Practice biochemistry amino acid. Introduction. Food are divided into three classes : 1- Carbohydrate Source of energy 2 - Lipid Principal of energy reserve 3 - Proteins Energy for growth and cellular maintance. Amino acid and protein.
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Source of energy
Principal of energy reserve
Energy for growth and cellular maintance
The carbon on all amino acids, except glycine, is a chiral carbonbecause it has four different groups bonded to it.
Is simple amino acid because R chain is H
an imino acidis any molecule that contains both imino (>C=NH) and carboxyl (-C(=O)-OH) functional groups
At acidic pH, the carboxyl group is protonated and the amino acid is in the cationic form
At neutral pH, the carboxyl group is deprotonated but the amino group is protonated. The net charge is zero; such ions are called Zwitterions
At alkaline pH, the amino group is neutral –NH2 and the amino acid is in the anionic form.
With all amino acid will give purple or deep blue with exception Proline gives yellow not violet (why)
Proline reacts with ninhydrin, but in a different way. While most ninhydrin tests result in a purple color, the proline reaction is more yellow due to substitution of the alpha amino group that ninhydrin reacts with carbon rings
it is result of condensation of two molecule of urea
peptides containing three or more amino acid residues form a colored chelate complex with cupric ions (Cu2+) in an alkaline environment containing sodium potassium tartrate.
Thus, the biuret reaction is the basis for a simple and rapid colorimetric reagent of the same name for quantitatively determining total protein concentration.
chelation involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central atom.
and casein (but not gelatin);
Sulfur containing amino acids, such as cysteine and cystine upon boiling with sodium hydroxide (hot alkali) yield sodium sulfide.
This reaction is due to partial conversion of the organic sulfur to inorganic sulfide, which can detected by precipitating it to lead sulfide, using lead acetate solution.S.(protein) + 2NaOH-------- Na2S
Na2S + (CH3COO)2pb ------- PbS + 2CH3COONa
1. Place 1 ml of 2% casein, 2% egg albumin, 2% peptone, 2% gelatine and 0.1 M cysteine into separate, labeled test tubes.
2. Add 2 ml of 10 % aqueous sodium hydroxide. Add 5 drops of 10 % lead acetate solution.
3. Stopper the tubes and shake them. Remove the stoppers and heat in a boiling water bath for 5 minutes. Cool and record the results.