This document discusses digestion and absorption of food. It begins by outlining the biological and medical importance of digestion and absorption. The major sites of digestion in the gastrointestinal tract and the digestive juices involved are described. Carbohydrates, proteins, and lipids are broken down into smaller molecules so they can be absorbed. Carbohydrates are digested into monosaccharides like glucose and galactose. Proteins are digested into amino acids through the action of proteases. Lipids are broken into fatty acids and glycerol. The absorbed nutrients are then transported through the intestinal mucosa and into circulation. Clinical conditions related to deficiencies in digestion and absorption are also mentioned.

1. When I prayed for success, I forgot
to ask for
sound sleep and
good digestion.
-Mason Cooley

2. Happiness: a good bank
account, a good cook, and a
good digestion.
#Jean-Jacques Rousseau

3. Digestion and Absorption of Food
-Dr. Ganesh

5. Digestion and Absorption of Food
Contents:
Biological Importance
Medical Importance
Digestion and Absorption – General Aspects
Digestion and Absorption of Carbohydrates
Digestion and Absorption of Proteins
Digestion and Absorption of Lipids

6. Biological Importance
Digestion
a chemical process –
large molecules in the food are
broken down to
smaller molecules
so that
they can be absorbed

7. Biological Importance
Food
large molecules
Digestion
small molecules
Absorption
BLOOD
small molecules
vitamins,
minerals,
monosaccharides
and
free amino acids

8. Biological Importance
• Absorption is
transport of molecules,
either digested products or
other small molecules which do not require
digestion,
from the intestinal lumen into
blood
across the
intestinal mucosal cells.

9. Medical Importance
• Lactose intolerance
deficiency of lactase
intake of milk causes diarrhea
• Hartnup’s disease
genetic defect in the absorption of
neutral amino acids,
especially tryptophan.

10. Medical Importance
• Steatorrhea
excess fat is excreted in feces and
is seen in diseases of
pancreas, biliary obstruction, etc.
• Chronic diarrhea can cause
malabsorption as seen in
celiac disease,
Sprue,
Crohn’s disease, etc.

11. Digestion – General Aspects
major foodstuffs
that require digestion
macromolecules
digestion
smaller molecules
carbohydrates,
monosaccharides
proteins
Amino acids
fats and oils
(triacylglycerol)
glycerol and fatty acids

12. Digestion – General Aspects
Digestion takes place in the aqueous medium of
various digestive juices –
Site of Digestion
Digestive Juices
Mouth
Saliva
Stomach
Gastric juice
Small intestinal lumen
Pancreatic juice,
Bile
Intestinal juice

13. Digestion – General Aspects
• Digestion
involves
action of enzymes
that are present in different
digestive juices.
• All digestive enzymes are
hydrolases
that hydrolyze the
anhydride linkages –

14. Digestion – General Aspects
anhydride linkages
carbohydrates,
Glycosidic linkage
proteins
Peptide linkage
fats and oils
(triacylglycerol)
Ester linkage

15. Digestion – General Aspects
• Bile,
synthesized in liver and
entering into duodenum,
• helps in fat digestion and
• neutralizes
acidic stomach contents when it enters
the duodenum.

16. Digestion – General Aspects
• Cooking
hydration of polysaccharides and
denaturation of proteins
helps digestion of these molecules.
• Mastication
helps in
breaking down of food particles
increases solubility and surface area for
enzyme action.
• Peristalsis
also important in
breaking down of food particles and
mixing them with enzymes.

17. Absorption– General Aspects
• small intestine
main absorptive organ.
About 90% of the ingested foodstuffs
absorbed
through the small intestine
• Considerably more water is absorbed
in the large intestine,
so that the contents,
gradually become more solid in the colon.

