Unit 1 (KA2) Transport Across Cell Membranes Flashcards
Describe the structure of the cell membrane using keywords.
The cell membrane consists of phospholipids and proteins and is selectively permeable.
Define passive transport.
Passive transport occurs down a concentration gradient and does not require energy.
State two examples of passive transport.
Diffusion
Osmosis
Define diffusion.
The movement of molecules from a higher concentration to a lower concentration, down a concentration gradient. Does not require energy.
Define osmosis.
The movement of water from a higher water concentration to a lower water concentration, through a selectively permeable membrane. Does not require energy.
What is the effect on the animal cell when placed in a salty/sugary solution?
The animal cell shrinks, because water moves out of the cell by osmosis.
What is the effect on the animal cell when placed in pure water?
The animal cell bursts, because water moves into the cell by osmosis.
What is the effect on the plant cell when placed in a salty/sugary solution?
The plant cell becomes plasmolysed, because water moves out of the cell by osmosis.
Define plasmolyed.
A plant cell that has shrunk as water moved out of it.
What is the effect on the plant cell when placed in pure water?
The plant cell becomes turgid, because water moves into the cell by osmosis.
Define turgid.
A plant cell that has filled up with water.
Define active transport.
The movement of molecules and ions against the concentration gradient that requires energy.
What does selectively permeable mean?
Allows some molecules through but not others.
What is a concentration gradient?
When there is a difference in concentration on each side of a cell membrane.
