Biology: Diffusion, Osmosis and Active Transport
How does increasing the temperature increase the rate of diffusion?
The particles have more kinetic energy and so they move around faster
Name four molecules that can diffuse through a cell membrane
oxygen, glucose, amino acids and water
1. cut equal-sized pieces of potato 2. blot with tissue paper and weigh 3. put pieces into different concentrations of sucrose solution for a few hours 4. remove, blot with tissue paper and reweigh
Describe the brief method for investigating osmosis in a potato cells
How does increasing the surface area increase the rate of diffusion?
A larger surface area means that more particles can cross the membrane in the same amount of time
Define osmosis
A special type of diffusion where water moves from a high concentration to a low concentration (down a concentration gradient) through a partially permeable membrane.
Identify three places in the body where diffusion takes place
Across the alveoli in the lungs, across a synapse between neurones, across the wall of the small intestine.
How are mineral ions absorbed into the root hair cells?
Active transport
How is active transport different to osmosis and diffusion?
Active transport uses energy compared to diffusion and osmosis that does not. Active transport moves substances against the concentration gradient, whereas diffusion and osmosis move substances down the concentration gradient
Why do plant cells not burst when they are placed in a hypertonic solution.
Because the have a strong cell wall
If blood cells are placed in a hypotonic solution they.........?
Burst
The rate of diffusion is affected by....
Concentration gradient, temperature and surface area
Define the term diffusion
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration (down a concentration gradient)
Give an example of where active transport occurs in humans
Glucose is absorbed from the lower gut into the blood where there is a higher concentration of glucose
percentage change in mass = start mass _______________ x 100 end mass
How do you calculate the change in mass of a potato chip when placed in a salt solution
Cells which are involved in active transport contain lots of which organelle?
Mitochondria to provide the energy for active transport
By what process does water move into a plant?
Osmosis
Which part of a plant is involved in the uptake of water?
Root hair cell
If blood cells are placed in a hypertonic solution they ..........?
Shrivel
Define the term hypotonic
The concentration of solutes outside the cell is lower that the concentration of solutes inside the cell
Define the term hypertonic
The concentration of solutes outside the cell is greater than the concentration of solutes inside the cell
Define the term Isotonic
The concentration of solutes outside the cell is the same as the concentration of solute inside the cell
Define active transport
The movement of substances from an area of low concentration to high concentration. Movement is against the concentration gradient
Why is osmosis important in plants?
To maintain plant cell turgor. (so plants can support their stems and leaves)
State two different adaptations that are found in living organisms to make gas exchange more efficient
Ventilation systems and circulating blood to help maintain a steep concentration gradient
Osmosis refers the the movement of ????? molecules
Water
Describe what happens to a cell when it becomes plasmolysed
When a plant cell loses water by osmosis, the vacuole and cytoplasm shrinks and the cell membrane pulls away from the cell wall
Where the line crosses the horizontal axis at 0% change in mass, the sucrose concentration is equal to the concentration of the contents of the potato cells. The sucrose concentration is isotonic with the cells' cytoplasm, so there is no net movement of water by osmosis
When plotting the change in mass of potato chips in different sucrose concentrations. What does the point at which the line crosses the horizontal line represent