b3- movement in and out of the cell Flashcards
What is diffusion?
Diffusion is the net movement of molecules and ions from a region of higher concentration to a region of lower concentration down the concentration gradient as a result of their random movement.
Give an example of diffusion in plants.
Plants need carbon dioxide for photosynthesis and carbon dioxide diffuses into the leaves from the air through the stomata by diffusion because there is a higher concentration of carbon dioxide outside the leaf and there’s a lower concentration of carbon dioxide inside leaf because the cells are using it up. Carbon dioxide therefore diffuses into the leaf down the concentration gradient. oxygen which is a waste product of photosynthesis diffuses out in the same way there is a higher concentration of oxygen inside the leaf because it is made there and there is a lower concentration of oxygen outside the leaf so the oxygen molecules diffuse out of the leave through the stomata into the air.
List three examples of diffusion in living organisms
- Oxygen and carbon dioxide dissolved in water are exchanged by diffusion in the lungs.
- the oxygen diffuses into the cell in living organisms for cellular respiration.
- The diffusion of falls water and other waste products occur in kidneys.
What effect does an increase in temperature have on the kinetic energy of molecules of a gas or a solute?
Temperature is increased so the average kinetic energy and RMS speed of the molecules will increase this means that the gas molecules are the solute molecules will hit the walls of the container more frequently and with greater force because they’re all moving faster there will be an increase the pressure as well.
Prediction explain how an increase in temperature will affect the rate of diffusion of a solute.
The higher the temperature the more kinetic energy the solute molecules will have so they will move and mix more quickly the greater the surface area the faster the rate of diffusion.
What is osmosis?
Osmosis is the net movement of water molecules from a region of higher water potential which is a dilute solution to a region of lower water potential that is a concentrated solution through a partially permeable membrane.
What is water potential?
It is actually rather confusing to talk about the concentration of water molecules because the term concentration is normally used to mean the concentration of solute dissolved in water. it is much better to use a different term instead. we say that dilute solution there where is a lot of water has a high water potential. a concentrated solution where there is less water has a low water potential.
Give two examples of partially permeable membranes
Plasma membrane and visking tubing.
How would you describe a solution that has a higher concentration of water molecules?
A dilute solution contains a high concentration of water molecule it has a high water potential.
How is cell membrane a partially permeable membrane?
There is always cytoplasm on one side of any cell membrane. cytoplasm is a solution of proteins and other substances in water. there is usually a solution on the other side of the membrane too. inside large animals cells are surrounded by tissue fluid. in the soil the roots of plants are often surrounded by a film of water. so cell membranes often separate two different solutions the cytoplasm and the solution around the cell if the solutions are of different concentrations then osmosis will occur.
What happens to an animal cell in pure water?
The pure water is separated from a concentrated solution by a partially permeable membrane. the concentrated solution is the cytoplasm and the partially prermeable membrane is the cell membrane. therefore osmosis will occur. water molecules will diffuse by osmosis from the dilute solution into the concentrated solution. what happens to the cell? as more and more water enters the cell its swells. the cell membrane has to stretch as the cell gets bigger until eventually the strain is too much and the cell bursts.
What happens to an animal cell in a concentrated solution?
If the solution outside the cell is more concentrated than the cytoplasm then water molecules will diffuse out of the cell as the water molecules go out through the cell membrane the cytoplasm shrinks the cell shrivels up.
Why does plant cell not burst in pure water?
Plant cells are surrounded by a cell wall this is fully permeable which means that it will let any molecules go through it plant cells also have a cell membrane which is partially permeable like animal cells. A plant cell in pure water will take in water by osmosis through its partially permeable cell membrane in the same way as an animal cell as the water goes in. the cytoplasm and the vacuole swell. however the plant cell has a very strong cell wall around it. the cell wall is much stronger than the cell membrane and it stops the plant cell from bursting the cytoplasm presses out against the cell wall but the wall resists and presses back on the contents.
What is a turgid cell?
When a plant cell has a lot of water in the state it is rather like a blown up tire tight and firm it is said to be turgid.
What is the outward pressure of the cytoplasm on the cell wall called?
turgor pressure
