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BIO108- GENERAL PHYSIOLOGY > LECTURE 2: MEMBRANES, CHANNELS & TRANSPORT > Flashcards

LECTURE 2: MEMBRANES, CHANNELS & TRANSPORT Flashcards

1
Q
  • separates the cytoplasm from the external
    environment
  • one of the most important cell organelles
  • a highly selective permeable barrier that
    surrounds all living cells
  • controls how molecules and compounds
    move in and out of the cell
  • very important for proper nutrition,
    maintenance of irritability of the cells, and
    homeostasis
  • define boundaries and serve as permeability
    barriers
  • surrounds all
    animal cells
  • extraordinary thin
    (6-23 nm)
  • lipid-based
    structure that
    encloses the cytosol
A

CELL MEMBRANE

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2
Q

Cell Membrane a _______ _______ _______barrier that surrounds all living cells

A

highly selective permeable

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3
Q

Cell Membrane is Important for

A

-proper nutrition,
-maintenance of irritability of the cells, and
-homeostasis
-signal detection
-cell to cell communication
-compartmentalization

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4
Q

Cell membrane is extraordinary thin, around _____

A

6-23 nm

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5
Q

Cell membrane sustains different concentrations of certain ions on
their two sides, leading to _____________

A

concentration gradient

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6
Q

__________ participates in the transport of substances

A

protein structures

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7
Q
  • describes the organization of cell
    membranes
  • phospholipids drift and move like a fluid
  • bilayer is a mosaic mixture of
    phospholipids, steroids, proteins, and
    other molecules
A

The Fluid Mosaic Model

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8
Q

Cell membrane is composed of _________, ________, ____________ and are arranged in a _____ ______ structure.

A

-phospholipids, proteins, and
carbohydrates
-Fluid Mosaic

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9
Q

Cell Membrane is composed of _______ and ________ molecules kept together by non-covalent interactions and mostly “_______” in the plane of the bilayer.

A
  • Lipid and Proteins
    -Float
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10
Q

lipid and protein molecules kept
together by ______________________

A

non-covalent interactions

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11
Q

impermeable to the passage of
most water-soluble molecules

A

Lipid Bilayer

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12
Q

fundamental structure of the
membrane

A

Lipid Molecules

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13
Q
  • inside surface maintain cell shape or cell
    motility
  • enzymes - catalyzing reactions in the
    cytoplasm.
  • act as receptors (specific binding site
    where hormones or other chemicals can
    bind; used for cell signaling and cell
    recognition)
    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)
  • can slide around the membrane very
    quickly and collide with each other, but
    seldom flip from one side to the other
  • responsible for most of the membrane’s
    properties
A

Proteins

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14
Q

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

A

Integral Proteins

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15
Q

Integral proteins embedded in the lipid bilayer provide a mechanism for trans-membrane
transport, includes:

A

-passive-transport pores and channels,
-active-transport pumps and carriers, membrane-linked enzymes,
-chemical signal receptors
-transducers

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16
Q

associated with the
surface of the membrane via electrostatic
interaction

A

Peripheral Proteins

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17
Q

Peripheral proteins are associated with the
surface of the membrane via_________

A

electrostatic
interaction

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18
Q

Proteins inside surface maintain ________ or ______

A

Cell shape or Cell Motility

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19
Q

Proteins acts as _______ catalyzing reactions in the cytoplasm.

