Oxford Tutorial Essay

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You are an amino acid in the lumen of the small intestine of a newborn mammal. You are looking at intestinal epithelial cells that bring important maternal proteins (immunoglobulins) across their apical surfaces by receptor-mediated endocytosis. Your ambition is to be part of a receptor that does that job.

A. beginning from the challenge of entering the cell, until you have been loaded onto an appropriate tRNA.

Amino acids are the building blocks of protein. Within the small intestine is the only site in the digestive tube for absorption of amino acids. Absorption takes place on the surface of small intestinal epithelial cells.
Diffusion is the movement of molecules from an area of higher concentration to an area of lower
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An anticodon is a set of three nucelotides that form base pairs with the mRNA codon.
There are at least 20 different tRNA's - one for each amino acid. The anticodon is used to "read" the codons on the mRNA. The tRNA "reads" the mRNA codon by using its own anticodon. The actual "reading" is done by matching the base pairs through hydrogen bonding following the base pairing principle, where each base has a pair. That is, A is paired with T, or U, and C is paired with G.
In this way, each codon is "read" by various tRNA's until the appropriate match of the anticodon with the codon occurs. In this example, the tRNA anticodon, let’s say, AAG, reads the codon UUC on the mRNA. tRNA will have this amino acid that this mRNA codes for on its 3`end. The anticodon of the tRNA that carries this amino acid will bind to the codon in the mRNA. These events occur within a ribosome, which are predominantly on the endoplasmic reticulum, but are also dispersed around the cell. Ribosomes are the protein assemblers of a eukaryotic cell. They contain a large subunit and a small subunit. The small subunit holds the mRNA in place during translation and peptide bonds take place in the large subunit. During protein synthesis, three tRNAs are lined up within the ribosome. All three are bound to their specific mRNA codon, at A, P, and E sites. The protein being synthesized grows by one amino acid at a time. The
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