NCERT Exemplar Solutions Class 9 Science The Fundamental Unit of Life

Multiple Choice Questions (MCQs)...............................

Question 1:  Which of the following can be made into crystal?

(a) A bacterium                       

(b) An Amoeba                  

(c) A virus                           

(d) A sperm

Solution 1:   (c) A virus.                          

Since viruses are unable to metabolize and replicate on their own, they are classified as an intermediate between living and non-living cells. They can only reproduce when they enter the body of a host. Cell theory does not apply to them.

Thousands of viruses make up a virus crystal. A virus crystal is a pore collection that can be used in chemical experiments.

Question 2:  A cell will swell up if

a)      the concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding medium

b)      the concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell

c)       the concentration of water molecules is same in the cell and in the surrounding medium

d)      concentration of water molecules does not matter 

Solution 2:   (b) the concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell.

Osmosis is a natural process in which solvent molecules migrate from a region of lower solute concentration to a region of higher solute concentration through a partially permeable membrane, attempting to balance the solute concentration on both sides.
Endosmosis is a mechanism that occurs when a solvent moves from the outside to the inside of the body (inward movement). It induces cell swelling as it happens in a hypotonic solution.

Exosmosis is a mechanism that occurs when a solvent moves from inside to outside of a cell (outward movement). It can only be used in hypertonic solutions. The cell shrinks as a result of this.

The solution in the surrounding medium is assumed to be isotonic because the concentration of water in both the surrounding medium and the cell is the same and there is no movement of water molecules.

Question 3:  Chromosomes are made up of
(a) DNA                 (b) Protein                (c) DNA and protein                    (d) RNA

Solution 3:  (c) DNA and protein.

Chromosomes are thread-like structures that are normally found in the nucleus and are only apparent during cell division. Each chromosome is made up of two parts:

(i)  Deoxyribonucleic acid (DNA)
(ii) Proteins (e.g., histones and acidic proteins)
These have two (unreplicated) or four (duplicated) sides, as well as a primary constriction or centromere that gives them their shape due to its location. Diploid refers to chromosomes that are paired, while haploid refers to chromosomes that are not paired.

Question 4:  Which of these options is not a function of ribosomes?
I.    It helps in manufacture of protein molecules.
II.   It helps in manufacture of enzymes.
III. In helps in manufacture of hormones.
IV. In helps in manufacture of starch molecules.

(a) I and II            

(b) II and III              

(c) III and IV               

(d) IV and I

Solution 4:   (c) III and IV.              

Ribosomes are dense, spherical, granular particles that float in the matrix or are attached to the endoplasmic reticulum. They are present in both prokaryotic and eukaryotic cells and are not membrane bound. They play a crucial role in protein synthesis. While all enzymes are proteins, not all hormones are proteins.

Question 5:  Which of these is not related to endoplasmic reticulum?
(a) It behaves as transport channel for proteins between nucleus and cytoplasm
(b) It transports materials between various regions in cytoplasm
(c) It can be the site of energy generation
(d) It can be the site for some biochemical activities of the cell

Solution 5:   (c) It can be the site of energy generation.

The endoplasmic reticulum is a membranous network that connects the nucleus' outer membrane to one side and the plasma membrane to the other. There are three forms of it:

(i) Cisternae-closed fluid filled sac

(ii) Vesicles

(iii) Tubules

It has two types-

(i) Smooth endoplasmic reticulum, which has no ribosomes on its surface, and

(ii) Rough endoplasmic reticulum, which has ribosomes on its surface. 

Question 6:  Following are a few definitions of osmosis.
Read carefully and select the correct definition.
(a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.
(b) Movement of solvent molecules from its higher concentration to lower concentration.
(c) Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane.
(d) Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane.

Solution 6:   (a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.

Osmosis is the movement of water molecules over a concentration gradient through a selectively permeable membrane.

It is the movement of water from a region of high water concentration to a region of low water concentration through a semipermeable membrane (only through semipermeable membrane).
Osmosis is used by unicellular freshwater species and most plant cells to obtain water. Osmosis also includes the absorption of water by plant roots.

