NCERT solutions for Science Exploration [English] Class 9 chapter 2 - Cell: The Building Block of Life [Latest edition]

Where does a cell come from?

How have technological interventions facilitated the creation of rich knowledge in understanding the world beyond the naked eye?

How is the cell structural and functional unit of life?

How does a cell multiply?

What if mung bean seeds are kept in a concentrated solution after soaking in water for 12 hours? What will happen to them?

What argument would you give for the necessity of a cell wall in plants, usually fixed in one place, versus in animals usually moving from one place to the other?

What consequences would you predict for a plant cell if its cell wall were to become as flexible as a cell membrane?

Why is it important to cut the two potato pieces in roughly equal size and measure their initial weight before placing them in different liquids?

Do white flowers contain any pigment? Give reasons.

Draw a well-labelled schematic diagram of a plant or an animal cell using these clues-

1. Nucleus appears as a dark and round body inside the cell.
2. ER spreads like a network of extended nuclear envelope.
3. Mitochondria and chloroplasts are rod-shaped.

You may refer to the given Fig.

Instead of many small ones, why does a cell not have a single giant mitochondrion? How does this relate to the concept of surface area?

If the skin cells start dividing by meiosis instead of mitosis, what do you think will happen to a cut on the skin?

Explore different ways by which cells maintain themselves.

Differentiate between the following pair of terms based on the clue given in parentheses:

Cell membrane and cell wall (permeability)

Differentiate between the following pair of terms based on the clue given in parentheses:

RER and SER (structure)

Differentiate between the following pair of terms based on the clue given in parentheses:

Chloroplasts and chromoplasts (pigments)

Two similar animal cells are placed in two different solutions:

• Cell X is placed in pure water.
• Cell Y is placed in a concentrated salt solution.

Cells are observed after some time. Cell X swells, and Cell Y shrinks. Which statement provides the correct explanation for the above observations?

Look at the diagram of a cell in the Fig. Identify the parts labelled from (a) to (g) and correctly match them with their functions given below:

1. Controlling all the activities of a cell.
2. Site of cellular respiration.
3. Storage organelle that also provides rigidity to the cell.
4. Separates the cell contents from surroundings.
5. Provides structural rigidity to the cell.
6. Packs and stores materials received from ER.
7. Helps in manufacturing food.

Which of the following option(s) of the pairs of cell organelles are correctly placed under the given categories?

Two students, Renu and Rohit, were having a discussion on the plastids. Renu emphasised that all parts of the plants, even roots, contain plastids. However, Rohit did not agree with the statement and told her that plastids are absent in plant roots since the roots are underground and do not need to perform photosynthesis. Who is correct? Justify your answer.

Mitochondria and chloroplasts are two important organelles in a plant cell. Discuss how these two organelles are structurally and functionally similar to each other.

Mitochondria and chloroplasts are two important organelles in a plant cell. Discuss how these two organelles are structurally and functionally different from each other.

Which of the following pairs of cell organelles contains DNA?

A researcher carried out an experiment in which she took two carrots of similar size. She placed one carrot in plain water and the other carrot in concentrated salt solution (Fig.). After 24 hours she recorded her observations.

1. What hypothesis does she want to test through this experiment?
2. What would you suggest for the improvement of this experiment?
3. Why does the carrot in plain water stay stiff and crunchy, but the carrot in concentrated salt solution become rubbery and limp?

Indicate the presence or absence of the following structures in bacterial and animal cells:

Identify the pair that incorrectly matches the cell organelle with its function.

What outcome do you expect, if all the mitochondria are removed from a eukaryotic cell?

Which phenomenon inhibits the formation of tumors in the human body? Can plants also develop tumors? Explain.

The cell membrane of a cell is made up of proteins and lipids. Which cell organelles help in the synthesis of cell membrane? Write the path of these compounds from their site of synthesis to the cell membrane and show this through a labelled diagram.

What would happen if gametes are formed by mitotic divisions?

Based on the above passage answer the following questions:

1. Which scientific concept has the farmer applied in the preservation of the farm produce?
2. How does the addition of high concentrations of salt and sugar create an environment that prevents the growth of spoilage-causing bacteria and fungi?
3. Suggest a healthy recipe of this kind for food preservation.
4. What are the scientific values addressed in this case?

What is the future of the development of synthetic cells using non-living chemicals? If a synthetic cell is developed, what may be the related ethical issues?