Transport Across The Cell Membrane Flashcards
State 2 components which make up the plasma cell membrane.
Proteins
Phospholipid
They form a bilayer
State another name for a plasma cell membrane.
Fluid mosaic model
Explain why the plasma cell membrane is known as the fluid mosaic model.
Due to the fluid nature of the phospholipids and mosaic describes the proteins which are randomly embedded into the phospholipids.
State what is meant by the term selectively permeable
This means the membrane allows small molecules for example glucose, oxygen and amino acids but not large molecules like starch to pass through it.
What is passive transport?
Passive transport is the movement of molecules from a region of high concentration to a region of low concentration. Down a concentration gradient it does not require energy.
State 2 passive processes.
Diffusion and osmosis
State the definition of diffusion.
Diffusion is the movement of molecules from a region of high concentration to a region of low concentration. Down a concentration gradient it does not require energy.
State the definition of osmosis.
Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration. Down a concentration gradient it does not require energy.
Why is diffusion important to the body?
Living cells depend on diffusion for the movement of materials into and out of the cells.
- Water, oxygen, glucose and amino acids are essential substances that enter an animal cell by diffusion.
- Carbon dioxide is a waste material that diffuses out of a cell.
- Gas exchange in our lungs.
Describe what happens when plant cells are in a high water concentration.
Cell is turgid.
Water moves into the cell causing the vacuole to swell.
The cell wall stops the plant cell from bursting.
Describe what happens when plant cells are in a low water concentration.
Cell is plasmolysed
Water moves out of the cell causing the vacuole to shrink and the cell membrane to pull away from the cell wall.
Describe what happens when animal cells are in a high water concentration.
Water moves into the cell causing it to swell.
It will eventually burst as animal cells have no cel wall.
Describe what happens when animal cells are in a low water concentration.
Water moves out of the cell causing it to shrink.
What is meant by the term active transport.
Active transport is the movement of molecules and ions against the concentration gradient by membrane proteins. Molecule move from an area of low concentration to an area of high concentration.
This process requires energy stored in ATP.
State what component of the membrane is responsible for active transport.
Protein.
