Download Cell Transport Powerpoint

Competencies
1. explain transport mechanisms in cells (diffusion
osmosis,facilitated transport, active transport)
STEM_BIO11/12-Ig-h-13
2. differentiate exocytosis and endocytosis STEM_BIO11/12-Ig-h-14
Activity (15 mins)
Video on Cell Membrane and Transport
Guide Questions
1. What is cell membrane and its composition based on
the video?
2. Initially, what is Cell Transport? Describe each type.
3. Why is Transport necessary in Cell?
Membrane Transport
• Motion of substances in and
out of the cell
• Cell membranes are
Selectively permeable
• Two Types of Transport
Mechanisms:
1. Passive Transport
2. Active Transport
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Membrane Transport
• Passive transport is movement of
molecules through the membrane in which no
energy is required from the cell
• Active transport requires energy
expenditure by the cell
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1. Passive Movement – requires no energy
Types: 1. Diffusion – process of scattering molecules from an area
of greater to a lesser concentration.
Types: A. Simple Diffusion – unassisted diffusion
1. Osmosis – movement of solvent materials
2. Dialysis – movement of solute materials.
B. Facilitated Diffusion – provides protein carriers as
transport vehicle.
2. Filtration – process by which water and solute are forced
thru a membrane by fluid or hydrostatic pressure
2. Active Transport – when cells uses ATP supply to move
substances across the membrane.
Types:
1. Solute Pumping – similar to facilitated diffusion that
requires carriers that reversibly with substances to be
transported across membrane.
2. Bulk Transport – some substances that cannot get
through the plasma membrane in any other way are
transported with the help of ATP into or out of cell.
Passive Transport
A process that does not require energy to move
molecules from a HIGH to LOW concentration
 Diffusion
 Facilitated Diffusion
• Diffusion is the movement of small particles across a
selectively permeable membrane like the cell membrane
until equilibrium is reached.
These particles move from an area of high concentration
to an area of low concentration.
outside of cell
inside of cell
• Diffusion is movement of solute
molecules from high concentration to low
concentration
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1. Passive Transport
• There are two types of diffusion
1. Simple Diffusion
2. Facilitated Diffusion
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1. Passive Transport
1. Simple Diffusion
• Substances pass directly through the
cell membrane
• The cell membrane has limited
permeability to small polar molecules,
water, and ions
• The motion of water across the
membrane is known as osmosis
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• Osmosis is the diffusion of water through a selectively
permeable membrane like the cell membrane
Water diffuses across a membrane from an area of high
concentration to an area of low concentration.
Semi-permeable
membrane is
permeable to water,
but not to sugar
Passive Transport
Osmosis
• Osmosis is the movement of water from an
area of high to low concentration of water
- movement of water toward an area of high
solute concentration
-
in osmosis, only water is able to pass through the
membrane
- Osmosis moves water through aquaporins
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Osmosis
• Osmotic concentration is determined by
the the concentration of all solutes in solution
• Relative Osmotic Concentrations
• Hypertonic solutions: have a higher relative
solute concentration
• Hypotonic solutions: have a lower relative
solute concentration
• Isotonic Solutions: have equal relative solute
concentrations
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1. Passive Transport
2. Facilitated Diffusion
• Substances must pass through
transported proteins to get through the
cell membrane
• The cell membrane is selectively
permeable
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• Facilitated Diffusion is the movement of larger
molecules like glucose through the cell membrane –
larger molecules must be “helped”
Proteins in the cell membrane form channels for large
molecules to pass through
Proteins that form channels (pores) are called protein
channels
outside of cell
inside of cell
Glucose molecules
Facilitated Diffusion
• Selective permeability: integral membrane
proteins allow the cell to be selective about
what passes through the membrane.
- Channel proteins have a polar interior allowing
polar molecules to pass through.
- Carrier proteins bind to a specific molecule to
facilitate its passage.
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Channel Proteins
• Channel proteins include:
- ion channels allow the passage of ions
(charged atoms or molecules) which are
associated with water
- gated channels are opened or closed
in response to a stimulus
– the stimulus may be chemical or electrical
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ion channels
Fig. 5.10
Channel Proteins
• Ion channels allow the passage of ions
(charged atoms or molecules) across the
membrane
• A concentration gradient of ions across the
membrane creates a membrane potential
-
a membrane potential is a charge difference
between the two sides of the membrane
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ion channels
Fig. 5.10
+
+
+ +
+
+
+
+
+
+
Carrier Proteins
• Carrier proteins bind to a specific molecule
to facilitate its passage.
