Chapter 7 Cell Structure and Function Continued Answers

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• Class 8
• Science
• cell: structure and function

Science_in_everyday_life Solutions for Class 8 Science Chapter 7 Cell: Structure And Function are provided here with simple step-by-step explanations. These solutions for Cell: Structure And Function are extremely popular among Class 8 students for Science Cell: Structure And Function Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science_in_everyday_life Book of Class 8 Science Chapter 7 are provided here for you for free. You will also love the ad-free experience on Meritnation's Science_in_everyday_life Solutions. All Science_in_everyday_life Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

Page No 111:

Question 1:

What is a cell? What variations do the cells of organisms show?

Answer:

A cell is the structural and functional unit of an organism. Cells in different organisms show variation in their shape, size and number.

Page No 111:

Question 2:

Differentiate between unicellular and multicellular organisms.

Answer:

Unicellular Organisms	Multicellular Organisms
Unicellular organisms are constituted of a single cell.	Organisms with many cells are multicellular organisms.
All activities are performed by a single cell.	All activities are performed different cells.
E.g. – Amoeba, Paramoecium	E.g. Human beings, cats, dogs etc.

Page No 111:

Question 3:

With the help of examples, show how the shape of a cell depends on the function it performs.

Answer:

Cell shape depends on their specific function, like skin cells are flat in shape as they cover a large surface area. As nerve cells carry messages between different parts of the body, they are elongated and muscle cells are thin and long to help in movement by their contraction and expansion.

Page No 111:

Question 4:

Differentiate between dry and wet mounts.

Answer:

Dry mount	Wet mount
Does not require water.	Water is used in their preparation.
Used for viewing inanimate objects.	Used for viewing live specimens like cells and organisms.

Page No 111:

Question 1:

Write one word for the following.

1.	Organisms whose body consists of a single cell	....................
2.	Organisms whose body consists of many cells	....................
3.	Placing the specimen on the slide	....................
4	Cells that have a well-defined nucleus with a nuclear membrane	....................
5.	Cells that lack a well-defined nucleus	....................

Answer:

1. Unicellular
2. Multicellular
3. Mounting
4. Eukaryotic cells
5. Prokaryotic cells

Page No 111:

Question 2:

Write two examples for each of the following.

1.	Commonly used staining dyes	....................	....................
2.	Kinds of plastids	....................	....................
3.	Form in which food is stored in leucoplasts	....................	....................
4.	Prokaryotes	....................	....................
5.	Eukaryotes	....................	....................

Answer:

1. Safranin, methylene blue
2. Chloroplasts, chromoplasts
3. Carbohydrates, fats
4. Bacteria, blue green algae
5. Cats, monkeys

Page No 111:

Question 1:

Write T for the true statement and F for the false one. Correct the false statement(s).
1. A multicellular organism is made up of many cells.
2. Cells exist in different shapes.
3. Cell wall is present in the animal cell.
4. Chloroplasts give colour to flowers and fruits.
5. Bacteria and blue-green algae are examples of eukaryotes.

Answer:

1. T. A multicellular organism is made up of many cells.
2. T. Cells exist in different shapes.
3. F. Cell wall is absent in animal cell and present in plant cell.
4. F. Chromoplasts give colour to flowers and fruits.
5. F. Bacteria and blue-green algae are examples of prokaryotes.

Page No 111:

Question 1:

The lowest level of organization in a multicellular organism is the
(a) cell
(b) organ
(c) tissue
(d) organ system

Answer:

(a) Cell
Cell is the smallest structural and functional unit of an organism.

Page No 111:

Question 2:

Skin cells cover a large area and are, therefore,
(a) elongated
(b) thin and long
(c) flat
(d) circular

Answer:

(c) Flat.
As skin cells cover a large surface area, they are flat in shape.

Page No 111:

Question 3:

The outer covering of a cell is the
(a) nuclear membrane
(b) endoplasmic reticulum
(c) cell membrane
(d) chloroplast

Answer:

(c) Cell membrane
The outer covering of the cell is called the cell membrane.

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Question 4:

Which of these is present only in animal cells?
(a) Cell wall
(b) Centrosome
(c) Ribosomes
(d) Cytoplasm

Answer:

(b) Centrosome
Centrosome is present only in animal cells.

Page No 111:

Question 5:

Which of the following is responsible for growth?
(a) Healing wounds
(b) Cell division
(c) Cell maturity
(d) Difference in shape

Answer:

(b) Cell division
Growth takes place because of cell division.

Page No 112:

Question 5:

What are cell organelles?

