Unit 1 Cells - Movement of substances into and out of cells Flashcards
What do cells need to be able to enter through the cell membrane?
Oxygen, water, dissolved food molecules and mineral ions.
What does ‘selectively permeable’ mean?
Cell membrane will allow some substances through but will prevent movement of others.
What is ‘diffusion’ ?
The random movement of a substance from where it is a high concentration to where the concentration is lower.
Is diffusion slower in liquids or gases?
Slower in liquids
Plant and animal cells are adapted to allow diffusion to happen at a rapid rate. What are these adaptations?
Large surface area, thin barriers.
How does the concentration gradient affect the rate of diffusion?
Concentration gradient is the difference in concentation betwen the high and low areas. The larger the difference the FASTER the diffusion.
How does temperature affect the rate of diffusion?
Higher temperatures increase the kinetic energy of the molecules making them move faster and increase the rate of diffusion.
How does the surface area affect the rate of diffusion?
The larger the surface area over which diffusion takes place th faster diffusion occurs.
Where does diffusion occur in living organisms?
- Diffusion of oxygen from the air spaces on the lungs into the blood.
- The diffusion of carbon dioxide from the bllodstream into the lungs.
How do microvilli in cells in the gut help adsorb food?
Microvilli increase surface area. This speeds up the rate at which food molecules diffuse from the gut into the cells.
In the selective permeability experiment using dialysis tubing and starch solution, explain the colour change of iodine.Iodine changes
The starch inside the bag turns a blue/black colour whilst the iodine outside the bag remains unchanged.
What 2 factors effect the rate of diffusion?
surface area and volume
If cells get too big, can they still rely on diffusion?
No … surface area to volume ratio decreases. Diffusion only works well over short distances so the cell would die.
