PROTIENS

1. BY: ALIA RAFIQUE

2. Proteins

3.  Proteins are organic nitrogenous compounds formed of C H O & “N”
 Proteins are the polymers of 20 naturally occurring amino acids
 Amino acids are organic acids in which one H is replaced by NH3
usually at α carbon (next to COOH group)
 All amino acids have in common
 central α carbon to which COOH & H & NH2 are attached
 α carbon is also attached to a side chain called R group which is different for each
amino acid
 N and C terminals
 There are 3 categories of Amino acids
1. Primary protein amino acids
2. Non primary protein amino acids
3. Non protein amino acids

4.  DYNAMIC
1. Transport of molecules across cell membrane or between cells
 Haemoglobin carries oxygen
 Protein carriers carry glucose across cell membrane
 Transferrin carry iron
 Albumin carries Ca, fatty acids and bile pigments
2. Catalytic role : Enzymes that are protein in nature
3. Metabolic regulations : some hormones are protein like Insulin
4. Contraction of the muscle : actin and myosin are proteins
5. Storage : ferritin is storage form of iron
 STRUCTURAL
1. They are components of cell membrane, cytoplasm and cell organelles
2. Mechanical support
 Collagen and elastin  ligaments tendon and blood vessels
 Keratin  skin, hair and nails
 Ossien  bone

5. 1. Essential amino acids
Cant be synthesized in the body so must be taken in the diet
Ex. Valine , leucine , isoleucine ,…..
1. Non essential amino acids
Can be synthesized in the body
Ex. Glycine , alanine , aspartic ,…..
 Arginine and Histidine are called semi-essential because they are
synthesized in the body in a rate enough for adults but not for growing
individuals

6. Digestion and Absorption of proteins
 Proteins play a vital role in the growth and replenishment of body cells
and tissues.
 The digestion of proteins takes place in the stomach with the help of
protease and pepsin enzymes, which breaks down the proteins into amino
acids. The process is facilitated by the hydrochloric acid present in the
stomach.
 Amino acids are tiny elements which get absorbed into the blood system
through the wall of the small intestine.

9. Nitrogen Balance
 Nitrogen balance is commonly referred to as the net difference between the intake (and/or
the effective absorption) of nitrogen contained in the diet and its excretion.
 Since nitrogen is contained predominantly in proteins, this term pertains mainly to the
balance of proteins and of amino acids.
 Nitrogen equilibrium is when the body maintains the same amount of protein in its tissues
daily (input = output). This applies to most healthy adults and is necessary for muscle
maintenance.
 Nitrogen balance can be positive and negative.

10. Continue…
 Positive Nitrogen Balance:
 If nitrogen intake from protein and other sources is greater than nitrogen output, the
body is in positive N balance. This is needed for muscle growth and pregnancy,
among many other things.
 Negative Nitrogen Balance:
 When the body loses protein, it is in negative N balance. This occurs with inadequate
protein intake, burns, severe injury, infection, and fever. Negative nitrogen balance will
lead to the breakdown of the body’s own protein structures, such as muscle, in order
to get the amino acids the body needs.