Cell Biology - Diffusion
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration
What type of process of diffusion?
A passive process as it does not require energy
What are the main examples of what diffuses into cells?
-Oxygen
-Glucose
What are the main examples of what diffuses out of cells?
-Carbon dioxide
-Urea
What are the factors that affect the rate of diffusion?
-Increasing the concentration gradient increases the rate of diffusion
-Reducing the distance particles have to travel increases the rate of diffusion
-Increasing the temperature increases the rate of diffusion
-Increaing the surface area of the membrane increases the rate of diffusion
What adaptations do exchange surfaces have to maximise the rate of diffusion and why?
-Thin cell walls (to reduce diffusion distance)
-Large surface area (increases rate of diffusion)
-Good blood or air supply (to maintain a steep concentration gradient)
Explain and describe the three specific exchange surfuces that you are required to know?
- Alveoli:
-Gases diffusing between lungs and blood in capillaries
- Villi in small intestine:
-Small molecules (amino acids,glucose,fatty acids, and glycerol) diffusing from small intestine into the blood in capillaries
-Leaves in plants:
-Gases diffusing in and out of stomata for gas exchange in cells for respiration and photosynthsis
How do you calculate surface area to volume ratio
suface area/volume
Do single-celled organisms need an exchange surface and why?
No because they have a very large sa:v and short distance for substances to diffuse to diffuse in/out
Do large organisms need an exchange surface an why?
Yes becuase the larger an organism gets the small its sa:v becomes so it needs specially adopted exchange surfaces and a transport system to increase the rate of diffusion of substance in/out of all cells