18. Absorption – General Aspects
Absorption of substances into mucosal cells involves
the passage across the plasma membrane
simple diffusion
carrier-mediated transports
passive
facilitated transport
(no energy expenditure)
(passive)
No carrier protein
active transport
(requiring energy expenditure)

20. Absorption – General Aspects
two pathways for the transport of nutrients
absorbed by the intestine
water-soluble nutrients
hepatic portal blood
liver
lipid-soluble nutrients
lymphatic vessels
thoracic duct
blood
blood

21. Digestion and Absorption
of
Carbohydrates
Contents:
• Introduction
• Digestion of Starch
• Digestion of Disaccharides
• Absorption of Carbohydrates
• Clinical Significance

22. Digestion and Absorption of Carbohydrates
Introduction
major carbohydrates in the diet
Monosaccharides
fructose (present in fruits)
Disaccharides
sucrose
lactose
maltose
Small amounts
(present in malt, beer)
Polysaccharides
starch
dietary fibers
Starch - more than 50% of carbohydrates

23. Digestion and Absorption of
Carbohydrates - Introduction
• Dietary fibers –
cellulose, hemicellulose, pectin, lignins, etc.
are
indigestible.
For ‘Dietary fibers’,
see Chapters –
‘Chemistry of Carbohydrates’ and
‘Nutrition’)

24. Digestion and Absorption of
Carbohydrates - Introduction
Human food also contains
small amounts of
• pentoses,
• glucose,
• trehalose
(disaccharide present in mushroom), and
• glycogen (present in liver in animal foods).

25. Digestion and Absorption of
Carbohydrates - Introduction
• All enzymes of carbohydrate digestion
cleave
glycosidic bonds by
hydrolysis.
• Disaccharides and polysaccharides are digested to
their respective constituent monosaccharides units and
absorbed in the small intestines
along with free monosaccharides present in the food

26. Digestion and Absorption of
Carbohydrates - Introduction
• The absorbed monosaccharides
hepatic portal circulation
liver cells
systemic circulation.

27. Digestion and Absorption of
Carbohydrates Introduction
Fructose
DIGESTION
ABSORPTION
(Small Intestine)
Fructose
Sucrose
FOOD
Starch
Glucose
Lactose
Galactose

28. Digestion of Starch1, 2
• Starch on complete digestion
yields
glucose
• Digestion of starch
takes place in
• mouth,
• small intestinal lumen and
• small intestinal brush border
(luminal surface of intestinal mucosal cells).

29. Digestion of Starch1, 2
• The enzymes and the steps of digestion of
glycogen are same as those of
amylopectin component of starch as
both have similar structure.
• Cooking hydrates the starch granules making it
more susceptible to digestion.

30. Digestion of Starch1, 2
Enzymes required for complete digestion of starch –
• amylase (salivary and pancreatic amylase),
• maltase and
• isomaltase.
• Amylase and maltase cleave
-1,4 glycosidic linkages and
isomaltase cleaves
-1,6 glycosidic linkages of
starch.
(Amylase hydrolyzes
internal -1,4 glycosidic linkages.)

31. Digestion of Starch
• Starch is mainly digested by
pancreatic amylase.
Contribution by
salivary amylase is very little
since the food remains in the mouth for
a very short period of time and
the enzyme is inactivated by
gastric HCl as it enters stomach.
• Maltase and isomaltase
are present on the
luminal surface of small intestinal epithelial cells
(brush border cells).

32. Digestion of
Starch
Starch (amylose and amylopectin)
Salivary amylase (in mouth)3
Or
Pancreatic amylase
(in small intestinal lumen
Small unbranched oligosaccharides
(e.g., Maltose, Maltotriose, etc)
Isomaltase
Maltase
(brush border cells)
(brush border cells)
Limit dextrins4
Maltase
Isomaltose
Glucose
Isomaltase (brush border cells)

33. Digestion of Starch
• Cl- is an activator of
Salivary amylase
(ptyalin)
• Limit dextrins
derived from
amylopectin component
by the action of amylase and
contain eight glucosyl units with
one or two branches with
α-1,6-glycosidic bonds.

34. Digestion of Disaccharides
Major disaccharides
present in the human diet are –
• sucrose and
• lactose
Small amounts of
• free maltose (present in malt, beer) and
• trehalose
(disaccharide present in mushroom)

35. Digestion of Disaccharides
• However, quantitatively
the major disaccharide digested in the gut is
maltose
• Most of the maltose in the gut is derived from
digestion of
starch.
• Isomaltose is another disaccharide
derived from starch and
is digested by
isomaltase.
(See ‘Digestion of Starch’).

