Cell The Building Block of Life Class 9 MCQ Questions Science Chapter 2

Directions: For Questions number (i) to (v), two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

Question 1.
Assertion (A): Plant cells do not burst when placed in a hypotonic solution.
Reason (R): Plant cells have a rigid cell wall that prevents them from bursting.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Explanation:
The rigid cell wall provides structural support and prevents the plant cell from bursting even when water enters by osmosis.

Question 2.
Assertion (A): Mitochondria are called the powerhouse of the cell.
Reason (R): Mitochondria contain chlorophyll for photosynthesis.
Answer:
(c) Assertion (A) is true, but Reason (R) is false.
Explanation:
Mitochondria produce ATP by breaking down glucose during cellular respiration. They do not contain chlorophyll; chlorophyll is found in chloroplasts.

Question 3.
Assertion (A): Meiosis produces four daughter cells with half the chromosome number.
Reason (R): During meiosis, the parent cell divides twice, one after the other.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Explanation:
The two rounds of division result in four cells, each with half the chromosomes.

Question 4.
Assertion (A): Cancer cells show contact inhibition.
Reason (R): Cancer cells divide uncontrollably and form tumours.
Answer:
(d) Assertion (A) is false, but Reason (R) is true.
Explanation:
Cancer cells actually lose contact inhibition, which is why they keep dividing uncontrollably and form tumours.

Question 5.
Assertion (A): Prokaryotic cells have a nucleoid region.
Reason (R): In prokaryotic cells, the genetic material is not enclosed within a nuclear membrane.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Explanation:
Since prokaryotic cells lack a nuclear membrane, their DNA is found in a region called the nucleoid.

1. A cell is usually too small to be seen by the ____________ eye.
Answer:
unaided

2. An electron microscope uses a beam of ____________ instead of light.
Answer:
electrons

3. The total magnification of a microscope = magnifying power of ____________ × magnifying power of ____________.
Answer:
eyepiece; objective lens

4. Robert Hooke named the small box-like compartments he saw in cork as ____________.
Answer:
cells

5. Resolution is the measure of ____________ of a microscope.
Answer:
clarity

6. The cell membrane is also called the ____________ membrane.
Answer:
plasma

7. The movement of water from a dilute solution to a concentrated solution through a selectively permeable membrane is called ____________.
Answer:
osmosis

8. Cells of plants, fungi, and bacteria have an additional layer called the ____________.
Answer:
cell wall

9. In the fluid-mosaic model, proteins in the membrane act like ____________.
Answer:
gatekeepers

10. Cellulose in our diet acts as ____________,helping in digestion.
Answer:
roughage

11. Bacteria lack a well-defined nucleus and are called ____________ cells.
Answer:
prokaryotic

12. The energy released in mitochondria is stored in the form of ____________.
Answer:
ATP (Adenosine Triphosphate)

13. The Golgi apparatus was first observed by ____________ in 1898.
Answer:
Camillo Golgi

14. The green pigment in chloroplasts is called ____________.
Answer:
chlorophyll

15. Chromoplasts help in attracting ____________ for pollination.
Answer:
pollinators

16. Cell division allows organisms to grow, repair damaged tissues, and ____________.
Answer:
reproduce

17. Mitosis produces ____________ genetically identical daughter cells.
Answer:
two

18. Meiosis produces gametes in the ____________ of males and of females.
Answer:
testes; ovaries

19. Errors in mitosis can lead to formation of ____________.
Answer:
tumours

20. In meiosis, the chromosome number in each daughter cell is reduced to ____________.
Answer:
half

21. Rudolf Virchow stated that new cells are formed from ____________ cells.
Answer:
pre-existing

22. Cancer cells keep dividing uncontrollably, leading to the formation of ____________.
Answer:
tumours

23. The ability of a single plant cell to develop into a complete plant is called ____________.
Answer:
totipotency

24. ____________ proposed the idea of totipotency in 1902.
Answer:
Gottlieb Haberlandt

25. Cell culture involves growing cells outside the body in a ____________ medium.
Answer:
nutrient-rich

1. Robert Hooke observed living cells for the first time.
Answer:
False.
Robert Hooke observed dead cork cells. He saw empty, box-like compartments in the thin slice of cork.

2. Electron microscopes can reveal structures at the nanometre scale.
Answer:
True

3. The near point of the human eye is about 25 cm.
Answer:
True

4. Animal cells have a cell wall.
Answer:
False.
Animal cells do not have a cell wall. Only plant cells, fungi, and bacteria have a cell wall.

5. The cell membrane allows all substances to pass through it freely.
Answer:
False.
The cell membrane is selectively permeable; it allows only certain substances to pass through.

6. When placed in a concentrated sugar solution, plant cells maintain their shape due to the cell wall.
Answer:
True.
The rigid cell wall prevents plant cells from shrinking, though the inner contents may pull away from the wall.

7. Lysosomes contain digestive enzymes.
Answer:
True.
Lysosomes are filled with enzymes that break down waste materials and damaged parts of the cell.

8. Plant cells do not contain mitochondria.
Answer:
False.
Plant cells contain both mitochondria and chloroplasts. Mitochondria are present in almost all eukaryotic cells.

9. Mitochondria and chloroplasts have their own DNA and ribosomes.
Answer:
True.
This suggests they share an evolutionary history with bacteria.

10. Mitosis is important for sexual reproduction.
Answer:
False.
Mitosis is important for growth, repair, and asexual reproduction. Meiosis is important for sexual reproduction.

11. In meiosis, the parent cell divides twice to form four daughter cells.
Answer:
True.

12. Errors in meiosis can cause genetic disorders.
Answer:
True.
Errors in meiosis may result in genetic disorders, developmental problems, early pregnancy loss, or reduced fertility.

13. According to Cell Theory, some living organisms are not made of cells.
Answer:
False.
Cell Theory states that all living organisms are made up of one or more cells.

14. Cancer cells show contact inhibition.
Answer:
False.
Cancer cells lose contact inhibition and keep dividing uncontrollably.

15. Plant cells do not show contact inhibition due to their rigid cell walls.
Answer:
True.

Cell The Building Block of Life Class 9 Match the Following