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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 mouth due to buccal expansion > water is accelerated across the gill filaments due to simultaneous contraction of the buccal cavity and expansion of the opercula > gaseous ...
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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.
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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.
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Answered by Owen F. • Biology tutor
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Define "cellular immune response".

An immune response mediated by T lymphocytes.
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Answered by Owen F. • Biology tutor
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Show that the two lines are parallel: L1: 4y = 24x +12, L2: 2y + 13 = 12x

Two lines are parallel when they have the same gradient. When the equation is written in the form: y = mx + c, m is the gradient. We need to arrange our equations in the form y = mx + c as this is the easies...
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Answered by Dominique T. • Maths tutor
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