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 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

Which of these will leave the stomach first in man?

  1. Beer

  2. Proteins

  3. Fats

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

Only some chemicals medicines and alcohol are absorbed in oro pharyngeal cavity. In the stomach, absorption of water, some salts, alcohol and glucose takes place, complete absorption of alcohol takes place in the stomach. Thus, carbohydrates, proteins and fats will remain in alimentary canal for complete digestion and when broken down completely in small intestine then only they will be absorbed in the intestine but beer will not be digested in alimentary canal and directly absorbed in the stomach.

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'

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

Stomach in vertebrates is the main site for digestion of 

  1. Proteins

  2. Carbohydrates

  3. Fats

  4. Nucleic acids
Reveal answer Fill a bubble to check yourself
A 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.

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

A man sits down to eat a large steak. Concerned about heartburn, he takes several antacid tablets before eating so as to neutralize his stomach acid.
Which of the following may result from this action?

  1. Increased chemical digestion of the protein in the steak by the stomach.

  2. Decreased absorption of the protein in the steak by the small intestines.

  3. An increase in the peristaltic actions of the mans digestive tract.

  4. Increased urine production by the man's kidneys.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Digestion typically begins in the stomach when pepsinogen is converted to pepsin by the action of hydrochloric acid. And continued by trypsin and chymotrypsin in the small intestine. 
  • Before the absorption in the small intestine, most proteins are already reduced to single amino acid or peptides of several amino acids. Hence, he takes several antacid tablets before eating so as to neutralize his stomach acid.
So, the correct answer is 'Decreased absorption of the protein in the steak by the small intestines'.
Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

One of the- following is needed for the conversion of trypsinogen into trypsin  _____________.

  1. HCI

  2. Enterokinase

  3. Lipase

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

In the presence of enterokinase, inactive trypsinogen is converted into active trypsin.

So, the correct answer is 'Enterokinase'

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

Rennin acts on ______________________.

  1. Milk changing casein into calcium paracaseinate at 7.2 8.2 pH

  2. Proteins in stomach

  3. Fat in intestine

  4. Milk changing casein into calcium paracaseinate at 1 3 pH
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rennin (chymosin) is an enzyme found in the stomachs of young mammals that coagulates milk by converting casein into calcium paracaseinate in an acidic environment (pH 1-3).

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

Which pair reaches the stomach totally undigested?

  1. Fat, cellulose

  2. Starch, cellulose

  3. Protein, starch

  4. Starch, fat
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cellulose cannot be digested by human enzymes, and fats are not digested in the stomach because gastric lipase is not effective at the stomach's low pH and lacks emulsification.

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

Which gastric secretion is correctly matched with its source

  1. Pepsin Chief cells

  2. Chymotrypsin Parietal cells

  3. HCl Goblet cells

  4. Mucus Oxyntic cells
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Chief cells (or zymogenic cells) in the gastric glands secrete pepsinogen, which is the inactive precursor to pepsin.

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

Gastric juice contains

  1. HCl and pepsin

  2. pepsin and trypsin

  3. trypsin and HCI

  4. amylopsin and pepsin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gastric juice comprising a mixture of substances, including pepsin and hydrochloric acid, secreted by glands of the stomach. Its principal function is to break down proteins into polypeptides during digestion.

Hence, the correct answer is 'HCl and pepsin'