KSEEB Solutions for Class 8 Science Chapter 5 Study of Cells

Karnataka Board Class 8 Science Chapter 5 Study of Cells

KSEEB Class 8 Science Chapter 5 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statements. Choose the right answer.

Question 1.
A cell lacking in the nucleus, also lacks
(a) plasma membrane
(b) mitochondria
(c) chromosome
(d) vacuole.
Answer:
(c) chromosome

Question 2.
Cell wall is absent in the cell of this organism.
(a) mushroom
(b) moss
(c)fern
(d) mosquito
Answer:
(d) mosquito

Question 3.
Organelle of the cell, which releases energy through respiration is.
(a) Golgi-complex
(b) Mitochondria
(c) Lysosomes
(d) Chloroplast
Answer:
(b) Mitochondria

Question 4.
Which of the following part of a cell is non-living?
(a) Cell wall
(b) Mitochondria
(c) Cell membrane
(d) Lysosomes
Answer:
(a) Cell wall

Question 5.
One of the following is the smallest organelle in a cell
(a) Lysosomes
(b) Nucleolus
(c) ribosome
(d) chromosortie
Answer:
(c) ribosome

II. Fill in the blanks with suitable words:

Question 1.
The instrument that led to the understanding of cell is ……….
Answer:
electron microscope

Question 2.
The organelle which controls the various activities of the cell is …………
Answer:
nucleolus

Question 3.
The organelle, which is called the kitchen of the plant cell is ………
Answer:
chloroplast

Question 4.
The sites of protein synthesis in the cell are ……….
Answer:
ribosomes

Question 5.
The main chemical component of the cell wall is ………..
Answer:
cellulose

III. Match the following:

Answer:

1. (c)
2. (f)
3. (a)
4. (g)

IV. Answer the following questions:

Question 1.
What are genes? Mention their importance.
Answer:
The hereditary units present in the DNA molecules are called genes.
The importance of genes are :

• Each gene determines a particular characteristic of an organism, for example, the height of a person, colour of eyes, etc.
• Genes control the structure and functions of cell in all organisms.

Question 2.
Which organelle is responsible for the formation of spindle fibres during cell division?
Answer:
Centrioles are responsible for the formation of spindle fibres during cell division.

Question 3.
What is the role of chloroplast in a plant cell?
Answer:
Chloroplasts are the sites of photosynthesis in eukaryotic cells. They capture sunlight and store the light energy in the form of adenosine triphosphate and nicotinamide adenine triphosphate and dinucleotide phosphate molecules and it also plays a role in carbon fixation, fatty acid synthesis, amino acid synthesis and the immune response of plants.

Question 4.
Which are the organelles that are found more in number in the following cells?
Answer:

• Muscle cells – Mitochondria
• White blood cells – Leucoplasts
• Leaf cells – chloroplast
• Pancreatic cells – Lysosomes.

Question 5.
List any four differences between a plant cell and an animal cell.
Answer:

1. Plant cell
   • Cell wall is present
   • Vacuoles are present in plenty
   • and large in size
   • Chloroplast is present
   • The centriole is absent in higher plant cell
2. Animal cell
   • Cell wall is absent
   • Vacuoles are present fewer in number and
   • smaller in size
   • chloroplast is absent
   • The centriole is present in all animal cells.

Question 6.
What happens when an empty potato cup is kept in a trough with water? Why?
Answer:
water does not gather in an empty potato kept in a trough whit water because the potato cup is empty. It is the control step in the experimenter.

Question 7.
0.9% sodium chloride solution is good and balanced to RBC. A lab technician accidentally places a sample of RBC’s in 1.8% sodium chloride solution. What happens. Why?
Answer:

1. R.B.C. gets shrunken
2. No clinical examination cannot be taken place

Question 8.
Diagrams of two different cells are given below which one of the two is a plant cell? Support your answer.

1. Name the parts 1, 2, 3, and 4.
2. Write the function of 1 and 3.
3. Draw a labelled diagram of 4 as seen under an electron microscope.
4. Draw a diagram of a plant cell and label its parts.
Answer:
The plant cell is ‘b’ Because it has a cell wall and chloroplasts which are present only in plant cells
(i) 1. Golgi complex
2. Centrioles
3. Ribosomes
4. Chloroplast.
(ii) Functions of Golgi complex: The main function is to secrete chemicals required for cellular activities. Functions of Ribosomes:
They play an important role in protein synthesis.
(iii).

