1. Proteins

2. essential life substance of all living matter .
act as structural unit to build our bodies .
specific structural chemical units amino acids
amino [alkaline substance carbon, hydrogen ,o2& NH2.
Essential amino acid are 9 in number :
Significant in our diet .
The body unable to syntheses these 9 amino acid so get it from our food

3. *types of protein :
1-myosin : found in muscle ,has role in contraction & relaxation of muscle .
2-collagen: has role in strength of bone .
3-hemoglobin attach with iron in the RBCs ,help in carrying o2.
4- albumin : major plasma protein .
5- globulin : alpha beta gamma globulin ,act as antibodies of immuno system

4. N.B:
complete protein foods comes from animal source as egg ,milk, cheese , meat .
Incomplete proteins food : plant food ,deficient of one or more essential amino acid , mostly of plant origin grains ,legumes ,nuts seeds .
Mixture of protein animals & plant animals give balance in the ratio of amino acid .

5. Functions of protein : A- growth & tissue building maintenance .
B- specific physiological roles :
Some types of amino acid used as neurotransmitter substance in the brain .
Aid in metabolic hormones as thyroxin
C- available energy

6. **digestion ,absorption & metabolism of proteins:
@ mouth : mechanical break down of food by chewing food mix it with saliva ,push it to stomach .
@ stomach : break down of protein to small particles by secreting enzymes pepsin ,HCL ** provide acidic media to convert pepsinogen to pepsin .
Rennin : found in infancy & childhood to digest milk , rennin prevent too rapid passage of food from the child stomach .
@ small intestine :alkaline media in the intestine ,also pancreatic secretion like trypsin & chemotropism.

7. ** absorption of amino acid :
the end product of protein digestion is the amino acid ,which is water soluble so absorption occur through blood stream .
absorption of amino acid at duodenum carried by pyridoxine [ vit B 6 ].
Metabolism of protein :
Important protein balance is anabolism & catabolism .
Protein more found in liver ,pancreas ,kidney & plasma lower protein in the brain ,muscle ,& skin .

8. Tissue catabolism occur in case of starvation & aging process { tissue break down are exceed than tissue building } .
Destruction of protein resulted in ; urea , uric acid ,ammonia .
Protein requirement :
Protein is essential nutrient .
Under develop countries protein energy malnutrition .
Primary role of amino acid important for growth ,& maintenance of tissue .

9. Age ,body size ,general physical state has role in protein requirement .
Disease increase need of protein diet especially in case of fever .
Traumatic injury ,post surgical state require protein for wound healing .
In case of burn , the need of protein increased .
Protein should be adequate in quantity & quality.
The need of protein increase in case of pregnancy .