bond with water
Decreased mobility with increased hydrogen bond with water.
82
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.
non-saturation kinetics
83
diffusion of water across a selectively permeable membrane is a special case of passive transport called
osmosis
84
Osmosis continues until the solutions are _____.
Isotonic
85
water moves from ___ to ____ water potential.
higher
lower
86
the movement of water can produce a __________, resulting in a pressure gradient across a semipermeable membrane
hydrostatic pressure (a fluid mechanical pressure)
87
pertains to solvent particles; determined by:- osmotic pressure
Osmosis
88
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
osmotic pressure
89
Osmosis (solution)
Isosmotic
Hypoosmotic
Hyperosmotic
Isotonic Solution
90
when two aqueous solutions exert the same osmotic pressure through a membrane permeable only to water.
Isosmotic
91
if one solution exerts less osmotic pressure than the other
Hypoosmotic
92
if one solution exerts greater osmotic pressure than the other
Hyperosmotic
93
The concentration of a solution expressed as the total number of solute particles per liter
Osmolarity
94
response of cells or tissues immersed in the solution
tonicity
95
–osmotic pressure property of a solution
Osmoticity
96
no osmotic pressure difference between the cell and interior and the extracellular solution; no net water gain; cell/tissue neither shrinks nor swell.
Isotonic solution
97
•If the tissue swells because it absorbs water, the solution is ___ to the tissue.
hypotonic
98
If the tissue shrinks because it loses water, the solution is ____ to the tissue
hypertonic
99
cell survival depends on ____ ___ ____ and _____.
water uptake
loss
100
more water content
Turgid cell
101
Lesser water content
Plasmolyzed cells
102
Hydrostatic pressue that puts cell walls in tension
Turgor pressure
103
-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
Facilitated Diffusion/Passive Transport
104
Two kinds of transport proteins:
channel and carrier
105
water-filled pore or channel in the membrane allows charged substances (usually ions) to diffuse across membranes
Diffusion through membrane channel
106
most channels can be _____, allowing the cell to control the entry and exit of ions
gated (opened or closed)
107
small organic compounds that specifically transports ions across the plasma membrane.
Ionophores
108
some channel proteins, gated channels, open or close depending on _____ or _____ of a physical or chemical stimulus.
the presence or absence
109
transports a single solute from one side of the membrane to the other
Uniporters
110
transfer one solute and simultaneously or sequentially transfer a second solute
Coupled Transporters
111
transfer solutes in the same direction
symporters
112
transfer solutes in opposite directions
antiporters
113
show saturation kinetics
Channel Mediated Transport
114
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
Saturation Kinetics
115
Diffusion Through Carrier: binding site for a __ ___ and constantly ___ two states so that the site is alternately open to opposite sides of the membrane
specific solute
between
116
substance will bind on the side with ___ concentration and be released at the ___ concentration side
higher
lower
117
require metabolic energy and moves substances against their gradients
Active Transport
118
supplies the energy for most active transport
ATP
119
actively maintains the gradient of sodium (Na+) and potassium ions (K+) across the membrane
Sodium-potassium pump
120
Important Features of Active Transport
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
_ __ __ ___ pump that transports one solute can indirectly drive the active transport of several other solutes through cotransport via a different protein.
A single ATP-powered
122
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.
active transport
123
run on energy stored in ion gradients
symporters
124
Small molecules and water enter or leave the cell through the ___ or by ____.
lipid bilayer
transport proteins
125
Large molecules, such as polysaccharides and proteins, cross the membrane via ___
vesicles
126
bilayers come into close apposition and then they fuse
Fusion of separate regions of the lipid bilayer
127
Movement Across Membranes
Endocytosis
Exocytosis
Receptor-Mediated endocytosis
128
cell brings in macromolecules and particulate matter by forming new vesicles from the plasma membrane.
Endocytosis
129
cell creates a vesicle around a droplet of extracellular fluid
Pinocytosis (cellular drinking)
130
Pinocytosis (cellular drinking)
non-specific process
131
Cellular eating
Phagocytosis
132
Depends on the presence of receptor molecules embedded in the cell membrane .
Receptor-mediated endocytosis
133
Receptor-mediated endocytosis:triggered when extracellular substances bind to special receptors, ____ , on the membrane surface, especially near coated pits
ligands
134
Upon binding of ligand, receptor
ligand complex accumulate within coated pits (internalizes the ligand)
135
•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.
Exocytosis
136
Membrane-Crossing Mechanisms
Junction between cells
137
Three main types of intercellular links:
tight junctions,
adhering junctions (zonula adherens, desmosomes),
and gap junctions
138
membranes of adjacent cells are fused, forming continuous belts around cells
Tight Junctions
139
prevent leakage of extracellular fluid across a layer of epithelial cells
Tight Junctions
140
fasten cells together into strong sheets, much like rivets
Desmosome (anchoring junctions)
141
reinforced by intermediate filaments of keratin
Desmosome (anchoring junctions)
142
attach muscle cells to each other in a muscle
Desmosome (anchoring junctions)
143
provide cytoplasmic channels between adjacent cells
Gap junction (communicating junctions)
144
salt ions, sugar, amino acids, and other small molecules can pass
Gap Junctions
145
every cell maintains concentrations of inorganic solutes inside the cell that are different from those outside the cell
Ionic steady state
146
Osmotic properties of Cells
Ionic Steady State
Cell volume
147
cells will change size when placed in different concentrations of impermeable substances dissolved in water
Cell Volume
148
shrinkage or swelling – osmotic movement of water
Cell Volume
149
Two ways to prevent osmotic swelling
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
major mechanism for regulation of cell volume
pump out solutes that leak into the cell
151
membrane permeability to charged particles depends both on the ___ and on the _____.
membrane permeability constant
electrical signal
152
Two Forces can act on charged atoms and molecules to produce a net __ ___ of each species across a membrane
passive diffusion
153
arising from differences in the concentration of the substance on the two sides of the membrane.
Chemical Gradient
154
difference in electric potential across the membrane
electric field
155
ion will move away from regions of ____ ___, and it that ion is ___ charged it will also move toward increasing negative potential
high concentration, positively
156
determined by the sum of the combined forces of the concentration gradient and electrical gradient
Electrochemical gradient
157
potential at which an ion is in electrochemical equilibrium
Equilibrium potential
158
influence the value of the equilibrium potential
ratio ions on opposite sides of the membrane
159
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
against
160
will not be affected by electrical forces but by the concentration gradient
uncharged molecules (sugar)
161
____ of cell has a greater negative charge than the equilibrium potential for K+
interior
162
will diffuse into the cell even if the intracellular concentration of K+ is much higher than the extracellular concentration
K+
163
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
Donnan Equilibrium
164
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.
more
less
