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BIO107- CELL AND MOLECULAR BIOLOGY > LESSON 2b: CELL MEMBRANE TRANSPORT > Flashcards

LESSON 2b: CELL MEMBRANE TRANSPORT Flashcards

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1
Q
  • is the boundary between
    inside & outside…
    – separates cell from its environment
A

Cell membrane

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2
Q

Comes in …..

A

Food:
-carbohydrates
-sugars,
-proteins
-amino acids
-lipids
-salts, O2,H2O

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3
Q

Comes out…..

A

Waste:
- ammonia
-salts
-CO2
-H2O products

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4
Q

Can cell membrane be an impenetrable boundary?

A

NO!

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5
Q

Cell membrane permeability is ___________

A

Selective

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6
Q

– Allows some materials to pass.
àWater, oxygen, carbon
dioxide
– Prevents others from passing.
àProteins, carbohydrates

A

Differentially (selectively)
Permeable

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7
Q

Factors that determine how a
substance may be transported
across a plasma membrane:

A

– Size
– Polar or Nonpolar
– charge

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8
Q

-2nd Law of Thermodynamics
governs biological systems
– universe tends towards disorder
(entropy)

A

PASSIVE DIFFUSION

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9
Q

Movement of molecules in passive diffusion

A

High —-> low concentration

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10
Q

Only________, _________
molecules are able to
diffuse across a
phospholipid bilayer
at significant rates by
using passive
diffusion

A

small and relatively hydrophobic molecules

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11
Q

In passive diffusion, Molecules have to
dissolve in _______

A

lipid interior

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12
Q

Molecules that can pass through plasma membrane by passive diffusion

A
  • Gases (oxygen, carbon
    dioxide)
  • Water molecules (rate
    slow due to polarity)
  • Lipids (steroid
    hormones)
  • Lipid soluble molecules
    (hydrocarbons,
    alcohols, some
    vitamins)
  • Small noncharged
    molecules (NH3)
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13
Q

Why is diffusion important to cells
and humans?

A

Important in:
* Cell respiration
* Alveoli of lungs
* Capillaries
* Red Blood Cells
* Medications: time-release capsules

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14
Q
  • Diffusion through protein channels which do not
    interact with hydrophobic interior
    – For biological mol unable to dissolve in hydrophobic
    interior
    – no energy needed
A

Facilitated Diffusion

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15
Q

Facilitated =___________
Open Channel= ____________

A

-with help
-fast transport

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16
Q

Molecules that transport using facilitated diffusion

A
  • Ions (Na+, K+, Cl-)
  • Sugars (Glucose)
  • Amino Acids
  • Small water soluble molecules
  • Water (faster rate)
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17
Q

The passage of material in facilitated diffusion is aided both by ____________ and ___________

A

concentration gradient and transport protein

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18
Q

Two kinds of protein in facilitated diffusion

A

-Carrier Protein
-Channel Protein

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19
Q

-bind specific molecules, undergo conformational
change to release molecule
- ex. Glucose transporters

A

Carrier Proteins

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20
Q
  • form open pores for free diffusion
  • found in gap junctions
A

Channel Proteins

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21
Q

Molecules will
randomly move
through the pores
in ____________

A

Channel Proteins.

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22
Q

Some Carrier proteins ____________
through the membrane

A

do not extend

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23
Q

Some carrier protein _____________ molecules
through the lipid bilayer and release
them on the opposite side.

A

bond and drag

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24
Q

Other carrier proteins
___________to move
materials across the cell
membrane

A

change shape

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25
Q

How do molecules move through the plasma
membrane by facilitated diffusion?

A
  • Channel and Carrier proteins are specific:
  • Channel Proteins allow ions, small solutes, and water to pass
  • Carrier Proteins move glucose and amino acids
  • Facilitated diffusion is rate limited, by the number of
    proteins channels/carriers present in the membrane.
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26
Q

Most cells, including _____________, are exposed to extracellular glucose concentrations that are higher than those inside the cell, so facilitated diffusion results in the net inward transport of glucose.

A

erythrocytes,

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27
Q
  • Cells obtain food for ______
  • __________ communicate
  • ____________ transport food to bloodstream
  • Muscle cells _____
A

-cell respiration
-Neurons
-Small intestine cells
-contract

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28
Q
  • Water Channels
  • Protein pores used
    during Osmosis
  • provide corridors allowing water
    molecules to cross the membrane.
  • Allow for fast transport
  • water channel proteins,
    make possible
    massive amounts of diffusion
A

Aquaporins

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29
Q

– is the diffusion of water across a differentially
permeable membrane.