A

Enzymes

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20
Q

Proteins acts as receptors that acts as the specific binding site where ___________ and other__________ can bind, used for __________ and ________

A
  • hormones or other chemicals
    -cell signaling and cell recognition
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21
Q

proteins in the plasma membrane may provide
a variety of major cell functions, this includes:

A

-Transport
-Enzymatic Activity
-Signal Transduction
- Intercellular Joining
-Cell-cell communication
-Attachment to the cytoskeleton and extracellular matrix

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22
Q

Each type of protein in a membrane has a
special function, including:

A

-Adhesion Protein
-Recognition Protein
-Receptor Protein
-Enzymes
-Transport Protein (active and passive)

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23
Q

-found on the outer surface and attached
to the proteins or sometimes to the
phospholipids
-form a cell coat or glycocalyx outside the
cell membrane

A

Carbohydrates

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24
Q

___________ is responsible for Maintaining the cell stability and cell recognition and is attached to the lipids

A

Glycolipids

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25
Q

bear oligosaccharide side chains
and are vital for cell recognition and
communication, attached to the protein

A

Glycoproteins

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26
Q

_______ is used for protection and cell
recognition

A

Glycocalyx

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27
Q

What are the primary types of lipids

A
  1. Phosphoglycerides
    2.Spingholipids
  2. Sterols
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28
Q

glycerol backbone

A

Phosphoglycerides

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29
Q

backbone
made of sphingosine
bases

A

Sphingolipids

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30
Q

cholesterol,
nonpolar and only slightly
soluble in water

A

Sterols

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31
Q

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

A

amphipathic

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32
Q

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

A

phosphoglycerides and sphingolipids

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33
Q

*lateral movement of lipids and proteins within a surface of the bilayer is very common
* depends on its composition and cholesterol
(binds weakly to phospholipids making the
membrane less fluid but stronger)

A

Membrane Fluidity

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34
Q

________________ of lipids and proteins within a surface of the bilayer is very common

A

lateral movement

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35
Q

binds weakly to phospholipids making the
membrane less fluid but stronger

A

Cholesterol

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36
Q

membrane molecules are held in place by
relatively _______________________

A

weak hydrophobic interactions

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37
Q

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

A

flip-flop

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38
Q

influenced by
temperature and
constituents

A

Membrane Fluidity

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39
Q

decreased temperature, membrane fluid state turns ________ where phospholipid are more closely packed.

A

solid state

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40
Q
  • wedged between phospholipid molecules in
    the plasma membrane of animals cells.
  • at warm temperatures, it restrains the
    movement of phospholipids and reduces
    fluidity
  • at cool temperatures, it maintains fluidity by
    preventing tight packing
A

Steroid Cholesterol

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41
Q

At _________________, steroid cholesterol restrains the
movement of phospholipids and reduces
fluidity

A

Warm temp

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42
Q

At ___________________, steroid cholesterol maintains fluidity by
preventing tight packing

A

Cool Temp

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43
Q
  • freeze-etch electron
    micrographs of the
    surface of a membrane
    shows the progressive
    removal of
  • proteins when subjected
    to digestion with
    proteolitic enzyme
A

Membrane Heterogeneity

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44
Q
  • splits a membrane
    along the middle of
    the phospholid bilayer
    prior to electron
    microscopy.
  • shows protein
    particles interspersed
    with a smooth matrix,
    supporting the fluid
    mosaic model.
A

Freeze Fracture

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45
Q
  • regulates the passage of materials (gases,
    nutrients, wastes) in and out of the cell
  • hydrophobic interior makes membranes
    highly impermeable to most polar
    molecules
A

Selective permeability

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46
Q
  • The rate at which a substance can
    passively penetrate a cell membrane
  • Influenced by inherent properties of both
    the membrane and the substance
A

Membrane permeability

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47
Q

What are the two transport systems?

A

-Passive Processes
-Active Transport

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48
Q
  • no energy expenditure and move down
    their normal gradient
A

Passive Transport

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49
Q

Types of Passive Transport

A
  • simple diffusion/lipid diffusion
  • osmosis
  • facilitated diffusion/passive Transport
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50
Q

What are the three basic routes

A
  1. Dissolving in Lipid Phase
  2. Diffusion through labile or fixed aqueous
    channels
  3. Carrier mediated transport (facilitated or
    active transport)
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51
Q
  • molecules diffuses 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
A