Answer:

A cell contains both living and non-living parts in it. The living parts of a cell having a definite structure, shape and function are called cell organelles.

Page No 112:

Question 6:

Name the different kinds of plastids.

Answer:

The different kinds of plastids are as follows:
(i) Chloroplasts that contain green pigment.
(ii) Chromoplasts that contain non-green, colourful pigment.
(iii) Leucoplasts, which are colourless.

Page No 112:

Question 7:

Differentiate between eukaryotic and prokaryotic cells.

Answer:

Eukaryotic cell	Prokaryotic cell
These cells having a well-defined nucleus surrounded by a nuclear membrane .	These cells lack a well-defined nucleus surrounded by nuclear membrane.
E.g. All organisms like human and animals other than bacteria, viruses or blue-green algae	E.g. Bacteria and blue-green algae

Page No 112:

Question 8:

How is cell division responsible for growth?

Answer:

When a cell reaches a certain size, it divides into two by the process of cell division. This cell division leads to an increase in the number of cells in the body, which is responsible for growth in organisms.

Page No 112:

Question 1:

With the help of examples, describe how cells vary in terms of shape, size, and number.

Answer:

Cells vary in shapes, sizes and number;

• Cells can have different shapes depending on their function. For example, nerve cells carrying messages between different parts of the body are elongated while muscle cells are thin and long as they help in movement.
• Cell sizes vary from a micrometre to few centimeters. Bacteria are the smallest cells ranging from size 0.1 to 0.5 micrometres. The Ostrich's egg is the largest cell of 170 millimeter in diameter.
• Unicellular organisms are those whose body consists of a single cell, which performs all functions of the body. E.g. Amoeba, Paramecium and bacteria. Some organisms are multicellular, whose body consists of many cells. E.g., animals and most plants. Thus, number of cells can vary in various organisms.

Page No 112:

Question 2:

With the help of a well-labelled diagram describe the different parts of a generalized cell.

Answer:

The main parts of a generalized cell are cell membrane, which is the outer covering, cytoplasm, a jelly like fluid containing several organelles and nucleus, which is the brain of the cell with chromosomes to transfer characteristics to the new cells. The organelles in cytoplasm are:

• Golgi apparatus made up of tubules, vesicles and vacuoles.
• Vacuoles are fluid filled space in a membrane.
• Lysosomes contain enzymes.
• Endoplasmic reticulum is a network of tubules and channels.
• Ribosomes are scattered in cytoplasm as small granular structures.
• Centrosome is present only in animal cells.
• Plastids are present only in plant cells and contain certain pigments. E.g., chloroplasts with green pigment, chromoplasts with non-green pigment and colourless leucoplasts.
• Mitochondria are tiny rod shaped or spherical bodies.

Page No 112:

Question 3:

What are the functions of different organelles in a cell?

Answer:

The functions of different organelles in a cell are:

• Golgi apparatus secrete chemical substances such as hormones, enzymes and proteins.
• Vacuoles are useful in storing excess water, minerals, pigments and other substances.
• Lysosomes contain digestive enzymes and can digest cells. In emergency, they can burst and destroy the cell.
• Endoplasmic reticulum helps in synthesis, storage and transportation of cell products.
• Ribosomes are sites of protein synthesis.
• Centrosome is responsible for initiating and regulating cell division.
• Plastids contain pigments such as chloroplasts that help plant to prepare food, chromoplasts that gives color to flowers and fruits and leucoplasts store food in form of carbohydrates, proteins and fats.
• Mitochondria, called the powerhouse of the cell, produces energy.

Page No 112:

Question 4:

Differentiate between plant and animal cells.

Answer:

Plant cell	Animal cell
Cell wall is present.	Cell wall is absent.
Cytoplasm is less dense.	Cytoplasm is more dense.
A large vacuole is present.	Vacuoles are usually absent and sized small if present.
Plastids are generally present.	Plastids are absent.
Centrosome is absent.	Centrosome is present.

Page No 112:

Question 5:

Describe stepwise how you would make a slide of an onion peel and observe it under a microscope.

Answer:

Steps to make a slide of an onion peel and observe under a microscope are

• Take onion, blade, forceps, glass slides and coverslip, iodine solution, glycerine, blotting paper, dropper and a microscope.
• Using forceps, separate the scales and peel one piece of onion scale.
• Place the scale on glass slide and add a drop of dilute iodine solution.
• Put a drop of glycerine on another glass slide, cover it with a coverslip and wipe the excess glycerine on sides with blotting paper and view under the microscope.
• Thick cell walls and large vacuoles, which are found in plant cells, can be observed.

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