Chapter 21: BUILDING BLOCKS OF LIFE — CELL AND TISSUES

Chapter 21: Building Blocks of Life - Cell and Tissues Class 10 Science and Technology (212) NIOS Textbook Solutions

Chapter 21. BUILDING BLOCKS OF LIFE — CELL AND TISSUES

INTEXT QUESTIONS 21.1

1. Mention whether the following statements are true (T) or false (F). Rewrite the wrong statements correctly.

i) Cell membrane permits inflow and outflow of all molecules. T/F

ii) Chloroplast and not chlorophyll is an organelle. T/F

iii) Ribosomes are often called suicide bags. T/F

Answer: (i) Cell membrane permits inflow and outflow of all molecules. → False
[ Cell membrane permits inflow and outflow of selected substances only (it is selectively permeable).]

(ii) Chloroplast and not chlorophyll is an organelle. → True
[ Chloroplast is a cell organelle, while chlorophyll is the green pigment present inside chloroplast.]

(iii) Ribosomes are often called suicide bags. → False
[ Lysosomes are often called suicide bags of the cell because they contain digestive enzymes.]

2. Name the part of the cell which:

(i) provides rigidity to the plant cell. _____________

(ii) bounds semi-fluid content of the cell. _____________

(iii) helps in intra-cellular distribution of molecules, enzymes and nutrients within the cell. _____________

Answer: (i) Provides rigidity to the plant cell → Cell wall.

(ii) Bounds semi-fluid content of the cell → plasma membrane (Cell membrane).

(iii) Helps in intra-cellular distribution of molecules, enzymes and nutrients within the cell →Cytoplasm.

3. Match the following items in Column A with those in Column B.

                Column A                            Column B

1. Master of the cell                       a. chloroplast

2. Powerhouse of the cell             b. endoplasmic reticulum

3. Protein factories of the cell      c. mitochondria

4. Kitchen of the cell                      d. nucleus

5. Circulatory system of the cell  e. ribosome

Answer: The correct matching is:

Column A	Column B
1. Master of the cell	d. Nucleus
2. Powerhouse of the cell	c. Mitochondria
3. Protein factories of the cell	e. Ribosome
4. Kitchen of the cell	a. Chloroplast
5. Circulatory system of the cell	b. Endoplasmic reticulum

4. All cells of organisms have 3 basic parts. Draw and name them.

Answer: Photo

5. Explain in your own words the three salient points of the cell theory in one sentence each.

Answer: The three salient points of the cell theory are:

(i) Body of all the living organisms are made of cells.

(ii) New cells arise by division of pre-existing cells.

(iii) Function of the body rebuilt from functions of its cells.

INTEXT QUESTIONS 21.2

1. A seedling grows into a small plant. What kind of division causes this — mitosis or meiosis?

Answer: A seedling grows into a small plant by mitosis.

2. Our nails have to be cut occasionally. Which kind of cell division makes the nails long?

Answer: Our nails become long due to mitosis.

3. Name the type of cell division that occurs during the following events:

(i) repair of skin and injury _______________

(ii) formation of eggs and sperms in animals _______________

(iii) increase in the length of stem in plants _______________

Answer: (i) repair of skin and injury mitosis .

(ii) formation of eggs and sperms in animals meiosis .

(iii) increase in the length of stem in plants mitosis.

4. Out of the following organs where does meiosis occur?

Hair, liver, testis (male reproductive organ), cheek cell, ovary (female reproductive organ)

Answer: Meiosis occurs in:
 (i) Testis (male reproductive organ)
 (ii)Ovary (female reproductive organ)

INTEXT QUESTIONS 21.3

1. Name the following:

(i) The kind of tissues present at the stem tip of a flowering plant.

(ii) The tissue which connects muscle to the bone.

(iii) The kind of tissue which forms the inner lining of blood vessels.

(iv) Undifferentiated cells which can divide through mitosis and differentiate into specialized cell types.

Answer: (i) Meristematic (ii) Fibrous tissue (ii) Unstriped or unstraited muscle (iii) Stem cells

2. Where do you find the following in the human body?

(i) Nodes of Ranvier

(ii) Ciliated epithelium

(iii) Smooth muscles

(iv) Fluid connective tissue

Answer: (i) Nodes of Ranvier: Found on nerve cells (neurons) along the axon

(ii) Ciliated epithelium: Found in inner lining of trachea (windpipe) / respiratory tract

(iii) Smooth muscles : Found in walls of blood vessels, urinary bladder, and uterus

(iv) Fluid connective tissue:  Found in blood and lymph.

3. In the flow chart given below fill in the blanks

Photo

Answer: (A) (i) Meristematic, (3) Protective (5) Conducting

(B) (b) Connective (c) Muscular (d) Nervous (e) Skin (f) Limb

TERMINAL EXERCISES

1. Name the kind of plant tissue found

(i) at the growing parts of the plant.

(ii) at the root tip.

(iii) in vascular bundles.

(iv) in the inner lining of the intestine.

(v) Connecting the adjacent muscle fibres.

