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Cellular Control Notes

This is a sample of our (approximately) 5 page long Cellular Control notes, which we sell as part of the OCR Biology F215 Notes collection, a A package written at Eastbourne College in 2013 that contains (approximately) 48 pages of notes across 10 different documents.

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Topic 5.1.1 Cellular Control: The way that DNA codes for proteins is central to our understanding of how cells and organisms function. The way in which cells control chemical reactions determines the ways in which organisms, grow, develop and function. Candidates should be able to:

• State that genes code for polypeptides, including enzymes.

• Explain the meaning of the term genetic code. The three letter code by which information is contained in a DNA molecule; a group of three bases specifies a particular amino acid to be added to a growing polypeptide chain.

• Describe, with the aid of diagrams, the way in which a nucleotide sequence codes for the amino acid sequence in a polypeptide. Proteins are made of polypeptides, which are long chains of amino acids. There are about 20 different types of amino acids The sequence in which the amino acids are joined together determines the structure and therefore the function of the protein (primary structure). DNA determines the sequence. The sequence of bases in a DNA molecule determines the sequences of amino acids in the proteins that the cell makes. A length of DNA that codes for one polypeptide is called a gene. The four different bases can be arranged in a huge variety of ways along a strand of DNA. Normally, only one of these strands is used for making proteins (the reference strand / sense strand). The code is a three-letter code. A sequence of three bases (known as a "base triplet") on the reference strand codes for one amino acid. The genetic code is almost universal meaning the same DNA triplets code for the same amino acids in almost every species of organism. This indicates it evolved very early on in the evolution of life on earth.

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