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Biology

A Level

Detail the pathway of oxygenated water in the ventilation of a fish. Name and briefly describe the mechanism by which gaseous exchange takes place.

Oxygen rich water enters the mouthdue to buccal expansion > water is accelerated across the gill filamentsdue to simultaneous contraction of the buccal cavity and expa...

Answered by Owen F. • Biology tutor

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Using knowledge of the pathogenicity of HIV, explain why it can't be transmitted through inanimate objects or hand shakes with an infected person.

HIV is a virus and therefore obligately intracelluar, with a very short survival time outside of its host.

Answered by Owen F. • Biology tutor

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How can antibody neutralisation of pathogenic antigens help prevent cellular damage? (4 marks)

Prevent:Antigen attachment to cell > cell invasion > pathogen replication > toxin production.

Answered by Owen F. • Biology tutor

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Define "cellular immune response".

An immune response mediated by T lymphocytes.

Answered by Owen F. • Biology tutor

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What are the similarities and differences between DNA and RNA?

DNA and RNA are structurally almost identical, but there are a number of key differences. The 'D' in DNA stands for deoxyribose - the sugar molecule that gives DNA a stable helical conformation (called a ...

Answered by Tristan D. • Biology tutor

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