Question 7:  Plasmolysis in a plant cell is defined as
(a) break down (lysis) of plasma membrane in hypotonic medium
(b) shrinkage of cytoplasm in hypertonic medium
(c) shrinkage of nucleoplasm
(d) None of the above

Solution 7:   (b) shrinkage of cytoplasm in hypertonic medium.

Osmosis is the mechanism by which water diffuses out of a cell while it is immersed in a hypertonic (highly concentrated) solution. This is because the concentration of water outside the cell is lower.
Despite the fact that water molecules move through the cell membrane in both directions, more water leaves the cell than reaches it. As a consequence, the cell is contracts. Exosmosis is the name for this operation. The cytoplasm of a plant cell tends to shrink if exosmosis continues. The process is known as plasmolysis, and the cell is said to have been plasmolyzed.

Question 8:  Which of the following are covered by a single membrane?

(a) Mitochondria                      

(b) Vacuole                      

(c) Lysosome                       

(d) Plastid

Solution 8:   (c) Lysosome.

Lysosomes are small, spherical sac-like structures that are uniformly distributed in the cytoplasm. Each lysosome is surrounded by a double membrane and contains powerful enzymes that can digest or break down any organic material. Rough endoplasmic reticulum produces these enzymes.

In our bodies, they perform the following tasks.

1. They aid in the breakdown (digesting) of large cell molecules.

2. They aid in the prevention of bacteria and viruses.

3. Lysosomes operate on and digest their own cellular organelles while they are starved. Cell death occurs as a result of this. The lysosomes are also known as the cell's suicide bags or demolition squads.

Question 9:  Find out the false sentences.
(a) Golgi apparatus is involved with the formation of lysosomes.
(b) Nucleus, mitochondria and plastid have DNA; hence they are able to make their own structural proteins.
(c) Mitochondria is said to be the power house of the cell as ATP is generated in them.
(d) Cytoplasm is called as protoplasm.

Solution 9:   (d) Cytoplasm is called as protoplasm.

The Golgi apparatus is involved in the synthesis of the cell wall, plasma membrane, and lysosome, in addition to secreting various enzyme proteins and creating vacuoles.
The genome (DNA) and ribosomes of the nucleus, mitochondria, and plastids are all unique. They are self-replicating organelles, meaning they have the ability to separate and synthesize structural proteins on their own (semi-autonomous organelles). Mitochondria are responsible for cellulose respiration as well as the synthesis of energy-dense compounds (ATP). As a result, it is known as the cell's powerhouse.

The cytoplasm is the part of the cell that lies between the plasma membrane and the nuclear envelope.

Question 10:  Find out the correct sentence
(a) Enzymes packed in lysosomes are made through RER (Rough Endoplasmic Reticulum)
(b) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively
(c) Endoplasmic reticulum is related with the destruction of plasma membrane
(d) Nucleoid is present inside the uncleoplasm of eukaryotic nucleus

Solution 10:   (a) enzymes packed in lysosomes are made through RER (Rough Endoplasmic Reticulum).

The nucleoid is the unidentified nuclear region in the cytoplasm of prokaryotic cells.

Prokaryotic cells have a single chromosome that is directly contained in the cytoplasm, while eukaryotic cells have a nuclear membrane that separates the nucleus from the cytoplasm.
The nuclear envelope encloses the liquid ground material, the nucleoplasm, and has several pores (nuclear pores). The nucleolus and chromatin material are two types of nuclear structures found within nucleoplasm. The nucleolus can have one or more nucleolus, and it is not bounded by any membrane. It contains a high concentration of protein and RNA (Ribonucleic Acid) molecules and serves as a site for ribosome formation, hence are also known as “ribosome factory."

Question 11:  Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell?

(a) Golgi apparatus                                      

(b) Lysosomes

(c) smooth endoplasmic reticulum           

(d) Vacuoles

Solution 11:   (c) Smooth endoplasmic reticulum.

The smooth endoplasmic reticulum in vertebrate liver cells helps in detoxification. Drugs, aspirin, insecticides (DDT), petroleum products, and contaminants are among the harmful or poisonous compounds it metabolizes. These poisonous substances enter an animal's body through food, air, or water.

Question 12:  The proteins and lipids, essential for building the cell membrane, are manufactured by
(a) endoplasmic reticulum
(b)  Golgi apparatus
(c) plasma membrane
(d)  mitochondria

Solution 12:  (a) endoplasmic reticulum. 