36. Digestion of Disaccharides
• Disaccharidases are attached to the surface of
the small intestinal brush border cells.
• (For ‘digestion of maltose’, see ‘Digestion of
Starch’.)

37. Digestion of Disaccharides
Site of digestion of disaccharides – attached to the
small intestinal brush border
surface of the
small intestinal brush
border cells
disaccharides disaccharidases
sucrose
sucrase (also called invertase)
lactose
lactase
trehalose
trehalase
maltose
maltase

38. Digestion of Disaccharides
sucrase
sucrose
glucose + fructose
lactase
lactose
glucose + galactose
trehalase
trehalose
2 glucose
maltase
2 glucose
maltose
isomaltase
Isomaltose
2 glucose

39. Absorption of Monosaccharides
The major monosaccharides
resulting from carbohydrate digestion are –
• D-glucose,
• D-galactose and
• D-fructose.
Absorption is
carrier mediated.
• Pentoses are absorbed by
simple diffusion.
• Monosaccharides are first transported
from the lumen to the small intestinal epithelial cells
and then into capillaries of portal venous system.

40. Absorption of Glucose
from the small intestinal lumen
into the intestinal epithelial cells by
carrier mediated mechanism
involving transporter proteins
situated on the luminal surface of
intestinal epithelial cells.
• Glucose is absorbed mainly by
• 1) Na+-dependent transporter
by secondary active transport and
to a less extent by
• 2) Na+-independent transporter
by passive transport.

41. Absorption of Glucose
from the small intestinal lumen
by carrier mediated mechanism
involving transporter proteins
1) Na+-dependent transporter
by secondary active transport
and to a less extent by
2) Na+-independent transporter
by passive transport
into the intestinal epithelial cells

42. 1. Na+-dependent transporter (SGLT)
• This carrier protein carries
glucose or galactose along with
sodium ion
from the lumen.
The driving force for the
Na+-dependent transport is
derived from the
maintenance of
low intracellular levels of Na+
by the action of the
Na+-K+ATPase
(secondary active transport).

43. 2) Na+-independent transporter
Small amounts of
glucose,
transported by
facilitated transport
utilizing
glucose transporter-5
(GLUT-5).

44. Transport of glucose
from cells to portal venous capillaries:
Glucose is transported
from the
intestinal epithelial cells into
portal venous capillaries by
glucose transporter-2 (GLUT-2).
• It is a
uniport facilitated transport system,
which is sodium independent.

45. Absorption of Glucose
facilitated transport
Intestinal
Epithelial Cell
Glucose
GLUT-5
Glucose
secondary active transport
Na+
Intestinal Lumen
Na+-dependent transporter
(SGLT)
Na+ K+
ATP
ADP + Pi
GLUT-2
Glucose
Na+
Portal Capillary Blood
K+
Na+–K+ ATPase

46. Absorption of Glucose
Fructose
Galactose
GLUT-5
Fructose
Galactose
Na+
Na+-dependent transporter
(SGLT)
Na+ K+
ATP
ADP + Pi
GLUT-2
Galactose
Fructose
Na+
K+
Na+–K+ ATPase

47. Absorption of
Other Monosaccharides
• Fructose
facilitated trasporter
GLUT-5,
sharing with glucose.
• Galactose
Na+-dependant trasporter (SGLT)
secodary active transport
sharing with glucose
• Any pentose present in food is absorbed by
simple diffusion.

48. Absorption of
Other Monosaccharides
• Both
fructose and galactose
transported from the intestinal epithelial cells
into portal venous capillaries by
glucose transporter-2 (GLUT-2),
sharing with glucose.

49. Clinical Significance
Lactose Intolerance
• This is a common condition
gastrointestinal symptoms like
diarrhea, abdominal cramps and flatulence
after ingestion of
milk or milk-based foods

50. Clinical Significance
Lactose Intolerance
• Cause
deficiency of lactase1.
Deficiency may be due to
• genetic
(primary/inherited) or
• acquired
(secondaryto other causes)
The reason for
acquired lactose intolerance may be
damage to intestinal epithelial cells
due to
colitis, gastroenteritis, alcohol consumption or
sudden change into a milk-based diet.