Dissolving in lipid phase

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52
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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53
Q
  • solute molecule combines with a carrier
    molecule dissolved in 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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54
Q

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

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55
Q

Diffusion is the random thermal motion of suspended
or dissolved molecules causes their dispersion
from______________________________________

A

regions of higher concentration to regions of
lower concentrations

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56
Q

Diffusion: Net movement of ________

A

Particles

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57
Q

movements of individual molecules are
________

A

random

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58
Q

In the absence of other forces, a substance will
diffuse from where it is_______________________________

A

more concentrated to
where it is less concentrated (down its
concentration gradient)

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59
Q

Each substance diffuses down its_____________________, independent of the
concentration gradients of other substances

A

own
concentration gradient

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60
Q

diffusion of a substance across a biological
membrane is ____________________-

A

passive transport (exergonic)

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61
Q

assist molecules with
limited permeability to diffuse through the lipid
bilayer

A

Transport Proteins

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62
Q
  • Net diffusion rate across a fluid membrane is
    proportional to the difference in partial
    pressure, proportional to the area of the
    membrane and inversely proportional to the
    thickness of the membrane
A

Fick’s Law of Diffusion

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63
Q

Fick’s Law of Diffusion: Formula

A

J = - DA (∆C/∆ X)

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64
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

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65
Q

INTRINSIC FACTORS GOVERNING DIFFUSION
ACROSS MEMBRANES:

A
  • Size rule (Ex. water > urea)
  • Polarity rule (Ex. Hexane - non polar > ethanol
    polar)
  • Ionic rule (Ex. O2 > -OH)
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66
Q
  • a few substances can diffuse directly through
    the lipid bilayer part
  • lipid-soluble molecules such as steroids, or
    very small molecules, such as H2O, O2 and CO2
A

Simple Diffusion/Lipid Diffusion

67
Q

Rate of diffusion depends on five
factors:

A

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

68
Q

Factors that influence mobility of solute molecule

A
  1. Lipid Solubility
  2. Hydrogen Bond with water
  3. Molecular Weight
  4. Molecular Shape
  5. Partition coefficient
69
Q

With increasing solubility the mobility increase

A

Lipid Solubility

70
Q

Increase in hydrogen bond with water decreases mobility

A

Hydrogen bond with water

71
Q

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

A

Partition coefficient

72
Q

Partition Coefficient: Formula

A

K = solute concentration in lipid/
solute concentration in water

73
Q

Passive Diffusion: 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

74
Q

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

A

Osmosis

75
Q

Osmosis continues until the solutions are _________

A

isotonic

76
Q

Osmosis: water moves from ______________________________
(down its concentration gradient)

A

higher to lower water potential

77
Q

the movement of water can produce a ____________ (a fluid mechanical pressure), resulting in a
pressure gradient across a semipermeable
membrane

A

hydrostatic
pressure

78
Q

Hydrostatic Pressure

A

A fluid mechanical pressure

79
Q

Osmosis pertains to solvent particles; determined by __________

A

Osmotic Pressure

80
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

81
Q

Osmotic Pressure is described by _________

A

Van t’Hoff equation

82
Q

Van t’Hoff equation

A

π = Φn (C/M)R

83
Q

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

A

Isosmotic

84
Q

if one solution exerts less
osmotic pressure than the other

A

Hypoosmotic

85
Q

if one solution exerts greater
osmotic pressure than the other

A

Hyperosmotic

86
Q

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

A

Osmolarity

87
Q

response of cells or tissues
immersed in the solution

A

Tonicity

88
Q

–osmotic pressure property of a solution

A

Osmoticity

89
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

90
Q

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

A

hypotonic

91
Q

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

A

hypertonic

92
Q

_______________ depends on the balancing water uptake and loss

A

Cell Survival

93
Q

What happen to animal cell and plant cell in Hypotonic Solution?

A

Animal Cell: Lysed
Plant Cell: Turgid (Normal)

94
Q

Why does plant cell don’t burst in hypotonic solution?

