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CLASS - XI/ZOOLOGY
HUMAN NUTRITION
Prof.Dr. R.S. Dhote
Class : XI
TOPIC : SUMMARY OF HUMAN NUTRITION
DIGESTION OF FOOD IN ORAL CAVITY :
Starch Ptyalin
→ α - Dextrin + Isomaltose + Maltose.
DIGESTION IN STOMACH :
pepsin
Pepsinogen
(proenzyme)
Prorennin HCl
→ Rennin
(proenzyme)
Casein Rennin
→ Paracasein
(Milk protein)
Paracasein + Ca → Calcium paracaseinate (curd)
Calcium paracaseinate
peptones
-
Starch
-
B
.
Proteins Pepsin
→ peptones
DIGESTION IN SMALL INTESTINE :
Digestion of Carbohydrates :
Maltase
Pepsin
- Dextrinase
ααHCl


→
→

→
→

Action of Pancreatic juice :
Pancreatic amylase converts starch in to maltose, isomaltose and dextrin
panreatic
S
.
C
.
Maltose + Isomaltose
+ α - Dextrins
Action of intestinal juice - Intestinal juice contains maltase, isomaltase, sucrase, lactase and
Dextrinase which act as follows :
Glucose + Glucose
Maltose
-amylase
D
.
.
-
Isomaltose Isomaltase
 → Glucose + Glusose
Sucrase
Sucrose → Glucose + Fructose
(i)
-
Lactose Lactase
→ Glucose + Galactose
Glucose
α - Dextrins
Digestion of Proteins :
Action of pancreatic juice :
Pancreatic juice contains proenzymes trypsinogen, chymotrypsinogen, elastase and
procarboxypeptidase.
se
Trypsinogen Enterokina

→ Trypsin
(proenzyme)
Chymotrypsinogen Trypsin
→ Chymotrypsins
(proenzyme)
Procarboxypeptidase Trypsin
→ Carboxypeptidase
(proenzyme)
Peptones Trypsin
→ Large peptides
D
Dr. Dhote-Shirsat’s Biology Classes, Latur
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Office : (02382) 242430
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CLASS - XI/ZOOLOGY
HUMAN NUTRITION
Elastin Elastase
→ Large peptides
in
Peptones Chymotryps


→ Large peptides
(ii)
-
-
Large peptides Carboxypep
  tidases

→ Dipeptides + Amino acids
Action of intestinal juice :
Peptides Aminopepti
  dases
→ Dipeptides +
Amino acids
Dipeptidas
es
Dipeptides   → Amino acids
Digestion of Fats :
Bile salts namely sodium glycocholate and sodium taurocholate reduce the surface tension of large fat
droplets and break them into small ones. The process is ‘Emulsification’.
The small droplets present large surface area to Lipase
Triglycerides Bile
 salts

→ emulsified Triglycerides
Pancreatic juice - It contains pancreatic lipase, which is the principal fat - digesting enzyme. It hydrolyses
fats in 3 stages.
In the first stage (I), lipase separates one fatty acid molecule, changing the emulsified triglyceride into a
diglyceride.
In the second stage (II), the diglyceride is broken down into another fatty acid molecule and a
monoglyceride.
In the third stage (III), the monoglyceride is hydrolysed to another fatty acid molecule and a glycerol
molecules.
Triglyceride
Pancreatic
Lipase
Diglyceride + Fatty Acid..............I
Pancreatic
Lipase
S
.
Monoglyceride + Fatty Acid .........II
Pancreatic
Lipase
D
.
B
.
C
.
.
Glycerol + Fatty Acid................III
Schematic representation of digestion of triglycerides
I)
DIGESTION OF NUCLEIC ACIDS :
Pancreatic juice - It contains two enzymes : DNAase and RNAase, which act as follows;
DNA DNase
→ Deoxyribonucleotides
II)
D
RNA RNase
→ Ribonucleotides
Intestinal juice - It contains enzymes ; nucleotidases and nucleosidases which act as under
Nucleotides
(Deoxyribonucleotides
Nucleosides
ses
Nucleotida


→
Nucleosides + Inorganic phosphate
or Ribonucleotides)
(Deoxyribonucleosides or Ribonucleosides)
ses
Nucleosida


→
Nitrogenous bases + Pentose sugar
(Deoxyribonucleosides or Ribonucleosides)
Dr. Dhote-Shirsat’s Biology Classes, Latur
(Purines/Pyrimidines) (Deoxyribose/Ribose)
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Office : (02382) 242430