4 interactive labs · AS & A Level Biology 9700
· Inspect each part of a moving bilayer, switch cholesterol off, follow a hormone to its target cells, and heat beetroot until its membranes leak.
Inspect each part of a moving bilayer, switch cholesterol off, follow a hormone to its target cells, and heat beetroot until its membranes leak.
You will be able to
Syllabus learning outcomes: 4.1.1, 4.1.2, 4.1.3, 4.1.4
· Watch molecules cross a membrane both ways by diffusion, channels, carriers and ATP-driven pumps, and see why vesicles move particles too large to diffuse.
Watch molecules cross a membrane both ways by diffusion, channels, carriers and ATP-driven pumps, and see why vesicles move particles too large to diffuse.
You will be able to
Syllabus learning outcomes: 4.2.1
· Put cells, potato tissue and Visking tubing in different solutions, watch water cross both ways, and find the tissue's water potential from a graph.
Put cells, potato tissue and Visking tubing in different solutions, watch water cross both ways, and find the tissue's water potential from a graph.
You will be able to
Syllabus learning outcomes: 4.2.1, 4.2.2, 4.2.5, 4.2.6
· Resize agar cubes, put them in the same acid, and compare the depth reached, the percentage coloured and the surface area to volume ratio over time.
Resize agar cubes, put them in the same acid, and compare the depth reached, the percentage coloured and the surface area to volume ratio over time.
You will be able to
Syllabus learning outcomes: 4.2.2, 4.2.3, 4.2.4
Each link is a piece of biology that carries an idea from one lab into another. Follow one to use what you found here in a new setting.
A bean plant grows in soil that dries out over a hot, windy afternoon. Follow the water from the soil to the leaf and work out what happens to its photosynthesis.
The soil solution's water potential falls below that of the root hair cells. Which way does water now move?
Water still moves from higher to lower water potential, so less water, or none, enters the root hair cells; if the soil is lower still, water leaves them.
Transpiration continues from the leaves while uptake falls. What happens to the tension in the xylem water column?
Evaporation from the leaf keeps pulling on the cohesive column, so the tension rises while less water enters at the root: the plant loses water faster than it takes it up and the leaf cells lose turgor.
Abscisic acid reaches the guard cells. What happens to the stomata, and through which signal?
ABA triggers a rise in calcium ions as a second messenger; ions leave the guard cells, their water potential rises, water leaves by osmosis, turgor falls and the stomata close, reducing water loss.
The light is bright but the stomata are now nearly closed. What limits the rate of photosynthesis?
Carbon dioxide concentration inside the leaf falls, so it becomes the limiting factor: brighter light would barely raise the rate.
With less sucrose made in the leaves, what happens to translocation to the roots and seeds?
Less sucrose is loaded at the source, so the hydrostatic pressure gradient to the sinks is smaller and mass flow to them slows.
