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 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

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

Three major types of cells in stomach are ________________.

  1. Mucous cells, chief cells, oxyntic cells

  2. Mucous cells, chief cells, enteroendocrine cells

  3. Mucous cells, enteroendocrine cells, oxyntic cells

  4. Enteroendocrine cells, chief cells, oxyntic cells
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The gastric glands contain mucous cells (secreting mucus), chief cells (secreting pepsinogen), and oxyntic/parietal cells (secreting HCl).

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'

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

Enzyme pepsin in the gastric juice helps in the digestion of :-

  1. carbohydrates

  2. fats

  3. nucleic acids

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

Pepsin is the chief digestive enzyme in the stomach that stomach that breaks down proteins. Cells produce pepsinogen that is produced to act on mucus by epithelial cells of the stomach that helps to protect the lining of the stomach from corrosive hydrochloric acid and pepsin.

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

In which of the following structures protein digestion first occurs?

  1. Mouth

  2. Stomach

  3. Large intestine

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

  • Digestion involves the mixing of food, its movement through the digestive tract, and the chemical breakdown of the large molecules of food into smaller molecules.
  •  Digestion begins in the mouth when we chew and swallow, and then it is passed on to the stomach where digestion takes place by gastric juices and enzymes secreted by the stomach and then it is passed to the small intestine where the digestion is completed. 
  • Pepsin is an enzyme which is released by zymogenic cells, the chief cells in the stomach and that degrades food proteins into peptides. Hence, the stomach is the structure where the protein digestion first occurs.
So, the correct answer is 'Stomach'.

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

A digestive juice with a pH of approximately 2 is found inside the

  1. mouth

  2. stomach

  3. pancreatic duct

  4. small intestine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • The pH of your stomach varies, from 1-2 up to 4-5. When you eat, the stomach releases enzymes called proteases as well as hydrochloric acid to help in digestion.
  • By itself, the acid doesn't really do much for digestion, but the proteases that cleave proteins work best in an acidic environment or low pH, so after a high-protein meal, your stomach pH may drop to as low as 1 or 2. 
  • However, buffers quickly raise the pH back to 3 or 4. After the meal has been digested, your stomach pH returns to a resting level of about 4 or 5. Hence, inside of the stomach, a digestive juice with a pH of approximately 2 is found.
So, the correct answer is 'stomach'.
Multiple choice parts of the digestive system digestive system of human human digestive system digestion and absorption biology nutrition deficiency diseases digestive system

Choose the correct answers from the alternatives given.
Which of the following enzymes has the lowest pH optimum?

  1. Pepsin

  2. Trypsin

  3. Salivary amylase

  4. Pancreatic amylase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • In humans and other mammals pepsin produced in the stomach by chief cells in an inactive form called pepsinogen. 
  •  Once the pepsinogen is released into the stomach, the low pH from the gastric acid helps in the conversion of pepsinogen into pepsin, the active enzyme.
  •  Many proteins are denatured at low pH, and most enzymes whether or not they denature require a higher pH for activity. Hence, pepsin is the enzymes has the lowest pH optimum.
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

Pepsin is an enzyme which acts in

  1. acidic medium in the stomach

  2. alkaline medium in the stomach

  3. alkaline medium in the duodenum

  4. acidic medium in the duodenum
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • Pepsin is an enzyme which is released by zymogenic cells, the chief cells in the stomach and that degrades food proteins into peptides.
  •  It is most active in acidic environments.
  •  It exhibits maximal activity at pH 2.0 and is inactive at pH 6.5. Hence, Pepsin is an enzyme which acts in an acidic medium in the stomach.
So, the correct answer is 'acidic medium in the stomach'.