cellular transport: movement of substances into and out of the cell the adventures of osmosis...
TRANSCRIPT
Cellular Transport:Movement of substances
into and out of the cell
The Adventures of Osmosis Jones……..X
All cells must exist in a liquid environment
Water
Cellular transport is needed: -because the cell needs specific items
-items needed to produce energy-through cell respiration
-items needed to produce food -through photosynthesis
- cell also needs to give off the waste it produces.
Carbon Dioxide and water
Oxygen and water
Two types of cellular transports:1. Passive Transport:
Movement of substances into and out of a cell with NO extra energy required to be used by the cell.
3 Examples:-Diffusion-Osmosis-Facilitated diffusion
2.Active Transport:Movement of substances into and
out of a cell but the cell must expend ATP energy in order to do so.
-These items are either very much needed, very dangerous or too big to fit through the pores of the cell membrane
3 Examples:-Membrane Associated
Pumps-Endocytosis-Exocytosis
Cell membranes are semi-permeable-certain items can move in and out of the cell and others can not.
Items can move through the pores/openings between the phospholipids or through the proteins embedded in the bilayer.
Passive TransportMovement of substances into and out of the cell and the cell does not use any extra energy.
All molecules have motion:
Solids….molecules vibrateLiquid….have more energy so
they have a little moremotion
Gas…… molecules have a lot of energy so they have much motion
It is the motion of the molecules that moves them through the membrane with passive transport.
Three forms of Passive Transport:
1.Diffusion
2. Osmosis
3. Facilitated Diffusion
All three move items into and out of cell with no extra energy required
by the cell.
Diffusion-Form of passive transport.-Movement of any substance from a high concentration into a lower concentration.
-Diffusion requires no extra energy.-Items move from a high concentration to a low concentration due to the motion of the molecules.
-When molecules move from a high concentration into a lower concentration we say the item is moving down the concentration gradient.
High
Low
If diffusion is the movement of any substance from a high concentration into a lower
concentration then when will diffusion stop?
When the concentration is equal on both sides…..no high or low remains.
This is called a Dynamic Equilibrium
Example of diffusion in our body:
Simple Diffusion
The rate of diffusion can be increased by:
1. Increase in temperature2. Increase in surface area3. Stirring or shaking
Osmosis:-Form of passive transport
Therefore requires no extra energy
-Osmosis is the diffusion of water-Therefore the water must move from a
high to a low concentration
-The diffusion of water is given its own name, osmosis, because water is such an important substance for all living organism.
When will osmosis stop?
When there is an equal amount of water on both sides of the membrane. This is called an osmotic balance.
The direction of osmosis is controlled by the concentration of the solution located inside and outside the cell.
H
HL
L
Remember substances like water move from a high concentration to a
low concentration.
Three types of solutions/environments for a cell:
1. Hypotonic solution:Hypo =
low
A solution where the concentration of solute molecules outside the cell is lower than the concentration of solute molecules inside the cell.
Hypotonic Environment:98% water2% solute
96% water4% solute
Water enters the cell.
Turgor pressure increases.
Cell swells in size.
This is called cytolysis.
2. Isotonic solution:Iso =
equal
A solution where the concentration of solute molecules outside the cell is equal to the concentration of solute molecules inside the cell.
Isotonic Environment:
96% water4% solute
96% water4% solute
Water enters and leaves the cell at an equal rate.
Turgor pressure remains constant.
Cell remains the same in size.
This is called homeostasis or osmotic balance.
3. Hypertonic solution:Hyper =
high
A solution where the concentration of solute molecules outside the cell is higher than the concentration of solute molecules inside the cell.
96% water4% solute
Hypertonic Environment:94% water6% solute
Water leaves the cell.
Turgor pressure decreases.
Cell decreases in size.
This is called plasmolysis.
Elodea
Elodea cell in a fresh water environment
1% Saline
1% solute dissolvedIn 99% water.
Elodea in a 6% Saline Solution
6% salt dissolvedIn 94% water
WHY DID THIS HAPPEN??????????????
Facilitated Diffusion-final form of passive transport
-requires cell to use NO extra energyFACILITATE:
-means to helpDIFFUSION:
-form of diffusion so………………-items move from a high concentration into a lower concentration.
Facilitated Diffusion:-allows for the movement of
important items that are too large to fit through the pores of the membrane from a high into a low concentration with the help of “carrier proteins”.
Carrier proteins: very specific, each helps only one type of molecule to pass through the membrane.
Role of Insulin as a carrier proteinInsulin moves glucose across the membrane 100X faster than it would move if insulin is not present.
Active Transport-movement across the membrane BUT the cell must expend energy in order for it to occur.
Examples:Membrane Associated Pumps MAPsEndocytosisExocytosis
MAPs ~ Membrane Associated Pumps
-energy driven protein motors that move specific types of solutes across the cell membrane against the concentration gradient.
-from a low into a high concentrationHigh
Low
-in order for the cell to expend energy to move items across there must be a “real” need. Items must be really, really needed or really, really toxic to the cell.
Two types of MAPs:
1. Calcium Pump2. Sodium-Potassium Pumps
The cell is only willing to pump these three items across the membrane.
Bones and teeth require a lot of calcium to remain strong. Therefore they must “hoard” large amounts of calcium. Calcium must move from a low concentration in our blood into a high concentration in the cells of both the teeth and the bones.
H
HL
Muscles require a lot of potassium and create a lot of sodium as a waste. Therefore they must “hoard” large amounts of potassium and get rid of the sodium. Both of these substances must move from a low concentration into a higher concentration.
Membrane Associated Pumps
EndocytosisEndo =
INCyto =
CELL
Cell membrane surrounds and engulfs items taking them into the cell.
Hyperlink
Three types of endocystosis:1. Phagocytosis:
-Cell surrounds and engulfs solid items taking them into the cell.
Examples:Amoeba:
White Blood Cells
2. Pinocytosis:
-Cell surrounds and engulfs substances dissolved in water, taking them into the cell.
3. Receptor-mediated Endocytosis:
-items like hormones, vitamins and minerals attach to specific receptor proteins. Once attached the membrane pinches together taking the items in.
Endocytosis
Exocytosis:Exo =
OUTCyto=
CELL
-Cell membrane opens up and forces items out of the cell.
Example:Contractile VacuolesAnal pores
Hyperlink
Types of Exocytosis:1. Excretion:
-waste is forced out of the cell
-mucus, sweat, tears…..
2. Secretion:-items made by the cell and needed in other places are forced out of the cell.
-hormones, digestive enzymes, saliva
Exocytosis
ScenarioIf a bone cell is surrounded by 100 units
of calcium and it has 50 units already stored in it what will occur?
50 units of Ca+
100 units of Ca+
25 units move in by diffusion
/75
75
/
Finally, as many as possible of the 75 units of Ca+ will move in due to MAPs