51. Clinical Significance
Lactose Intolerance
• Cause
lactase enzyme
defective at
birth
early onset lactose intolerance
(inherited lactase deficiency).
A significant number of adults
exhibit
late onset lactase deficiency
(primary low lactase activity)
especially
Asian-, Native- and African-Americans.

52. Biochemical basis of Clinical Manifestation
Lactase deficiency
Accumulation of
lactose,
organic acids
and gases (CO2
and H2)
(Produced by action of bacteria on lactose
in the gut)
Osmotic movement of water
from the intestines to the lumen
flatulence
Abdominal cramps
diarrhea

53. Lactose Intolerance
Treatment
• avoiding milk
• Curd
is an effective treatment,
because
Lactobacilli
in curd
contains the enzyme
Lactase

54. Digestion and Absorption of Proteins
Contents:
• Digestion of protein – general aspects
• Reactions of protein digestion
• Absorption of amino acids
• Clinical significance

55. Digestion of Proteins – General Aspects
•
•
•
•
•
•
Contents:
Introduction
Sites of protein digestion, GIT juices and proteases
Endopetidases and exopetidases
Specificity of proteases
Proteases - zymogen form and activation
Role of HCl in protein digestion

56. Digestion of Proteins – General Aspects
Introduction
• Digestion of dietary proteins –
hydrolysis of peptide bonds
catalyzed by a group of
enzymes called
proteases or peptidases
in the gastrointestinal tract
•
• Complete digestion of proteins yields
amino acids.

57. Digestion of Proteins – General Aspects
Introduction
• Dietary proteins
denatured on cooking
and therefore,
cooked proteins
more easily digested1.
During the process of denaturation
unfolding of protein molecule takes place and thus
peptide bonds become
more accessible for
enzyme action.

58. Digestion of Proteins – General Aspects
Sites of Protein Digestion, GIT Juices and Proteases
Protein digestion takes place in
• stomach and
• intestinal lumen.
Enzymes of protein digestion are secreted in
• gastric juice,
• pancreatic juice and
• intestinal juice.

59. Digestion of Proteins – General Aspects
GIT Juices and Proteases
GIT Juices
Proteases Present
Gastric juice
Pepsin (chief cells of stomach), Rennin2
Pancreatic Juice
Trypsin
Chymotrypsin
Elastase
Carboxypeptidases
Intestinal Juice
Aminopeptidases Dipeptidases
Tripeptidases

60. Rennin
• Rennin,
a protease,
active in infants and
involved in
curdling of milk.
Rennin
denatures casein of milk to
paracasein irreversibly,
which then is acted upon by
pepsin.

61. Endopeptidases and Exopeptidases
Pepsin
Trypsin
Carboxypeptidases
carboxy terminal
Chymotrypsin
Elastase
Aminopeptidases
amino terminal
hydrolyze peptide bonds in the
interior of the protein chain to
cleave the protein molecule into
more than one
smaller polypeptides and peptides.
hydrolyze terminal bond
releasing one amino acid
at a time.

62. Digestion of Proteins – General Aspects
Specificity of Proteases
• Endopeptidases
hydrolyze
specific
peptide bonds
in protein molecules.
Specificity differs from
one protease to another3.

63. Specificity of Proteases
Enzyme
Hydrolysis of petide bonds formed by
carboxyl groups of
Pepsin
Phe, Tyr, Trp, Met
Trypsin
Arg, Lys (basic amino acids)
Chymotrypsin
Phe, Tyr, Trp, Val, Leu
(Aromatic, uncharged amino acids)
Elastase
Ala, Gly, Ser (small amino acid residues)

64. Digestion of Proteins – General Aspects
Proteases – Zymogen Form and Its Activation
Proteolytic enzymes are secreted as
inactive
zymogens/proenzymes,
which are converted to their
active form
in the intestinal lumen4.

