3. Proteins from animal sources
• Have a high quality since they contain all
essential amino acids in proportions similar
to those required for synthesis of human
tissue proteins
• Gelatin prepared from animal collagen
deficient in certain essential amino acids;
poor quality
Proteins from plant sources
• Have lower quality than animal proteins
• May be combined in such a way as to improve
quality
4. Biological value of some dietary proteins
Source BV
Egg 100
Beef 100
Milk 85
Soya bean protein 67
Potato
30
67
Whole wheat bread
Ability to provide the all essential amino acids required for
tissue maintenance
Measured on a relative scale with egg albumin scored at 100
6. Essential amino acid
• H VITTAL LMP
• Building blocks for body tissues, bones, muscles,
cartilage, skin, and blood.
• During starvation, provide energy (10-15%)
• Enough carbohydrate intake, act as protein
sparing effect
• It is a component of every cell in your body. In
fact, hair and nails are mostly made of protein
• Your body uses it to build and repair tissue.
• You need it to make enzymes, hormones, and
other body chemicals
7. Maintain nitrogen balance
•Nitrogen loss is 3.5 g
of N/day 22 g of
protein (65 kg
person)
•For protein turnover
(0.75-0.8 g/kg of
good quality protein)
•For growth
8. POSITIVE NITROGEN BALANCE
• Occurs when nitrogen intake exceeds nitrogen excretion
• Observed during situations in which tissue growth occurs
Eg: childhood, pregnancy, during recovery from an illness
NEGATIVE NITROGEN BALANCE
• Occurs when nitrogen losses exceed nitrogen intake
Occurs due to
• Inadequate dietary protein, lack of essential amino acid
• Trauma, burns, illness, surgery
9. Mutual Supplementation
Proteins from different plant sources may be
combined in such a way that deficiency of an
essential amino acid in one protein is
compensated by the adequate amount of the
same in another protein
10. • Eg: Wheat protein (lysine-deficient,
methionine-rich) with kidney bean protein
(methionine-deficient, lysine-rich)
• Results in a protein mixture of improved
biological value, equivalent to animal protein
11. REFERENCES
• Vasudevan, D., S, S., & Vaidyanathan, K.
(2013).Textbook of biochemistry for medical
students.New Delhi: Jaypee Brothers Medical
Publishers (P) Ltd.
• http://www.detourbar.com/protein-
basics/the-importance-of-protein-in-your-
diet/
