Dr. Tarek El Sewedy Department of Medical Laboratory Technology Faculty of Allied Medical Sciences Faculty of Allied Medical Sciences

Amino acids and proteins Part 1

By the end of this lecture, students will learn: 1.Structure and function of amino acids 2.Amino Acids classification. INTENDED LEARNING OUTCOMES

LECTURE CONTENT structure of Amino Acids Characteristics of amino acids Classification of amino acids Amino Acids and proteins nutritional facts

The basic structure of an amino-acid molecule consists of a carbon atom bonded to an amino group (-NH 2 ), a carboxyl group (-COOH), a hydrogen atom, and a fourth group that differs from one amino acid to another and often is referred to as the-R group or the side chain. The-R group, which can vary widely, is responsible for the differences in chemical properties.

Amino Acids Amino acids are the building blocks of proteins. There are 20 different amino acids that make up human proteins. Groups of two amino acids are called di-peptides,whereas three amino acids together are called tri-peptides. more than 10 in a chain, they are termed polypeptides. Peptide bonds A.A are linked together by Peptide bonds a special covalent bond found in proteins.

 11 out of 20 A.A can be synthesized in the body (non essential)  9 (essential) amino acids have to be obtained from food  The properties of each amino acid are determined by its specific side chain ( R –groups )  R-groups vary in structure, Nature, electric charge and solubility in water from one amino acid to other.

20 naturally occurring Amino acids Amino acids names are often abbreviated as either 3 letters or single letters.

 As the properties of the amino acids and their role in proteins are determined by the side chain, therefore amino acids are classified according: 1-Polarity of the side chain.  -Acid  -Basic  -Neutral 2- Structure of side chain  - Aliphatic  - Aromatic Classification of Amino Acids (Depending on structure)

Neutral Amino Acids These amino Acids are considered neutral. There is one carboxyl group per amino group

Acidic Amino Acids There are two acidic amino acids. twoonly one There are two carboxyl groups and only one amino group per molecule

Basic Amino Acids They have more amino groups than carboxyl groups

 Aliphatic side chain  Aromatic side chain  Sulphur – containing side chain  Acidic side chain  Basic side chain  Hydroxyl side chain  Imino Side Chain CLASSIFICATION Depending on side chain structure

α, β, or γ Amino acids may be characterized as α, β, or γ depending on the location of the amino group on the carbon chain. α are on the carbon adjacent to the carboxyl group. β are on the 2 nd carbon γ on the 3 rd carbon from the carboxyl group. α, β, or γ Amino Acids

α− amino acids Amino acids found in proteins are α− amino acids. The amino group is always found on the carbon adjacent to the carboxyl group

Metabolic Classification of the Amino Acids Essential and Non-essential Glucogenic and Ketogenic

Essential Amino Acids Only 11 Of the 20 amino acids that make up proteins can be synthesized by the human body The other 9 amino acids must be acquired from food sources. These amino acids are known as essential amino acids

Non essential Amino Acids

Glucogenic or ketogenic Amino acids Glucogenic amino acids are degraded to compounds that can be used as carbon skeletons for glucose synthesis via gluconeogenesis. Ketogenic amino acids are degraded to compounds that can only be used to generate the ketone bodies.

Glucogenic Amino Acids

Ketogenic Amino Acids Metabolized to acetyl CoA or acetoacetyl CoA Leucine Lysine

Amino Acid Functions 1. Amino acids are the building blocks of proteins. 2. Some amino acids and their derivatives function as neurotransmitters hormones and other regulators (Ex. L- dopamine-Epinephrine-Thyroxine). 3. It may supply the carbohydrates pool with glucose ?????????.

Protein functions 1. - Catalytic functions [enzymes] 2. - Receptor [insulin receptor] 3. - Structural function [collagen] 4. - Transport [hemoglobin] 5. - Protective functions [Antibodies]

Protein function (cont…) 6. - Hemostasis [clotting factors] 7. - Hormonal functions [insulin, glucagon, GH] 8. - Control of gene expression [transcription factors] 9. - DNA packing [histones] Act as buffers.

Protein nutritional facts

Spirulina quinoa soybeans Almond

Good sources of protein

Amino Acid nutrition Our body doesn’t use proteins in a direct way; first proteins are decomposed into amino acids and then amino acids are used for the resynthesize of muscular proteins

أحمد محمد محمود عابدين ساري ابراهيم احمد

ASSIGNMENTS Selected students are requested to prepare slides about one of the following topics (To be delivered before next lecture): Digestion of proteins Essential amino acids. Non essential amino acids Physical properties of amino acids. Chemical properties of amino acids. Disease resulting from disturbance in amino acid metabolism. Ketone bodies and amino acids Translation of RNA

Study Question Write three points about : Function of amino acids

1- Tryptophan is amino acid a-Essential b-Non essential c-Non-protein Choose: Correct the incorrect word: There are 30 alpha standard amino acids participate in protein synthesis.

Principles of Biochemistry, Donald J. Voet, Judith G. Voet, Charlotte W. pratt; Willey, 3 rd ed. Suggested readings: