digestion and absorption of proteins how proteins are digested and how they are absorbed in our body are discussed here

1. VIGNESWARAN G B.Sc. , M.Sc.
ASSISTANT PROFFESSOR,
DEPARTMENT OF BIOCHEMISTRY
NANDHA DENTAL COLLEGE AND HOSPITAL

2.  What are proteins ?
 What are the building blocks of proteins ?
 How proteins are organized ?
 Name of the bond which is present in proteins

3. The structure of the protein
molecule includes four
organization levels
Primary (1º)
Secondary(2º)
Tertiary (3º)
Quartenary(4º)

4. PRIMARY STRUCTURE
defined as the chain of sequence
of amino acids
IMPORTANCE
 Detection of genetic diseases
 Improper folding
 Loss of impairment of normal function
Peptide bond
- amide linkages between two amino
acids
α- carboxyl group of amino acid --- α-
amino group of amino acid

5. SECONDARY STRUCTURE
 The secondary protein structure is
made by folding of the polypeptide
chain.
 There are two main types of
secondary protein structures: the α-
helix and the β-pleated sheet.

6. TERTIARY STRUCTURE
 A protein isn’t fully functional until it has a
3D shape. The 3D structure of a protein is
referred to as its tertiary structure and is
made by further folding of secondary
proteins.
 Interactions between the side chains of
amino acids lead to the formation of the
tertiary structure, and bonds form between
them as the protein folds. These include
hydrogen bonds, ionic bonds,
and disulfide bonds.
 Disulfide bonds are covalent bonds that
form between sulfur-containing side
chains and are much stronger than other
types of bonds. The disulfide bonds are
what hold the tertiary structure of the
protein in place.

7. QUARTENARY STRUCTURE
 The spatial arrangement of various
tertiary structures gives rise to the
quaternary structure.
 Some of the proteins are composed of
two or more polypeptide chains
referred to as sub-units.
 The spatial arrangement of these
subunits with respect to each other
is known as quaternary structure

8. VIGNESWARAN G B.Sc. , M.Sc.
ASSISTANT PROFFESSOR,
DEPARTMENT OF BIOCHEMISTRY
NANDHA DENTAL COLLEGE AND HOSPITAL

9.  Dietary proteins – 125g/day
 Digestive enzymes and
proteins – 25g/day (15- 25g)
 Proteins from worn out cells
 Digestion of proteins
DIGESTION
INTESTI
NE
MOUTH
STOMAC
H

10. MOUTH
No digestion of proteins
in mouth due to absence
of proteolytic enzymes
STOMACH
 Protein digestion starts in stomach
 Major proteolytic enzymes is pepsin
Pepsinogen pepsin
HCl
autocatalysis
proteins small
peptides
pepsin
Rennin
found in infants
helps for curdling of milk

11. INTESTINE
Pancreas
Pancreatic juice
Proteases

12. TRYPSIN
CHYMOTRYPSIN
ELASTASE
Endopeptidases
Cleaves randomly
Produces amino acids and oligopeptides, di and tripeptides
CARBOXYPEPTIDASES
Exopeptidases
Cleaves single peptides from carboxy terminal end
Carboxypeptidases- A
Cleaves aromatic amino acids
Carboxypeptidases- B
Cleaves basic amino acids
From
intestinal
brush
border
Amino peptidases
• Cleaves from
amino terminal
end
From
epithelial
cells
Di and tri-peptidases
• Di-peptidases - cleaves dipeptides
• Tri-peptidases - cleaves tripeptides