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 bio-chemistry digestion digestion in small intestine digestive glands and their secretions alimentary canal

Which is absorbed in ileum?

  1. Vitamin K

  2. Bile salt

  3. Fat

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

Bile salts are actively reabsorbed in the final part of the small intestine, known as the terminal ileum, returning to the liver via enterohepatic circulation. Most other basic nutrients like glucose and fats are primarily absorbed earlier in the duodenum and jejunum.

Multiple choice bio-chemistry digestion digestion in small intestine digestive glands and their secretions alimentary canal

In jejunum, which of the following enzymes is required for the digestion of amino acid containing compounds?

  1. Chymotrypsin

  2. Pepsin

  3. Trypsin

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

Peptidases are the intestinal proteases, which act on peptides as follows:
$Polypeptide\xrightarrow[Alkaline \,medium]{Polypeptidase} Dipeptides$


$Dipeptide\xrightarrow[Dipeptidase]{Alkaline \,medium} Amino acids$
Pepsin, trypsin, and chymotrypsin, etc are aminopeptidases, which act upon amino groups of the peptide bond. 
Thus the correct answer is option D.

Multiple choice bio-chemistry digestion digestion in small intestine digestive glands and their secretions alimentary canal

If the inner surface of the ileum in the human small intestine was smooth, rather than being folded and subdivided into vilii, which of the following statements would be true? 

  1. The rate of absorption of digested food molecules would be higher, because the digested food would pass more easily through the digestive tract.

  2. Digestion would not be as effective, because there would be fewer cells secreting trypsin (a protein-digesting enzyme).

  3. Humans would have needed to evolve a much longer small intestine to absorb sufficient nutrients from their food.

  4. Humans would not be able to survive, because the digestive tract would be more susceptible to damage.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The correct answer is (c).

Multiple choice bio-chemistry digestion digestion in small intestine digestive glands and their secretions alimentary canal

Which of the following statements is false?

  1. The breakdown of most of biomacromolecules occurs in duodenum.

  2. Simple substances (digested foods) are absorbed in the jejunum and ileum.

  3. Significant digestive activity occurs in large intestine.

  4. Undigested and unabsorbed substances are passed on to the large intestine.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The correct answer is (c).

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Digestion of food
Which one of the following is the coned matching of the site of action on the given substrate, the enzyme acting upon it and the end product ?

  1. Small intestine : Proteins $\overset{Pepsin}{\rightarrow}$ Amino acids
  2. Stomach : Fats $\overset{Lipase}{\rightarrow}$ Micelles
  3. Duodenum : Triglycerides $\overset{Trypsin}{\rightarrow}$ Monoglycerides
  4. Small intestine.: Starch $\overset{\alpha - amylase}{\rightarrow}$ Disaccharide (maltose)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Starch is broken down by alpha-amylase into disaccharides like maltose in the small intestine. Option A is wrong because pepsin works in the stomach, and Option C is wrong because trypsin acts on proteins, not triglycerides.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Fat is completely digested in the

  1. Stomach

  2. Mouth

  3. Small intestine

  4. Large intestine
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Digestion of some fats can begin in the mouth where lingual lipase breaks down some short chain lipids into diglycerides. However, fats are completely digested in the small intestine.
  • Fat is completely digested in the small intestine because it gets bile from the liver through gallbladder which is responsible for fat digestion.
  • Hence Fat is completely digested in the Small intestine.
  • So, the correct answer is 'Small intestine'.
Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Carbohydrates in the chyme are hydrolysed to disaccharide by amylase of 

  1. Pancreatic juice

  2. Gastric juice

  3. Brunners gland

  4. Crypts of Lieberkuhn
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chyme produced by digestion in the stomach is passed on to the small intestine for further digestion and absorption where the enzyme pancreatic amylase of the pancreatic juice converts the carbohydrates present in the chyme into disaccharides and monosaccharides. 

So, the correct answer is 'Pancreatic juice'.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

(A) Teeth and tongue with help of saliva masticate and mixed up the food thoroughly.
(B) Mucus in saliva helps in lubricating and adhering the masticated food particles into chyme
(C) Mucus and bicarbonate present in gastric juice plays an important role in lubrication and protection from excoriation by highly concentrated $HCL$
(D) The function of bile is emulsification of fat and activation of lipase
How many sentences given above are true?

  1. One

  2. Two

  3. Three

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

  • During the mastication process, the food is positioned by the cheek and tongue between the teeth for grinding. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food. After chewing, the food (now called a bolus) is swallowed.
  •  The salivary glands produce two different types of secretions: thin, watery saliva and thick mucus. This mucus is an excellent lubricant and makes swallowing food easier.
  • Secretion of bicarbonate into the adherent layer of mucus gel creates a pH gradient with a near-neutral pH at the epithelial surfaces in stomach and duodenum, providing the first line of mucosal protection against luminal acid.
  • Bile contains bile acids, which are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine. The function of bile is to bring ingested fats into the emulsion to facilitate the work of the lipases.

So, the correct answer is 'Four'.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Stomach is the site digestion mainly of ______________.

  1. Carbohydrates

  2. Fats

  3. Proteins

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

The stomach is the site for the digestion of Protein. Pepsin present in duodenum breaks down the food proteins into polypeptides which are then broken down by various exopeptidases and dipeptidases into amino acids.

So, the correct answer is 'Proteins'.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Amylopsin and Rennin are carbohydrate and protein digesting enzymes respectively. Amylopsin acts in ____ medium and Rennin acts in ____ medium :-

  1. Acidic only

  2. Alkaline and acidic

  3. Acidic and alkaline

  4. Slightly acidic and acidic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Amylopsin is a pancreatic enzyme that converts starch to sugar. It is most active in an alkaline pH. Rennin functions best in an acidic environment and loses its activity when pH is higher than 7. So, the correct option is 'Alkaline and acidic'.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Most of the fats absorbed in the small intestine enters the?

  1. Lacteals

  2. Arterioles

  3. Venules

  4. Microvilli
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fats are broken down into fatty acids and glycerol, which are absorbed into the intestinal villi. Because they are large, they enter the lymphatic vessels called lacteals rather than the blood capillaries.