KSEEB Solutions for Class 8 Science Chapter 5 Study of Cells

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Karnataka State Syllabus Class 8 Science Chapter 5 Study of Cells

KSEEB Class 8 Science Study of Cells Textbook Exercise Questions and Answers

I. Four alternatives are given to each of the following incomplete statements/ questions. 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.
The 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) Lysosome
(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) lysosome
Answer:
(a) cell wall

Question 5.
One of the following is the smallest organelle in a cell
(a) lysosome
(b) nucleolus
(c) ribosome
(d) chromosome
Answer:
(c) ribosome

II. Fill in the blanks with suitable words:

1. The instrument that led to the understanding of the cell was ………………………..
2. The organelle, which controls the various activities of the cell, is ………………………..
3. The organelle, which is called the Kitchen of the plant cell” is ………………………..
4. The site of protein synthesis in the cell is ………………………..
5. The main chemical component of the cell wall is ………………………..

Answer:

1. electron microscope
2. nucleus
3. chloroplast
4. ribosomes
5. cellulose

III. Match the following:

Answers:
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 molecule are called genes. The importance of genes are:-
1. Each gene determines a particular characteristic of an organism. For example, the height of a person, the colour of eyes, etc.
2. Genes control the structure and functions of cells in all organisms.

Question 2.
Which organelle is an animal cell that is useful during cell divisions?
Answer:
Centrioles are responsible for the formation of spindle fibers during cell division.

Question 3.
What is the role of chloroplast in a plant cell?
Answer:
To carry out photosynthesis as they are in the chloroplast.

Question 4.
Which are the organelles that are found in more numbers in the following cells?
(a) muscle cells
(b) white blood cells
(c) leaf cells
(d) pancreatic cells
Answer:
(a) Muscle cells — mitochondria
(b) White blood cells — leucoplasts
(c) leaf cells — chloroplasts
(d) pancreatic cells — Lysosomes

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

• The cell wall is present.
• Vacuoles, are present in plenty and are large in size.
• The chloroplast is present.
• The centriole is absent in higher plant cells.

Animal cell:

• The cell wall is absent.
• Vacuoles are present fewer in number and smaller in size.
• The chloroplast is absent.
• 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 cup kept in a trough with water because the potato cup is empty. It is the control setup in the experiment

Question 7.
0.9% sodium chloride solution is good and balanced to RBC. A lab technician accidentally places a sample RBCs of in 1.8% sodium chloride solution. What happens? Why?
Answer:
When samples of RBCs 1.8% sodium chloride solution, the cells lose their normal biconcave shape. Undergoing collapse [leading to cremation] due to the rapid osmotic effect of water.

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

1. Name the parts 1, 2, 3, and 4
2. Write the functions of 1 and 3.
3. Draw a diagram to show the structure of 4 and label the parts.

Question 9.
Draw a diagram of a plant cell and label the parts.

Answer:
1. Plant cell is cell

(b) because it has a dell wall and chloroplasts which are present only in a plant cell.
1. Golgi complex
2. centrioles
3. ribosomes
4. Chloroplast

2. The functions of
(1) Golgi complex: secrete chemicals required for cellular activities.
(2) ribosome: the role of the ribosome is to synthesize the protein.

3.

Each chloroplast is covered by a double membrane. The inner membrane encloses matrix-stroma and grains. Grana has chlorophyll

Question 10.
Draw a neat labelled diagram of a plant cell.
Answer:

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 now 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 the places 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 Study of Cells Additional Questions and Answers

I.

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

Question 2.
Cells are called structural and functional units of an organism. Give reason.
Answer:
Cells perform 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.

Question 3.
Who put forth the cell theory? Mention the year?
Answer:
Schleiden, a German botanist, and Schwann, a German Zoologist together put forth the cell theory in 1839.

Question 4.
What are the principles of cell theory?
Answer:

• The body of Ali living organisms is formed by one or more cells.
• All the cells arise only from preexisting cells through cell division.

Question 5.
Cells have different shapes to carry out different functions. Substantiate the above statement.
Answer:
A nerve cell is long and has branched fiber-like structures. A nerve cell carries messages from one part of the body to another, whereas a red blood cell is biconcave and round in shape. It transports oxygen to different parts of the body Qf an organism. Thus ceils have different shapes to carry out different functions.

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

Question 7.
In a compound microscope, the magnification of eyepiece lens is 10 X and that of the objective lens is 40 X. What do you mean by this?
Answer:
This means that the total magnification is 400 x ie. the object appears 400 times larger than its actual size.

Question 8.
What are the functions of the cell wall?
Answer:

• Cell wail gives a definite shape to the cell.
• It gives shape, strength, protection rigidity, and support to the plant body.

Question 9.
Mention the functions of the cell membrane.
Answer:

• It separates the interior of the cell from the outside environment.
• It forms the boundary of the cell.
• It helps to maintain the shape of the cell.
• It controls the movement of the selected substance into or out of it.

Question 10.
The cell membrane is described as a semi-permeable membrane. Why?
Answer:
Cell membrane controls the movement of selected substances into or out of it. Hence, the cell membrane is described as a semi-permeable membrane.

