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 5

Amino acids and proteins Part 2

By the end of this lecture, students will learn:

1. Amino Acids classification.

INTENDED LEARNING OUTCOMES

LECTURE CONTENT

• 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 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 11 Of the 20 amino acids that make up proteins can

be synthesized by the human bodyThe 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 AcidsMetabolized to acetyl CoA or acetoacetyl

CoA then to ketone bodies

Leucine

Lysine

Amino Acid Functions1. Amino acids are the

building blocks of proteins.

2. Some amino acids and

their derivatives function

as neurotransmitters

hormones.

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

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

Protein and diet

Protein and diet

• An individual's daily protein requirement depends on several factors, including:

1. Age - a growing child's needs will not be the same as an individual aged 80 years

2. Sex - males generally require more protein than (non-pregnant or non-breastfeeding) females

3. Weight - an individual who weighs 100 Kg will require more protein compared to somebody who

weighs 50 Kg.

4. Muscular exertion - an individual who earns his living delivering pianos will require more protein

than a computer programmer of the same age and height.

5. Muscle mass - a muscle-bound weight trainer will need more dietary protein than a marathon

runner

6. Health - a person who is recovering after an illness or medical procedure may need more dietary

protein than other people.

• Percentage of energy that should come from protein:

• Children aged 1 to 3 years - 5% to 20%

• Children aged 4 to 18 years - 10% to 30%

• Adults - 10% to 35%

• According to the US Department of Agriculture, our protein intake should be:

• Infants - 10 grams per day

• Teenage boys - up to 52 grams per day

• Teenage girls - up to 46 grams per day

• Adult men- approximately 56 grams per day

• Adult women - approximately 46 grams per day

• Pregnant or lactating (breastfeeding) women - about 71 grams per day

Protein deficiency Mental retardation and reduced IQ.

Growth problems

Wasting and shrinkage of muscle tissue

Apathy

Swollen belly

Anemia

Weaker immune system

Protein Excess

Weight gain.

Intestinal irritation.

Risk of heart disease

Kidney problems

Gout disease

Students selected for assignment

الخضري صالح أالء

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 :

Classification of amino acids1-

2-

3-

Principles of Biochemistry, Donald J. Voet,

Judith G. Voet, Charlotte W. pratt; Willey, 3rd

ed.

Suggested readings: