HBG 2 ( Introduction to Amino Acids and Proteins)

• Every life process depends on proteins which are made up of amino acids.
• Virus or bacteria infection can affect proteins and amino acids.
• Proteins are made up of amino acids which have various properties such as general properties, side-chain properties, and nutritionally essential amino acids.
• Amino acids have a carboxyl group, an amino group, and 20 different side chains.
• The carboxyl group in amino acids is responsible for their acidity.
• The amino group in amino acids is responsible for their basicity.
• Nutritionally essential amino acids are those that cannot be synthesized by the human body and must be obtained from the diet.
• Amino acids have various general properties such as being covalent, having a chiral carbon, and being optically active.
• Amino acids also have various side-chain properties such as being stereogenic, having a hydrogen atom, and having a chiral carbon.
• Amino acids can have different L- and D-configurations.
• Animal proteins such as milk, meat, and eggs contain all essential amino acids.
• Histidine is essential for growing age only.
• Nine amino acids cannot be synthesized in the body are phenylalanine (Phe, F), valine (Val, V), tryptophan (Trp, W), threonine (Thr, T), isoleucine (Ile, I), methionine (Met, M), histidine (His, H), leucine (Leu, L), and lysine (Lys, K).
• Arginine is a basic amino acid.
• When methionine is deficient in the diet, cysteine becomes an essential amino acid.
• Animal proteins are deficient in essential amino acids.
• Histidine is semi-essential; it is essential in growing children only.
• Histidine offers buffer function for the body.
• In an healthy adult, phenylalanine cannot be synthesized in the body.
• Kwashiorkor results from inadequate intake of protein.
• Phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, and lysine are precursors to cysteine, methionine, serine, tyrosine, phenylalanine, arginine, glutamine, glutamate, aspartate, proline, and glycine respectively.
• The amino acids embedded in the plasma membrane containing non-polar side-chain B are serine and threonine, which have a –OH group for phosphorylation.
• Lysine is a sulfur-containing amino acid.
• Basic side chains (positive).
• C + H 3 N COO - H CH 2 CH 2 CH 2 NH
• Trans-membrane protein across the cell membrane.
• C + H 3 N COO - H CH 2 HN: N: C + H 3 N COO - H CH 2 HN: N + + 2H +
• C + H 3 N COO - H CH 2 Tyr
• C + H 3 N COO - H CH 2 SH
• Acidic side chains (negative).
• There are 20 different amino acids with 20 different side chains.
• Side chain properties can be grouped into 6: Non-polar, aliphatic side chains; Uncharged polar side chains; Acidic side chains; Basic side chains; Sulfur containing side chains; Aromatic ring containing side chains.
• Hydrophobic, water insoluble, stay away from water.
• Arg is positively charged.
• Phospholipid bilayer.
• Methionine (met, M)
• Tyrosine (Tyr, Y)
• Phenylalanine ( phe , F)
• Polar, pH< 6.
• Some amino acids can be categorised into two or more groups: Val, Ile, Leu, Met, Phe, Trp, Ala, Pro, Gly.