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Chapter 8: Cell - Structure and Functions


              Science

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                Chapter 8: Cell - Structure and Functions

             Class VIII

                    Exemplar Solutions

                                                MULTIPLE CHOICE QUESTIONS

Question 1

Choose the correct statement with respect to unicellular organisms:

(a) in unicellular organisms, tissues work in co-ordination to perform different functions.

(b) unicellular organisms do not require food.

(c) unicellular organisms respire and reproduce.

(d) all unicellular organisms move by cilia.

Answer 1 (c)

Question 2

 Majority of cells cannot be seen directly with our naked eyes because:

(a) organisms are generally unicellular

(b) cells are microscopic

(c) cells are present only inside the body

(d) cells are grouped into tissues

Answer 2 (b)

Question 3

 Read the different combinations of terms given below:

(a) cell wall, cell membrane, nucleus, plastid

 (b) cell wall, nucleus, ribosome, chromosome

(c) cell membrane, mitochondria, ribosome, chromosome

 (d) cell membrane, ribosome, mitochondria, chloroplast.

 The correct combination of terms with reference to an animal cell is _____.

Answer 3 (c)

Question  4

Which one of the following term is not a part of the nucleus?

 (a) ribosome     (c) chromosome

 (b) nucleolus     (d) gene

Answer 4 (a)

Question 5

 A suitable term for the various components of cells is

(a)tissue         (c) chromosomes

(b)cell organelles                   (d) genes

Answer 5 (b)

Question 6

 The jelly-like fluid substance present in cells is called

(a)protoplasm                            (c) chloroplast

(b) chromosome                        (d) cytoplasm

Answer 6 (d)

Question 7

 Read the following pairs of examples of organisms:

(a) moss and sponge                    (c) bacteria and blue-green alga

(b) yeast and Amoeba                  (d) penicillium and Spirogyra

The pair that belongs to the group prokaryotes is_____

Answer 7 (c)

Question 8

 Read the following terms and select the pair that is related to inheritance of characters.

(a) cell wall and cell membrane

(b) chromosome and mitochondria

(c) chloroplast and cell membrane

(d) chromosome and genes

Answer 8 (d)

Question 9

 Choose the correct statement:

(a) Genes are located in the chromosomes.

(b) Cell is located in the nucleus.

(c) Chromosomes are located in the nucleolus.

(d) Cell membrane surrounds the nucleus.

Answer 9 (a)

Question 10

 Green colour of leaves is due to presence of the pigment_____

 (a) chlorophyll     (c) mitochondira

 (b) ribosomes                       (d) chloroplast

Answer 10 (a)

Question 11

 The unit of measurement used for expressing dimension (size) of cells is:

(a) centimetre                        (c) micrometer

(b) millimetre                          (d) metre

Answer 11 (c)

Question 12

 The most important function of cell membrane is that it:

(a) controls the entry and exit of materials from cells.

(b) controls only the entry of materials into cells.

(c) controls only the exit of materials from cells.

(d) allows entry and exit of materials without any control.

Answer 12 (a)

Question 13

Paheli accidentally placed her hand over a flame and immediately pulled it back. She felt the sensation of heat and reacted due to the action of

 (a) blood cells                  (c) nerve cells

 (b) skin surface                (d) nucleus of cells

Answer 13 (c)

Question 14

 Of the following parts of a cell listed below, name the part that is common to plant cell, animal cell and a bacterial cell.

(a) chloroplast                     (c) cell membrane

 (b) cell wall                         (d) nucleus

Answer 14 (c)

 Question 15

 The thread-like structures present in the nucleus are

 (a) nucleolus                        (c) genes

 (b) chromosomes                 (d) ribosomes

Answer 15 (b)

Question 16

 Identify the statement which is true for cells.

(a) Cells can be easily seen with naked eyes.

(b) Insect’s egg is not a cell.

(c) A single cell can perform all the functions in a unicellular organism.

(d) The size and shape of cells is uniform in multicellular organisms

Answer 16 (c)

Question 17

 Which of the following is not a cell?

 (a) Red Blood Corpuscle (RBC)

 (b) bacterium

 (c) spermatozoa

 (d) virus

Answer 17 (d)

 

Question 18

 Which of the following feature will help you in distinguishing a plant cell from an animal cell?

 (a) cell wall                           (c) mitochondria

(b) cell membrane                 (d) nucleus

Answer 18 (a)

Question 19

Under a microscope Paheli observes a cell that has a cell wall but no distinct nucleus. The cell that she observes is

(a) a plant cell                         (c) a nerve cell

(b) an animal cell                    (d) a bacterial cell

Answer 19 (d)

Question 20

 Cheek cells do not have _______

 (a) cell membrane                     (c) golgi apparatus

 (b) nucleus     (d) plastids

Answer 20 (d)

Question 21

 Identify the correct statement.

(a) Tissue is a group of dissimilar cells.

(b) An organ consists of similar cells.

(c) Vacuoles are not found in plant cells.

(d) Prokaryotes do not have nucleus.

Answer 21 (d)

Question 22

 Which of the following statements are true for eukaryotic cells?

  • They do not have a nuclear membrane.
  • They have a well organised nucleus.
  • They have a nuclear membrane.
  • Blue green algae are eukaryotic cells.