A

Because of the Cell Wall

95
Q

What happen to animal cell and plant cell in Isotonic Solution?

A

Animal Cell: Normal
Plant Cell: Flaccid

96
Q

What happen to animal cell and plant cell in Hypertonic Solution?

A

Animal Cell: Shriveled
Plant Cell: Plasmolyzed

97
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

98
Q

Two kinds of transport protein

A

Channel and Carrier

99
Q

*____________________ in the membrane
allows charged substances (usually ions) to
diffuse across membranes

A

water-filled pore or channel

100
Q

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

A

gated (opened or
closed)

101
Q

small organic compounds
that specifically transports ions across
the plasma membrane

A

Ionophores

102
Q

some channel proteins, gated channels,
open or close depending on the ________________________

A

presence or
absence of a physical or chemical stimulus

103
Q

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

A

Uniporters

104
Q

transfer one solute
and simultaneously or sequentially transfer a
second solute

A

Coupled transporters

105
Q

-transfer solutes in the same
direction
-run on energy stored in
ion gradients

A

symporters

106
Q

transfer solutes in opposite
directions

A

antiporters

107
Q

Channel Mediated Transport: 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

108
Q

*binding site for a specific solute and
constantly flip between two states so that the
site is alternately open to opposite sides of
the membrane
*substance will bind on the side with higher
concentration and be released at the lower
concentration side

A

Diffusion through a carrier

109
Q

binding site for a specific solute and
constantly flip between two states so that the
site is alternately open to opposite sides of
the membrane

A

Carrier

110
Q

show saturation kinetics

A

Channel and carrier-mediated transport

111
Q

*require metabolic energy
and moves substances against their gradients
* proteins are highly specific -
different protein pump for
each molecule to be
transported
* critical for a cell to maintain
its internal concentrations of
small molecules that would
otherwise diffuse across the
membrane.
* ATP supplies the energy for
most active transport

A

Active Transport

112
Q

supplies the energy for
most active transport

A

ATP

113
Q

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

A

Sodium-potassium pump

114
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 inhibited by specific blocking agents
  7. Energy is released by the hydrolysis of ATP by enzymes (ATPases) present in the membrane
115
Q

In _________, a membrane protein couples the transport of two solutes

A

Cotransport

116
Q

A single ATP-powered pump that transports
one solute can indirectly drive the active
transport of several other solutes through
___________ via a different protein

A

cotransport

117
Q

As the solute that has been actively
transported diffuses back passively through a
transport protein, its movement can be
______________________________ against its concentration gradient

A

coupled with the active transport of another
substance

118
Q

Na+ /H+ antiporter in
the proximal tubule of the
mammalian kidney
- for each H+ expelled, one Na+ is
taken up into the cell
- advantages: avoiding the
expenditure of energy to perform
electrical work (two equivalent +
charges are exchanged)
- enables the kidney to reclaim
Na+ from urine and excess protons

A

Antiporters

119
Q

No Energy, No Proteins, No Specific, Not controllable

A

Lipid Diffusion

120
Q

No Energy, No Proteins, Yes Specific, Not Controllable

A

Osmosis

121
Q

No energy, Yes Protein, Yes Specific, Controllable

A

Passive Transport (Facilitated)

122
Q

Yes Energy, Yes Protein, Yes Specific, Contollable

A

Active Transport

123
Q

Small molecules and water enter or leave the
cell through____________________

A

the lipid bilayer or by transport
proteins

124
Q

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

A

vesicles

125
Q

Fusion of separate regions of the lipid bilayer:
bilayers come into_________ and then
they ______

A

close apposition,
fuse

126
Q
  • transport large
    molecules
A

Endocytosis and Exocytosis

127
Q

Types of Endocytosis

A

*Pinocytosis
*Phagocytosis
*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
◦ non-specific process

