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Biology

A Level

What is the difference between DNA, mRNA and tRNA? and why are they different?

DNA, tRNA and mRNA are all essential macromolecular biological molecules involved in genetics and protein production. The two major categories of genetic molecules are DNA and RNA, with both tRNA and mRNA...

Answered by Tristan V. • Biology tutor

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How do cell membranes form and what is their structure

The cell membrane consists of a phospholipid bilayer. Phospholipids are molecules with a hydrophilic (water loving) tail. And a hydrophobic (water repelling) tail. The cell environme...

Answered by Emily D. • Biology tutor

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List the structures of the nephron in kidneys and which parts of the nephron differ in permeability to water?

The bowman's capsule, Proximal convoluted tuble, loop of Henle (descending and ascending lims), distal convolued tubule and the collecting duct. The descending limb is permeable to water. The ascending li...

Answered by Tahmid I. • Biology tutor

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Describe how mRNA is produced in a cell (5 marks)

Double-helix DNA strands are separated by breaking the hydrogen bonds between complementary bases. One strand acts as a template strand which complementary bases bind to (adenine to uracil, thymine to ade...

Answered by Shubham G. • Biology tutor

6165 Views

When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob. Describe how.

The arrival of a nerve impulse at a synapse causes Ca2+ channels to open (1 mark). Ca2+ ions enter the presynaptic knob by facilitated diffusion (1 mark). The presence of Ca2+ ions causes synaptic vesicle...

Answered by Andrew B. • Biology tutor

4455 Views