I. Tick() the correct options

1. 1. During digestion, complex substances are broken down into

 large molecules.

 small simple molecules.

 different molecules.

 more complex molecules.

2. Pancreatic juice mixes with the food in the

 stomach.

 small intestine.

 mouth.

 oesophagus.

3. Saliva contains a digestive juice called

 bile.

 pepsin.

 amylase.

 hydrochloric acid.

4. During digestion, fat is broken down into

 fatty acids.

 lactic acid.

 amino acids.

 glucose.

5. Bile helps in the digestion of

 only proteins.

 only fats.

 sugars.

 fats and carbohydrates.

6. Glucose combines with oxygen and produces

 sugar.

 carbon dioxide.

 water.

 energy.

7. The process by which a living cell releases energy from glucose is called

 digestion.

 cellular respiration.

 ingestion.

 photosynthesis.

8. During digestion, proteins are broken down into

 acids.

 amino acids.

 fatty acids.

 sugars.

Ans:

1. small, Simple molecules 2. Small intestine 3.Amylase 4. Fatty Acid 5.Only Fats 6. Carbon dioxide, water, energy 7. Cellular respiration 8. Amino acids

II. Match the following:

1. salivary glands       a. mucus

2. gastric juice            b. bile juice

3. mucosa                    c. pancreatic juice

4. liver                         d. pepsin and hydrochloric acid

5. pancreas                 e. saliva

Ans: 1.e 2.d 3.a 4.b 5.c

III. Name the following:

1. It digests carbohydrates, proteins and fats in the small intestine

2. It transports the nutrients from the digested food to every cell of the body.

3. It breaks down starch into sugar in the mouth.

4. It produces bile juice.

5. It secretes pepsin.

6. They are building blocks of proteins.

7. It protects the lining of the stomach.

8. It secretes pancreatic juice.

Ans: 1. Pancreatic juice        2. Blood       3. Amylase       4. Liver        5. Glands in the inner walls of the stomach       6. Amino acids       7. Mucus     8.Pancreas

IV. Answer the following questions in two to three sentences.

1. What is digestion?

Ans: The breaking down of complex food into simple soluble with the help of certain enzymes secreted by various organs of the digestive system is called digestion.  

2. Name the organs of the human digestive system.

Ans: Organs of the human digestive system are mouth, oesophagus, stomach, liver, pancreas, small intestine and large intestine.

3. Differentiate between incisors and canines.

Ans: Incisors are the four front teeth which are used to bite or cut food into smaller pieces. The canines are the tearing teeth present, one each on either side of the incisors, on each jaw.  

4. Name any one digestive juice and describe its role in digestion.

Ans: Saliva is a digestive juice. It contains salivary amylase that breaks down carbohydrates into sugar.  

5. Where are villi located? What is their function?

Ans: The inner walls of the small intestine have finger-like projections called villi. Villi are richly supplied with blood vessels. They increase the surface area for absorption of useful substances.  

6. How does the human body obtain fatty acids?

Ans: Complex fat molecules present in the food items such as butter, oil, milk and meat are broken into simple fatty acids in the small intestine.

 V. Answer the following questions in about four to five sentences.

1. Describe the digestion of carbohydrates.

Ans: The digestion carbohydrates starts from our mouth. Amylase present in saliva breaks down the carbohydrates inyo sugar. In small intestine the pancreatic juice released by pancreas breaks down the large starch (carbohydrates) molecules into simple sugar (glucose) molecules.

2. How are proteins in your food digested?

Ans: In the stomach a juice called pepsin is released which digests the protein into amino acids in presence of hydrochloric acid. Further the pancreatic juice  in the small intestine also breaks down the complex protein molecules into small molecules of amino acids.

3. How is energy obtained by the cells of our body?

Ans: In the digestion process the carbohydrates are converted into glucose molecules. These glucose molecules are transported to each and every cells of our body. Inside the cell the glucose molecules reacts with the oxygen and produces energy along with the production of carbon dioxide and water. This is how the cells of our body obtain energy.

4. Describe the digestive system of a ruminant.

Ans: The grass eating animals are called ruminants. They have four-chambered stomach. These herbivores eat quickly and store grasses in their rumen (first chamber). Inside rumen the grasses get partially digested. Later when these animals take rest, they regurgitate the grass from the rumen and and chew again which helps to digest the cellulose contents. Further the food passes to the rest of the chambers and reaches the stomach where the digestion of protein and carbohydrates and fats begins in presence of hydrochloric acid and gastric juices.

5. Explain nutrition in Amoeba

Ans: Amoeba lives in freshwater puddles and ponds and feeds mostly on remains of plants. Nutrition in Amoeba involves the following:  

• Ingestion: Amoeba senses a food particle, moves towards it and engulfs it forming pseudopodia.

Digestion: A food vacuole is formed around the engulfed food particle containing digestive juices, which break down the food particle into simple substances.  

Assimilation: Amoeba uses these substances.

Egestion: The undigested portion is removed from the body by diffusion.