A

Pinocytosis

130
Q

Pinocytosis or also known as

A

Cell Drinking

131
Q

Cell Eating

A

Phagocytosis

132
Q
  • Depends on the presence of receptor molecules
    embedded in the cell membrane
  • triggered when extracellular substances bind to special receptors, ligands, on the membrane
    surface, especially near coated pits
  • Upon binding of ligand, receptor-ligand complex
    accumulate within coated pits (internalizes the
    ligand)
  • Formation of vesicle that pinches off into the
    cytoplasm
A

Receptor-mediated endocytosis

133
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

134
Q

Three main types
of intercellular
links:

A

-tight junctions,
-adhering junctions (zonula adherens,
desmosomes),
- gap junction

135
Q

➢membranes of
adjacent cells
are fused,
forming
continuous belts
around cells
➢prevent leakage of extracellular fluid
across a layer of epithelial cells

A

Tight junction

136
Q

➢fasten cells together
into strong sheets,
much like rivets
➢reinforced by
intermediate filaments
of keratin
➢attach muscle cells to
each other in a muscle

A

Desmosome (anchoring junctions)

137
Q

➢provide cytoplasmic channels
between adjacent cells
➢salt ions, sugar, amino
acids, and other small
molecules can pass

A

Gap junction (communicating junctions)

138
Q

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

A

Ionic steady state

139
Q
  • animal cell do not have rigid
    walls and cannot resist any buildup of large intracellular pressure
  • cells will change size when
    placed in different concentrations
    of impermeable substances
    dissolved in water
A

Cell volume

140
Q

osmotic movement of water

A

shrinkage or swelling

141
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

142
Q

membrane permeability to charged particles
depends both on the ________________ and on the ____________.

A

-membrane permeability constant
-electrical signal

143
Q

Two Forces can act on charged atoms and
molecules to produce a net passive diffusion of
each species across a membrane:

A

Chemical Gradient and Electric Field

144
Q

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

A

chemical gradient

145
Q

difference in electric potential
across the membrane

A

electric field

146
Q

ion will move away from regions of ______________, and if that ion is positively charged it will also move toward ___________

A

-high concentration
-increasing negative potential

147
Q

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

A

*Electrochemical gradient

148
Q

potential at which
an ion is in electrochemical equilibrium

A

*Equilibrium potential

149
Q

*Equilibrium potential

A

V or mV

150
Q

ratio of the ion concentrations on opposite
sides of the membrane influence the________________

A

value of
the equilibrium potential

151
Q

an ion species can passively diffuse against its
chemical concentration gradient if the electrical gradient (potential difference) across the membrane is in the___________ to and ________ the concentration gradient

A
  • opposite direction
    -exceeds
152
Q

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

A

uncharged molecules (sugar)

153
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

154
Q

Cell is dead if _________________

A

Cell Membrane is not responsive

155
Q

Diffusion is fast until equilibrium is reached

A

Dissolving in Lipid Phase

156
Q

Diffusion/ Concentration slows down until equilibrium is reached

A

Diffusion through labile or fixed aqueous channel

157
Q

Diffusion is very slow because the carrier is occupied, the diffusion will continue if the carrier is empty. This continues until equilibrium is reached

A

Carrier mediated transport (Facilitated or Active Transport)

158
Q

Water pass through the membrane through ____________

A

Aquaporins

159
Q

Process of Endocytosis

A
  1. Invagination
  2. Formation of Pouch
  3. Formation of Vesicle
  4. Lysosome Digest
  5. Undigested molecules undergo exocytosis
160
Q

Na+

A

Exterior: 120 mM
Interior: 10 mM

161
Q

K+

A

Exterior: 2.5
Interior: 140

162
Q

Ca2+

A

Exterior: 2.0
Interior: <10-3

163
Q

Cl-

A

Exterior: 120
Interior: 3-4

164
Q

A-

A

Interior: 140

BIO108- GENERAL PHYSIOLOGY (5 decks)

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