Proteins, Membranes & Cellular Activity Notes

Proteins, Membranes & Cellular Activity Water is approx 50-60% of an adult's body weight 60% is intracellular and 40% is extracellular Ionisation of water Weak acid pH = -log [H+] Buffers Resist pH change around pKa due to buffering pI = isoelectric point where a molecule has an electric charge of 0 Blood must be buffered to maintain the optimum pH Amino acids 20 common AAs ionised at pH 7 to form a zwitterions l-isomers only in biology Side chains Aliphatic: glycine, alanine, valine, isoleucine, leucine, methionine Aromatic: phenylalanine, tyrosine, tryptophan Neutral: serine, threonine, cysteine, asparagines, glutamine, proline Positive: lysine, arginine, histidine Negative: aspartic acid, glutamic acid Polymerisation Condensation reaction between carboxylic acid and amino group to form a peptide bond Grows from the N-terminus to the C-terminus Protein folding Hydrogen bonding Usually found within the interior of a protein As beta-sheets or alpha-helices Page 1 

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