2d Movement of Substances into and out of cells Flashcards
What is diffusion?
The net movement of particles down a concentration gradient. It is a passive process
How do you calculate surface area to volume ratio?
1) Calculate the surface area (SA) and volume
2) Establish which one of these values is the lowest
3) Divide the SA and volume by this number
4) This gives the ratio comparison between the 2
What are the 4 factors that affect the rate of diffusion?
Diffusion happens faster when…
1) … The temperature is higher because the particles move quicker
2) … There is a greater surface area to volume ratio
3) … There is a bigger difference between the concentration on each side of the partially permeable cell membrane. In other words a steeper concentration gradient
4) … The particles have a shorter distance to travel
What is osmosis?
This is the net movement of water molecules from an area of high water potential (ie. dilute solution) to an area of low water potential (ie. concentrated solution) across a partially permeable membrane
What are the similarities between osmosis and diffusion?
- Passive process (doesn’t require energy)
- Both diffuse from an area of high concentration to an area of low concentration
- Both affected by temperature, surface area, distance and concentration
What are the differences between osmosis and diffusion?
- Osmosis only happens in water
- High concentration = high water potential
What is active transport?
- Active transport across a partially permeable membrane and moves particles from a low concentration to a high concentration. This is against the concentration gradient and requires energy input.
How does active transport work?
Step 1: Glucose molecules outside the cell move to the carrier molecules in the membrane
Step 2: The carrier molecules use energy to close the outside membrane channel and open the inside membrane channel
Step 3: The glucose molecules move into the cell against the concentration gradient
