Top answers

Describe the transmission of a nerve impulse across a synapse.

An action potential arrives at a presynaptic neurone, which causes calcium ion channels to open. Calcium ions enter the presynaptic knob, which causes synaptic vesicles containing neurotransmitter to detach ...
Answered by • Biology tutor
6309 Views

Give 3 main differences between RNA and DNA.

DNA is double stranded while RNA is a single stranded polynucleotide chain. In DNA the pentose sugar is deoxyribose (one less oxygen containing hydroxyl group) and in RNA it is ribose. In DNA the four bases ...
DL
Answered by Dora L. • Biology tutor
3043 Views

How does speciation occur?

A barrier separates the original population into two groups. Due to the different environmental conditions (selection pressures) either side of the barrier, different alleles are selected that better adapt t...
HB
Answered by Hasna B. • Biology tutor
3794 Views

Describe how a change in temperature affects enzyme activity.

Enzymes are substrate specific proteins which act as biological catalysts and as temperature increases, we see an increase in enzyme activity. This occurs because an increase in temperature causes molecules ...
FH
Answered by Freya H. • Biology tutor
7238 Views

Describe how the structures involved in a reflex action help co-ordinate a reflex: (image with receptor, effector, spinal cord, synapse and neurones)

A receptor detects a stimulus e.g. pressure. The receptor generates electrical signals. Neurones conduct impulses, a sensory neurone conducts to the spinal cord. There is a synapse between the neurones and t...
PA
Answered by Pareya A. • Biology tutor
4589 Views