This document discusses the role of dietary proteins and amino acids. It begins by explaining that proteins are made up of amino acids and are important for growth, repair and maintenance of tissues. It then classifies amino acids and proteins in different ways, such as essential vs non-essential amino acids, and complete vs incomplete proteins. Animal proteins are described as higher quality complete proteins compared to plant proteins, which are often incomplete. The concepts of nitrogen balance, protein sparing effect of carbohydrates, and protein-calorie malnutrition are explained. Protein requirements for different populations are provided.

1. Nutrition and Biochemistry
(Lecture No. 2)

2. ROLE OF DIETARY PROTEINS
1. Word protein is derived from Greek word “Proteious” means holding first
place. Protein is organic nitrogenous compound, utmost important to life.
Most abundant organic molecule of living system and serves as basis of all
cells & tissues in body.
2. Proteins are not meant for energy. But they are body building Macro –
Nutrient required for body growth and repair of worn out tissues.
3. Proteins are polymer of Amino Acids and yield essential & non-essential
Amino Acids on their Hydrolysis. We primarily depend on for essential
amino acid which cannot be synthesized in human body and needed in diet.
4. Amino Acids are linked together by peptide linkage to form proteins. Amino
Acids are building blocks of Proteins, containing two functional groups:
i. Amino Group
ii. Carboxyl Group
i. The Amino group is (- NH2) actually basic
ii. Carboxylic group is (- COOH) Acidic
iii. R is variable carbon side chain

3. CLASSIFICATION OF AMINO ACID:-
1. Standard and Non-Standard
2. On Side Chain Basis = Aliphatic, Aromatic, Hydroxyl, Sulphar, Acidic, Basic & Imino
Group
3. On Polarity Basis = Non-Polar, Polar, Polar = R(+) Polar = R(-) Polar = (±)
4. On Metabolic Basis = Glucogenic Amino Acids, Ketogenic Amino Acid, Both Gluco &
Keto Group
5. On Nutritional basis = 1. Essential Amino Acids 2. Non-Essential Amino Acids
ESSENTIAL AMINO ACIDS:
Or Indispensable which cannot be synthesized by body and needed to supplied through
diet for proper growth development & maintenance of individual.
NON-ESSENTIAL AMINO ACID:-
Or Dispensable which can be synthesized by the body and need not be supplied through
diet for growth, development & maintenance of individual.
CLASSIFICATION OF PROTEINS:-
1. On Physico-chemical Basis = Simple proteins, compound proteins, Derived proteins.
2. On Functional Basis = Structural Hormonal Enzymatic (SHE), Storage Transport
Defensive (STD), Genetic Contractile Receptor (GCR).
3. On Structural basis: primary secondary, tertiary Quaternary
4. On Nutritional Basis: 1. Animal Proteins 2. Plant Proteins

4.  ANIMAL PROTEINS: -
Found in cheese, egg, milk, meat, beef, fish etc. Higher biological value, are
highly digestible They have all essential amino acids in right proportion and
quantity for synthesis of tissue proteins. So they are called complete proteins,
high quality proteins and A class proteins.
 PLANT PROTEINS:-
All plant proteins found in Cereals i.e. Wheat rice corn legumes peas, beans,
pulse and vegetables have low Biological values. These plant proteins are
deficient or in complete absence of one or more essential Amino Acids. So they
are called incomplete proteins, low quality proteins or 2nd class proteins. Plants
proteins are inferior to animal proteins.
 COMPLETE PROTEINS:-
Contain all ten essential Amino Acids in Right Quality & Proportion for
synthesis of tissue protein in human body e.g. egg, milk, and meat, fish etc.
 INCOMPLETE PROTEIN:-
In these proteins one or more essential Amino Acids are found completely
absent.
Gelatin from Collagen lacks Tryptophan A. Acid
Zein from Corn lack Tryptophan A. Acid

