Download Pharos university Faculty of Allied Medical SCIENCE Biochemistry 1

Dr. Tarek El Sewedy
Department of Medical Laboratory Technology
Faculty of Allied Medical Sciences
Amino acids and proteins
Part 1
INTENDED LEARNING OUTCOMES
By the end of this lecture, students will learn:
1.
Structure and function of amino acids
2.
Amino Acids classification.
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 (-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 .
Classification of Amino Acids
(Depending on structure)
 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
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.
 There are two carboxyl groups and only one amino
group per molecule
Basic Amino Acids
 They have more amino groups than carboxyl groups
CLASSIFICATION Depending on side chain structure
 Aliphatic side chain
 Aromatic side chain
 Sulphur – containing side chain
 Acidic side chain
 Basic side chain
 Hydroxyl side chain
 Imino Side Chain
α, β, or γ Amino Acids
 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− 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 11Of 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. Ldopamine-Epinephrine-Thyroxine).
3. It may supply the
carbohydrates pool with glucose
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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]
10. - 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 2 3-
Choose:
1- Tryptophan is ---------------------amino acid
 a-Essential
 b-Non essential
 c-Non-protein
Correct the incorrect word:
There are 30 alpha standard amino acids participate
in protein synthesis.
Suggested readings:
Principles of Biochemistry, Donald J. Voet, Judith G.
Voet, Charlotte W. pratt; Willey, 3rd ed.