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One of the most important roles of cell membranes is to control what substances enter and leave the cell. Describe the difference and a briefly outline the mechanism for passive and active transport of molecules over cell membranes.

Passive transport requires no energy and is dependent on concentration difference gradient of intra and extracellular spaces. Channel protein can be opened or closed to allow or stop the free flow of molecul...
AC
Answered by Aaron C. • Biology tutor
3777 Views

Describe how the information in DNA is used during transcription and translation to construct polypeptides, including the role of messenger RNA (mRNA), transfer RNA (tRNA) and the ribosomes.

RNA Is synthesised in the nucleus from a DNA template. During synthesis of RNA, the two strands of the DNA molecule separate temporarily; one of these strands is used as a template for synthesis of an RNA mo...
NS
Answered by Nikolaos S. • Biology tutor
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How is the heart beat controlled?

The heart is composed of myogenic muscle and generates its own rate in normal condition. This rate can be modified during increased or decreased respiratory demand. The heart beat is initiated by a group of ...
TD
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An airtight compost heap causes anaerobic decay. Explain why the gardener might be against producing compost using this method

Anaerobic decay produces two main gases. Carbon dioxide and Methane. Methane, more importantly, is one of the five greenhouse gases that results in global warming.
JP
Answered by Jananiy P. • Biology tutor
12533 Views

Can you explain the circulatory system of the blood?

The heart is divided in half by a septum, giving a right side and a left side. Both sides will also be divided again and have an atrium on the top and a ventricle on the bottom. We will begin at the left ven...
AS
Answered by Annabel S. • Biology tutor
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