Class 9 Science Chapter 5 Important Questions

Class 9 Science Chapter 5 Important Questions of the Fundamental Unit of Life. All the questions are taken from latest NCERT Books for academic session 2020-2021. Class 9 Science Chapter 5 Extra Question answers are important for class tests as well as terminal exams.

After going through NCERT Book, everyone should read these questions to be confident in chapter’s concepts.

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Class 9 Science Chapter 5 Important Extra Questions for 2020-2021

Class: 9Science
Contents:Important Questions with Answers
Chapter: 5The Fundamental Unit of Life

9th Science Chapter 5 Extra Question Answers for 2020-2021

Class 9 Science Chapter 5 Extra Question answers for preparation of exams. After doing these important extra questions, one can score better in school examination. These are not only for scoring mark but it clears the concepts also. These practice questions are comprised of intext and exercises questions from NCERT Books for class 9 Science.

Class 9 Science Chapter 5 Important Extra Questions Set – 1

Plasma membrane is made up of which two components?

Plasma membrane is made up of a liquids and proteins.

What is hypotonic solution?

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

What is hypertonic solution?

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

What is isotonic solution?

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

Cell wall is made up of which component?

Cell wall is made up of cellulose.

Which cell organelle controls most of the activities of the cell?

Answer: Nucleus also known as the brain of the cell controls most of the activities of the cell because it contains DNA (Deoxyribonucleic acid) which contains all the information of the cell.

Class 9 Science Chapter 5 Important Extra Questions Set – 2

Give an example of unicellular organism.

Amoeba, Bacteria, Paramecium.

Give an example of multicellular organism.

Fungi, plants, animals

What is active transport?

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

What is the intracellular source of digestive enzymes?

Lysosome

What is endocytosis?

Endocytosis is the ingestion or engulfment of food and other material by following of the plasma membrane it as seen in Amoeba.

Difference between Bacterial cell and Onion Peal

Bacterial cellOnion peel
1. Size is small (1^–10 mm)1. Size is larger (5^–100 mm).
2. Nucleus is absent.2. Nucleus is present.
3. It is a prokaryotic cell.3. It is a eukaryotic cell.
4. Cell division take place by fission or budding.4. Cell division takes place by mitosis.




Class 9 Science Chapter 5 Important Extra Questions Set – 3

Where are genes located?

Genes are located on chromosomes in the nucleus.

Name two structure found in plant cells but not in animal cells.

Cell wall and chloroplast

Name two structures found in animal cells but not in plant cell.

Lysosomes and centrioles

Which organelle is involved in the formation of lysosomes?

Golgi apparatus

Why are peroxisomes mostly found in kidney and liver cells?

Peroxisomes contain various oxidative enzymes which detoxify the toxic material. Since the blood carries various toxic substances to kidney and liver, large number of peroxisomes are present in them to oxidase the toxic material.

Plasmodesmata

Due to the presence of cell wall the exchange of materials between the plant cells is not possible. Therefore, protoplast of plant cells is connected by cytoplasmic channels through their walls which are called as plasmodesmata. These channels are used for the exchange of the material between two cells.

Class 9 Science Chapter 5 Important Extra Questions Set – 4

What is the outermost layer found in animal cell?

Plasma membrane

What is the outermost layer found in the plant cell?

Cell wall

Which organelle is storage sac of solid and liquid material?

Vacuoles

Why do the animal cells not have cell walls?

Animals do not have rigid walls because cell walls are incompatible with the way in which an animal moves and grow. The flaccid cell membrane provides the animal cell freedom of mobility and formation of different tissues which is not present in plants.

What are secretory proteins? Give an example of secretory protein.

Proteins which are synthesised by the cell and then released into outer medium of the cell are called secretory proteins include mucus, digestive enzymes and hormones.

Difference between Diffusion and Osmosis
DiffusionOsmosis
1. It occurs in any medium.1. It occur in liquid medium only.
2. Diffusing molecules may be solid, liquid or gaseous solute.2. It involves movement of solvent molecules only.
3. Semipermeable membrane is not required.3. Semipermeable membrane is required.