The following are the functions of the endoplasmic reticulum:

i)        It raises the cytoplasm's surface area for the cell's different metabolic activities.

ii)       It provides internal protection for the colloidal matrix, such as the cytoplasm.

iii)     It has to do with metabolic product synthesis, storage, and transport.

iv)     During cell division, it aids in the development of the cell plate and nuclear membrane.

v)      The Routh Endoplasmic Reticulum (RER) is involved in protein synthesis.

vi)     Membrane biogenesis is a mechanism in which the Smooth Endoplasmic Reticulum (SER) secretes lipids, which, along with proteins, form the cell membrane.

Question 13:  The undefined nuclear region of prokaryotes is also known as

(a) nucleus                                               

(b) nucleolus

(c) nucleic acid                                          

(d) nucleoid

Solution 13:   (d) nucleoid.

Prokaryotic cells lack a true nucleus, and their cytoplasm contains a circular DNA strand.

Nucleoid refers to the cell's unidentified nuclear zone. The nucleoplasm of a prokaryotic cell is not distinct from the cytoplasm because it lacks chromosomes and a nucleolus or nuclear membrane.

Question 14:  The cell organelle involved in forming complex sugars from simple sugars are
(a) endoplasmic reticulum
(b) ribosomes
(c) plastids
(d) Golgi apparatus

Solution 14:   (d) Golgi apparatus.

Camillo Golgi was the first to discover the Golgi body. Stacks of flattened (saucer-shaped) membranes or flattened sacs called cisternae form the Golgi bodies, or Golgi complex. In plants, Golgi bodies are known as dictyosomes. Bacteria, blue-green algae, mature sperm, and red blood cells in humans and other species lack the Golgi apparatus.

The Golgi apparatus develops from the smooth endoplasmic reticulum's membrane, which is derived from the rough endoplasmic reticulum.

The proximal Golgi saccules (cisternae on the cis face) are produced by fusion of ER-derived vesicles, while the distal saccules (cisternae on the trans face) “give it all” to vesicle formation and then vanish. As a result, the Golgi saccules are continuously and quickly renewed.

The Golgi apparatus has two main functions:

i)        They store, modify, package, and condense the proteins synthesized in the ribosomes.

ii)       During cell division, they form the cell plate.

iii)     Digestive enzymes are stored in tiny membrane-bound vesicles that eventually become lysosomes.

iv)     Polysaccharides for the cell membrane are synthesized.

Question 15:  Which out of the following is not a function of vacuole?
(a) Storage
(b) Providing turgidity and rigidity to the cell
(c) Waste excretion
(d) Locomotion

Solution 15:   (b) Providing turgidity and rigidity to the cell. 

Vacuoles can range in size from small to massive. These membrane-bound organelles are packed with liquid or sap. Vacuoles in animal cells are smaller and less in number than those in plant cells. Just one large vacuole can be found in some plant cells. Vacuoles take up the majority of a plant cell's space.
The (approximately 90% in some cases) may be contractile (can contract) or non-contractile (can't contract). When the pressure of the contents of a contractile vacuole rises, the vacuole contracts and the contents are released. Food particles are found within food vacuoles in unicellular organisms like Amoeba. However, they have little to do with locomotion.

The key functions of vacuoles are:

1. They are often associated with the maintenance of water balance in animals.

2. They are involved in osmoregulation, i.e., the control of internal strain.

3. They store a variety of substances, including waste.

Question 16:  Amoeba acquires its food through a process, termed

(a) exocytosis                                         

(b) Endocytosis

(c) plasmolysis                                         

(d) Both exocytosis and endocytosis both

Solution 16:  (b) Endocytosis.

Endocytosis is the process by which cells consume material via their plasma membrane. Phagocytosis (cell eating), potocytosis (cell drinking), and receptor-mediated endocytosis are three processes that are all related.
There are internalization pathways for solid particles, small molecules and ions, and macromolecules, respectively. Since them all need resources, they can be classified as different types of active transportation.

