Extra Questions for Class 9th: Ch 5 The Fundamental Unit of Life Science

Extra Questions for Class 9th: Ch 5 The Fundamental unit of Life (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Plasma membrane is made up of which two components?
Answer
Plasma membrane is made up of lipids and proteins.

Q2. What is hypotonic solution?
Answer
A solution having solute concentration lower than that of the cell sap is called hypotonic solution.

Q3. What is hypertonic solution?
Answer
A solution having solute concentration higher than that of the cell sap is called hypertonic solution.

Q4. What is isotonic solution?
Answer
A solution having solute concentration same as that of the cell sap is called isotonic solution.

Q5. Cell wall is made up of which component?
Answer
Cell wall is made up of cellulose.

Q6. Give an example of unicellular organism.
Amoeba, Bacteria, Paramecium. (Any one)

Q7. Give an example of multicellular organism.
Answer
Fungi, plants, animals. (Any one)

Q8. What is active transport?
Answer
The movement of molecules across a membrane in cells against a concentration gradient with the help of ATP units is called active transport.

Short Answer Questions-I (SAQs-I) : 2 Marks

Q1. Cell size may range from a few micro metre to a metre. Support this statement with the help of examples.

Answer

Many cells are visible only under a microscope
Example: Mycoplasma is the smallest cell and longest cell in human body is nerve cell or neuron.

Q2. What is plasmolysis? What happens to a plasmolysed cell when it is placed in water?

Answer

Shrinkage of protoplast from the cell wall in presence of hypertonic solution due to exosmosis is know as plasmolysis. When a plasmolysed cell is placed in water, the concentration of water in the outside medium is more than the concentration in the cell. Hence, water moves inside the cell leading to its swelling.

Q3. What is plasma membrane ? What are its functions?

Plasma membrane also called as cell membrane, is the outer covering of a cell that separates its contents from the surrounding medium. It is made up of lipids and proteins, and provides a mechanical barrier to protect the inner contents of the cell. It encloses the nucleus and cytoplasm of the cell.

Q4. What do you mean by a nucleoid?

Answer

In prokaryotes and lower organisms like bacteria, the nuclear region of the cell may be poorly defined because of the absence of a nuclear membrane. Such an undefined and incipient nucleic region containing only naked nucleic acids without any membrane covering them is called a nucleoid.

Short Answer Questions-II (SAQs-II) : 3 Marks

Q1. (a) Write two points of difference between nuclear region of a bacterial cell and nuclear region of an animal cell.
(b) Which structure present in the nuclear region of a living cell bear genes?

Answer

Nuclear region of bacterial cell
Nuclear region of animal cell
Poorly defined and lacks any covering. Well defined and membrane bound.
Has single chromosome.  Lacks true organelles.
Has more than one chromosome.  Well defined membrane bound cell organelles present.

(b) Chromosomes is the structure present in the nuclear region of a living cell which bear genes.

Q2. (a) Label the parts marked 1, 2, 3 in a prokaryotic cell.

(b) Mention any three features of prokaryotic cells.

Answer

(a) 1 - Cell wall, plasma membrane,
2- Nucleoid,
3 - Cell wall

(b) (i) Lack nuclear membrane.
(ii) Lack cytoplasmic organelles.
(iii) Chlorophyll is associated with membranous vesicles.

Q3. (a) Why is the cell called the structural and functional unit of life?
(b) Why is the plasma membrane called a selectively permeable membrane ?
(c) Name the factor which decides the movement of water across the plasma membrane.

Answer

(a) Because shape and size of cells are related to specific functions they perform. Cells constitute various components of plants and animals.

(b) Because it permits exit and entry of some selected materials in and out of the cells.

(c) Amount of substance dissolved in water or solute concentration.

Q4. (i) Where are chromosomes present in the cell? What is their chemical composition?
(ii) How many pairs of chromosomes are present in human?

Answer

(i) Chromosomes are present in the nucleus of a cell. Their chemical composition is of DNA, RNA and proteins.
(ii) Hum have 23 pairs of chromosomes.

Long Answer Questions (LAQs) : 5 Marks

Q 1. (a) What are the consequences of the following conditions ?
(i) A cell having higher water concentration than the surrounding medium.
(ii) A cell having lower water concentration than the surrounding medium.
(iii) A cell having equal water concentration to its surrounding medium.
(b) Name the materials of which the cell membrane and cell wall are composed of.

Answer

(a) (i) When a cell possess higher water concentration than the surrounding medium then exosmosis occurs in the cell due to difference in concentration and cell shrinks.

(ii) When a cell has low water concentration than surrounding medium then endosmosis occurs that results in the swelling of the cell.

(iii) A cell having equal water concentration to its surrounding medium will not show any changes.

(b) Cell wall is composed of cellulose and cell membrane is composed of lipids and proteins.

Q2. (i) Explain the terms: (a) Endocytosis, (b) Plasmolysis.
(ii) What will happen if the organisation of a cell is damaged due to certain physical or chemical reasons?
(iii) How do substances like CO2 and water move in and out of the cell?

Answer

(i) (a) Endocytosis: The flexibility of the cell membrane enables the cell to engulf food and other materials from its external environment. Such process is known as endocytosis.

(b) Plasmolysis: When a living plant cell loses water through osmosis, there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.

(ii) When the organisation of a cell gets damaged, lysosomes will burst and their enzymes will eat up their own cell organelles. Therefore, lysosomes are also known as the suicidal bags of the cell.

(iii) Gases like CO2 and O2 move in and out of the cell by diffusion from their higher concentration to lower concentration. Water enters the cell by endosmosis through semi-permeable plasma membrane from its higher concentration to lower concentration. Similarly, water moves out of the cell by exosmosis when a cell is placed in a hypertonic solution.

NCERT Solutions of Chapter 5 The Fundamental Unit of Life

Notes of Chapter 5 The Fundamental of Life

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