5 interactive labs · AS & A Level Biology 9700
· Start with a taste receptor and a reflex arc, then step through the channels that make the resting potential and the action potential.
Start with a taste receptor and a reflex arc, then step through the channels that make the resting potential and the action potential.
You will be able to
Syllabus learning outcomes: 15.1.3, 15.1.4, 15.1.5, 15.1.6, 15.1.8
· Race impulses along myelinated and unmyelinated axons, remove the refractory period, then step through a cholinergic synapse and block it.
Race impulses along myelinated and unmyelinated axons, remove the refractory period, then step through a cholinergic synapse and block it.
You will be able to
Syllabus learning outcomes: 15.1.7, 15.1.8, 15.1.9
· Follow the signal from neuromuscular junction to Ca²⁺ release, measure the bands of a sarcomere as it shortens, and remove Ca²⁺ or ATP to see why.
Follow the signal from neuromuscular junction to Ca²⁺ release, measure the bands of a sarcomere as it shortens, and remove Ca²⁺ or ATP to see why.
You will be able to
Syllabus learning outcomes: 15.1.10, 15.1.11, 15.1.12
· Touch a Venus fly trap's hairs, watch auxin acidify a cell wall, and compare these plant signals with nervous and endocrine signalling in mammals.
Touch a Venus fly trap's hairs, watch auxin acidify a cell wall, and compare these plant signals with nervous and endocrine signalling in mammals.
You will be able to
Syllabus learning outcomes: 15.1.1, 15.1.2, 15.2.1, 15.2.2
· Follow gibberellin from the embryo to the aleurone layer, DELLA breakdown and amylase, then block a step and predict what the starch store does.
Follow gibberellin from the embryo to the aleurone layer, DELLA breakdown and amylase, then block a step and predict what the starch store does.
You will be able to
Syllabus learning outcomes: 15.2.3, 16.3.4
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 sprinter's leg muscles go from rest to maximum effort in a few seconds. Follow oxygen from the alveoli to the mitochondria and ATP to the sarcomere.
Ventilation rate and blood flow to the lungs both rise. Why does that keep oxygen uptake high?
Fresh air keeps the alveolar partial pressure of oxygen high and flowing blood keeps the capillary partial pressure low, so a steep diffusion gradient is maintained across the thin squamous epithelium.
Working muscle has a higher partial pressure of carbon dioxide. How does that change oxygen unloading?
More carbon dioxide gives more hydrogen ions (carbonic anhydrase), which bind haemoglobin and lower its affinity for oxygen: the Bohr shift moves the curve right, so more oxygen is released at the same partial pressure.
Where is that oxygen used, and why is it essential for ATP synthesis?
On the inner mitochondrial membrane oxygen accepts electrons at the end of the chain and forms water; without it the chain stops, protons are no longer pumped and ATP synthase has no gradient to use.
Oxygen supply cannot keep up. How does the muscle still make some ATP?
Pyruvate is reduced to lactate, which regenerates NAD so glycolysis can continue; only the ATP from glycolysis is made, so the yield per glucose is far smaller.
What does each contraction cycle use ATP for?
ATP binds the myosin head so it detaches from actin, and its hydrolysis re-cocks the head; calcium ions released from the sarcoplasmic reticulum expose the binding sites.
