8.2 Bellringer.. - pretzelpride.com Cell Transport.pdf · 8.2 Bellringer.. (1)In your own words,...
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Transcript of 8.2 Bellringer.. - pretzelpride.com Cell Transport.pdf · 8.2 Bellringer.. (1)In your own words,...
8.2 Bellringer.. (1)In your own words, define passive, active, and
transport
Now, imagine sitting in a boat that is moving downstream with the current. Then, imagine a small motor to move the same boat upstream against the current.
(2)Determine which action shows passive transport and which shows active transport
(3)Which requires an input of energy?
8.2 Cell Transport
**The cell must move different substances into and out of the cell
This happens in a variety of ways….
Sometimes the cell has to use energy, sometimes they do not
**8.2 discusses the different methods of cell transport
Passive Transport Diffusion – passive transport of substances DOWN a
concentration gradient (from high to low concentration)
Concentration gradient – one area has a higher concentration than another area
Equilibrium – when a space is filled evenly
Diffusion is simplest type of passive transport
Some substance diffuse through lipid bilayer
Others though transport proteins
Diffusion Cell membrane is selectively permeable
Nonpolar interior of lipid bilayer repels ions and most polar molecules
These substances are prevented from diffusing across membrane
Very small or nonpolar molecules can diffuse across the membrane down their concentration gradient
Facilitated Diffusion Moves ions and polar molecules that simple diffusion
cannot
Transport proteins help these substances diffuse through the cell membrane
Two types:
Channel protein
Carrier protein
Channel Proteins Ions, sugars, and amino acids can diffuse with help of
channel proteins
Proteins, sometimes called pores, serve as tunnels through the lipid bilayer
Each channel allows the diffusion of a specific substance
Ex – only sodium ions can pass through sodium ion channels
Carrier Protein Transport substances that fit within their binding site
(1)Carrier protein binds to specific substances on one side of cell membrane
(2)Binding causes protein to change shape
(3)As shape changes, the substance is moved across the cell membrane and released on other side
Osmosis Definition – diffusion of water across selectively
permeable membrane
Type of facilitated diffusion (passive transport)
From high to low concentration
Allows cells to maintain water balance as environment changes
Pass through water channels
Protein channels specific to water..
Osmosis There are three possibilities for the direction of
water movement:
Water moves out – (hypertonic solution)
Causes cell to shrink
Water moves in – (hypotonic solution)
Causes cell to swell
Cell could burst if it swells too much
Plant cells have rigid cell wall to prevent this
No net water movement – (isotonic solution)
No change in cell volume
Effects of Osmosis **Plants and fungi have cell walls to help regulate
Most plants are healthiest in a hypotonic environment
Some unicellular eukaryotes have contractile vacuoles
Force excess water in cell out
Animals cells do not have cell walls or contractile vacuoles
They actively remove solutes from cytoplasm
Active Transport Transports of substance against concentration
gradient
Low to high concentration
Active Transport – requires energy
Most energy supplied directly or indirectly in the form of ATP (adenosine triphosphate)
Pumps Substances bind to carrier proteins in low
concentrations, released in higher concentration
Carrier proteins function as “pumps” – move substances against their concentration gradient called membrane pumps
Sodium-Potassium Pump One of the most important membrane pumps in
animal cells
In a complete cycle, the sodium-potassium pump transports three sodium ions, Na+, out of a cell and two potassium ions, K+, into the cell. Pump actively transports against their concentration
gradients Energy supplied by ATP
Sodium-Potassium Pump **The sodium-potassium pump has four steps:
1. Three sodium ions inside the cell bind to the sodium-potassium pump.
2. The pump changes shape, transporting the three sodium ions across the cell membrane and releasing them outside the cell.
3. Two potassium ions outside the cell bind to the pump.
4. The two potassium ions are transported across the cell membrane and are released inside the cell.
Sodium-Potassium Pump Important:
Pump prevents sodium from accumulating in the cell
Pump helps maintain the concentration gradient of sodium ions and potassium ions across cell membrane
Many cells use this pump to help transport other substances (glucose) across the cell membrane
Movement in Vesicles Many substances, like proteins and polysaccharides,
are too large to be transported by carrier proteins So, they are moved across the cell membrane by vesicles
The movement of a substance into a cell by a vesicle is
called endocytosis
The movement of a substance by a vesicle to the outside of a cell is called exocytosis