Biology · Paper 1
Transport in Cells
How substances move into and out of cells. Diffusion and what changes its rate, surface area to volume ratio and the exchange surfaces that large organisms need, osmosis and the required practical on plant tissue, and active transport. Matches AQA Biology topic 4.1.3, and the matching sections of Edexcel and OCR. Every lesson is for both Combined Science and separate Biology, at Foundation and Higher.
Lessons
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1
Diffusion
Cells constantly need to take things in and get rid of waste. Much of this happens by diffusion, with no energy needed. This lesson explains what diffusion is…
9 terms -
2
Surface Area to Volume Ratio and Exchange Surfaces
A single cell can get what it needs by diffusion through its surface, but a whole animal cannot. This lesson shows how to calculate a surface area to volume…
10 terms -
3
Osmosis
Water moves in and out of cells too, and it follows its own rule. This lesson explains osmosis, how to predict which way water will move, and what it does to…
10 terms -
4
Investigating Osmosis in Plant Tissue
This is the required practical on osmosis. You put pieces of plant tissue in solutions of different concentrations and see whether they gain or lose mass. This…
10 terms -
5
Active Transport
Diffusion and osmosis only move things down a gradient. Sometimes a cell has to move a substance the other way, and that costs energy. This lesson covers…
9 terms
Key terms in this chapter
All 48, gathered from every lesson.
- Diffusion
- The spreading out of particles of a gas, or of a substance in solution, resulting in a net movement from an area of higher concentration to an area of lower concentration.
- Concentration
- The amount of a substance in a given volume.
- Concentration gradient
- The difference in concentration between two places.
- Net movement
- The overall movement of particles in one direction, after those moving the other way are taken into account.
- Particle
- A very small piece of a substance, such as a molecule of oxygen.
- Cell membrane
- The thin layer around a cell that controls what enters and leaves it.
- Urea
- A waste product made in cells, which diffuses into the blood plasma and is excreted by the kidneys.
- Rate
- How much something changes in a given time.
- Surface area
- The total area of the outside of an object, or of a membrane.
- Surface area to volume ratio
- The surface area of an object divided by its volume.
- Exchange surface
- A specialised surface through which substances are exchanged between an organism and its surroundings.
- Transport system
- A system, such as the blood and blood vessels, that carries substances around a large organism.
- Diffusion path
- The distance particles have to travel to cross an exchange surface.
- Villi
- Tiny finger-like folds in the lining of the small intestine that increase its surface area.
- Alveoli
- The tiny air sacs at the ends of the airways in the lungs, where gas exchange takes place.
- Gill
- The organ a fish uses to take oxygen from water, made of many thin filaments.
- Root hair cell
- A cell in the root with a long thin extension that increases the surface area for taking up water and ions.
- Stomata
- Tiny pores in the surface of a leaf that let gases in and out.
- Ventilation
- Moving air or water over an exchange surface so that the concentration gradient stays steep.
- Osmosis
- The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
- Partially permeable membrane
- A membrane that lets some substances, such as water, pass through but not others, such as large dissolved molecules.
- Dilute solution
- A solution with a low concentration of dissolved substance.
- Concentrated solution
- A solution with a high concentration of dissolved substance.
- Solute
- A substance that is dissolved in a liquid, such as sugar in water.
- Turgid
- Firm and swollen with water. A turgid plant cell is pressed against its cell wall.
- Flaccid
- Soft and limp after losing water.
- Plasmolysis
- When a plant cell loses so much water that its membrane pulls away from the cell wall.
- Cell sap
- The solution inside the vacuole of a plant cell.
- Isotonic
- Having the same concentration of dissolved substances as the body's fluids.
- Independent variable
- The variable that is deliberately changed in an investigation.
- Dependent variable
- The variable that is measured in an investigation.
- Control variable
- A variable that is kept the same so that the test is fair.
- Percentage change
- The change in a value divided by the starting value, multiplied by 100.
- Cork borer
- A metal tube with a sharp edge used to cut cylinders of equal width from potato.
- Anomalous result
- A result that does not fit the pattern of the other results.
- Reliable
- Giving similar results when the investigation is repeated.
- Mean
- The sum of the values divided by the number of values.
- Cell sap
- The solution inside the vacuole of a plant cell.
- Isotonic
- Having the same concentration as the solution inside the cells, so there is no net movement of water.
- Active transport
- The movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient, using energy from respiration.
- Against the concentration gradient
- From a lower concentration to a higher concentration.
- Respiration
- The process in cells that releases energy from glucose.
- Mineral ions
- Dissolved substances, such as nitrate ions, that plants take up from the soil for healthy growth.
- Carrier protein
- A protein in the cell membrane that picks up a particular substance and moves it across.
- Root hair cell
- A root cell with a long thin extension, adapted to take up water and mineral ions from the soil.
- Mitochondria
- The sub-cellular structures where aerobic respiration releases energy.
- Absorption
- Taking a substance in, for example sugar moving from the gut into the blood.
- Passive
- Not needing energy from the cell. Diffusion and osmosis are passive.