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A gene is a section of DNA used to produce a single polypeptide, or protein molecule, which is made of amino acids. The process of protein synthesis can be divided into two parts.
The first part is transcription, which produces a molecule of messenger RNA (mRNA) from the gene. Transcription takes place in the nucleus of the cell. First, the gene to be transcribed dips into the nucleolus and the DNA is unwound, so the bases of the transcribing DNA strand are exposed. Complementary nucleotide base pairs which are in the nucleus then line up next to the exposed bases. C pairs with G, and A pairs with U, because U replaces T in RNA molecules. Phosphodiester bonds form between the RNA bases to form the mRNA molecule, catalysed by the enzyme RNA polymerase. This molecule of mRNA can then leave the nucleus through a nuclear pore, and the DNA rewinds.
The second part of protein synthesis is translation. It takes place outside the nucleus of the cell, on a ribosome. The mRNA produced in transcription attaches to the groove in the ribosome. Three bases on the mRNA make up a codon, and each group of three codes for a specific amino acid found in the cell. A tRNA molecule-another type of RNA-has the anticodon which is specific to each codon on the mRNA, and a specific amino acid is bound to the opposite end of the tRNA. tRNAs line up alongside the complementary codons on the mRNA, and then peptide bonds form between the adjacent amino acids. The mRNA moves through the ribosome, adding amino acids until the entire length of the mRNA has been translated. The completed polypeptide then leaves the ribosome and may go to another organelle for completion before it can perform its function.see more
The conclusion is the last part of the essay that the examiner will read, and therefore you should try to explicitly link it back to the specific question. This will tell the examiner that you have understood the exact question and will help you yourself to focus your conclusion, as you can get a bit lost whilst writing the bulk of the essay. You should aim to summarise the essay, without introducing any new points or evidence.
The main point of the conclusion is to come to a final decision regarding your answer. This does not mean that you need to come to an absolute and definite answer, as in fact the bast essays discuss the various factors of the question and place them in the context of each other. Therefore, you should aim to layer your conclusion, and assess the importance of each factor in comparison to the others. For example, you could suggest which factors were more important in the short or long term, or perhaps one was more significant because it set the background for the other factors to have an impact on the event.
A good way to decide which factor is the most important is to imagine whether the event you are discussing would have happened without each contributing factor. This means you can get a clearer understanding of the historical discussion, and give a sophisticated answer.
To end your answer, try to have a summary sentence so that the ending of the answer is not abrubt. This shouldn't introduce any new material, and a good way is to finish with a final question link to emphasise your point.see more
Primarily, the function of synapses is allow communication between nerones in the nervous system.
Additionally, the structure of synapses means that they can perform further functions. Specific receptors for the neurotransmitter are found only on the post-synaptic membrane, and therefore this means that the impulse can only be transmitted through this membrane. As a result, this means that synapses ensure impulses travel in the correct direction through the nervous system.
As more neurotransitter diffuses across the synaptic cleft, the excitatory postsynaptic potential increases. It must reach the action potential of +40mV before an impulse is generated in the post-synaptic neurone. This means that weak impulses in the pre-synaptic neurone do not cause enough neurotransmitter to be released for an action potential in the post-syptic neurone to be generated. As a result, synapses are able to filter out low level stimuli that the body doesn't need to repond to, as such conserving energy. Furthermore, repeated low level stimuli can be amplified as each impulse arriving at the synapse causes the release of more neurotransmitter, resulting in one larger impulse in the post-synaptic neurone.Therefore, this allows the body to respond to the stimuli more effectively.see more