National 5 Biology: KA2: Transport Across Membranes Flashcards
What is the meaning of ‘hydrophillic’?
Water “loving”
What is the meaning of ‘hydrophobic’?
Water “hating”
What is the membrane made up of?
Two types of molecules - phospholipids and proteins
Why do phospholipids arrange themselves into a double layer?
The head and tails are different in their affinity for water
What is the ‘double layer’ called?
Bi-layer
Why is it called the fluid mosaic model?
fluid - phospholipids are able to move around the cell.
mosaic - proteins are in this plasma membrane making it look like a mosaic
Why is the membrane called selectively permeable?
It only allows certain molecules to diffuse into the cell - mainly smaller ones.
Why do larger molecules not get through the membrane?
They find it too difficult. eg glucose and amino acids
Where does the oxygen that enters the cell come from?
The breathing system, delivered by the blood to the extracellular fluid.
Where does the food that enters the cell come from
The digestive system, delivered by the blood to the extracellular fluid.
Waste and carbon dioxide may build up to toxic levels, so what happens?
They have to be removed to extracellular fluid and then to the blood to be carried away.
Define:
Diffusion
Movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient.
What does diffusion result in?
Even distribution of particles
Define:
Passive transport
The cell doesn’t use energy, which includes diffusion and osmosis - going from high to low concentration
Define:
Active transport
The cell does use energy - going from low to high concentration
