Fundamental Unit of Life Class 9 NCERT Solutions – The notes provided on our website for CBSE students are designed to align with CBSE and NCERT syllabus guidelines. By referring to these notes, students can save time and gain a comprehensive understanding of important topics and questions in each chapter.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. Who discovered cells, and how?
Answer – In 1665, the English scientist Robert Hooke discovered cells by examining a thin slice of cork through a microscope that he designed himself. Upon observing the cork, he noticed that it had a structure that resembled a honeycomb, consisting of many small compartments. Hooke described these small compartments as “cells”, which is the term still used today to describe the basic unit of life.
Q. Why the cell is referred to as the structural and junctional unit of life?
Answer – Cells are considered the fundamental and structural units of life because they are responsible for forming the basic structure of living entities. Groups of cells come together to form tissues, which further combine to form organs, and ultimately organ systems. These structures perform essential life processes such as respiration, digestion, and excretion, among others.
Q. How does water and carbon dioxide move through and out of the cell?
Answer – C02 moves in and out of the cell by diffusion, from an area of higher concentration inside the cell to an area of lower concentration outside the cell.
Water moves into and out of the cell by osmosis, from an area of higher concentration to an area of lower concentration across a selectively permeable membrane until an equilibrium is reached.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. Why plasma membrane is referred to as a selectively permeable membrane?
Answer – The plasma membrane is selectively permeable because it only allows certain molecules to pass through it while restricting others. The movement of molecules in and out of cells is regulated by the membrane’s composition and structure, which selectively permits or prevents the passage of molecules based on their size, charge, and polarity. This feature ensures that only the necessary molecules enter and exit the cell, maintaining the cell’s internal environment and enabling it to function correctly.
Q. Fill in the blanks in the following table that shows how prokaryotic and eukaryotic cells differ from one another.
Answer –
| Characteristic | Prokaryotic cell | Eukaryotic cell |
|---|---|---|
| Presence of nucleus | Absent | Present |
| DNA | Singular circular chromosome | Multiple linear chromosomes |
| Membrane-bound organelles | Absent | Present |
| Size | Generally smaller (1-10 μm) | Generally larger (10-100 μm) |
| Examples | Bacteria, Archaea | Protists, fungi, plants, animals |
Fundamental Unit of Life Class 9 NCERT Solutions
Q. Which of the two organelles we’ve studied that have their own genetic material can you name?
Answer – The two organelles we have studied that contain their own genetic material are:
- Mitochondria
- Chloroplasts (in plant cells)
Q. What will happen if a cell’s organisation is damaged by a physical or chemical influence?
Answer – Lysosomes are known as “suicide bags” because in case of damage to cells where cell revival is not possible, lysosomes burst and release enzymes which lead to the digestion of the damaged cells. This process is essential for maintaining the health and proper functioning of the surrounding cells and tissues.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. Why are lysosomes referred to as “suicide” hags?
Answer – Lysosomes are called suicide bags because they contain enzymes that can break down biomolecules, and in case of cell damage, they can burst and cause autolysis or self-destruction of the cell.
Q. Where do proteins get synthesized inside of cells?
Answer – Proteins are synthesized inside the cell in the ribosomes, which are present in both prokaryotic and eukaryotic cells. In eukaryotic cells, ribosomes can be found either free in the cytoplasm or attached to the endoplasmic reticulum. In prokaryotic cells, ribosomes are free in the cytoplasm. The process of protein synthesis is called translation and involves the assembly of amino acids into a polypeptide chain according to the instructions encoded in messenger RNA (mRNA).
Q. Compare the differences between plant and animal cells, then list the ways in which they differ from each other.
Answer –
| Characteristic | Plant Cells | Animal Cells |
|---|---|---|
| Cell wall | Present, made of cellulose | Absent |
| Chloroplasts | Present, for photosynthesis | Absent |
| Central vacuole | Large, occupies most of the cell volume | Small, multiple vacuoles present |
| Shape | Usually rectangular or square-shaped | Round or irregularly shaped |
| Centrioles | Absent | Present in most animal cells |
| Storage of carbohydrates | Stored as starch | Stored as glycogen |
| Plasma membrane | Plasmodesmata present for intercellular communication | No plasmodesmata present |