Phagocytosis is the most common mode of feeding among Protozoan (such as Amoeba) and lower Metazoan (e.g., sponges). The phagocyte engulfs the particle lysosomes, joins with the vacuole containing the ingested particle, and pours their contents into the vacuole to kill the particle in pseudopodia movement.

Question 17:  The cell wall of which out of these is not made up of cellulose

(a) bacteria             

(b) Hydrilla                

(c) mango tree                    

(d) Latus

Solution 17:   (a) bacteria.

Plant cells have a solid outer coating called the cell wall in addition to the plasma membrane. Outside of the plasma membrane is the cell wall. Cellulose makes up the majority of the plant cell wall. Cellulose is a complex material that gives plants their structural strength. Since bacteria are not plants, their cell walls are made of peptidoglycan.

Question 18:  Silver nitrate solution is used to study
(a) endoplasmic reticulum
(b) Golgi apparatus
(c) nucleus
(d) mitochondria

Solution 18:   (d) mitochondria. 

Camillo Golgi was the first to discover a revolutionary technique for staining individual cell structures. The black reaction is the name given to this form. It uses a mild silver nitrate solution and is useful for tracing cell processes and delicate implications.

Question 19:  Organelle other than nucleus, containing DNA is
(a) endoplasmic reticulum
(b) Golgi apparatus
(c) mitochondria
(d)  lysosome

Solution 19:   (c) mitochondria. 

Apart from the nucleus, mitochondria are considered semiautonomous organelles because they contain DNA and can synthesis their own proteins.

Question 20:  Kitchen of the cell is
(a) mitochondria
(b) endoplasmic reticulum
(c) chloroplast
(d) Golgi apparatus 

Solution 20:   (c) chloroplast.

Green algae and higher plants all have chloroplasts. They are active in food photosynthesis and have a green pigment called chlorophyll. As a result, they're also known as the "cell kitchens." Like mitochondria, each chloroplast is surrounded by two unit membranes.

It depicts two distinct areas:

i)        The major functional units of chloroplast are grana. They're stacks of membrane-bound, flattened discoid sacs (known as thylakoids) that contain chlorophyll molecules.

ii)       The grana are embedded in a homogeneous matrix called stroma. It's packed with photosynthetic enzymes, starch grains, DNA, and ribosomes.

Question 21:  Lipid molecules in the cell are synthesized by

(a) smooth endoplasmic reticulum

(b) rough endoplasmic reticulum

(c) Golgi apparatus

(d) plastids 

Solution 21:   (a) smooth endoplasmic reticulum. 

The smooth endoplasmic reticulum, which is present in the cell, synthesizes lipid molecules.

Question 22:  Cell arises from pre-existing cell was stated by
(a) Haeckel              

(b) Virchow             

(c) Hooke                 

(d) Schleiden

Solution 22:   (b) Virchow.

Schleiden suggested the theory in 1938 that plants are made up of cells. Schwann independently confirmed later in 1839 that all animals and plants are made up of cells . Cell theory is based on this joint discovery.

R. Virchow proposed the notion in 1855 that all cells originate from a pre-existing cell , further refining the cell theory. His amorphism was unmistakable (Omnis Cellula-e-Cellula).

Question 23:  Cell theory was given by

(a) Schleiden and Schwann                   

(b) Virchow

(c) Hooke                                                   

(d) Haeckel

Solution 23: (a) Schleiden and Schwann. 

The cell theory was developed by Schleiden (1836) and Schwann (1834) and refined by R. Virchow  in the (1855). The following are the core postulates of cell theory:

i)        Cells and cell products make up all organisms.

ii)       Cells are the sites of all metabolic reactions. As a result, cells serve as both structural and functional units throughout life.

iii)     Only pre-existing cells give rise to new cells. No cell may form spontaneously; instead, it is formed by the division of pre-existing cells.

iv)     Any living thing begins as a single cell.

Question 24:  The only cell organelle seen in prokaryotic cell is

(a) mitochondria                        

(b) ribosomes                    

(c) plastids                        

(d) lysosomes

Solution 24:  (b) ribosomes.

A prokaryotic cell, unlike a eukaryotic cell, lacks membrane-bound organelles such as plastids, mitochondria, and the endoplasmic reticulum, but it does have smaller, randomly spaced ribosomes.