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Click
Hypertonic Solutions: contain a high concentration of solute
relative to another solution (e.g. the cell's cytoplasm). When
a cell is placed in a hypertonic solution, the water diffuses
out of the cell, causing the cell to shrivel.
Hypotonic Solutions: contain a low concentration of solute
relative to another solution (e.g. the cell's cytoplasm). When
a cell is placed in a hypotonic solution, the water diffuses
into the cell, causing the cell to swell and possibly explode.
Isotonic Solutions: contain the same concentration of solute
as another solution (e.g. the cell's cytoplasm). When a cell is
placed in an isotonic solution, the water diffuses into and
out of the cell at the same rate. The fluid that surrounds the
body cells is isotonic.
Click
• Organisms can maintain osmotic balance in
different ways:
1. Some cells use extrusion in which
water is ejected through contractile vacuoles.
2. Isosmotic regulation involves
keeping cells isotonic with their environment.
3. Plant cells use turgor pressure to
push the cell membrane against the cell wall
and keep the cell rigid.
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B. Active Transport
Active transport is the movement of molecules from LOW to HIGH
concentration.
Energy is required as molecules must be pumped against the
concentration gradient.
Proteins that work as pumps are called protein pumps.
Ex: Body cells must pump carbon dioxide out into the surrounding
blood vessels to be carried to the lungs for exhale. Blood vessels are
high in carbon dioxide compared to the cells, so energy is required
to move the carbon dioxide across the cell membrane from LOW to
HIGH concentration.
outside of cell
inside of cell
Carbon Dioxide
molecules
ANALOGY:
ENERGY NEEDED:
Active Transport
NO ENERGY NEEDED:
Diffusion
Osmosis
Facilitated Diffusion
2. Active Transport
Active transport
• Requires energy – ATP is used directly or
indirectly to fuel active transport
• Able to moves substances against the
concentration gradient - from low to high
concentration
- allows cells to store concentrated substances
• Requires the use of carrier proteins
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Active Transport
• Carrier proteins used in active transport
include:
-uniporters – move one molecule at a
time
-symporters – move two molecules in
the same direction
-antiporters – move two molecules in
opposite directions
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1. Solute Pumping
Sodium-potassium (Na+-K+) pump
• An active transport antiport mechanism
• Uses an antiporter to move 3 Na+ out of the
cell and 2 K+ into the cell
• ATP energy is used to change the
conformation of the carrier protein
• The affinity of the carrier protein for either
Na+ or K+ changes so the ions can be carried
across the membrane
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Active Transport
Sodium-potassium (Na+-K+) pump
• Used by animal cells to maintain a high
internal concentration of K+ ions and a low
internal concentration of Na+ ions
• Maintains a concentration gradient that is
used to power many other important
physiological process
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Fig. 5.15-1
Fig. 5.15-2
Fig. 5.15-3
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Active Transport
Coupled transport
• Uses the energy released when a molecule
moves by diffusion to supply energy to active
transport of a different molecule
• A symporter is used
• Glucose-Na+ symporter captures the energy
from Na+ diffusion to move glucose against a
concentration gradient
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2. Bulk Transport
• Bulk transport of substances is accomplished
by
1. Endocytosis – movement of
substances into the cell
2. Exocytosis – movement of materials
out of the cell
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Ex: White Blood Cells, which are part of the immune
system, surround and engulf bacteria by endocytosis.
Bulk Transport
• Endocytosis occurs when the plasma
membrane envelops food particles and liquids.
1. phagocytosis – the cell takes in
particulate matter
2. pinocytosis – the cell takes in only
fluid
3. receptor-mediated endocytosis –
specific molecules are taken in after they bind
to a receptor
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Bulk Transport
• Exocytosis occurs when material is
discharged from the cell.
• Vesicles in the cytoplasm fuse with the cell
membrane and release their contents to the
exterior of the cell
• Used in plants to export cell wall material
• Used in animals to secrete hormones,
neurotransmitters, digestive enzymes
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(10mins) Application:
1. What did you learn today?
2. How do you relate the Cell Transport to real
life situation? Make an analogy