Biology · Science General

Human Digestive System

1,953 Questions

The human digestive system explores the breakdown of biomacromolecules, covering organs from the stomach to the small intestine. It involves physiological processes like chyme movement, pH levels, and nutrient absorption in the gut. These fundamental biology concepts are regularly featured in medical and general science competitive exams.

Small intestine functionsBiomacromolecule breakdownStomach and digestionIntestinal bacteria

Human Digestive System Questions

Multiple choice biology food through digestive tract role of large intestine in digestion busy at work - our internal organs parts of the digestive system: structure and function

Fermentation chamber of herbivores is

  1. Gall bladder

  2. Pancreas

  3. Liver

  4. Caecum
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In herbivores, the caecum stores food material where bacteria are able to break down the cellulose. This function no longer occurs in the human caecum, so in humans it is simply a dead-end pouch forming a part of the large intestine.

Multiple choice biology food through digestive tract role of large intestine in digestion busy at work - our internal organs parts of the digestive system: structure and function

The part of alimentary canal that absorbs maximum amount of water and minerals is 

  1. Small intestine

  2. Large intestine

  3. Stomach

  4. Oesophagus
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The major function of the large intestine is to absorb water from the remaining indigestible food matter and transmit the useless waste material from the body.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Digestion of protein takes place in

  1. Duodenum and stomach

  2. Stomach and oesophagus

  3. Small and large intestine

  4. Intestine and rectum
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Protein digestion begins in the stomach with pepsin and continues in the duodenum with pancreatic enzymes like trypsin and chymotrypsin.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Which of the following is incorrect regarding the given digestion and absorption of protein?

  1. The breakdown of proteins to peptides is catalyzed by pepsin in the stomach and by the pancreatic enzymes trypsin and chymotrypsin in the small intestine.

  2. Peptides are broken down into amino acids by pancreatic carboxypeptidase and intestinal aminopeptidase.

  3. Small peptides consisting of two or three amino acids can diffuse through the epithelial cell and broken down into carbon dioxide and ammonia which are released into the blood.

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Digestion of protein is initiated in the stomach by the enzyme pepsin.
  • In the small intestine, further digestion is done by trypsin, chymotrypsin, and carboxypeptidase into dipeptidase that releases from the pancreas.
  • Dipeptidase are broken into amino acids by intestinal dipeptidase.
  • These amino acids are absorbed actively by walls of intestine and release in the bloodstream.
  • These are utilized by tissues and broken down into carbon dioxide and ammonia.
  • Proteins require maximum energy to digest.

So the correct option is 'Peptides are broken down into amino acids by pancreatic carboxypeptidase and intestinal aminopeptidase.'

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

How does pepsinogen change into its active form?

  1. In the presence of hydrochloric acid

  2. In the presence of trypsin

  3. In the presence of bile

  4. In the presence of carboxypeptidae
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 Parietal cells of stomach secrets hydrochloric acid which convert inactive pepsinogen to partially active pepsinogen, partially activates pepsinogen then cleaves the peptide from other pepsinogen molecules to form active pepsin which converts protein into proteases and peptides.

So, the correct answer is 'In the presence of hydrochloric acid'.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Which of the following is the correct matching of the site of action on the given substrate, the enzyme acting upon it and the end product?
(i) Small intestine: Protein $\xrightarrow{Pepsin}$ Amino acid
(ii) Stomach : Fat $\xrightarrow{Lipase}$ Micelles
(iii) Duodenum : Triglycerides $\xrightarrow{Trypsin}$ Monoglyceride 
(iv) Buccal cavity : Starch $\xrightarrow{Amylase}$ Disaccharide
(v) Jejunum: Peptones $\xrightarrow{Pepsin}$ Amino acid
(vi) Buccal cavity : Starch $\xrightarrow{Amyloglycerate}$ Maltose

  1. (i),(ii) and (iii) are correct

  2. (iv) only

  3. (iv) and (v) are correct

  4. All are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

(i) Pepsin digest protein in the stomach.

(ii)Lipase digest emulsified fat in the intestine.
(iii)In duodenum trypsin digest protein or dipeptides.
(iv) Starch is digested into maltose by salivary amylase in the buccal cavity.
(v)Pepsin digest protein in the stomach.
(vi) Starch is digested into maltose by salivary amylase in the buccal cavity.
So the correct option is '(iv) only '

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

If PH of stomach is made 7, which component of the food would be affected?