Question 25:  Organelle without a cell membrane is

(a) ribosome           

(b) Golgi apparatus               

(c) chloroplast         

(d) nucleus

Solution 25:   (a) ribosome. 

The nucleus is surrounded by two nuclear membranes that form a nuclear envelope; the Golgi apparatus is a collection of fluid-filled vesicles, vacuoles, and flattened cisternae that are all membrane-bounded. Although plastids are membrane-bound organelles, ribosomes can move freely in the matrix or remain attached to the endoplasmic reticulum.

Question 26:  1 µm is

a)      10^-6

b)      10^-9

c)       10^-10

d)      10^-3 

Solution 26:   (a) 10^-6. 

The micrometre, also known as the micron, is a SI-derived length unit equaling 10-6 of a metre.

Question 27:  Lysosome arises from
(a) endoplasmic reticulum
(b) Golgi apparatus
(c) nucleus
(d) mitochondria

Solution 27:   (b) Golgi apparatus.

The Golgi apparatus is involved in lysosome development.

Question 28: Living cells were discovered by

(a) Robert Hooke      

(b) Purkinje           

(c) Leeuwenhoek          

(d) Robert Brown

Solution 28:  (c) Leeuwenhoek .

When Anton Van Leeuwenhoek, a Dutch biologist, examined pond water under a microscope made of lenses in 1670, he discovered the living cell.

Question 29:  Select the odd one out
(a) The movement of water across a semi permeable membrane is affected by the amount of substances dissolved in it.
(b) Membranes are made of organic molecules like proteins and lipids
(c) Molecules soluble in organic solvents can easily pass through the membrane.
(d) Plasma membranes contain chitin sugar in plants.

Solution 29:  (d) Plasma membranes contain chitin sugar in plants. 

The plasma membrane is an extremely fragile, thin, elastic living membrane that surrounds each cell. The plasma membrane consists of two layers of lipid (fat) molecules with protein molecules sandwiched between them.

Only an electron microscope will reveal the structure of the plasma membrane. It is a selectively permeable membrane that enables only certain substances to enter and exit the cell. Viruses are without membranes.

i)        It has the following functions:

ii)       It gives the cell a defined form.

iii)     It shields the contents of the cell from damage.

iv)     It controls the flow of substances into and out of the cell.

v)      It can in fold or stretch around solid and liquid materials to internalize them. This is the active material intake process.

It is involved in adhesion, recognition, and the development of vesicles, cilia, flagella, microvilli, and other structures in animal cells.

Short Answer Type Questions........................

Question 30:  Why are lysosome known as suicidal-bags of a cell?

Solution 30:   The lysosomes may split during the breakdown of cell structure, when the cells are weakened, and enzymes capable of digesting or breaking down all organic nutrients may be released into the cell. Because of their digestive abilities, they can feed, digest, or break down other cell organelles, resulting in hampered metabolic activities and, eventually, cell death.

Because of this, lysosomes are also known as cell suicidal bags.

Question 31:  Do you agree that ‘A cell is a building unit of on organism’. If yes, explain why?

Solution 31:   A cell is made up of numerous organelles that each serve a different purpose. A cell is the smallest unit of life, structurally, functionally, and functionally capable of performing all living functions.

The number of cells in each organism varies. An Amoeba is a single-celled or unicellular organism that performs all of its basic functions in a single cell.

A human, on the other hand, is multicellular; with up to 60 x 1015 cells (weight about 60 kg). Cells form tissues in a multicellular body, which then combine to form organs and Different organs perform different functions, indicating that they have a well-developed division of labor.

Question 32:  Why does the skin of your finger shrink when you wash clothes for a long time?

Solution 32:   A hypertonic solution is one that is more concentrated than our skin cells. Water diffuses out of the cells through osmosis (water diffusion through a semipermeable membrane), when the cell is submerged in a hypertonic solution, as we know, due to the lower concentration of water outside the cell. The cell shrinks as a result. Exosmosis is the name for this operation.

Exosmosis occurs in the skin cells during the washing of clothing. That’s why, when washing clothes for a long time, this causes skin shrinkage over the fingertips.

Question 33:  Why is endocytosis found in animals only?

