Chapter 3: Movement into and out of cells Flashcards
Define ‘diffusion’
The net movement of particles from a region of higher concentration to a region of lower concentration as a result of random movement
Where does the energy for diffusion come from?
Kinetic energy from random movement of molecules and ions
What are the factors that influence the rate of diffusion?
- Surface area
- Temperature
- Particle size
- Concentration gradient
- Distance
How do you investigate how surface area affects diffusion?
Cut 2 cubes of agar jelly of equal size, and cut one into 4 smaller cubes of equal size. Put the large cube into a test tube and the other 4 into another test tube. Add equal volumes of dilute hydrochloric acid to each tube, ensuring all cubes are covered with acid. Then use a stopwatch and time how many seconds it takes for each of the cubes to become fully yellow.
How do you investigate how temperature affects diffusion?
Fill 3 glasses with cold water, tap water, and hot water, then add 2 drops of food colouring to each and observe how fast it spreads
What is the role of water as a solvent?
- In digestion, some swallowed food is dissolved in the alimentary canal, where it can be acted on by enzymes also dissolved in water
- In excretion, the kidney secretes urea, which is dissolved in water and forms urine
- In transport, substances are dissolved in the water in blood plasma and are transported around the body
Define ‘osmosis’
The net movement of water from a region of higher water potential to a region of lower water potential through a partially permeable membrane
How do you investigate osmosis with dialysis tubing?
Fill a section of dialysis tubing with concentrated sucrose solution, suspend it in a boiling tube of distilled water for some time, and note how the water level changes
How do you investigate the effects on plant tissues of immersing them in solutions of different concentrations?
Cut 2 cylinders of potato of equal size, weigh them, place one into a dilute sugar solution and the other into a concentrated sugar solution for 20-30 minutes, remove and dry them to remove excess liquid, then reweigh them and compare
What happens to animal cells when immersed in pure water?
The cell swells and bursts
Define ‘turgid’
A plant cell that is tight and firm, the cytoplasm presses against the cell wall
Define ‘flaccid’
A plant cell that is soft, loses its firmness
Define ‘plasmolysis’
When the cell membrane tears away from the cell wall
Define ‘turgor pressure’
The pressure of the water pushing outwards on a plant cell wall
Define ‘hypertonic’
Water potential of the solution is lower than water potential of a cell
Define ‘isotonic’
Water potential of the solution is equal to water potential of a cell
Define ‘hypotonic’
Water potential of the solution is higher than water potential of the cell
Define ‘active transport’
The movement of particles from a region of lower concentration to a region of higher concentration against the concentration gradient, using energy from respiration
How are molecules or ions moved across a membrane during active transport?
Carrier proteins
What is the importance of active transport?
A process for movement of molecules and ions across membranes, e.g. allows plants to take in ions through the root hair cells
