Diffusion and Osmosis (Complete) Flashcards
What is a membrane?
A lipid bilayer with embedded protein.
Where are biological membranes found?
Cell membranes. Membranes surrounding: Nucleus Chloroplasts Mitochondria
What is a selectively permeable membrane?
A selectively permeable membrane only allows some substances through.
What substances do selectively permeable membranes allow through?
Water
Carbon dioxide
Oxygen
What substances do selectively permeable membranes not allow through?
Larger sugars
Salts
Proteins
Where are selectively permeable membranes located?
Chloroplasts
Surrounding the nucleus
Vacuoles
Mitochondria
What is a permeable membrane?
A permeable membrane allows all substances through.
Give an example of a permeable membrane.
Cell wall
What is diffusion?
Diffusion is the passive movement of substances from a region of higher concentration to a region of lower concentration through a concentration gradient. Does not require ATP energy.
What is another name for diffusion, why?
Passive transport, as it does not require ATP energy.
Describe diffusion in the lungs.
Oxygen diffuses into the blood
Carbon dioxide difuses from the plasma into the alveoli
Describe diffusion in the leaf.
Oxygen diffuses out through the stomata into the atmosphere
Carbon dioxide diffuses into mesophyll cells in the leaf
Describe diffusion in the blood.
Oxygen diffuses from the blood into tissue cells
Carbon dioxide diffuses from the tissue cells into the blood
Name three factors that affect diffusion
Temperature
Concentration
Distance
How does temperature affect the rate of diffusion?
The higher the temperature, the faster the rate of diffusion
How does concentration affect the rate of diffusion?
The greater the concentration difference between the two regions, the faster the rate of diffusion
How does distance affect the rate of diffusion?
The shorter the distance between the two regions, the faster the rate of diffusion
That is why:
Leaves are thin
Alveoli wall is one cell thick
What is active transport?
The movement of substances from a region of lower concentration to a region of higher concentration along a concentration gradient. Requires ATP energy
What is osmosis?
The movement of water molecules along a selectively permeable membrane from a region of high water concentration to a region of low water concentration
Why is osmosis considered a special type of diffusion?
Because osmosis is the diffusion of water along a selectively permeable membrane
How does a plant cell become turgid?
Plant cell contains more concentrated solution than its surroundings
Water enters the sap vacuole and cytoplasm by osmosis
Cell swells up against the restraining cell wall
Exerts outward turgor pressure- turgor is defined as the pressure of the cell contents up against the inelastic cell wall
Plant cell does not burst as cell wall is not very elastic
Plant cell is now turgid- the rigid expanded state of a plant due to the entry of water by osmosis
How does a plant cell become plasmolysed?
Plant contains less concentrated solution than its surroundings.
Water exits the cytoplasm and sap vacuole by osmosis.
Cell shrinks and the cell membrane pulls away from the cell wall.
As the cell wall is fully permeable, external solution fills up the empty space.
The inelastic cell wall prevents the cell from bursting.
The cell is now plasmolysed. Plasmolysed means the loss of turgour due to water leaving the plant cell by osmosis causing the cell membrane to pull away from the cell wall.
Explain the biological basis of using high sugar or high salt concentration in the preservation of food.
Bacteria and fungi lose water by osmosis, and become inactive allowing food to be preserved.
What is turgor?
Turgor is the pressure of cell contents up against the restraining cell wall.
What happens to a plant if it loses turgidity?
It wilts
What would happen if an animal cell were to become turgid?
It would burst as theres no inelastic cell wall.
