CBSE Questions for Class 11 Medical Biology Digestion And Absorption Quiz 15 - MCQExams.com

Digestion in the human body is a complex process where pH of the digestive tract plays a crucial role. pH level in the region of pharynx and mouth is controlled by the saliva and is maintained at about 6.8. However, in the stomach, the gastric acid lowers the pH to 1-3 making it highly acidic. This acidic condition activates the digestive enzyme pepsinogen and converts it into pepsin for protein digestion and kills the pathogenic bacteria. Therefore, the correct answer is option A.

• Digestion is a  process where the food is broken down by the mechanical and chemical process. Digestion begins at the mouth where the only carbohydrate is digested due to the presence of salivary amylase. 
• Food then moves to the stomach through oesophagus where the gastric juice is secreted by the stomach wall which contains pepsin for protein digestion with HCl and mucus.  
• Maximum protein is digested in the stomach.

• In human beings, the process of digestion starts at the mouth or buccal cavity where the secretion of saliva works on the foods broken down into smaller particles and helps it to pass through the esophagus to the stomach. 
• The stomach is the major digestive organ where mucus with embedded gastric glands produces gastric juices that continue with the digestion process. 
• Most of the digestion takes place in the small intestine where the complete breakdown of the food and absorbed into the lymphatic system occurs.
  
  Hence, the correct option is D.

• The muscular layer in the stomach differs from that of other organs of the alimentary canal because it has three layers of muscle instead of two.

1. The external coat is called the longitudinal muscle layer.
2. The middle, or circular muscular layer.
3. The innermost layer of smooth muscle is called the oblique muscular layer. 

A) Correct Option – 
B) Explanation for correct option -

• The sphincter of Oddi is a muscular valve which is mostly surrounding the exit of the bile duct and the pancreatic duct into the duodenum region.
• The sphincter remains normally closed, opening only when a meal is eaten so that digestive juices can enter the duodenum and mix with food for the digestion process.
• So bile can be prevented from entering the duodenum by the Sphincter of Oddi.

• Emphysema is a lung condition that causes shortness of breath. In people with emphysema, the air sacs in the lungs (alveoli) are damaged. Over time, the inner walls of the air sacs weaken and rupture — creating larger air spaces instead of many small ones.
• Jaundice, Constipation, and Vomiting are digestive system related disorders.

• The increased liquidity of fecal discharge associated with reduced absorption of food is diarrhoea. Frequent diarrhoea causes dehydration and electrolyte balance.
• In vomiting, the stomach content are forced upward through the oesophagus and pharynx and out of the mouth.
• Indigestion is caused due to inadequate enzyme secretion, anxiety, spicy food, food poisoning, and overeating.
• Constipation is the difficult defaecation caused by decreased motility of the intestine.
• So, the correct answer is option D.

$$\textbf{Correct answer: C}$$ 

$$\textbf{Option (A):}$$ 

$$\bullet$$ Microvilli are also called cell cells containing finger-like projections on their surface. 

$$\bullet$$ But it is not the brush border cells like the ciliated epithelial cells present in different regions of the body. 

$$\textbf{Option (B):}$$ 

$$\bullet$$ Microvilli cells are found in the small intestine.

$$\bullet$$ The cells that are present on the linings of the proximal convoluted tubule are simple cuboidal cells.

$$\textbf{Option (C):}$$ 

$$\bullet$$ Microvilli are the cells present on the surface of the villi.

$$\bullet$$ This further increases the surface area of the small intestine and facilitates more absorption of nutrients. 

$$\textbf{Option (D):}$$ 

$$\bullet$$ The infoldings in the cell membranes are called mesosomes. This type of infolding is present in the mitochondria of eukaryotes too. 

Hence, the correct answer is option (C).

After digestion, most of the monosaccharides are absorbed into the body via active transport using sodium ions. Fructose is absorbed via facilitated diffusion. Amino acids are absorbed via secondary active transport using sodium ions. Chylomicrons cannot enter blood capillaries and hence enter lacteals. Only 5% of starch is hydrolyzed in the mouth. Proenzyme pepsinogen is secreted by chief cells in the stomach

So, the correct answer is 'Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like Na+'.