AQA A-Level Biology 3.6 Organisms respond to changes in their internal and external environments quiz

A directional growth response of a plant either towards or away from an external stimulus

A directional movement of the whole organism straight towards or directly away from a particular stimulus source

A non-directional response in which the rate of movement and turning change with stimulus intensity

A rapid, automatic protective response that is coordinated entirely by the spinal cord

IAA stimulates cell elongation in both shoots and roots

IAA inhibits elongation in shoots but stimulates it in roots

IAA has no effect on cell elongation

IAA stimulates elongation in shoots but inhibits it in roots

The sodium-potassium pump (3 Na+ out, 2 K+ in) and the membrane being more permeable to K+

Voltage-gated sodium channels opening to let a large influx of Na+ into the axon rapidly

Acetylcholinesterase continually breaking down the neurotransmitter within the synaptic cleft

Calcium ions binding to troponin and shifting the tropomyosin away from the binding sites

A single larger action potential with a greater peak voltage at the membrane

A higher frequency of action potentials of the same size

A faster action potential that still remains exactly the same size as before

No action potential at all because the threshold has already been exceeded

The myelin sheath actively pumps ions along the whole length of the axon to speed it up

Myelin greatly increases the overall diameter of the axon and so lowers its resistance

Depolarisation occurs only at the nodes of Ranvier, so the impulse jumps between them

The refractory period is completely removed by the presence of the myelin sheath

Potassium ions leaving the synaptic knob through open potassium channels

Acetylcholinesterase activity within the cleft breaking down transmitter

Sodium ions entering the postsynaptic membrane and depolarising it fully

Calcium ions entering through voltage-gated channels

Only the presynaptic neurone releases neurotransmitter and only the postsynaptic membrane has receptors

Acetylcholinesterase is found only on the presynaptic side of the synapse and nowhere else within the whole cleft

Calcium ions are only ever able to flow in one single fixed direction throughout the whole of the body

The synaptic cleft is far too wide to allow any neurotransmitter to diffuse back across it in reverse

Many cones share a single bipolar neurone, allowing the effects of light to be summed together

Each cone connects to its own bipolar neurone, so close points produce separate impulses

Cones contain the pigment rhodopsin, which is far more sensitive to dim light than iodopsin

Cones are found mainly in the peripheral retina rather than at the central fovea region

The I band

The H zone

The A band

The distance between Z lines

It binds directly to troponin in order to expose the actin-myosin binding sites for the heads

It is released in a flood from the sarcoplasmic reticulum to start the muscle contraction

It binds to and blocks all of the actin-myosin binding sites during muscle relaxation

It causes the myosin head to detach from actin and provides energy to recock the head

Beta cells secrete insulin, increasing glucose uptake and glycogenesis

Alpha cells secrete the hormone glucagon, which stimulates glycogenolysis in the liver

The adrenal glands release the hormone adrenaline to raise the blood glucose level

The liver carries out gluconeogenesis to make new glucose from non-carbohydrate sources

Less ADH is released, which makes the collecting duct wall far less permeable to water so very dilute urine is then produced

More ADH is released, inserting more aquaporins so more water is reabsorbed and concentrated urine is produced

ADH actively transports water molecules out of the collecting duct against the gradient

ADH directly triggers the process of ultrafiltration within the Bowman's capsule of the nephron