(iv).

(V). SUGGESTED ACTIVITIES:

Question 1.
Put dried raisins [dry grapes] in a dish with water. What is the change in raising after some time? Why?
Answer:
When raisins are placed in water, they absorb water by a process called osmosis and swell up [osmosis is the net movement of solvent molecules from the region of their higher concentration to a region of their lower concentration through a semi-permeable membrane]

Question 2.
Remove the shell of an egg by dissolving it in dilute hydrochloric acid. A thin outer skin new encloses the egg put the egg in water observe after a few minutes. What is your inference?
Answer:
By removing the shell which is mostly calcium carbonate by dissolving it in dilute hydrochloric acid, only a thin outer skin now encloses the egg and when we put this egg in pure water, after a few minutes we can see that he egg swells, because water passes into it by osmosis.

Question 3.
Place a similar de-shelled egg in a concentrated salt solution for a few minutes. Observe the changes. Record your observation giving reasons.
Answer:
When we place a de-shelled egg in a concentrated salt solution for a few minutes, the egg shrinks because water passes out of the egg solution into the salt solution because the salt solution is more concentrated.

KSEEB Class 8 Science Chapter 5 Additional Questions & Answers

Question 1.
What is a cell?
Answer:
A cell is a basic and structural and functional unit of living organisms.

Question 2.
Cells are called structural and functional units of an organism. Give reason.
Answer:
Cells perform all activities such as nutrition respiration and cell division which contribute to the overall growth of an organism. Hence cells are called structural and functional units of an organism.

Question 3
Who put forth the cell theory? Explain.
Answer:
Schleiden a German botanist and Schwann a German zoologist together put forth the ‘cell theory’ in 1839.

1. Cell theory States.
   • The body of a living organism is formed of one or more cells.
   • All the cells arise only from preexisting cells through cell division.

Question 4.
Draw a diagram of the Nerve cell, Red blood cells.
Answer:

Question 5.
What are the Functions of Nerve Cell and RBC?
Answer:
Nerve Cell: A Nerve cell is long and has a branched fiber-like structure. It carries messages from one part of the body to another.
RBC: A, red blood cells are biconcave and round in shape. It transports oxygen to different parts of the body of an organism.

Question 6.
Define micron?
Answer:
Micron is the most commonly used unit to express the size of the cell. One micron is equal to 1/1000 of a millimeter.

Question 7.
How to find the magnification produced by the compound microscope?
Answer:
The eyepiece in the compound microscope. An eyepiece lens is the one, through which we see. An objective lens is the one, which is facing the object.

Question 8.
Find the magnification, written on the eyepiece lens and the objective lens
Answer:
In a compound microscope, magnification of eyepiece lens is 10 × and that of the objective lens is 40 × the total magnification is 400 ×. It means, the object appears 400 times larger than its actual size.

Question 9.
Mention the functions of the cell membrane.
Answer:
The functions of the cell membrane are,

1. It Separates the interior of the cell from the outside environment.
2. Cell membrane forms the boundary of the cell.
3. It helps to maintain the shape of the cell.
4. It controls the movement of selected substances in to or out of it.

Question 10.
Write the functions of cell wall?
Answer:
The Functions of cell wall.

1. Cell wall gives a definite shape to the cell.
2. It gives Shape, Strength, Protection rigidity and support to the plant body.

Question 11.
Cell membrane is described as a semi-permeable membrane. Give reason.
Answer:
Cell membrane controls the movement of selected substances in to or out of it. Hence, the cell membrane is described as a semi permeable membrane.

Question 12.
Draw a neatly labelled Animal cell.
Answer:

Question 13.
Write an experiment to demonstrate diffusion.
Answer:

Procedure: Take some water in a beaker. Drop a crystal of potassium permanganate into it. observe the change in the color of the water. The purple color spread in water gradually and becomes uniformly colored. This process of movement of molecules is called ‘diffusion’. Diffusion is a process in which molecules move from a region of higher concentration to a region of lower concentration.

Question 14.
Write an experiment to demonstrate osmosis.
Answer:

Procedure: Make a cup-shaped cavity in the potato as shown in figure four Sugar solution into the cavity place the potato in a container half immersed in water. Mark the level of sugar solution. Leave it for about half an hour. Note the rise in the level of sugar solution.
It is due to the movement of water molecules from a region of higher concentration to a region of lower concentration through the semipermeable membrane of the. potato. This process is called ‘osmosis’ osmosis is a special kind of diffusion.

