Movement through cell membranes Flashcards
Cell membranes are
Semi permeable
Diffusion
The movement of substances from an area of high concentration to an area of low concentration
Diffusion takes place along a
Concentration gradient
Example of diffusion in plants
Carbon dioxide diffusion into a leaf and oxygen diffusion out of a leaf through the stomata
Example of diffusion in humans
Oxygen diffusion from the alveoli of the lungs into the blood and carbon dioxide diffusing out of the blood into the alveoli
Osmosis
The diffusion of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration
Does osmosis require energy
No it’s passive
Does diffusion require energy
No it’s a passive process
Osmosis is a
Special type of diffusion
Solvent
A liquid that dissolves other substances eg. water
Solute
A substance that has been dissolved eg. Salt dissolved in water
Solution
The mixture of solvent and the solute eg. Salty water
Salty water
Solution
Water
Solvent
Salt
Solute
Animal cell membranes are …
Semi permeable
Water can move in and out of cell by osmosis depending on
The water concentration in the cell compare to its external environment
If a cell is surrounded by a solution with a higher water concentration
And what will happen
Water will move into the cell by osmosis and it will swell up
If a cell is surrounded by a solution with the same water content concentration
Osmosis will not occur
If a cell is surrounded by a solution with lower concentration of water
Water will pass out of the cell by osmosis and the cell will shrink
Plant cell membrane
Semi-permeable
Cell wall is
Fully permeable
Turgid or turgid pressure
The pressure of the cytoplasm and vacuole against the cell wall of a plant
If an plant cell is surrounded by a solution with a higher water concentration (long
Water will pass out of the cell by osmosis
Cytoplasm and vacuole swell and push out on cell wall
Wall becomes stretched and rigid
Cell is very firm -turgid
What is turgid important for
Gives support in plants
By doesn’t a plant cell burst instead of becoming turgid
It’s cell wall prevents that
Plasmolysis
The shrinkage or the cell content due to loss of water by osmosis
If a plant cell is surrounded by a solution of the same water content
Osmosis will not occur
If a plant cell is surrounded by a solution with a lower water concentration (long)
Water will move out of the cell by osmosis
Vacuole shrinks
Membrane comes away from cell wall
Cell is plasmolysed and flaccid
How is plasmolysis reversible
Placing the plant in water as water will enter the cells by osmosis
What happens to a plasmolised plant?
It wilts
How is food preservation osmosis
Food soaked in salty solutions (or sugar)
Water out of microorganisms cells into food
Cells become plasmolised
Prevents their growth
2 plant examples of osmosis
Absorption of water by plant root epidermal cells
Absorption of water by germinating seeds
2 animal examples of osmosis
Absorption of water in the intestine
Re absorbtion of water in the kidney tubule (nephron)
Osmoregulation
The maintenance of water and sat balance in body fluids
Human osmoregulation example
Kidneys ate osmoregulation you organs
Non human example of osmoregulation
In amoeba the contractile vacuoles regulate the water balance
Phagocytosis
The process by which large particles are engulfed (eaten) by the cell and become incorporated into a vacuole within the cell
Example of phagocytosis
Feeding in amoeba by pseudopods
Food into food vacuole
Active transport
The movement of a substance from an area of lower concentration to an area of higher concentration
How is active transport different to diffusion (2)
Against a concentration gradient.
Requires energy.
Where does the energy for active transport come from
In the form of ATP generated inside the mitochondria
Example of active transport in plants
Absorption of minerals eg.magnesium by root epidermal cells
Example of active transport in animals
Reabsorption of saltine the nephron of the kidneys
How do plant cells remain turgid fora considerable period of time
Keep absorbing water
Water enters the outermost cells of the root by diffusion, what does this tell you about the cell shape of these cells?
Lower water concentration than soil
Why is osmosis a special type of diffusion
Still movement of substance from high concentration to low concentration - just specific to water