  1. Starch

  2. Proteins

  3. Fat

  4. Sucrose
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If pH of the stomach is made 7 protein digestion will affect as pepsin works ar pH of 2 to 3 and enzymes are highly precise about there function so it does not activate.

So the correct option is 'proteins'.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Which of the following statements are correct about the function of the acidic environment of the stomach?
(i) Provides defence against bacteria entering the digestive system
(ii) Converts pepsinogen to pepsin
(iii) Assists the breakdown of cells in animal and plant food stuffs

  1. ii only

  2. i and ii only

  3. ii and iii only

  4. i, ii, and iii
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The HCl is secreted by the oxyntic cells in the stomach. The HCl provides the acidic medium in the stomach that is responsible for converting the inactive pepsinogen to the active pepsin. Pepsin is required for protein digestion. The acidic medium provides defence against bacteria entering the digestive system.

Hence, the correct answer is 'i and ii only'

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Which of the following enzymes is not useful in the digestion of proteins?

  1. Chymotrypsin

  2. Pepsin

  3. Trypsin

  4. Lipase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Protein digestion occurs in the stomach and duodenum in which 3 main enzymes: Pepsin, trypsin and chymotrypsin.
  •  pepsin secreted by the stomach and trypsin and chymotrypsin secreted by the pancreas, break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids. 
  • Hence, Lipase enzymes are not useful in the digestion of proteins.
  • So, the correct answer is 'Lipase'.
Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Where are proteins first digested in the alimentary canal?

  1. Small intestine

  2. Oesophagus

  3. Mouth

  4. Stomach
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The digestion of the food starts at the mouth where the enzyme amylase is secreted which digests the start that is present in the food and converts it into maltose. From there through the esophagus the food arrives in the stomach where it is stored for 4 hours and mixed with acid. The food when arrives at the stomach where the wall of the stomach secrets HCl with a pH of 1.8. This acid activates the inactive pepsinogen enzyme and forms active pepsin which digests proteins and converts them into proteases and peptides. From here the food moves to the small intestine where secretion from the liver and pancreas reach through a hepatopancreatic duct which is alkaline in nature and neutralizes the acidic food that comes from the stomach. Here majority of the digestion of protein to amino acids, fat to fat droplets, polysaccharides to monosaccharides etc takes place.


Therefore the correct answer is option D 

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

In the stomach proteins are hydrolysed by enzyme pepsin and $H^+$ to give-

  1. Peptones

  2. Proteoses

  3. Polypeptides
  4. $\alpha-$amino acids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the stomach, proteins are hydrolysed by enzyme pepsin. It begins the digestion of proteins by splitting them into peptones (see peptidase). It is produced by the action of $HCl\left( { H }^{ + } \right) $ on pepsinogen, which is secreted by the stomach in gastric glands.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

The type of food which starts digesting in stomach is

  1. Fats

  2. Carbohydrate

  3. Protein

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Carbohydrate digestion starts in the mouth as salivary amylase is present there. Protein digestion starts in the stomach as protein digesting enzymes is present in stomach and fat digestion occurs in the small intestine.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Rennin is found in  

  1. Liver

  2. Kidney

  3. Pancreatic juice

  4. Gastric juice in stomach
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rennin is a milk-curdling enzyme, that occurs in the gastric juices of infants and is also contained in the rennet produced in the stomach of calves and other ruminants. It is an endopeptidase, that converts casein to paracasein and was formerly used extensively as a curdling agent by the cheese industry. 

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Main function of HCl in stomach is to

  1. Activates amylase enzyme

  2. Facilitate absorption of food

  3. Dissolve enzymes

  4. Activate pepsinogen to pepsin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stomach in vertebrates is the main site for digestion of proteins. Pepsin is the chief proteolytic enzyme of stomach secreted in the inactive form called as pepsinogen. The pepsinogen is activated to pepsin in presence of hydrochloric acid secreted in stomach by oxyntic or parietal cells. The optimum pH for activity of pepsin is 1.8.

Therefore, the correct answer is option D.

Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

If the stomach did not produce any hydrochloric acid, which enzyme will not function?

  1. Ptyalin

  2. Trypsin

  3. Pepsin

  4. Collagenase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hydrochloric acid (HCl) converts pepsinogen to pepsin which breaks down proteins to peptides. HCl maintains a pH in the stomach of approximately 2.0. It also dissolves food and kills microorganisms. Without enough HCl, pepsinogen is no converted to pepsin which do not allow the breakdown of proteins

So, the correct answer is 'Pepsin'