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When an antigen binds to a receptor on a T cell, the T cell becomes activated and differentiates into different types of T cells. What are these T cells and what are their functions? (6 marks)

There are three main types of T cell. T helper (CD4+), T killer (CD8+) and T memory. The CD4+/8+ are complex proteins on the surface of each respective T cell that they use in their function. T helper cells ...
ZM
Answered by Zachary M. • Biology tutor
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From the definition of the decay constant for nuclear decay, derive the exponential decay equation.

By definition, dn/dt = - λ N , If you separate the variables which contain N and t, and then integrate w.r.t N and w.r.t t you get, lnN = -λt + C (1), To find the constant of integration, solve (1) by settin...
JP
Answered by Jake P. • Physics tutor
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How should I improve my portfolio in order to achieve an A/A*?

In order to achieve the highest marks possible in A Level Fine Art, you must continuously make sure that you are hitting all of the Assessment Objectives (AOs) at different stages along your path. This can m...
DD
Answered by Deniz D. • Art tutor
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outline the mechanism for the nitration of methyl benzoate and show how sulfuric acid behaves as a catalyst

You will be given the equationThis reaction is an electrophilic substitution which is the most common reactions among benzene groups that you will come across at A levelThe question tells you that it is a ni...
MA
Answered by Monica A. • Chemistry tutor
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Explain the role of the Loop of Henle in the absorption of water from the glomerular filtrate

After the filtrate in the nephron undergoes Selective Reabsorption in the Proximal Convoluted Tubule, it then travels to the Loop of Henle. The Loop of Henle is a ‘U’ shaped structure found in the Medullary ...
AA
Answered by Akshee A. • Biology tutor
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