| Mitochondria | Present | Present |
| Cilia and Flagella | Rarely present | Present in some animal cells |
| Nucleus | Membrane-bound nucleus present | Membrane-bound nucleus present |
Fundamental Unit of Life Class 9 NCERT Solutions
Q. How are eukaryotic and prokaryotic cells distinct from one another?
Answer –
| Feature | Prokaryotic Cells | Eukaryotic Cells |
|---|---|---|
| Size | 1-10 µm | 5-100 µm |
| Nucleus | No | Yes |
| Membrane-bound organelles | No | Yes |
| Chromosome | Single, circular | Multiple, linear |
| Histones | Absent | Present |
| Ribosomes | Smaller | Larger |
| Cell division | Binary fission | Mitosis and meiosis |
| Mitochondria | Absent | Present |
| Respiration | Performed on cell membrane | Performed in mitochondria |
| Reproduction | Asexual | Both sexual and asexual |
Q. What would happen if the plasma membrane was to break or degrade?
Answer – A ruptured or broken-down plasma membrane can allow harmful substances to enter the cell, cause the loss of important cell components, disrupt the cell’s energy balance, and ultimately lead to cell death.
Q. What would happen to a cell’s life if the Golgi apparatus were absent?
Answer – In eukaryotic cells, the Golgi apparatus is essential for the storage, packing, and manufacturing of substances. It participates in cell development as well as the storing and transport of components made by cells. Cells would be unable to adequately store and transfer materials without the Golgi apparatus, which could result in malfunction or cell death.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. Which organelle is considered as the cellular powerhouse? Why?
Answer – The organelle known as the powerhouse of the cell is the mitochondrion. Mitochondria are responsible for producing the majority of the cell’s energy in the form of ATP (adenosine triphosphate) through the process of cellular respiration. This is why mitochondria are often referred to as the cell’s “powerhouse”. Mitochondria are unique in that they have their own DNA and can self-replicate, which suggests that they may have originated as independent prokaryotic organisms that were engulfed by eukaryotic cells through endosymbiosis. The presence of mitochondria in eukaryotic cells greatly increased the energy production capacity of these cells, allowing them to develop more complex structures and functions.
Q. What is the location of cell membrane lipid and protein synthesis?
Answer – The lipids and proteins that make up the cell membrane are synthesized in the endoplasmic reticulum (ER) of the cell. Specifically, the rough endoplasmic reticulum (RER) synthesizes and packages membrane proteins, while the smooth endoplasmic reticulum (SER) synthesizes membrane lipids. Once synthesized, these components are transported to the Golgi apparatus for modification and packaging, before being transported to the cell membrane.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. How does Amoeba obtain it’s food?
Answer – Amoeba is a single-celled organism that feeds on other smaller organisms, such as bacteria, algae, and other protozoans. The process by which Amoeba obtains its food is known as phagocytosis.
During phagocytosis, the Amoeba extends its pseudopodia (temporary projections of the cell membrane and cytoplasm) to surround and engulf its prey, forming a food vacuole. The food vacuole is then transported into the cell, where it fuses with lysosomes containing digestive enzymes. These enzymes break down the food into smaller molecules that can be absorbed by the cell and used for energy or other cellular processes. Any undigested material is eliminated from the cell through exocytosis.
Fundamental Unit of Life Class 9 NCERT Solutions
Q. What is osmosis?
Answer – Osmosis is the transfer of water molecules from an area with a higher concentration of water to an area with a lower concentration of water through a membrane that is selectively permeable. A concentration gradient of solutes that can’t pass the membrane triggers this movement of water. Osmosis aims to reach equilibrium, where water and solute concentrations are equal on both sides of the membrane. Osmosis is an essential process for many living things because it controls the flow of nutrients and water into and out of cells.
Q. Carry out the following osmosis experiment:
Four potato halves should be peeled, then each half should be scooped out to create a potato cup, one of which should be constructed from a boiling potato. Each potato cup should be placed in a water-filled trough. Now,
(a) Leave cup A empty
(b) fill cup B with one teaspoon of sugar
(c) Fill cup C with one teaspoon of salt.
(d) Add one teaspoon of sugar to the cup of cooked potatoes
For two hours, keep these. Next, take a look at the four potato cups and respond to the following:
(i) Describe the reason water collects in B and C’s hollow areas.
(ii) What purpose does potato A serve in this experiment?
(iii) Describe why the hollowed-out areas of A and D do not collect water.
Answer –
In this osmosis experiment, four potato cups are created by scooping out the center of each potato half. Each potato cup is then placed in a trough containing water, and various substances are added to each cup to observe the effects of osmosis. The boiled potato cup is included to serve as a control for comparison.
After two hours, the following observations can be made:
(i) Water gathers in the hollowed portion of B and C due to the process of osmosis, where water moves from a region of higher concentration to a region of lower concentration, towards the solution with a higher concentration of solute.
(ii) Potato A is necessary to serve as a control group or a standard for comparison, as it has no solute added to it.
(iii) Water does not gather in the hollowed-out portions of A and D because the concentration of solutes in these potato cups is the same as that in the surrounding water, causing no net movement of water.