Question 11.
What is meant by diffusion?
Answer:
Diffusion is a process in which molecules move from a region of higher concentration to a region of lower concentration.

Question 12.
What is meant by Osmosis?
Answer:
Osmosis is a special kind of diffusion that involves the movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.

Question 13.
What is meant by active transport?
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 14.
What are organelles? Mention the types.
Answer:
A number of living substances in the cytoplasm that carry out life processes are called organelles.
The two types are:

• Membranous organelles
• Non-membranous organelles.

Question 15.
What is Endoplasmic reticulum? Mention its function.
Answer:
The endoplasmic reticulum is a network of membranes which extends from the cell membrane to the nuclear membrane Functions:

• It forms the cytoskeleton and provides support to the cell.
• It transports substances from one part of the cell to the other and from one cell to another.

Question 16.
Mitochondria are called as the powerhouses of the cell.
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 ATR Hence, they are called the powerhouses of the cell.

Question 17.
What is the Golgi complex? Mention its function.
Answer:
Golgi complex is a sac-like organelle having a number of tube-like structures and a few in the form of granules. The main function is to secrete the chemicals required for cellular activities.

Question 18.
What are lysosomes? Mention their function.
Answer:
Lysosomes are spherical sac-like cytoplasmic organelles which contain a variety of hydrolytic enzymes.
Function: help in digestion of organic substances present in the cell.

Question 19.
Lysosomes are called as suicide bags. Why?
Answer:
Lysosomes destroy their own cell, when it becomes old, weak, damaged, or diseased by autolysis. Hence they are called, as the suicide bags of the cell.

Question 20.
Write an experiment to demonstrate osmosis.

Answer:
Make a cup-shaped Cavity in a cut potato as shown in the figure. Pour some sugar

Question 21.
Draw a neat labeled diagram of mitochondrial.
Answer:

solution into the cavity. Place the potato in a container half immersed in water. Mark the level of sugar solution. Leave it for half an hour. Note the rise on the level of sugar solution. This is due to the movement of water molecules from a region of higher concentration to a region of lower concentration through semi-permeable membrane of potato.

Question 22.
Draw a neat labeled diagram of the chloroplast.
Answer:

Question 23.
Draw a neat labeled diagram of the Animal cell.
Answer:

Question 24.
Draw a neat labeled diagram of Nucleus.
Answer:

II. Fill in the blanks:

1. A red blood cell is and in shape.
2. The cell membrane is also called as
3. Cell the wall is composed of
4. Plastids without colouring pigments are called
5. Plastids with colouring pigments are called
6. Centrioles are located near the
7. Vacuoles are filled with a fluid called
8. The largest organelle in a cell is
9. Every human cell has chromosomes
10. Mammalian cells do not contain nucleus at maturity.

Answers:

1. biconcave and round
2. plasma membrane
3. cellulose
4. leucoplast
5. chromoplast
6. nucleus
7. cell sap
8. nucleus
9. 46
10. red blood

III. Choose the most appropriate alternative.

Question 1.
Robert Hook identified
(a) molecule
(b) an atom
(c) a cell
(d) an organ
Answer:
(c) a cell

Question 2.
Study of the cell is called
(a) Cytology
(b) Histology
(c) Biology
(d) Microbiology
Answer:
(a) Cytology

Question 3.
Robert Hook gave the name ‘cell’ when he was observing
(a) a piece of Cork
(b) section of skin
(c) section of onion
(d) section of stem
Answer:
(a) a piece of Cork

Question 4.
A tadpole loses its tail because of the activity of
(a) vacuole
(b) centrosome
(c) nucleus
(d) lysosome
Answer:
(d) lysosome

Question 5.
Tonoplast is the membrane of
(a) chloroplast
(b) vacuole
(c) lysosome
(d) Golgi body
Answer:
(b) vacuole

Question 6.
An annual cell does not have
(a) Centrosome and Nucleus
(b) ribosome and centriole
(c) chloroplast and cell wall
(d) Endoplasmic reticulum and vacuole
Answer:
(c) chloroplast and cell wall

Question 7.
Ribosomes are made up of
(a) Ribosomes and DNA
(b) Protein and Nucleolus
(c) RNA and Protein
(d) DNA and Protein
Answer:
(c) RNA and Protein

Question 8.
Two regions of the chloroplast are
(a) matrix and cell sap
(b) Cristae and granny
(c) Granna and stroma
(d) Cristae and stroma
Answer:
(c) Granna and stroma

Question 9.
A non-membraneous organelle among the following
(a) Nucleolus
(b) Nucleus
(c) Leucoplast
(d) Lysosome
Answer:
(a) Nucleolus

Question 10.
A membraneous organelle among the following
(a) Nucleolus
(b) Nucleus
(c) Ribosome
(d) Centriole
Answer:
(b) Nucleus

IV. Match the following:
A – B
1. cytoskeleton – (a) contractile vacuole
2. site of respiration – (b) Nucleolus
3. removal of excess of water – (c) genes
4. involves protein synthesis – (d) Endoplasmic reticulum
5. responsible for characteristic – (e) mitochondria of organism, (f) plastid
Answers:
1. d
2. e
3. a
4. b
5. c