Key area 1.2 - Transport across membranes Flashcards
Describe structure of cell membrane
Consists of a double layer of phospholipid molecules and has proteins embedded in the membrane s
What is one function of proteins in the cell membranes ?
Some proteins are involved in the transport of materials across the membrane
What does selectively permeable mean ?
It allows some molecules to move through it easily, others move through it slowly and some can’t pass through at all
Name the two types of passive transport
Diffusion (molecules)
Osmosis (water)
Describe diffusion
The movement of molecules in a liquid or gas from high to low concentration until they’re evenly spread out
What can enter and exit an animal cell by diffusion ?
Enter - glucose and oxygen (for aerobic respiration)
Exit - carbon dioxide and other waste materials
Describe osmosis
The movement of water from a higher water concentration to a lower concentration through a selectively permeable membrane
What happens to a plant cell when placed in pure water ?
As there is more water outside the cell than inside, water will move into the cell by osmosis
This causes the cell to swell and become turgid
What happens to a plant cell when placed in a strong salt or sugar solution
As there is more water inside the cell than outside then water will move out of the cell by osmosis
This causes the cell to become plasomolysed
What happens to an animal cell when placed in pure water ?
As there’s more water outside the cell than inside then the water will move out of the cell by osmosis
This cause the cell to swell and burst
What happens to an animal cell when placed in a a strong salt or sugar solution
As there is more water inside the cell than outside then the water moves out of the cell by osmosis
This causes the cell to shrink
What is active transport ?
It’s the movement of ions and molecules against the concentration gradient
molecules/ions move from low to a high area of concentration
It requires energy
Membrane proteins are involved in the process
