Nutrition and Biochemistry(Lecture No. 2)

ROLE OF DIETARY PROTEINS1. 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 Groupii. Carboxyl Group

i. The Amino group is (- NH2) actually basicii. Carboxylic group is (- COOH) Acidiciii. R is variable carbon side chain

CLASSIFICATION OF AMINO ACID:-1. Standard and Non-Standard 2. On Side Chain Basis = Aliphatic, Aromatic, Hydroxyl, Sulphar, Acidic, Basic &

Imino Group3. On Polarity Basis = Non-Polar, Polar, Polar = R(+) Polar = R(-) Polar = (±)4. On Metabolic Basis = Glucogenic Amino Acids, Ketogenic Amino Acid, Both

Gluco & Keto Group5. On Nutritional basis = 1. Essential Amino Acids 2. Non-Essential Amino AcidsESSENTIAL 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:-6. On Physico-chemical Basis = Simple proteins, compound proteins, Derived

proteins.7. On Functional Basis = Structural Hormonal Enzymatic (SHE), Storage

Transport Defensive (STD), Genetic Contractile Receptor (GCR).8. On Structural basis: primary secondary, tertiary Quaternary9. On Nutritional Basis: 1. Animal Proteins 2. Plant Proteins

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. AcidZein from Corn lack Tryptophan A. Acid

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.

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/ dayChildren = 2gm / kg/ dayAthletes = 1gm/ kg/ day extraPregnancy & 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.

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 extremitiesHair dry, thin + De-pigmented

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%)