A

OSMOSIS

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30
Q

the pressure that develops in a
system due to osmosis

A

Osmotic pressure

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31
Q

Concentrations of Water

A
  1. Hypertonic
  2. Hypotonic
  3. Isotonic
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32
Q

Direction of osmosis is determined by
comparing ___________

A

total solute concentrations

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33
Q

more solute, less water

A

Hypertonic

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34
Q
  • less solute, more water
A

Hypotonic

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35
Q

equal solute, equal water

A

Isotonic

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36
Q

Cell survival depends on ___________

A

balancing water uptake & loss

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37
Q

Cell in Hypotonic Solution (Freshwater)

A

Animal Cell: Lysed
Plant Cell: Turgid (Normal)

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38
Q

Cell in Isotonic Solution (Balanced)

A

Animal Cell: Normal
Plant Cell: Flaccid

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39
Q

Cell in Hypertonic Solution (Saltwater)

A

Animal Cell: Shriveled
Plant Cell: Plasmolyzed

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40
Q

When membrane permeable to both solute molecules and water, both solution have same osmolarity: _____________, even if one solution have lower osmolarity and the other have greater osmolarity.

A

Volume Unchanged

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41
Q

When membrane is impermeable to solute molecules but permeable to water. both solution have same osmolarity: _____________,

A

but volume move to area with greater solute because water is free to move.

42
Q

Isotonic: animal cell immersed in
______ solution

A

mild salt

43
Q

Example: Blood cell in plasma membrane in isotonic solution. Thus:

A
  • no net movement of water, it flows across membrane equally, in both directions
    – volume of cell is stable
44
Q

Example for hypotonic: Paramecium in Fresh water.
Problem?
Solution?

A

Problem: gains water, swell and can burst
Solution: Contractile Vacuole (pumps water out of the cell using ATP)

45
Q

Example of Hypertonic: Shellfish in Saltwater
Problem?
Solution?

A

Problem: Lose water and Die
Solution: take up water or pump out salt

46
Q

Non-lipid soluble substances
diffuse through__________

A

membrane
channels.

47
Q

Why is osmosis important to cells and
humans?

A
  • Cells remove water
    produced by cell
    respiration.
  • Large intestine cells
    transport water to
    bloodstream
  • Kidney cells form
    urine
48
Q
  • Non lipid soluble passively diffuse ____________________ through channels
    that cross the lipid bilayer;
    some channels are open all
    the time whereas others are
    gated.
A

-down their electrochemical gradient

49
Q
  • The _____________ regulates the
    opening/closing of the
    channel
A

membrane potential
(voltage)

50
Q

Example of a specific stimulus:

A

-Voltage (Voltage-gated channel)
-Ligand (ligand-gated channels)
-Specific Stress (Stress-activated channels)

51
Q

______ permit the free passage
of ions and small polar
molecules through the outer
membranes of bacteria.

A

Porins

52
Q

______ mediate the
passage of ions across plasma
membranes

A

Ion channels

53
Q

__________ open in
response to the binding of
neurotransmitters or other
signaling molecules.

A

Ligand-gated channels

54
Q

___________ open in
response to changes in electric
potential across the plasma
membrane.

A

Voltage-gated channels

55
Q
  • open or close depending
    on the presence or absence
    of a physical or chemical
    stimulus.
  • Ex. neurotransmitters bind
    to specific gated channels
    on the receiving neuron,
    these channels open.
  • This allows sodium ions
    into a nerve cell.
  • When the
    neurotransmitters are not
    present, the channels are
    closed
A

Gated Channels

56
Q

example of voltage-gated channels

A

Membrane Potential
- K+ voltage-gated channels
-Na+ voltage-gated channels

57
Q

regulates opening/closing
of the channel.

A

membrane potential

58
Q

exist as either open or close
depending on the
membrane voltage. It has
only an activation gate.

A

K+ voltage-gated channels

59
Q

-opens when the membrane
potential depolarizes (i.e.
becomes more positive).
- It has activation and
inactivation gates.