65. Digestion of Proteins – General Aspects
Proteases – Zymogen Form and Its Activation
Activation of enzymes
involves
cleavage of
small peptides so that
active sites
are exposed.
prevents auto-digestion of the
secretory acini.

66. Digestion of Proteins – General Aspects
Proteases – Zymogen Form and Its Activation
Active Enzyme
Inactive Zymogen
Pepsin
Pepsinogen
Trypsin
Trypsinogen
Chymotrypsin
Carboxypeptidase
Elastase
Chymotrypsinogen
Procarboxypeptidase
Proelastase

67. Digestion of Proteins – General Aspects
Proteases – Zymogen Form and Its Activation
(Parietal cells of stomach)
Pepsinogen
HCl
Pepsin
Autoactivation
(a protease present on the intestinal
Enterokinase mucosal membranes)
Trypsinogen
Trypsin
Autoactivation

68. Digestion of Proteins – General Aspects
Proteases – Zymogen Form and Its Activation
Trypsin
Chymotrypsinogen
Proelastase
Procarboxypeptidase
Chymotrypsin
Elastase
Carboxypeptidase

69. Digestion of Proteins – General Aspects
Role of HCl in Protein Digestion
1) Activation of pepsinogen
2) Denaturation of dietary proteins and
3) Providing optimum pH (pH 2 to 3) for the
action of pepsin.
• (HCl also kills microorganisms present in food).

70. Reactions of Protein Digestion
(In Stomach and Small Intestinal Lumen)
Dietary Proteins
In Stomach
Pepsin
HCl
Gastric Juice
(polypeptides and
Proteoses + Peptones smaller polypeptides)
In
Small
Intestinal
Lumen
Trypsin
Chymotrypsin
Elastase
Small Polypeptides + Peptides
Pancreatic Juice

71. Dietary Proteins
In Stomach
Pepsin
HCl
Gastric Juice
(polypeptides and
Proteoses + Peptones smaller polypeptides)
In
Small
Intestinal
Lumen
Trypsin
Chymotrypsin
Elastase
Small Polypeptides+ Peptides
Pancreatic Juice

72. HCl
(polypeptides and
Proteoses + Peptones smaller polypeptides)
In
Small
Intestinal
Lumen
Trypsin
Chymotrypsin
Pancreatic Juice
Elastase
Small Polypeptides+ Peptides
In
Small
Intestinal
Lumen
Carboxypeptidases
Pancreatic Juice
Aminopeptidases
Dipeptidases
Amino acids
Intestinal Juice

73. Absorption of Amino Acids
absorbed from the intestine
into
portal blood.
•
transported by
a number of carriers
many by secondary active transport –
Na+-dependent carriers
similar to
glucose transporter system.

74. Absorption of Amino Acids
Different Na+-dependent carriers are:
• Neutral amino acid carrier
• Phenylalanine and methionine carrier
• Carrier specific for imino acids (proline and
hydroxy proline)
There are also Na+-independent carriers
specializing in the transport of
• Neutral and lipophilic amino acids (e.g.
Phe, Leu)
• Cationic amino acids (e.g. Lys)

75. Clinical Significance
• Allergy to certain food proteins
(milk, fish)
believed to result from absorption of
partially digested
proteins.

76. Clinical Significance
• Defect in non-tropical sprue is
located within the mucosal cells of the
intestine
and permits the polypeptides
(resulting from the peptic and tryptic digestion of
gluten,
the principal protein of wheat)
to be absorbed into the circulation and thus
elicit the production of
antibodies.

77. Clinical Significance
• Defect in the intestinal amino acid transport
systems
seen in
-- Hartnup’s disease,
[defect in intestinal neutral amino acid (Trp)
carrier], I
-- iminoglycinuria, cystinuria etc.

78. Clinical Significance
• Acute pancreatitis
(acute inflammation of pancreas)
caused by
autodigestion
of pancreas by its proteolytic enzymes
a life threatening disorder.
Autodigestion is
due to unusual conversion of
proenzymes into active enzymes by
trypsin.

