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What is active transport?

Active transport is the transport of substances against their concentration gradient with the use of energy. Molecules naturally flow down their concentration gradient, ie. from where they are more concentra...
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Answered by Chris D. • Biology tutor
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Describe how oxygen in the air reaches the capillaries surrounding the alveoli.

As you breathe in, air passes down your trachea and then into the bronchi and bronchioles. The bronchioles divide further into even narrower branches which end in small air filled sacks called alveoli. The a...
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Answered by Naomi A. • Biology tutor
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What is the sequence of events involved in transmission across a cholinergic synapse

For transmission across the synapse to be initiated, an action potential must arrive at the pre-synaptic knob and open voltage- gated ion channels. Once the channels are open, calcium ions are able to diffus...
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Answered by Ellen S. • Biology tutor
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how does the chemical structure of amino acids lead to variable physical structures of proteins

Amino acids are made up of an amine group, a carboxyl group, a hydrogen and a variable group (often noted as R) all bound to one Carbon. These amino acids can bind to one another by the amine group and the c...
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Answered by Adam B. • Biology tutor
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How to go about writing an essay in A level biology (for exampe: The importance of proteins in the control of processes and responses in organisms)

When attempting an essay question like this it is important to pull together topics from different areas of the course. Start by writing a quick plan including 5 relevant topics that you feel confident talki...
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Answered by Elys H. • Biology tutor
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