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Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus of the cell. (6 marks)

This process is called transcription . In the nucleus, an enzyme helicase is used to break the hydrogen bonds between the two strands of the double helix. Only one DNA strand is used the template, which we c...
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Answered by Kirstin P. • Biology tutor
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During anaerobic respiration, pyruvate is converted to lactate by the enzyme lactate dehydrogenase. Explain the significance of this reaction.

This reaction involves a transfer of hydrogen from NADH to pyruvate to produce lactate and NAD + . In order for glycolysis to continue to produce ATP for the cell to use, NAD + is required and the recycling ...
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Answered by Thomas S. • Biology tutor
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Explain key differences between prokaryotic and eukaryotic cells.

The student should give an answer that reflects that eukaryotic cells evolved later and have had lots of time to become different through evolution, for instance: “prokaryotic and eukaryotic cells have many ...
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Answered by Ryan T. • Biology tutor
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Describe an action potential.

A stimulus excites a neuron by causing the opening of sodium channels. This causes an influx of sodium which causes the opening of other voltage-gated sodium channels. This causes the membrane to depolarise ...
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Answered by Maciek K. • Biology tutor
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Emphysema is a disease of the lungs. Explain why people suffering from this condition may feel weak and short of breath.(6 marks)

Emphysema is an obstructive lung disease(1), where alveoli collapse due to break down of elastin in their walls(2). This means that the lungs cannot recoil(3), making expiration difficult. There is less surf...
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Answered by Sara I. • Biology tutor
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