Chapter 21: Building Blocks Of Life — Cell And Tissues

NIOS Class 10 Science Chapter 21 Question Answers

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

Ans:

(i) False. It allows only selected substances to pass into and out of the cell.

(ii) True.

(iii) False. Lysosomes are often called suicide bags.

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 intracellular distribution of molecules, enzymes, and nutrients within the cell. Ans:

(i) Cell wall

(ii) Plasma membrane

(iii) 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

Ans:

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.

Ans: All cells have three basic parts:

The cell membrane, which limits the cell and gives it shape.
DNA, which may be contained in a nucleus
A fluid called cytoplasm fills the space within the cell.

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

Ans:

(i) The bodies of all the living organisms are made of cells

(ii) New cells arise by division from pre-existing cells

(iii) The functions of the body are rebuilt from the 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?

Ans: Mitosis

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

Ans: 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 _______________

Ans:

(i) Mitosis

(ii) Meiosis

(iii) Mitosis

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

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

Ans: Testis and ovary.

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.

Ans:

(i) Meristematic

(ii) Fibrous tissue

(iii) Unstriped or unstriated muscle

(iv) 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

Ans:

(i) Nerve cell

(ii) Inner lining of stomach/inner lining of intestine/inner lining of trachea (wind pipe).

(iii) Wall of blood vessels/urinary bladder/uterus

(iv) Blood and lymph

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

Ans:

(A)

(i) Meristematic,

(3) Protective

(5) Conducting

(B)

(b) Connective

(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.

Ans:

Meristematic tissue
Apical meristem
Conducting tissue
Columnar epithelium
Tendon

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

Ans:

(i) Cytoplasm and protoplasm: Cytoplasm is the translucent, homogeneous, colloidal semi-fluid filling the space between the plasma membrane and nucleus. The nucleus and cytoplasm together form the protoplasm.
(ii) Cell wall and cell membrane: The Cell wall is the rigid and protective covering of plant cells. The cell membrane is the delicate membrane enclosing each cell.
(iii) Ribosomes and mitochondria: Ribosomes are where protein synthesis occurs, and mitochondria are the site of cellular respiration.
(iv) Blood and lymph: Blood is responsible for the transport of gases and chemical substances. Lymph protects from disease-causing germs.
(v) Cell and tissue: Cells are the functional units of living organisms, and tissues are formed by cells.
(vi) Cartilage and bone: Cartilage is a semi-transparent and elastic tissue that provides support. Bones are hard and a mass of non-living cells that also provide support, but also assist in movement.
(vii) Meristematic tissue and permanent tissue: Meristematic tissue is made of cells that are capable of dividing indefinitely. Permanent tissue is made of cells that have lost their ability to multiply

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.

Ans:

Mitochondria
Cell membrane limits the cell and gives it shape.
Mitochondria are called the powerhouse of the cell because energy is released and stored in them during respiration.
Without a nucleus, the cell will not be able to perform metabolic activities, as the nucleus is the master of the cell.
False. Plant cells have both chloroplasts and mitochondria.
Parts found only in plants are – Cell wall, Chloroplasts, and Leucoplasts. A part found only in animals is the centrosome.
Three types of permanent tissues: protective tissue, supportive tissue, and conducting tissue.
Protective tissue is made of cells with thick walls and occurs on the surface of leaves, stems, and roots. The epidermis in plants forms a protective layer that safeguards the cells below.
Stem cell technology is the technology of using stem cells that can divide through mitosis and differentiate into specialised cell types and can self-renew to produce more stem cells. It is used to obtain more cells that can replace damaged tissues, and for gene therapy.

4. Given below is an incomplete table relating to certain structures found in animal/ plant cells, 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 ________

Ans:

Structure	Location	Function
1 Chloroplast	2 Leaves	Photosynthesis
3 Centrosome	Animal cell	Spindle formation during cell division
Cell wall	4 Plant cell	5 Provides a definite shape and rigidity to the cell.
6 Cell membrane	7 Plant & animal cells	Selectively permeable membrane
Nucleolus	8 Nucleus	9 Contains the genetic material or DNA.

5. Given alongside is a figure of a cell.

(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 the part labelled ‘a’.

Ans:

It is an animal cell.
a- Cell membrane, b- ribosome, c- Mitochondria, d- Endoplasmic Reticulum and e- nucleus
Ribosomes are the site of photosynthesis.
Mitochondria are the powerhouse of the cell because energy is released and stored in them during respiration.

The cell membrane (part a) is selectively permeable, allowing only specific substances to pass in and out of the cell.