Answer: (i) Meristematic tissue
(ii) Apical meristem
(iii) Vascular tissue (Xylem & Phloem)
(iv) Epithelial tissue (columnar epithelium)
(v) Connective tissue (areolar tissue)

2. State one point of difference between the following (one key difference only).

(i) Cytoplasm and protoplasm

(ii) Cell wall and cell membrane

(iii) Ribosomes and mitochondria

(iv) Blood and lymph

(v) Cell and tissue

(vi) Cartilage and bone

(vii) Meristematic tissue and permanent tissue.

Answer: (i) Cytoplasm and Protoplasm

Difference : Cytoplasm is the part of the cell excluding nucleus, while protoplasm includes cytoplasm + nucleus.

(ii) Cell wall and Cell membrane

Difference : Cell wall is fully permeable and rigid, while cell membrane is selectively permeable and flexible.

(iii) Ribosomes and Mitochondria

Difference : Ribosomes are sites of protein synthesis, while mitochondria are sites of cellular respiration (energy production).

(iv) Blood and Lymph

Difference: Blood contains RBCs, WBCs and platelets, while lymph mainly contains WBCs and no RBCs/platelets.

(v) Cell and Tissue

Difference : A cell is the basic structural unit, while a tissue is a group of similar cells performing a function.

(vi) Cartilage and Bone

Difference : Cartilage is flexible and softer, while bone is hard and rigid due to calcium deposition.

(vii) Meristematic tissue and Permanent tissue

Difference : Meristematic tissue consists of actively dividing cells, while permanent tissue consists of non-dividing, differentiated cells.

3. Answer these questions.

(i) Which cell organelle is responsible for the release of energy in the form of ATP?

(ii) What is the significance of cell membrane?

(iii) Why are mitochondria known as the ‘powerhouse’ of the cell?

(iv) What will happen to a cell if its nucleus is removed?

(v) Is this statement true or false: Plant cells have chloroplasts, but no mitochondria? Justify your answer.

(vi) Mention three features found only in plant cells and one found only in animal cells.

(vii) Name three kinds of permanent tissues found in plants. Write one function of each.

(viii) What is a protective tissue? Why is epidermis considered as a protective tissue?

(ix) What is stem cell technology? Give its two uses in disease control.

Answer:  (i) Mitochondria release energy in the form of ATP.

(ii) The cell membrane acts as a selective barrier, controlling the entry and exit of substances in and out of the cell, and thus helps maintain the cell’s internal balance.

(iii) Mitochondria are called powerhouse because they produce energy (ATP) during cellular respiration.

(iv) The cell will stop functioning, cannot divide, and eventually die, because the nucleus controls all metabolic activities and contains genetic material .

(v) False. 

Plant cells have both chloroplasts (for photosynthesis) and mitochondria (for cellular respiration).

(vi) Plant cells only: Cell wall, chloroplasts, large central vacuole

Animal cells only: Centrioles

(vii)

Tissue	Function
Parenchyma	Storage of food
Collenchyma	Provides flexibility and mechanical support
Sclerenchyma	Provides rigidity and strength

(viii)  A protective tissue covers and protects the plant body. The epidermis is a single outer layer covering the entire plant surface. It prevents water loss, mechanical injury and entry of pathogens, so it is considered a protective tissue.

(ix) Stem cell technology uses undifferentiated cells capable of developing into any cell type.
Two uses: (i) Treatment of blood cancers (leukaemia) via bone marrow transplant

(ii) Regeneration of damaged tissues/organs in diseases like diabetes and Parkinson's

4. Given below is an incomplete table relating to certain structures found in animal/ plant cell, their location and function. Study the table and then give the appropriate answer in terms of structure, location and function for the blanks numbered from 1 to 9.

Structure	Location	Function
1. ………………..	2.   ……………………..	Photosynthesis
3. …………..	Animal cell	Spindle formation during cell division
Cell wall	4.  ……………..	5.  ……………..
6.  ……………….	7. ……………….	Selectively permeable membrane
Nucleolus	8. ………………..	9.  ……………….

Answer:

Structure	Location	Function
1. Chloroplast	2. Plant cell (green parts)	Photosynthesis
3. Centrosome (Centriole)	Animal cell	Spindle formation during cell division
Cell wall	4. Plant cell (outermost layer)	5. Provides rigidity, shape, and mechanical support
6. Cell membrane (Plasma membrane)	7. Outer boundary of all cells (animal/plant)	Selectively permeable membrane
Nucleolus	8. Inside the nucleus	9. Synthesizes ribosomal RNA (rRNA) and forms ribosomes

5. Given alongside is a figure of a cell.

Photo

(i) Is this a plant cell or an animal cell?

(ii) Name the parts labelled a, b, c, d and e.

(iii) Which of these parts help(s) in protein synthesis?

(iv) Which of these parts is also known as the powerhouse of the cell? Give reasons in support of your answer.

(v) Write the most important function of part labelled ‘a’.

Answer: (i) It is an Animal cell .

(ii) (a) Cell Membrane (Or Plasma Membrane)

(b) Ribosomes .

(c) Mitochondia.

(d) Endoplasm reticulum.

(e) Nucleolus.

(iii) (d) Endoplasm reticulum.

(iv) Mitochondrion .

It conducts cellular respiration to break down food and release energy in the form of ATP molecules, which the cell uses to perform various activities.

(v)  (a) Cell membrane .

The primary function of the cell membrane is to control and regulate the entry and exit of substances into and out of the cell because it is selectively permeable .

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