A

Na+ voltage gated channels

60
Q

-a large family of cell surface proteins that respond to a variety of signals, including hormones, neurotransmitters, and light
-a type of cell surface receptor that interacts with G proteins to initiate intracellular signaling pathways

A

G protein-linked receptor

61
Q

-Cells may need to move molecules against concentration
gradient
– shape change transports solute from
one side of membrane to other
– protein “pump”
– “costs” energy = ATP

A

Active Transport

62
Q

The Importance of
Active Transport

A
  • Bring in essential
    molecules: ions,
    amino acids, glucose,
    nucleotides
  • Rid cell of unwanted
    molecules (Ex.
    sodium from urine
    in kidneys)
  • Maintain internal
    conditions different
    from the
    environment
    *Regulate the volume of cells
    by controlling osmotic
    potential
    *Control cellular pH
    *Re-establish concentration
    gradients to run facilitated
    diffusion. (Ex. Sodium- Potassium pump and Proton
    pumps)
63
Q

Example of Active transport

A

Pumping Na+ (sodium ions) out and K+
(potassium ions) in against strong concentration
gradients

64
Q

Process of Sodium-Potassium Pump Action

A
  1. binding of cytoplasmic Na+ to the protein stimulates phosphorylation by ATP
  2. Phosphorylation causes the protein to change its conformation
  3. The conformational change expels Na+ to the outside and extracellular K+ binds.
  4. K+ binding triggers release of a phosphate group.
  5. Loss of phosphate restores original conformation.
  6. K+ released and Na+ sites are receptive again., the cycle repeats.
65
Q

____________ move out of
the cell and then _________ move into
the cell

A

-3 Sodium ions
-2 Potassium ions

66
Q

Driven by the splitting of
ATP to provide energy and
conformational change to
proteins by adding and then
taking away a phosphate
group

A

Sodium-Potassium Pump (Active Transport)

67
Q

Sodium Potassium pump is used to establish an _______________
across neuron cell
membranes

A

electrochemical gradient

68
Q

Active transport can be classed into 2 groups

A
  1. PRIMARY ACTIVE TRANSPORT
  2. SECONDARY ACTIVE TRANSPORT
69
Q
  • _____________ is
    directly used to move
    substances across the
    membrane against its
    concentration gradient (i.e.
    from an area of low
    concentration .to an area of
    high concentration)
A

Cellular energy (i.e. ATP)

70
Q

A substance is actively transported using ATP through one channel. Then it diffuses back passively through a channel and its energy harnessed from transport is used to move another substance against it concentration gradient.

A

PRIMARY ACTIVE TRANSPORT

71
Q

Active transport, a process in
which energy is provided by
another coupled reaction, is used
to drive the uphill transport of
molecules in the _______________

A

energetically unfavorable direction

72
Q

Ion pumps responsible for
maintaining gradients of ions
across the plasma membrane,
provide important examples of
active transport driven directly by
______________.

A

ATP hydrolysis

73
Q

Some molecules are transported against their concentration gradients using energy derived not from ATP hydrolysis, but from the ________________ in the energetically favorable direction.

A

coupled transport of a second molecule

74
Q

The __________ of the intestine provide a good example of active transport drive by the Na+ gradient. (Na+ is coupled by glucose, where the energy harnessed by Na+ is used for transport)

A

epithelial cells lining

75
Q
  • Two substances are transported in the same direction across a
    plasma membrane.
  • One of the substance moves passively down its concentration
    gradient while the second substance uses ATP to move against
    its concentration gradient across the plasma membrane.
A

SECONDARY ACTIVE TRANSPORT:SYMPORTER

76
Q

-Two substances are transported across the membrane in opposite
directions across the plasma membrane.
- One of the substance moves passively down its concentration
gradient while the second substance uses ATP to move against its
concentration gradient across the plasma membrane.

A

SECONDARY ACTIVE TRANSPORT: ANTIPORTER

77
Q

A ____________ can
transport only
a single
molecule
using the
facilitated
diffusion of
glucose.