Solution 33:   Endocytosis is the formation of an interacellular membrane-bound vesicle by the invagination of a small area of plasma membrane. It's been seen in a variety of animal cells where the plasma membrane is in close contact with the outside world.

Plant cells lack endocytosis since their plasma membrane is protected by a rigid cell wall. As a result, only animals exhibit this mechanism.

Question 34:  A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.

Solution 34:   Exosmosis is caused by concentration salt solution, which is a hypertonic solution (water concentration lower than the cell). Irritation and dehydration result from the external flow of water from the cell. This causes reversible motions and, as a result, vomiting.

Question 35:  Name any cell organelle which is non-membranes.

Solution 35:   Ribosome is a non-membranous cell organelle. Ribosomes are incredibly tiny round bodies that can be located either free in the cytoplasm or connected to the ER's surface. They are made up of ribonucleoprotein acids (ribonucleic acid and protein). The primary function of ribosomes is to serve as a platform for protein synthesis.

Question 36:  We eat food composed of all the nutrients like carbohydrates, proteins, fats, vitamins, minerals and water. After digestion, these are absorbed in the form of glucose, amino acids, fatty acids, glycerol, etc.What mechanisms are Involved in absorption of digested food and water?

Solution 36:  Diffusion and osmosis are the mechanisms involved in the absorption of digested food and water, respectively.

i)        Digested food-through diffusion, i.e., the mechanism by which molecules travel from a higher concentration region to a lower concentration region until they are evenly distributed across the available space.

ii)       Water: Through osmosis, i.e. or the passage of water from a high-concentration region to a low-concentration region through a semi-permeable membrane.

In this situation, the concentration is high in the small intestine and low in the blood.

Question 37:  If you are provided with some vegetables to cook. You generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?

Solution 37:   The external medium becomes hypertonic when salt is added; meaning the concentration of water in the external medium is lower than the concentration of water within the cell. As a consequence of exosmosis, water is released from the vegetables (water molecules go out of the cell resulting in shrinkage of cell).

Question 38:  If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for you.
(a) Both the cells will swell.
(b) RBC will burst easily while cells of onion peel will extent.
(c) Both (a) and (b) are correct.
(d) RBC and onion peel cells will behave similarly

Solution 38:  Both (a) and (b) are correct. Hypotonic solution is described as a solution with a higher concentration of water than the cell. Endosmosis, or the inward flow of water, happens when the cells are kept in a hypotonic solution.

Cells puff up as a result of this. RBCs easily burst when kept in hypotonic solution because they are animal cells with no cell wall, whereas the onion peel has a cell wall and is resistant to bursting due to endosmosis-induced swelling.

As a result, option (c) is the correct one.

Question 39:  Bacteria do not have chloroplast, but some bacteria are photoautotrophic in nature and perform photosynthesis. Which part of bacterial cell performs this?

Solution 39:  While bacterial cells lack chloroplasts, some photoautotrophic bacteria are able to perform photosynthesis due to the existence of chlorophyll in the membrane. Reaction centres embedded in the cell membrane absorb light energy precisely. Depending on the amount of surface area required, these reaction centres come in the form of sacs-tubes or sheets.

Question 41:  Write the name of different plant parts in which chromoplast, chloroplast and leucoplast are present.

Solution 41:  Plastids are found in the majority of plant cells, but not in animal cells. Plastids, including mitochondria, have their own genome (DNA) and ribosomes. They, like mitochondria, are self-replicating organelles with the ability to separate. There are three types of plasmids.

1. Chromoplasts (non-green colored plastids) - They add color to organs, such as flowers and fruits, to attract animals for pollination and fruit dispersal.
2. Chloroplasts (green-colored plastids) - These are the photosynthesis sites found in the plant's leaves.
3. Leucoplasts (the colorless plastids) - Leucoplasts play a role in food storage and can be found in any organism.

