Nutrition in Amoeba: Holozoic Nutrition, Process of Nutrition

Important Questions Based on Nutrition in Amoeba

Ques: How does amoeba engulf its food? (1 Mark)

Ans: Amoeba engulfs its food by extending its finger-like projections called pseudopodia. The process of extending pseudopodia is known as Phagocytes.

Ques: What substances enter into the food vacuole in Amoeba to break down the food? (1 Mark)

Ans: Digestive enzymes enter the food vacuole in Amoeba to break the food particles. 

Ques: From which part of the body, undigested food is egested in Amoeba? (1 Mark)

Ans: There is no fixed part in Amoeba for the process of egestion. The undigested food gets collected inside the amoeba. The cell membrane suddenly ruptures and the undigested food is thrown out of it.

Ques: What type of cell is an amoeba? (1 Mark)

Ans: Amoebae are eukaryotes whose bodies most often consist of a single cell. The cells of amoebae possess certain characteristic features. Their cytoplasm and cellular contents are enclosed within a cell membrane. Their DNA is packaged into a central cellular compartment called the nucleus.

Ques: How does an amoeba look like? (1 Mark)

Ans: When seen through a microscope, an amoeba looks like a tiny blob of colorless jelly with a dark spot inside it. The colorless jelly is called cytoplasm and the dark spot is the nucleus.

Ques: How does an amoeba get oxygen? (2 Marks)

Ans: Amoebas live in water. Water moves in and out of the cell, through the semi-permeable cell membrane by osmosis controlled by the cell of Amoeba. Oxygen and carbon dioxide, on the other hand, pass through the amoeba cell membrane easily via simple diffusion without active transport or osmotic actions. The environment inside the cell and outside the cell will come into equilibrium in terms of oxygen concentration, if there is a higher concentration of oxygen in the water outside the amoeba; oxygen will diffuse through the cell membrane until the concentration of oxygen inside and outside of the cell are equal.

Ques: Does amoeba die? (2 Marks)

Ans: No, Amoeba does not die. It simply divides itself into two or more daughter cells and each cell becomes a new amoeba. Amoeba is an acellular organism. So it is simply a mass of cytoplasm surrounded by the cell membrane. When it gets injured, the cytoplasm breaks and the membrane recovers itself.

Ques: Is amoeba a plant cell or an animal cell? (2 Marks)

Ans: Amoeba belongs to the kingdom Protista and phylum protozoa. Thus, in a broad sense, the amoeba is a protozoan cell or a Protista cell.

Also, Protista is a very controversial group because it has such unicellular organisms that can perform photosynthesis, if the light is present, and also in absence of light become heterotrophic. This complex nature fits them neither into Animalia, or Plantae kingdom.

Ques: How does osmoregulation take place in amoeba? (2 Marks)

Ans: Amoeba lives in freshwater as well as ocean water. The freshwater amoeba has a contractile vacuole for osmoregulation. The difference between solute concentration inside the body of amoeba and the concentration of solvent in water causes the water to move towards the hypertonic environment inside the body. Thus the contractile vacuole removes the excess water which comes inside the body. But the marine amoebas do not have contractile vacuole because there is already a hypertonic environment in the water so they have to control the water loss.

Ques: How does the amoeba sense food around it? (2 Marks)

Ans: Chemical signals on the surface of an item (food, predator or another object) are detected by receptors on the surface of the amoeba. The amoeba then decides using chemical signaling/pathways whether it is something to go towards or to avoid and reacts accordingly. They sense the direction to move towards food based on the concentration of chemical signals. The stronger/more numerous the chemical signals, the more likely the food is in that direction so the amoeba will move towards that point.

Ques: (i) Name an animal whose process of obtaining food is called phagocytosis.

(ii) Name an animal that depends on the simple diffusion of gases for breathing. (2 Marks)

Ans: (i) Amoeba obtains food by the process of phagocytosis. 

(ii) Amoeba depends on the process of simple diffusion of gases for breathing.

Ques: (a) What are the methods used by plants to get rid of their waste products?

(b) How are waste products excreted in Amoeba? (2 Marks)

Ans: (a) The various methods used by the plants to get rid of their waste products are-

(i) They get rid of the waste products that are in a gaseous state through lenticels in stems and stomata in leaves.

(ii) They excrete solid and liquid waste by shedding off leaves, peeling off bark and fruits.

(iii) By secretion of gums and resins.

(iv) Some waste substances are also excreted into the soil around them.

(b) Excretion in amoeba: In amoeba, carbon dioxide is removed by diffusion through the cell membrane and nitrogenous waste or excess water is removed by the contractile vacuole.

Ques: a) Draw a diagram to show the nutrition in Amoeba and label the parts used for this purpose. Mention any other purpose served by this part other than nutrition.

(b) Name the glands associated with digestion of starch in human digestive tract and mention their role.

(c) How is required pH maintained in the stomach and small intestine? (3 Marks)

Ans: (a) Pseudopodia is used for the purpose of nutrition. 

Pseudopodia is also responsible for the process of locomotion apart from nutrition.

(b) The salivary gland is associated with digestion of starch in human digestive tract.

It secretes saliva which contains enzyme known as salivary amylase. 

Salivary amylase enzyme is responsible for the convertion of starch into maltose.

(c) Gastric glands present on the walls of the stomach release HCl. HCl creates an acidic medium, which facilitates the action of enzyme pepsin. Bile juice present in the liver makes the food alkaline in small intestine. 

Ques: Explain the process of nutrition in Amoeba. (5 Marks)

Ans:  Amoeba is a protozoan which is found in freshwater. It intakes microscopic plants and animals. The mode of nutrition in amoeba is Holozoic nutrition and it intakes food through the process of phagocytosis. The different processes involved in the nutrition of amoeba are:

1. Ingestion: Ingestion is the process of taking food in the body. Amoeba engulfs food particles by extending finger-like projections called pseudopodia from its body and then forms a food vacuole. This process of engulfing food is called phagocytosis.
2. Digestion: The digestive enzymes present in the surrounding cytoplasm enter the food vacuole and break down the food into small and soluble molecules by chemical reaction for digestion.
3. Absorption: This process of diffusion of food into the cytoplasm is called absorption, after which the food vacuole disappears. The excess food is stored in the form of glycogen and lipids.
4. Assimilation: A part of the absorbed food is used for respiration to obtain energy while the remaining is used for the growth of the amoeba by forming new parts of the cell. This process of utilizing absorbed food for obtaining energy, repair and growth is called assimilation.
5. Egestion: When the undigested food gets collected in the food vacuole, it is thrown out of the body by rupturing the cell membrane. This process of removal of undigested food from the body is called egestion.