iGCSE Biology Notes Movement into and out of cells

[q] How do particles move? 

Can you remember the ways molecules move?

How do particles move in biological systems?

[a] 

• Diffusion
• Osmosis
• Active transport

[q] Diffusion

Can you fill in the gaps?

[a] Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient. Diffusion is due to the random movement of particles and therefore the energy comes from the kinetic energy of the particles.

[q] Osmosis 

Can you fill in the gaps?

[a] Osmosis is the net movement of water from an area of high water potential to an area of low water potential, through a partially permeable membrane.

[q] Osmosis – What effect does it have on cells? 

Osmosis effects

[a] Now you know what osmosis is, what effect would it have on the cell in these two situations? Water moves into the cell! 

[q] Osmosis – What effect does it have on cells? 

Osmosis effects

[a] Now you know what osmosis is, what effect would it have on the cell in this situation? Water moves out of the cell!

[q] Osmosis – Some key words 

Do you know this key vocabulary?

[a] 

• Turgor pressure: The amount of outward pressure from the inside of a cell due to the amount of water in it
• Turgid: A cell with high turgor pressure, so it is firm and tight
• Flaccid: A cell with low turgor pressure, so it is floppy
• Plasmolysis: When a plant cell becomes so flaccid the cell membrane tears away from the cell wall

[q] Active transport 

What is active transport?

[a] Active transport is the movement of particles from an area of low concentration to an area of high concentration, against the concentration gradient. This requires energy from respiration, and it requires protein carriers in the cell membrane to move the molecules.

[q] How do plants use active transport? 

How do plant roots absorb ions? 

[a] 

• Plants must absorb important mineral ions like magnesium, phosphates and nitrates.
• These ions are usually higher in concentration inside the root cells than in the soil
• This means roots must absorb these ions by active transport, against the concentration gradient

[q] Can we make movement faster? 

What are the ways organisms make diffusion and osmosis faster?

[a] 

• Temperature
• Surface area
• Concentration gradient
• Diffusion distance