79. Digestion of Fat (Triacylglycerols)
Contents
• Digestion of fat
• Digestion of other lipids
• Absorption of lipids
• Clinical significance

80. Digestion of Fat (Triacylglycerols)
main site
Small intestinal lumen
Hydrolysis of ester bonds
Fat
Lipases
Fatty acids
Glycerol
Monoacyl glycerols (MAGs)
main enzyme for digestion of most of the fat - Pancreatic lipase
other lipases
lingual
lipase, gastric their contribution is negligible
lipase and
intestinal lipase
Colipase cofactor
a proteinsalts
Bile secreted by pancreas digestion by emulsifying fat
help fat

81. Role of Bile Salts in Fat Digestion
Bile salts
present in the bile
lower the surface tension
– emulsify fat in the intestine.
– Intestinal peristalsis also helps in this.
Emulsification increases the surface area of
fat droplets
enabling more enzyme (lipase) molecules to
act
and thus
speeding up digestion

82. Reactions of Digestion of Fat (Triacylglycerol)1
Triacylglycerol (Fat)
Lipase
Pancreatic Juice
Colipase
Fatty Acid
Diacylglycerol (DAG)
Lipase
Colipase
Fatty Acid
Monoacylglycerol (MAG)
Lipase
Colipase
Fatty Acid
Glycerol

83. Reactions of Digestion of Fat (Triacylglycerol)1
Digestion of fat
requires another enzyme also
an isomerase
which isomerzes 2-MAG into 1-MAG,
as lipase cannot hydrolyze 2-MAG.

84. Reactions of Digestion of Fat
(Triacylglycerol)1
The major end products of
digestion of fat are –
• monoacylglycerols (MAGs),
• glycerol and
• fatty acids

85. Digestion of Other Lipids
Pancreatic secretion also contains
cholesterol esterase
cholesterol ester
cholesterol
Fatty acid
phospholipase A2
phospholipid
lysophospholipid
Fatty acid

86. Absorption of Digested Products of Lipids
Digested Products of Lipids
Water-insoluble
Water-soluble
Monoacylglycerols
Glycerol
Long-chain fatty acids Micelles
Short- and Medium-chain
Fat-soluble fatty acids(SMCFA)
Cholesterol
vitamins
Mixed micelles
SMALL INTESTINAL LUMEN
Intestinal
Epithelial Cell Monoacylglycerols
Long-chain fatty acids
Cholesterol
Fat-soluble
Triacylglycerol
vitamins
Phospholipids
Apolipoproteins
Chylomicron
LYMPHATIC VESSELS Chylomicron
Glycerol
(SMCFA)
PORTAL
BLOOD

87. Absorption of Digested Products of
Lipids
• Normally
over 98% of the dietary lipid is
absorbed.

88. Clinical Significance
• Steatorrhea
• Chyluria and Chylothorax
When daily excretion of fat in feces
more than 6g per day
• may be due to
defective digestion or
defective absorption of fat.
• - Defective digestion
may be due to absence of or deficiency of
pancreatic lipase
as in
chronic diseases of pancreas or
surgical removal of pancreas. bile salt

89. Clinical Significance
• Steatorrhea
• Defective absorption of fat occurs
when bile salts do not enter the intestine as in
biliary obstruction (e.g. due to biliary stone)
• - Defective absorption may also be due to
malabsorptive diseases
e.g. celiac disease,
Sprue,
Crohn’s disease, etc or
surgical removal of large lengths of the
intestine.

90. MCQS on Digestion and Absorption
1. All of the below are true about digestion,
EXCEPT,
A. All digestive enzymes are hydrolases.
B. Digestion ensures the absorption of
nutrients.
C. Sites of digestion in the GIT are mouth,
stomach, and the lumen of small and the
large intestines.
D. Vitamins, minerals, monosaccharides and
free amino acids do not need digestion.