Class 9 Science Chapter 5 Important Extra Questions Set – 5

Which organelle serves as a chemical for transport of materials between cytoplasm and nucleus?

Endoplasmic reticulum

What is microscope?

Microscope is an optical instrument consisting of a lens or combination of lenses which renders minute objects distinctly visible.

Why is light microscope called a compound microscope?

Light microscope is called compound microscope because it consists of two or more lens systems.

Why is endocytosis found in animal only?

For endocytosis to occur the outermost membrane should be flexible like the plasma membrane of animals. But in plant cells, cell wall is the outermost membrane which is very rigid. Hence endocytosis occurs only in animals and not in plants.

Describe the microscopic structure of the cell.

The cork cells were the first cells to be observed. They were composed of box-like compartments, forming a honeycomb structure. Cell organelles are found embedded in the cytoplasm. These are smaller in size and bounded by plasma membrane.

Asters and Spindles fibres
    • Asters are two star-like structure radiating fibres from the centrosome. They help in locating spindle and trigger cleavage of cytoplasm.
    • Spindle fibres are formed from microtubules during cell division. The pull the chromosomes apart and bring them at the poles. These are broader in the middle and narrower at the poles.

Class 9 Science Chapter 5 Important Extra Questions Set – 6

Which organelle is associated with ribosomes formation?

Nucleolus

What are chromosomes made up of?

Chromosomes are made DNA and protein.

Define plasmolysis.

It is shrinkage nuclear region in the cytoplasm due to loss of water

Do you agree “A cell is a building unit of an organism”. If yes explain why.

A organism is made up of various organ systems like digestive system, nervous system, etc. These organ systems in turn are made up of various organs which are made up of tissue. Also tissues are a Cell < tissue < organ < organ system < organism

If you are provided with some vegetables to cook, you generally add salt into the vegetables. After adding salt, vegetable release water. Why?

When salt is added a hypotonic medium is created, i.e. the concentration of salt molecules is more outside the vegetables than. Hence due to osmosis water from the vegetables come out.

Cell Division

Cell division is a process of formation of two or more daughter cells of its own type from the mother cell. These are similar in structure and function.
In each case division of nucleus occurs before the division of cytoplasm. Cell division occurs in three ways:

    1. Amitosis
    2. Mitosis
    3. Meiosis



Class 9 Science Chapter 5 Important Extra Questions Set – 7

What is a nucleoid?

The undefined nuclear region in the cytoplasm of prokaryotes is known as nucleoid.

Which organelles other than nucleus contain DNA?

Mitochondria and plasmids contain DNA.

Name the only cell organelle seen in prokaryotic cell.

Ribosomes.

What is cytosol and cytoskeleton?

Cytosol is the semifluid part of the cell cytoplasm which is embedded in between cell organelles. Cytoskeleton is a network of protein fibres present in the cell which provides a supporting framework for the organelles.

What is the significance of pores present on the nuclear membrane?

The pores present on the nuclear membrane allow transport of water soluble molecules across the nuclear envelop. RNA and ribosomes move out of the nucleus, whereas carbohydrates, lipids and protein moved into the nucleus.

Difference between Rough and Smooth Endoplasmic Reticulum
Rough Endoplasmic ReticulumSmooth Endoplasmic Reticulum
1. They have ribosomes attached on their surfaces.1. They do not have ribosomes attached on their surfaces.
2. RER manufactures proteins and transports them to various places.2. SER helps in manufacturing lipids and transport them to various places.

Class 9 Science Chapter 5 Important Extra Questions Set – 8

Which microorganism can be made into crystal?

Viruses

Which organelle detoxify many poisonous and drug into a cell?

Peroxisome

Name a cell organelle which is non membranous.

Ribosome.

How can you calculate the magnification of a microscope?

Magnification of a microscope is calculated by multiplying the power of eyepiece and objective lenses.
Mathematically, M = P1 × P2 where P1 is the power of eyepiece and P2 is the power of objective.

How will absence of any one of the cell organelle affect the cell’s working?

