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Explain how an action potential is transmitted across a cholinergic synapse.

The action potential arrives at the synaptic knob of the presynaptic neurone. The action potential stimulates the opening of voltage-gated calcium ion channels in the presynaptic neurone, allowing calcium io...
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Answered by Kathryn E. • Biology tutor
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The pancrease secretes protease enzymes. How do organelles within a cell work together to PRODUCE and RELEASE these protein molecules from the cell?

The nucleus contains the gene that codes for the enzyme and is where transcription happens to produce mRNA . The mRNA leaves the nucleus and attaches to a ribosome on the rough endoplasmic reticulum. The rib...
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Answered by Jessica E. • Biology tutor
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Describe how phagocytosis of a virus leads to presentation of its antigens and how presentation of this antigen leads to the secretion of an antibody against this virus antigen.

The macrophage engulfs the virus and the phagosome fuses with a lysosome, the virus is then broken down by hydrolytic enzymes inside the lysosome, and virus' antigens are displayed on the cell surface membra...
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Answered by Oenone R. • Biology tutor
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Give two ways in which the presence of synapses are advantageous to the nervous system.

They ensure unidirectional transmission - Nerve impulses can also pass from the pre-synaptic neurone to the post-synaptic neurone. This is due to the neurotransmitter being made in the pre-synaptic membrane ...
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Answered by Lucy C. • Biology tutor
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Each amino acid contains a different R group specific to the amino acid. Describe how the R group of an amino acid contributes to the tertiary structure of a protein. (4 marks)

Cysteine contains an S atom in its R group. Where 2 molecules of cysteine are found together, strong covalent bonds or "disulfide bridges" can form between the two S atoms (S=S). R groups may have ...
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Answered by Jake G. • Biology tutor
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