Question

Describe the digestion of food in small intestine.

Answer 1

Digestion in small intestine:

1. Digestion of carbohydrates in the small intestine:

40% starch is partially digested by ptyalin while remaining 60% starch is digested by pancreatic amylase. Starch ——Panerestic__, maltose + Isomaltose + Limit dextrin.
The enzymes of intestinal juice act as below:
Maltose —Mslt2s°_, 2 Glucose
Isom altose —lomaltase_. 2 Glucose
Surcrose —SU&*® _, Glucose + Fructose
Lactase Lactose —————— _ Glucose + Galactonse
Limit Dextrin Set Glucose fe xtrinase
The humans cannot digest the cellulose due to the absence of cellulose enzyme.

2. Digestion of protein the small intestine:

Action of pancreatic juice. It contains proenzymes trypsinogen, chymotry-psinogen and procarboxy peptidase.
Enterokinase . Tryp sin ogen of int erstinal juice Tryp sin
Chymotryp sin ogen —25"_ chymotrypsin
Pr ocarboxypeptidase —lrypsin_, Carbody - peptidase
Peptones ——25" _, pentides
Peptones —Shymotrypsin_. peptides
Peptides —atboxypentidase_, cry aller
peptides + Amino acid
Trysinogen converts into trypsin in the presence of enterokinase. Trypsin converts chymotrypsinogen into chymotrypsin; procarboxypeptidase into carboxy-peptidase; and peptones into peptides. Chymotrypsin also converts peptones into peptides. Peptides gets converted into smaller peptides and amino acids in the presence of carboxypeptidase.
Action of intestinal juice. Intestinal juice contains endokinase, aminopeptidase and dipeptidase. Actions of these enzymes are summarized below:
Peptides —Aminopentidase _. cm aller peptides + Amino acid Peptides —Dipentidase_. amino acid

3. Digestion of Fats:

Digestion of fats occurs in small intestine and reactions occur as below:
Fat —bile_. emulsified fat Emulsified fat —Fancreatic _, Fatty acid + Glycerol lipase

4. Digestion of Nucleic Acids:

Nucleic acids are digested in the small intestine as below:
DNA —2285€_, Deoxyribonucleotides
RNA —808S2_, Ribonucleatides
Nucleotides —Nudeotidase_. Nudeosides + Phosphate
Nucleosides —-Nudeoside_. Nitragenous bases + Pentose phosphate Phosphorylase
The enzyme Dnase converts DNA into Deoxyribonucleotides, Rnase converts RNA into ribonucleotides, nucleotidase converts the nucleotides into nucleosides and phosphate and finally nucleoside phosphorylase converts nucleosides into nitrogenous bases and pentose phosphate.