Question 42:  Name the organelles which show the analogy written as under

a)      Transporting channels of the cell

b)      Power house of the cell

c)       Packaging and dispatching unit of the cell

d)      Digestive bag of the cell

e)      Storages sacs of the cell

f)       Kitchen of the cell

g)      Control room of the cell 

Solution 42:

a)      The cell's transport pathway. The endoplasmic reticular binds the cell membranes to the nuclear membrane and serves as the cell’s transport channel.

b)      Mitochondria are known as the cell's powerhouse because they provide energy in the form of ATP (Adenosine Triphosphate).

c)       The Golgi complex is the cell's packaging and dispatching structure, as it stores, modifies, packages, and condenses the proteins synthesized by ribosomes.

d)      Lysosomes are referred to as the cell's digestive bags because they contain enzymes capable of degrading any organic content.

e)      Vacuoles are referred to as the cell's storage sacs because they store food.

f)       Because of their function in photosynthesis, chloroplasts are referred to as the "kitchen" of the cell.

g)      The nucleus is the cell's control room, since it controls nearly all of the cell's activities.

Question 43:  How is bacterial cell different from onion peel?

Solution 43:   The main differences between a prokaryotic bacterial cell and a eukaryotic onion peel are mentioned below.

Question 44:  How do substances like carbon dioxide (C0₂) and water (H₂0) move in and out of the cell?

Solution 44:   Diffusion occurs when (C0₂) accumulates in high concentrations within the cell. C0₂ shifts from a high-concentration region to a low-concentration region within the cell.

When a cell is put in a solution with a particular solute concentration, the mechanism of osmosis causes water to pass in or out of the cell according to the concentration gradient.

Question 45:  How does Amoeba obtain its food?

Solution 45:   Phagocytosis is the mechanism by which amoeba obtains its food. It literally translates to "cell feeding." It is a popular feeding method used by Protozoa and lower Metazoa. It's also how white blood cells (leucocytes) in the blood engulf cellular debris and unwelcome pathogens (viruses and bacteria). In phagocytosis, a pocket forms on the plasma membrane, which is initially coated with actin-myosin, and the solid material is engulfed (e.g., bacteria, debris).

The phagosome, a membrane-enclosed vesicle that detaches from the cell surface (plasma membrane) and enters the cytoplasm, where lysosomal enzymes digest its contents. 

Question 46:  Name the two organelles in a plant cell that contain their own genetic material and ribosome.

Solution 46:   Mitochondria and plastids both have their own DNA and ribosomes, allowing them to produce their own protein and genetic material.

Question 47:  Why are lysosomes also known as scavengers of the cells?

Solution 47:   Endoplasmic reticulum synthesizes hydrolytic enzymes, which are found in lysosomes. These enzymes digest worn-out and under-performing cell organelles, allowing for the development of new replacements. They are known as scavengers, cellular housekeepers, and cell demolition squads because they remove cell debris.

Question 48:  Which cell organelle controls most of the activities of the cell?

Solution 48:   Natural phenomena and their incidence The nucleus is a large, spherical cellular component that is located in the centre of the cell. It is separated from the rest of the cell by two nuclear membranes that form a nuclear envelope. The nuclear envelope is a membrane system that connects two nuclear membranes and encloses a space between them (Endoplasmic Reticulum). The nucleolus, nuclear pore, and nucleoplasm are all included within it.

The following functions of the nucleus are very important.

1. All metabolic activities of the cell are regulated by the nucleus. The protoplasm of a cell dries up and dies when the nucleus is removed.
2. The cell cycle is regulated by this protein.
3. It is concerned with the transfer of genetic characteristics from parents to children.

Question 49:  Which kind of plastid is more common in

a)      Roots of the plant                           

b)      Leaves of the plant

c)       flowers and fruits 

Solution 49:

a)      Plant roots, they contain leucoplast, which are colorless plastids that function as food storage.

b)      Plant leaves, in which contain green chlorophyll for photosynthesis.

c)       Multicolored chromoplast in flowers and fruits attract pollinators.

Question 50:  Why do plant cells possess large sized vacuole?

Solution 50:  Since plant cells must store food and water, their vacuoles are larger than those of animal cells. This is due to the fact that plants lack the freedom to travel freely like animals. As a result, they have large vacuoles that function as a reservoir in adverse conditions.

Question 51:  How are chromatin, chromatid and chromosomes related to each other?

Solution 51:   Chromatin is a twisted mass of thread-like structures found within the nucleoplasm. They are made up of proteins and an acid called Deoxyribonucleic Acid (DNA). When a cell divides, the twisted mass of chromatin condenses into long threads and then chromosomes, which are rod-like bodies. The chromosomes contain DNA stretches that carry protein synthesis information.