A

Uniport

78
Q

An _________
uses active
transport to
move two
molecules
in opposite
direction

A

antiport

79
Q
  • moving things out.
    – Transport of large molecules
    – Requires energy
    – Keeps the macromolecule contained
A

Vesicle Formation

80
Q

Vesicles form as a way to transport molecules out of a cell

A

Exocytosis

81
Q

Exocytosis of Proteins

A
  1. Vesicle formation: Proteins destined for export are enclosed in membrane vesicles by the trans Golgi.
  2. Vesicle movement: The vesicles are transported to the plasma membrane.
  3. Vesicle fusion: The vesicle fuses with the plasma membrane.
  4. Content release: The contents of the vesicle are released into the extracellular space.
82
Q

Vesicles
form as a way to
transport molecules
into a cell

A

Endocytosis

83
Q

Types of Endocytosis

A

-Phagocytosis
-Pinocytosis
-Receptor-Mediated Transport

84
Q

-Cell eating
- engulf Large, particulate
matter (Bacteria,
viruses, and aged or
dead cells).
-Example: Phagocytes

A

Phagocytosis

85
Q

How insulin works in regulation of blood sugar level and how endocytosis take place when insulin level drops?

A
  1. Glucose transporters are stored within the cell in membrane vesicles,
  2. When insulin interacts with its receptor, this vesicles move to the surface to fuse with the plasma membrane, increasing the number of glucose transporters in the plasma membrane.
  3. When insulin level drops, glucose transporters are removed from the plasma membrane by endocytosis, forming small vesicles.
  4. The smaller vesicles fuse with larger endosomes.
  5. Patches of the endosomes enriched for the glucose transporters bud off to become small vesicle, ready to return to the surface when insulin levels rise again,
86
Q

-Most common form of endocytosis
-* Cell forms an invagination
* Materials dissolve in water
to be brought into cell
* Called “Cell Drinking”
* Ex. Intestinal cells, Kidney
cells, Plant root cells
-Takes in dissolved molecules as vesicles

A

Pinocytosis

87
Q

Best example for Pinocytosis

A

Plant Roots

88
Q

Movement of very
specific molecules
into the cell with the
use of vesicles coated
with the ______________

A

Clathrin Protein

89
Q

-a form of
pinocytosis, provides a
mechanism for the selective
uptake of specific
macromolecules.
-Coated pits are specific
locations coated with clathrin
and receptors. When specific
molecules (ligands) bind to
the receptors, then this
stimulates the molecules to
be engulfed into a coated
vesicle
- Ex. Uptake of cholesterol
(LDL) by animal cells

A

Receptor-Mediated Transport

90
Q

Some integral
proteins have
receptors on their
surface to
_________________, hormones
cholesterol, etc

A

recognize & take in

91
Q

are specialized regions of the
plasma membrane where
specific cell surface receptors
are found.

A

Clathrin-coated pits

92
Q

a membrane associated GTP-binding
protein, assists in the
budding off of pits from the
plasma membrane.

A

Dynamin

93
Q

Clathrin assembles into a _____________-that distorts the membrane, forming invaginated pits.

A

basketlike structure

94
Q

Clathrin coated pits occupy about ____ of the surface area of plasma membranes.

A

1-2%

95
Q

are vesicles with tubular
extensions, located at
the periphery of the
cell, that fuse with
clathrin-coated
vesicles which have
shed their coats.

A

Endosomes

96
Q

An important
feature of
early
endosomes is
that they
maintain an
______________ as the
result of the
action of a
membrane H+
pump.

A

acidic internal pH

97
Q

Process of endocytosis from clathrin-coated pits.

A
  1. Arrival of a nerve impulse at the terminus of a neuron triggers the fusion of synaptic vesicles with the plasma membrane, releasing neurotransmitters.
  2. The synaptic vesicle membrane is retrieved by endocytosis from clathrin-coated pits.
  3. The endocytosis vesicles fuse with early endosomes.
  4. Synaptic vesicles are regenerated by budding from the endosome and refilled by the uptake of neurotransmitters from the cytosol.
98
Q

_________________ is the major
fate of membrane proteins taken up by receptor-mediated endocytosis.

A

Recycling to the plasma membrane

99
Q

Ligands and membrane proteins destined for
_____________________ are transported from early endosomes to late endosomes, which are located near the nucleus

A

degradation in lysosomes

100
Q

a phenomenon
where receptor-ligand complexes are removed
from the plasma membrane, thereby terminating
the response of the cell to growth factor
stimulation.

A

Receptor down-regulation

101
Q

are phagosomes fused to lysosomes,
contain lysosomal acid hydrolases that digest the ingested
material

A

Phagolysosomes

102
Q

The ______________ by phagocytosis plays distinct roles in different kinds of cells

A

ingestion of large particles

BIO107- CELL AND MOLECULAR BIOLOGY (6 decks)

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