Biology · Science General

Human Digestive System

2,002 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 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.

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

Match the digestive juices with the enzymes given under. Choose the choice which gives the correct combination of the alphabets of the two columns.

   List I (Digestive juices)    List II (Enzymes)
 A  Saliva p  Maltase
 B Gastric juice  q  Trypsinogen
 C  Pancreatic juice r  Ptyalin
 D  Intestinal juice s   Pepsin
    t   Cellulase

  1. A- r, B- s, C- q, D- p

  2. A- s, B- r, C- p, D- t

  3. A- r, B- t, C- p, D- q

  4. A- r, B- s, C- p, D- t
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Salivary juice contains starch splitting enzyme amylase. The amylase of saliva is called as ptyalin. Pepsin is the major proteolytic enzyme of stomach. Pepsin is secreted as a proenzyme pepsinogen and is activated to pepsin on exposure to acid in stomach. Trypsin is a component of pancreatic juice where it is present as trypsinogen. Trypsinogen is activated to trypsin on exposure to enterokinase. The intestinal juice contains a number of disaccharidases like maltase, lactase, sucrase for splitting disaccharides into monosaccharides, which can be readily absorbed.

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

How many enzymes in the list given below infound in pancreatic juice?
Enterokinase, Chymotrypsin, Aminopeptidase, Pepsin, Lactase, Rennin, Carboxypeptidase, Nuclease, Nucleotidase & Elastase:-

  1. Six

  2. Three

  3. Five

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

Trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, nuclease are the enzymes secreted by the pancreas.

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

Emulsification of fats by bile takes place in  

  1. Duodenum

  2. Liver

  3. Stomach

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

Secretion and synthesis of bile is the main function of liver. Bile is yellowish-green, alkaline fluid. In bile juice, bile salts, sodium carbonate, glycolate, taurocholate, bile pigments, cholesterol, lecithin etc. are present. Bile salts help in emulsification of fats in small intestine. It mainly act at the duodenum part of the small intestine.

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

In rabbit, the digestion of cellulose takes place in

  1. Colon

  2. Ileum

  3. Caecum

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

In herbivores like rabbit, the symbiotic bacteria and protozoans present in the caecum, help in digestion of cellulose into glucose. So, the digestion of cellulose takes place in caecum by the process of decomposition. This decomposition process is very slow. So, very less amount of cellulose is digested at a time in caecum.

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

Which one 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?

  1. Small intestine : $\rightarrow $ Proteins Pepsin Amino acids
  2. Stomach : $\rightarrow $ Fats Lipase Micelles
  3. Duodemum : $\rightarrow $ Triglycerides Trypsin Monoglycerides
  4. Small intestine : $\rightarrow $ Starch Amylase Disaccharide (Maltose)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Amylase digests complex starch (polysaccharide) molecules into smaller, simpler maltose (disaccharide) molecules. 

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

Lactase is found in

  1. Saliva

  2. Bile

  3. Pancreatic juice

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

Lactase is an enzyme produced by the small intestine, found in the digestive system of humans. It is essential to complete the digestion of whole milk. Lactase breaks down lactose, a simple sugar which gives milk its sweetness.