Functions of all the organelles are inter-linked to each other and ultimately to the working of the cell. So if even a single link is missing, the cell ultimately suffers and die. For example, DNA from the nucleus passes the information for protein formation to the ribosomes which send the proteins to Golgi complex and ER for modification and transport.

Golgi Apparatus and its Functions

Golgi apparatus or Golgi bodies or Golgi complex is composed of membrane bound fluid-filled vesicles, vacuole and cisternae. In animal cells they are larger and only one or two in number, while in plants they are smaller and more in number while in plants they are smaller and more in number. Also in plant cells they are disturbed throughout the cytoplasm and are called dictyosomes.
Functions:

    • It is involved in the transport and modification of protein, lipids as well as carbohydrates.
    • It helps in the formation of cell plate during cell division.
    • It is also involved in the formation of cell wall, plasma membrane lysosomes and peroxisomes.
    • The material synthesised near endoplasmic reticulum is packaged and dispatched to various targets and outside the cell through the Golgi apparatus.




Class 9 Science Chapter 5 Important Extra Questions Set – 9

Define diffusion.

Movement of molecules from a region of higher concentration to the region of lower concentration is called diffusion.

Which is a cell wall and how is it formed?

Cell wall is non living and freely permeable rigid structure bounding the plant cell. It is secreted by the cell itself for the protection of its plasma membrane and cytoplasm.

Why was the scientist not able to observe most of the cell organelles before 1940?

Before 1940, scientist could view the cell only under a light microscope. The investigation of the electron microscope in 1940 enabled the scientist to observe the cell in greater detail.

There would be no plant life if chloroplast did not exist. Justify.

Chloroplast contains the pigment chloroplast which is responsible for food preparation in plants by the process of photosynthesis. Hence if there were no chloroplasts then there would not have been any plant life.

Why is the Golgi apparatus called the secretary organelle of the cell?

This is because it packages material synthesised in the ER and dispatches it to intercellular (plasma membrane and lysosomes) and extracellular (cell surface) targets.

The functional differences between Plasma Membrane and Cell Wall

Plasma MembraneCell Wall
1. It holds cellular contents and control passage of materials in and out of cell.1 It gives protection, strength and rigidity to the cell.
2. It is semipermeable in nature and allows entry of selected molecules into the cell.2. It is completely permeable in nature.
3. It is not elastic.3. It is elastic and controls the cell’s turgidity preventing its bursting.

Class 9 Science Chapter 5 Important Extra Questions Set – 10

What are the functional unit of a cell?

There are three major functional regions of cells: (i) Cell membrane or plasma membrane, (ii) nucleus and (iii) cytoplasm.

What is cell sap? Give its composition.

Liquid content in the vacuoles of plant cell is called cell sap. The sap contains sugars, amino acid, proteins, minerals and metabolic waste.

Why are Golgi bodies found in large number of cells which secrete digestive enzymes?

The main function of Golgi bodies is to release proteins or enzymes by vesicles. No other organelle has this property. Therefore, these are largely present in secreting cells.

How is chromatin, chromatid and chromosomes related to each other?

Chromatin is a thin thread-like structure which is composed of DNA (Deoxy Ribonucleic Acid) and proteins to form a rod like chromatid. Two similar chromatids attach to a centromere to form a chromosome.

Write the name of different plant parts in which chloroplasts, chromoplasts and leucoplasts are present?

Chromoplasts are present in flowers, fruit or any other coloured part of the plant (other than green part).
Chloroplasts are present in leaves and steam of plant (green part).
Leucoplasts are present anywhere in plant as they are colourless and store food.

The Functions of Nuclear Membrane
    • A nuclear envelop separates the environment of nucleus from that of rest of the cell.
    • It protects the genetic material from damage.
    • It facilitates and regulates exchange of materials in and out of nucleus.



Class 9 Science Chapter 5 Important Extra Questions Set – 11

Why cell is called fundamental unit of life?

The cell helps to perform all the function of the body. It is a building block for the body like a brick for the building. That’s why cell is called the fundamental unit of life.

What is plasma membrane? Write its function?

