PHAROS UNIVERSITY FACULTY OF ALLIED MEDICAL SCIENCE
BIOCHEMISTRY 1 (MGBC-101)
Dr. Tarek El Sewedy
Department of Medical Laboratory Technology
Faculty of Allied Medical Sciences
Lecture 4Amino 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
Structure of amino acids
• The basic structure of an amino-acid molecule consists of a carbon atom
bonded to an amino group (-NH2), 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.
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 -Neutral2- Structure of side chain - Aliphatic - Aromatic
Classification of Amino Acids (Depending on structure)
Neutral Amino AcidsThese amino Acids are considered neutral.
There is one carboxyl group per amino group
Acidic Amino AcidsThere are two acidic amino acids.There are two carboxyl groups and only one
amino group per molecule
Basic Amino AcidsThey 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
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 2nd carbon
γ on the 3rd carbon from the
carboxyl group.
α, β, or γ Amino Acids
α− amino acidsAmino 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 AcidsOnly 11Of the 20 amino acids that make up proteins
can be synthesized by the human bodyThe other 9 amino acids must be acquiredfrom 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 AcidsMetabolized to acetyl CoA or acetoacetyl
CoA
Leucine
Lysine
Amino Acid Functions1. 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 functions1. - 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]
10.- Act as buffers.
Protein nutritional facts
Spirulina
quinoa
soybeansAlmond
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
Students selected for assignment
عابدين محمود محمد أحمداحمد ابراهيم ساري
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 QuestionWrite three points about :
Function of amino acids1-
2-
3-
1- Tryptophan is ---------------------amino acida-Essentialb-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, 3rd ed.
Suggested readings: