AQA B2 notes Cells diffusion Osmosis

Breif overview of osmosis and cells and diffusion

HideShow resource information

life and cells

Mitochondria - These are where most of the reactions for respiration take place.

Ribosomes - These are where protiens are made in the call

Rigid Cell Wall -  Made from cellulose

Permentant Vacuole - Contains cell sap a weak solution of sugar and salts

1 of 8

Specialised Cells

Palaside Cells - are adapted for photosynthesis

Packed with Chloroplasts

Tall shape means large surface area exposed down the side for absorbing Carbon Dioxide from the air in the cell.

Thin shape, can pack a large number of chlorphyll on the top of the cell.

Palaside cells are grouped together to give palaside layers.

2 of 8

Specialised cells con....

Guard cells - are adapted to open and close pores

Special Kidney shape opens and closes the stomata in a leaf

Plant has lots of water, guard cells fill go plump & turgid, causes stomata to open so gases can be exhanged for photosynthesis

Plant short of water guard cells loose water become Flaccid, stomata closes to stop too much water vapour escaping

Thich outer wall and thicker inner wall make the opening and closeing network, sensetive to light  close at night saving water without loosing out on any photosynthesis

3 of 8

Specialised cells con....

Red Blood Cells - are adapted to carry oxygen

Concave shape gives big surface area for absorbing oxygen.

Also helps them pass smoothly throught the capillaries to reach body cells.

Packed with haemoglobin - pigement that abaorbs Oxygen

Have no nucleus leaving more room for haemoglobin

4 of 8

Specialised cells con....

Sperm and Egg cell - are specialised for reproduction

Egg cell main fucntion to carry female DNA and to nourish the devloping Embryo in the early stages, egg cell contains huge food reserves for the embryo.

When a sperm fuses with an egg, eggs membrane instantly changes it structure to stop more sperm getting into the egg, making sure Embryo has correct amount of DNA.

Sperm to get the male DNA to the female DNA, long tale and streamlined head to swim to the egg, lot of mitocondira in cell to provide the energy needed. 

Sperm also carries enzymes in their heads to digest through the egg cell membrane

5 of 8


Diffusion is the passive movement of particles from area of high concentration to low concentration

Both Liquids and gases - simmplest type = Gases diffuse through each other

The bigger diffrence in concetration the faster the diffusion rate

Only very small moecules can diffuse through the membrane e.g glucose, ammino acids, water & oxygen. Big molecules like starch and proteins cant fit through the membrane.

Particles flow through the cell membrane from high concentration to low concentration

Particles moving randomly as they can go both ways

6 of 8

Rate of Diffusion depends on 3 things

Distance -   Substances diffuse more quickly when they haven't as far to move

Concentration difference (gradient) - Substances diffuse faster if there's a bigger diffrence in concentration. If there are a lot more on one side there are more there to move across

Surface Area - The more surface area there is avaliable for the molecules to move across, the faster they can get from one side to the other

7 of 8


Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.

Osmosis is a type of diffusion

Water moves in and out of cells by osmosis

(Common GCSE question is on osmosis at work, using potatoes in beakers with diffrent sugar solutions, if the potato cylinder has drawn water in by osmosis they cyclinder will be longer (pure water), if the cyclinder has had water drawn from it (rich sugar concetration) it will have shrunk a bit)Dependant variable = cylinder length, Independant variable = concentration of sugar solution)

8 of 8


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cells, tissues and organs resources »