NCERT Solutions for Class 9 Science Chapter 5

(i) These are capable of dividing for long periods to generate replacement for the cell which that cannot produce adenosine deaminase.
(ii) Stem cells can trigger immune response.
(iii) Stem cells can differentiate into white blood cells against the infectious diseases.

A cell is a smallest part of the living organisms which is fully alive and is capable of performing basic processes of life like, reproduction and respiration, therefore, it is called the structural and functional unit of life.

Amoeba, They are called Unicellular organism.

Single cell forms a zygote which is first cell formed after fertilization. It further leads to the formation of large number of cells by cell division.

A single cell takes in food, excrete waste, move, grow and reproduce.

Robert Hooke saw the cork which resembled the structure of a honey comb consisting of many little compartments. He observed these through a microscope. He called these boxes as cell.

It is because it allows only certain material to pass through it and not all the materials.

(i) Mitochondria
(ii) Chloroplast

Plasma membrane is a selectively permeable membrane of the cell that maintains its homeostasis, i.e., constant internal composition of the cell. If it ruptures or breaks down the constant internal chemical composition of the cell will be lost and it will not be able to perform its basic functions. Such a cell with ruptured plasma membrane is killed.

The materials synthesized in the ER are stored, sorted, modified, packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus packs products in vesicles, the secretary vesicles. In some cases complex sugars e.g. cellulose, may be made from simple sugars in Golgi apparatus. The Golgi apparatus is also involved in the formation of the cells which will not be possible if Golgi apparatus is not there.

Mitochondria are known as the powerhouse of the cell because they contain enzymes that are needed for stepwise oxidation of food stuffs (carbohydrate, fats and lipids) present in the cells to CO2 and water. Oxidation of food releases energy which is used to form high-energy ATP (adenosine triphosphate) molecules. ATP is known as Energy Currency of the cell and it is used as cellular fuel. Energy stored in ATP is used to bring about energy requiring activities of the cell such as photosynthesis, protein synthesis and muscle contraction.

Rough Endoplasmic Reticulum (RER) – synthesizes proteins constituting cell membrane. Smooth Endoplasmic Reticulum (SER) – synthesizes lipids constituting cell membrane.

Amoeba has flexible cell membrane. It enables amoeba to engulf in food by the process called endocytosis.

The diffusion of water or solvent through a semi-permeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes, to which the membrane is relatively impermeable, is called osmosis.