(a) ii and iv                      (b) ii and iii

(c) i and ii                        (d) i and iv

Answer 22 (b)

Question 23

 Identify the correct statement about cells.

(a) All the cells have nucleus.

(b) Cells of an organ have similar structure.

(c) Cells of a tissue have similar structure.

(d) Shape of all types of cells is round.

Answer  23 (c)

Question 24

The table given below has certain terms and four blank spaces named A, B, C and D.

 

 

  Cell

 

             Feature/Part

 

            Functions

 

 

Amoeba

Plant Cell

C

Nerve Cell

 

 

A

Plastid

Spindle Shaped

D

 

Movement

B

Contraction

Stimuli and response

 

From the options given below choose the correct combination of terms.

(a) A-Pseudopodia; B-Respirations; C-Muscle cell; D-Branched

(b) A-Pseudopodia; B-Photosynthesis; C-Muscle cell; D-Branched

(c) A-Contractile vacuole; B-Photosynthesis; C-Blood cell; D-Spindle shaped

(d) A-Pseudopodia; B-Photosynthesis; C-Cheek cell; D-Spindle shaped

Answer 24 (b)

 

VERY SHORT ANSWER QUESTIONS

Question 25

 In leaves, name the cell organelle and pigment that is responsible for green colour.

Answer 25

Chloroplast and chlorophyll

Question 26

 The instrument used to observe cells is ________

Answer 26

Microscope

Question 27

 We do not sense any pain when we clip our nails or cut our hair. Why?

Answer 27

Nails and hair are both made up of dead cells. They do not have nerve cells. Hence we don’t feel the pain when they are cut.

Question 28

 In a cell, where are the genes located?

Answer 28

Nucleus/chromosomes.

Question 29

 Amoeba and Paramecium belong to which category of organisms?

 Answer 29

Unicellular and Eukaryotic/Protozoan.

Question 30

 What are the functions of cell wall in plant cells?

Answer 30

Cell wall protects the cell contents, gives shape to the cell.

 

 

SHORT ANSWER QUESTIONS

Questions 31

 Is the following statement correct? If it is wrong, correct the statement

 Statement : "Unicellular organisms do not respire, only multicellular organisms respire"

Answer 31

No, the statement is wrong.

Both unicellular and multicellular organisms respire/all organisms respire.

Question 32

Match the terms given in column I with their functions given in column II and fill the blanks given below the table:

 A-_____; B-______; C-______; D-______

 

 

 

                Column I

       Column II

A.    Chloroplast

B.    Cell membrane

C.   Nucleus

D.   Chromosome

(i)            Carries hereditary characters

(ii)           Controls the activities of cells

(iii)          Site of photosynthesis

(iv)         Controls the movement of materials into and out of cells

 

 

Answer 32

Ans. A-iii, B-iv; C-ii; D-i

 

Question 35

 Classify the following terms into cells, tissues and organs and write in the tabular column given below.

                  RBC, WBC, Nerve cell, blood, muscle, blood vessels, brain, heart, hand

 

Answer 35

 

 

              Cell

 

                      Tissue

 

 

                   Organ

 

 

RBC

WBC

Nerve Cell

 

Blood

Muscle

Nerve

 

 

Blood vessels

Heart

Hand

Brain

 

Question 36

 Read the following statements and write the appropriate term against each statement.

  1. I control the functions of a cell. Who am I? . .................
  2. I am like a policeman. I do not allow anything and everything to get in and out of the cell. Who am I? . .................
  3. I transfer characters from parents to offsprings. Who am I? ..................

Answer 36

A- Nucleus; B-Cell membrane; C-Genes/Chromosomes

Question 37

 Fill in the blanks with the terms given in the box below:

                          Nucleus, chromosomes, cell wall, cell membrane, protoplasm,

           cytoplasm, ribosome, cell organelles

The outermost layer of plant cells is the (a)               beneath which is the (b)                  . The term (c)               refers to the jelly-like substance containing all the (d)                 . The

(e)                contains thread-like structures called (f)                .

Answer 37

 a-cell wall; b-cell membrane; c-cytoplasm; d-cell organelles; e-nucleus; f-chromosomes.

 

LONG ANSWER QUESTIONS

Question 38

Cells consist of many organelles, yet we do not call any of these organelles as structural and functional unit of living organisms. Explain.

Answer 38

Although cell organelles have specific structures and perform specific functions but they cannot be called structural and functional units of living organisms. This is so because they can perform their functions only when they are within a living cell. They cannot function outside the cell as an independent unit.

Question 39

Why do plant cells have an additional layer surrounding the cell membrane? What is this layer known as?

Answer 39

As plants cannot move they need protection against variations in temperature, high wind speed, atmospheric moisture, etc. Therefore, for protection plant cell membrane. This layer is called the cell wall. Plant cells have an additional layer surrounding the cell membrane.

Question 40

The size of the cells of an organism has no relation with the size of its body. Do you agree? Give reason for your answer.

Answer 40

  • I agree because of the cells in the body of an elephant is not necessarily bigger than those in a rat, it is not true that bigger organisms have cells of bigger size in their body.
  • The size of the cell in an organism is related to the function to performs. For example, the nerve cells in both, the elephant and the rat is are long and branched. They perform the same function, that of transferring messages.

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