Two Science Lessons
1. The primary structure of proteins I
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1. The primary structure of proteins is the amino acid sequence of which they are composed (Devlin). Amino acids are strung together on the ribosomes in the cytoplasm of the cell according to the blueprint provided by mRNA which is a copy of a gene read off a stretch of DNA on a chromosome in the nucleus. Protein synthesis occurs in a stepwise fashion, with ribosomal peptidyltransferase transferring the growing peptide chain from its tRNA carrier to the alpha-amino group of the amino acid residue of the aminoacyl-tRNA specified by the next codon, or in the case of the first step, to the initiating methionine residue. Nonribosomal elongation factors aid in the process. A chain-terminating UAG, UAA, or UGA codon promotes binding of a release factor once the protein chain is complete, and it is released from the ribosome. The secondary structure of a protein refers to the local three-dimensional folding of the polypeptide chain of the protein (Devlin). The polypeptide chain has covalently linked atoms of the peptide bonds and alpha-carbon linkages that sequentially link the amino acid residue of the protein. Side chains of amino acid are not considered at the level of the secondary structure of the protein. The tertiary structure of a protein refers to the three-dimensional structure of the polypeptide, and it includes the conformational relationships in space of the side chains and the geometric relationship between distant regions of the polypeptid
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onding is the double helix of DNA (Devlin). Hydrogen bonds have important consequences for the functions in which the double helix of DNA participates. Hydrogen bonds are highly directional so are able to provide a discriminatory function for choosing between correct and incorrect base pairs. The directionality of the hydrogen bonds tends to orient the bases in a way that favors stacking, so they hydrogen bonds are essential for the stability of the double helix. The effects of a number of reagents on the stability of the double helix suggest that the destabilizing effect of a reagent is not related to its ability to break hydrogen bonds, but to its ability to solubilize the free bases in the reagent. The stability decreases as the solubility increases. This emphasizes the importance of hydrophobic forces in maintaining the structure of the double helix.
Lesson 3
3. The average cell in the human body is about 0.05mm in diameter, and the average size of bacterial cells is about one tenth of that (Why). The reason for this is that as cells get bigger, the volume increases more rapidly than the surface area of the cell membrane. Everything a cell needs to maintain itself, and all its waste products need to cross the c
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Some common words found in the essay are:
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Approximate Word count = 1900
Approximate Pages = 8 (250 words per page)
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