Question 15.
What is meant by active transport? Give example.
Answer:
Under certain conditions, molecules move from a region of lower concentration to a region of higher concentration with the expenditure of energy. This is known as active transport.
Ex: movement of sodium ions from blood to the heart muscle cell.

Question 16.
What is the function of cell wall?
Answer:
In-plant cells, in addition to the cell membrane, there is a cell wall. The cell wall provides shape strength, protection, and rigidity to the cell.

Question 17.
What is meant by cytoplasm?
Answer:
The cytoplasm is a jelly-like substance found within the cell membrane. It is the seat for most of the cellular activities.

Question 18.
What are organelles? Mention the types.
Answer:
A number of living substances in the cytoplasm that carry out life processes are called organelles. Or organelles are the specialized structure found in the cell. They carry out specific functions.
They are grouped under two categories. They are :

1. Membranous organelles.
2. Non membranes organelles.

Question 19.
What is the endoplasmic reticulum? Mention its function.
Answer:
Endoplasmic reticulum is a network of membranes which extends from the cell membrane to the nuclear membrane.
The functions of endoplasmic reticulum are,

1. It forms cytoskeieton and provides support to the cell.
2. It transports substances from one part of the cell to the other and from one cell to another.

Question 20.
Explain the structure of mitochondria.
Answer:
Mitochondria occur in various shapes, such as cylindrical, oval, and rod shapes. Each mitochondrion is bound by a double membrane. The outer membrane is smooth while inner membrane produces finger-like projection called cristae. The inner membrane encloses a mass known as a matrix. Mitochondria are the site of respiration in a cell.

Question 21.
Mitochondria are called the powerhouses of the cell. Give reason.
Answer:
Mitochondria are the sites of respiration in the cell where glucose is oxidized to release carbon dioxide water and energy. This energy is stored in the form of ATP. Hence. They are called the powerhouses of the cell.

Question 22.
What are the Golgi complex? Mention its function.
Answer:
Golgi complex consists of different types of structures, some are tube-like, a few are it the form of granules.
Function: The main function of the Golgi complex is to secrete chemicals required for cellular activities.

Question 23.
What are lysosomes? mention its function.
Answer:
Lysosomes are spherical sac-like cytoplasmic organelles which contain a variety of hydrolytic enzymes.
Function of Lysosomes are,

1. It helps in the digestion of organic substances present
2. Lysosomes destroy their own cell when it becomes old, weak, damaged, or diseased by autolysis.
3. Suicide bags of the cell.

Question 24.
Lysosomes are called as suicide bags. Give reason.
Answer:
Lysosomes destroy their own cell, when it becomes old weak damaged or diseased by autolysis. Hence they are called the suicide bags of the cell.

Question 25.
Write a short note on the structure of chloroplast found only in a plant cell.
Answer:
Each chloroplast is covered by a double membrane. The inner membrane encloses a matrix. Consists of stroma and grana. Grana has chlorophyll plays an important role in preparing food.

Question 26.
Write a short note a Ribosomes
Answer:
Ribosomes are the nonmembranous structure attached to the endoplasmic reticulum. They are also found attached to the nuclear membrane and even in the nucleus.
Functions of ribosomes are
1. They play an important role in protein synthesis.

Question 27.
Ribosomes are called as protein factories of the cell. Give reason
Answer:
Ribosomes play an important role in protein synthesis. Hence They are called protein factories of the cell.

Question 28.
Write a short note on centriole.
Answer:
Centrioles are found in some algae, fungi, and all animal cells. Two centrioles are located usually near the nucleus. Centrioles help during cell division.

Question 29.
What are vacuoles?
Answer:
In the cell found some membrane-covered cavities are called vacuoles. They are filled with a fluid called cell sap, Vacuoles are the structure which stores food, water, and waste products.

Question 30.
Draw a neat labelled diagram of the nucleus.
Answer:

Question 31.
Explain the structure of the nucleus.
Answer:
The nucleus is the largest organelle in the cell It is covered by a double membrane called nuclear membrane. Nucleoplasm has a network of a thread-like structure called chromatin. During cell division chromatin.
Undergoes coiling and becomes short and thick chromosomes contain genetic material called DNA which has genes. Genes determine the particular characteristic of an organism.

KSEEB Solutions for Class 8 Science