91. 2. The anhydride linkages that are
broken during digestion are:
A.glycosidic, peptide and ester linkages
carbohydrates, proteins and fats, respectively.
of
B.ester, peptide and glycosidic linkages
carbohydrates, proteins and fats, respectively.
of
C.glycosidic, peptide and ester linkages
carbohydrates, fats and proteins, respectively.
of
D.peptide, glycosidic and ester linkages
carbohydrates, proteins and fats, respectively.
of

92. 3. Factors, other than enzymes that
help in digestion are the following,
EXCEPT,
A.Cooking
B.Exercise
C.Mastication
D.Peristalsis

93. 4. All the following are true about
absorption, EXCEPT,
A.Considerably more water is absorbed in the
large intestine than in the small intestines.
B.Absorption of all substances require carriermediated transports.
C.Water-soluble nutrients are absorbed through
hepatic portal system.
D.Lipid-soluble nutrients are absorbed through
the lymphatic vessels.

94. 5. The full set of enzymes required for
complete digestion of starch are –
A.amylase, maltase and isomaltase.
B.amylase, maltase and sucrase.
C.amylase, maltase, isomaltase and
sucrase.
D.amylase, sucrase and isomaltase.
•

95. 6. Contribution by salivary amylase in
digestion of starch is very little
because:
A.activity of the enzyme is very low.
B.the food remains in the mouth for a very short
period of time.
C.the food remains in the mouth for a very short
period of time and the enzyme is inactivated
by gastric HCl.
D.the enzyme is inactivated by gastric HCl.

96. 7. Which of the following is FALSE
about digestion of starch?
A.The enzymes and the steps of digestion of
glycogen are same as those of amylopectin
component of starch.
B.Cooking hydrates the starch granules making
it more susceptible to digestion.
C.Cl- is an activator of salivary amylase.
D.Limit dextrins are derived from amylose
component of starch by the action of amylase.

97. 8. Quantitatively the major
disaccharide digested in the gut is
A.sucrose
B.maltose
C.lactose
D.isomaltose

98. 9. The major monosaccharides resulting
from carbohydrate digestion are
A.glucose, galactose and ribose.
B.glucose, mannose and fructose.
C.glucose, ribose and fructose.
D.glucose, galactose and fructose.

99. 10. Glucose is absorbed mainly by
A.simple diffusion
B.Na+-dependent transporter
C.Na+-independent transporter
D.passive transport
•

100. 11. Enzymes of protein digestion are
secreted in
A.gastric juice, pancreatic juice and
intestinal juice.
B.saliva, gastric juice and pancreatic juice.
C.saliva, gastric juice and intestinal juice.
D.saliva, gastric juice and intestinal juice.

101. 12. Proteases secreted in the pancreatic
juice are
A.pepsin,
trypsin,
chymotrypsin
carboxypeptidases.
B.trypsin,
chymotrypsin,
elastase
carboxypeptidases.
C.trypsin,
chymotrypsin,
elastase
aminopeptidases.
D.trypsin, chymotrypsin, aminopeptidases
carboxypeptidases.
and
and
and
and

102. 13. HCl has following roles in protein
digestion, EXCEPT.
A.kills microorganisms present in food
B.activation of pepsinogen
C.denaturation of food proteins
D.providing optimum pH for the action of
pepsin

103. 14. Intestinal absorption of amino
acids involves all of the
following, EXCEPT,
A.simple diffusion
B.Na+-dependent transporter
C.Na+-independent transporter
D.passive transport

104. 15. Which of the following is false
about action of bile salts?
A.They help both in digestion of fat and
absorption of digested products of lipids.
B.They lower the surface tension and
emulsify fat in the intestine.
C.They stimulate pancreatic secretion.
D.Emulsification increases the surface area
of the fat droplets.

105. 16. Digestion of fat produces:
A.fatty acids, glycerol and diacyl
glycerols.
B.fatty acids and glycerol.
C.glycerol and monoacyl glycerols.
D.fatty acids, glycerol and monoacyl
glycerols.

106. 17. Lipases other than pancreatic lipase
present in the human GIT are:
A.salivary lipase, gastric lipase and intestinal
lipase
B.lingual lipase, gastric lipase and intestinal
lipase
C.lingual lipase, gastric lipase and hepatic lipase
D.gastric lipase, biliary lipase and intestinal
lipase

107. 18. Steatorrhea is a condition when
daily excretion of fat in feces is more
than:
A.6g
B.8g
C.10g
D.12g