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Biology
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Describe how a sperm cell is adapted for it's function. (4 marks)

1 mark each for one of the following:
Describe the sperm cell's function; i.e. fertilising the egg
(Proportionally large) flagellum for mobility
Possess an Acrosome filled with enzymes to p...

JM
Answered by Jack M. Biology tutor
2489 Views

Explain how the cardiac muscle controls the regular beating of the heart.

Cardiac muscle is myogenic. This means signals for contraction and relaxation originate from the heart itself. The process is initiated in the sinoatrial node (SAN), located in the right atrium. The SAN i...

CJ
Answered by Christie J. Biology tutor
2954 Views

Explain the transmission of a nerve impulse across a cholinergic synapse referring to action potentials. (6)

When an action potential reaches the terminal of a pre-synaptic cleft, voltage-gated calcium channels are stimulated to open, causing an influx of Ca+ ions in the pre-synaptic neuron. This infux of Ca+ io...

SW
Answered by Sarah W. Biology tutor
2234 Views

Describe how phagocytic white blood cells destroy bacteria. (4)

The phagocyte recognises antigens on the surface of the bacteria as foreign, causing it to be attracted to the bacteria. The phagocyte then engulfs the bacteria, forming a vesicle around it. Lysozomes fus...

SW
Answered by Sarah W. Biology tutor
13608 Views

Why does a base substitution in DNA not always result in the formation of non-functional proteins?

Protein structure is determined by amino acid sequence. Each amino acid is coded for by a triplet of RNA bases. These are transcribed from a DNA molecule. If a DNA base is substituted for another base, th...

AR
Answered by Abby R. Biology tutor
3106 Views

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