The outermost covering of the cell that separates the contents of the cell from its external environment is called plasma membrane. It allows the entry an exist of some materials in which and out of the cell. It also prevents movement of some other materials.

What is biogenesis?

The SER helps in the manufacture of fat molecules or lipids, important for the cell function. Some of these proteins and lipids helps in the building cell membrane. This process is called biogenesis.

Why lysosomes are called suicide bags?

Lysosomes are a kind of waste disposal system of the cell. Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles. Foreign materials entering the cell, such as bacteria or food, as well as old organelles end up in the lysosomes, which break them up into small pieces. Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking down all organic material. During the disturbance in cellular metabolism, for example, when the cell gets damaged, lysosomes may burst and the enzymes digest their own cell. Therefore, lysosomes are also known as the ‘suicide bags’ of a cell.

Why mitochondria are called the power house of cell?

Mitochondria are known as the powerhouses of the cell because the energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphopshate) molecules. ATP is known as the energy currency of the cell. The body uses energy stored in ATP for making new chemical compounds and for mechanical work. Mitochondria have two membrane coverings instead of just one. The outer membrane is very porous while the inner membrane is deeply folded. These folds create a large surface area for ATP-generating chemical reactions.

What is active transport? Differentiate between active and passive transport?

Answer: The process in which are moved uphill against the concentration gradient. Active transport always involves the expenditure of energy because the materials are pumped against the concentration gradient.

Active TransportPassive Transport
1. It involves movement of molecules against the concentration gradient.1. It involve movement of molecules along the concentration gradient.
2. It requires energy in the form of ATP molecules.2. No energy is required.
3. It is a rapid movement.3. It is a slow movement.
4. Movement of large molecules occur by active transport.4. Only small molecules or water molecules are transported passively.
Practice Questions

What happen when:

    1. dry apricots are left for some time in pure water and later transported to sugar solution?
    2. a red blood cell is kept in concentrated saline solution?
    3. the plasma membrane of a cell breaks down?
    4. rheo leaves are boiled in water first and then a drop of sugar syrup is put on it?
    5. Golgi apparatus is removed from the cell?
Answers
    1. The apricots swell due to osmosis initially and when transferred to sugar solution shrink again due to exosmosis.
    2. RBC’s shrink due to exosmosis.
    3. It would lead to scattering of cell organelles and there will be no functioning of the organs.
    4. There will be no change in cell shape or size because the cells re dead due to boiling.
    5. Function of the Golgi apparatus is packing, storage and transfer of protein. It would affect the functioning of cell.
What is ER? Write its function?

Answer: The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets. It looks like long tubules or round or oblong bags (vesicles). The ER membrane is similar in structure to the plasma membrane. There are two types of ER– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). RER looks rough under a microscope because it has particles called ribosomes attached to its surface. The ribosomes, which are present in all active cells, are the sites of protein manufacture. The manufactured proteins are then sent to various places in the cell depending on need, using the ER.

What are vacuoles?

Answer: Vacuoles are storage sacs for solid or liquid contents. Vacuoles are small sized in animal cells while plant cells have very large vacuoles. The central vacuole of some plant cells may occupy 50-90% of the cell volume. In plant cells vacuoles are full of cell sap and provide turgidity and rigidity to the cell. Many substances of importance in the life of the plant cell are stored in vacuoles. These include amino acids, sugars, various organic acids and some proteins. In single-celled organisms like Amoeba, the food vacuole contains the food items that the Amoeba has consumed. In some unicellular organisms, specialised vacuoles also play important roles in expelling excess water and some wastes from the cell.



What are lysosomes? Write their function?

Answer: Lysosomes are a kind of waste disposal system of the cell. Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles. Foreign materials entering the cell, such as bacteria or food, as well as old organelles end up in the lysosomes, which break them up into small pieces. Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking down all organic material. During the disturbance in cellular metabolism, for example, when the cell gets damaged, lysosomes may burst and the enzymes digest their own cell. Therefore, lysosomes are also known as the ‘suicide bags’ of a cell. Structurally, lysosomes are membrane-bound sacs filled with digestive enzymes.