The hereditary unit is referred to as a gene, and the hereditary material is referred to as DNA. A chromatid is one copy of a duplicated chromosome that is connected to the other copy by a centromere in most cases.

Question 52:  What are the consequences of the following conditions?
(a) A cell containing higher water concentration than the surrounding medium
(b) A cell having low water concentration than the surrounding medium.
(c) A cell having equal water concentration to its surrounding medium.

Solution 52:

a)      When a cell's water content is greater than that of the surrounding medium, exosmosis occurs in the cell as a result of the difference in water concentration between the cell and the surrounding medium, and the cell shrinks.

b)      Endosmosis occurs when a cell's water content is lower than the surrounding medium, causing the cell to swell.

c)       As long as isotonic conditions exist in the solvent, a cell with the same concentration as its surrounding medium will not shift.

Long Answer Type Questions............................

Question 53:  Draw a plant cell and label the parts which

a)      determines the function and development of the cell.

b)      packages materials coming from the endoplasmic reticulum.

c)       provides resistance to microbes to withstand hypotonic external media without bursting.

d)      is site for many biochemical reactions necessary to sustain life.

e)      is a fluid contained inside the nucleus. 

Solution 53: The following is a diagram of a plant cell and its components.

Question 54:  Illustrate only a plant cell as seen under electron microscope. How is it different from animal cell?

Solution 54:

The following are the major distinctions between a plant cell and an animal cell: 

i)        The presence of chloroplasts in the cell of a plant.

ii)       In plant cells, the presence of a large central vacuole.

iii)     The presence of a cell wall. 

Question 55:  Draw a neat labeled diagram of an animal cell.

Solution 55:   The following is a diagram of an animal cell.

Question 56:  Draw a well labeled diagram of an eukaryotic nucleus. How is it different form nucleoid?

Solution 56: The following is a diagram of a eukaryotic nucleus.

The main distinction between eukaryotic and prokaryotic nuclei is that a prokaryotic nucleus –

i)        is undifferentiated;

ii)       is not bound by the nuclear membrane;

iii)     lacks chromosome; and

iv)     lacks nucleolus and nucleoplasm. 

Question 57:  Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?

Solution 57:   Rough and smooth endoplasmic reticulum have significant variations.

Endoplasmic reticulum is responsible for the formation of membranes by synthesizing lipids (smooth endoplasmic reticulum) and proteins (rough endoplasmic reticulum). As a result, they aid membrane biogenesis.

Question 58:  In brief state what happens when
(a) Dry apricots are left for some time in pure water and later transferred to sugar solution?
(b) A red blood cell is kept in concentrated saline solution?
(c) The plasma-membrane of a cell breaks down?
(d) Rheo leaves are boiled in water first and then a drop of sugar syrup is put on it?
(e) Golgi apparatus is removed from the cell?

Solution 58:

a)      When dry apricots are put in pure water, they swell due to end osmosis (water moving inward), but when they are moved to a sugar solution, exosmosis (water moving outward) occurs, and they shrink.

b)      Exosmosis occurs when a Red Blood Cell is put in a concentrated saline solution, causing the RBCs to shrink due to excessive water loss.

c)       The cell organelles disperse when the plasma membrane, which serves as the cell's fundamental structural unit, breaks.

d)      Osmosis does not occur when Rheo leaves are first boiled in water and then sprayed with a drop of sugar syrup, leading to the death of the leaf's cells. This demonstrates that the living plasma membrane has selective permeability.

e)      The Golgi complex aids in the packaging, storage, and transition of ribosome-produced proteins. As a result, removing ribosomes will cause the cell to malfunction.

Question 59:  Draw a neat diagram of plant cell and label any three parts which differentiate it from animal cell.

Solution 59:   The following is a diagram of a plant cell and label of parts that distinguishes it from an animal cell.

i)        The cell wall is a distinguishing feature of plant cells.

ii)       Chloroplast is a component of plant cells that aids in photosynthesis. Since animal cells lack chloroplast, they are unable to synthesize their own food.

iii)     Plant cells have large vacuoles that hold the cell's excretory waste. Animal cells do not have vacuoles, or if they have present, they are tiny.