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Why is an action potential an all or nothing process?

An action potential is the signal neurons use to communicate with each other. It is caused by the rapid opening of sodium channels and influx of sodium ions. Because at rest the inside of the neuron is negat...
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Answered by Gemma G. • Biology tutor
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Explain what happens when there is a mutation in a gene whereby 2 bases are deleted ?

As there are 2 bases which are deleted a frameshift will occur at the site of the mutation. This means that all other amino acids coded for by the genes after the point of mutation will be different. This is...
KT
Answered by Kevin T. • Biology tutor
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Describe the role of RUBISCO in plants and evaluate the importance of RUBISCO in the Calvin Cycle? (8 Marks)

combines CO 2 with { ribulose bisphosphate / RuBP } two molecules of { glycerate 3-phosphate / GP } RUBISCO is important for the Calvin Cycle because: It is an enzyme SO it lowers the activation energy for a...
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Answered by John O. • Biology tutor
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Bob and Brenda are both heterozygous for a genetically inherited recessive trait. (a) Calculate the probability that they would have a healthy child. Use a genetic diagram to help. (b) Suggest an example of a recessive inherited disorder

Heterozygous means that the parents both carry a dominant allele (A) and a recessive allele (a). Dominant alleles are always expressed in the phenotype. Recessive alleles are expressed in the phenotype only ...
CM
Answered by Charlotte M. • Biology tutor
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Neurons do not make direct contact but are separated by synapses. Impulses cross a synapse by means of a neurotransmitter. Describe the process of neurotransmitter release at a synapse. You may use a labelled diagram.

Action potential arrives at axon terminal of presynaptic neuron Voltage-gated Ca2+ channel opens Ca2+ enters the cell Ca2+ signals to vesicles Vesicles move to the membrane Neurotransmitters are released by ...
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Answered by Charlotte M. • Biology tutor
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