5.  PARTIALLY COMPLETE PROTEIN:-
Although Contain all ten essential Amino Acids but such proteins are deficient
in one or more Amino Acids required for synthesis of tissue protein. Cereals
wheat deficient of lysine, kidney bean – methionine plant protein are
nutritionally inferior to animal proteins.
But their nutritive value can be enhanced by combining two or more plant
proteins wheat deficient of Lysine rich methionine and kidney beans rich in
lysine and deficient in methionine when mixed + combine, they produce
complete protein of improved nutrition of biological value.
 NITROGEN BALANCE:-
Nitrogen balance is said when amount of nitrogen consumed is equal to
nitrogen excreted through urine, faces + sweat protein 1gm/ kg/ day is advocate
to maintain N. equilibrium elderly people requirement is more than 1gm/ kg/
day.
 NEGATIVE NITROGEN BALANCE:-
When nitrogen loss exceeds, N-intake e.g. in-adequate N- in diet, Trauma,
burn, severe illness, surgery and loss of Essential Amino Acids.
 POSITIVE NITROGEN BALANCE:-
When N-intake exceeds nitrogen excretion e.g. Tissue growth, Children,
pregnancy, GH, insulin, N. Positive balance GH, insulin increases the positive
nitrogen balance.

6.  PROTEIN REQUIREMENT IN HUMAN:-
Proteins of mixed biological value 0.8gm/ kg/ day i.e. 70 x 0.8 =
56gm/day
according to AMDR 10 – 35% 1gm/ kg/ day
Children = 2gm / kg/ day
Athletes = 1gm/ kg/ day extra
Pregnancy & Lactation = 20 – 30gm / day extra
 CONSUMPTION OF EXCESS PROTEINS:-
As proteins are not meant for energy proteins are primarily required for
growth of body and repair if worn out tissue.
If consumed in excess from the body needs, are De-aminated,
catabolized resulting C – Skeleton to yield (or Provide) energy Acetyl
Co for fatty acid synthesis. Excreted as urinary – Nitrogen (Urea Cycle)
+ but leads excess Nephrolithiasis, osteoporosis.
 PROTEIN SPARING EFFECT OF CHO:-
when CHO intake are less than 130 gm/ day there is decrease glucose
supply to CNS (where glucose is only energy supply) then from A.A
(Gluconeogenesis) i.e. Glucose from proteins.
So consumption of ample quantity of CHO decreases the protein
required of body i.e. CHO spares Proteins.

7.  PROTEINS CALORIES MAL-NUTRITION (PCM):-
PCM is seen in hospitals with chronic illness Pts with major trauma, severe infection +
undergoing major surgeries there are two extreme PCM.
MARASMUS KWASHIORKOR
(Greek word – to waste)
Age: Less than 1 year
(African word – weaning disease)
Age: 1-5 year
Results: inadequate or insufficient calories intake causing under
nutrition child calories is the Limiting Factor. (quality)
Result: from Protein deficiency (Protein in sufficient) while
caloric intake is sufficient here protein is the limiting factor not
calorie
Cause: Child is exclusively breast fed, mother milk decreases
inadequate artificial feed, Mal formation of mouth & nose
interfere with adequate feed.
Cause: Seen protein deficiency (additional feed) during weaning
or months after weaning, protein is low, child is on cereals,
grains, starchy food, no milk or egg.
Clinical Features: Growth retarded, extremely underweight,
muscle wasting, loss of sub- cutaneous fats – “Monkey face”, very
Hungary, cries continuously – appetite better
Clinical features: Growth retarded thin, lean underweight, here
fats is present, “Puffy moon face”, miserable looking appetite
poor, even refuse to eat.
Diarrhea: Vomiting common, dehydrate signs (+) edema is not
present.
Skin & hair, skin is thin, hair thin & lusterless
Pitting edema (+): Due to hypo albuminemia 2g/ 100ml is main
clinical feature. It is soft, painless 1st on legs then spreads to
upper extremities
Hair dry, thin + De-pigmented

8. BIOCHEMICAL CHANGES BIOCHEMICAL CHANGES
1 Anemia: Hb and hematocrit is ↓ Anemia: Mild and Moderate
2 BMR. RMR: Sub Normal BMR. RMR: May be↓ but not sub normal
3 Serum Protein: Total Proteins ↓ A/G ratio maintained Serum Protein: Always ↓Hypo- albuminemia frequently
reversible A/G ratio not maintained
4 Plasma Lipids: not effected Plasma Lipids: in Plasma↓ Cholesterol & TG
5 Fatty Liver: Not Common Fatty Liver: May be seen
6 CHO Metabolism: Hypoglycemia not common. Hypoglycemia: Frequently seen
7 Serum Enzymes: Not effected Serum Enzymes: ↓Amylase, ↓Alkaline phosphatase
8 Prognosis: Good & Reversible
(200 Kcal/ Kg)
Prognosis: Not good even under best conditions admitted in
hospital mortality rate high (10 – 20%)