Unit 1 transport across membranes Flashcards
A cell membrane consists of
Phospholipid and proteins
Why is the cell membrane selectively permeable
This means the membrane is selective, so only certain substances/molecules can pass through
Passive transport
Occurs down a concentration gradient and does not require energy
Examples of passive transport
Diffusion and osmosis
Diffusion
The movement of molecules down a concentration gradient from a high to low concentration
Why is diffusion important for humans
Aerobic Reparation
Example of diffusion in plants
Oxegen diffuses out the cell as a byproduct of photosynthesis
Example of diffusion in animals
In the lungs the oxegen is from a high oxegen concentration outside the cell to a low concentration inside
Osmosis
The movement of water molecules from a high water concentration to a low water concentration through a selectively permeable membrane
Result of osmosis on animal cells
Burst or shrink
Result of osmosis on plant cells
Turgid or plasmolysed
Example of osmosis in animals
Fresh water fish take in water by osmosis through their gills which act like selectively permeable memebrane
Burst/turgid
When water passes in from high water to a low water concentration
(Vacuole swells)
Higher water concentration
Full of water
Shrink/plasmolysed
Weh water passes out from a high water concentration to low water concentration
(Vacuole shrinks)
Lower water concentration
Loss of water
Active transport
Movement of molecules from a low concentration gradient to a high concentration gradient against the concentration gradient.
This requires energy.
