1.2 Transport across the membrane Flashcards
The cell membrane
The cell membrane is selectively permeable. This means it only allows some molecules to pass through but not others
What are cell membranes made up of
Phospholipids
Proteins
Passive transport
This occurs down a concentration gradient and does not require energy
Examples of passive transport
Diffusion = oxygen, carbon dioxide, glucose
Osmosis = water
What three ways can the cell membrane move molecules through
Diffusion
Osmosis
Active transport
Diffusion
Is the movement of molecules down a concentration gradient from a high to a low concentration
Concentration gradient
A concentration gradient is the difference in concentrations between two solutions
Different concentrations of substances exist between cells and their environment
Inside cell: low oxygen
Outside cell: high oxygen
Osmosis
The movement of water molecules from a region of high water concentration to a region of low water concentration
This is passive transport which means it does not require energy
What happens if you put an animal cell in pure water (higher concentration)
The cell will burst as water moves in
What happens when you put an animal cell in the same water concentration
It will stay the same
What happens if you put an animal cell in salt or sugar solution (lower concentration)
The cell will shrink as water moves out of the
What happens if you put a plant cell in pure water (higher concentration)
It will turn turgid as water moves in
What happens if you put a plant cell in the same water concentration
It will stay the same
What happens if you put a plant cell in salt or sugar water (lower concentration)
It will become plasmolysed as water moves out
Why is there different effect of osmosis on plant and animal cells
A plant cell has a cell wall which provides structure and support to the cell.
An animal cell doesn’t.
