The cell-Its Structure and Functions Chapter 1 of D.A.V School Science book.

A. Fill in the blanks.

1. All living organisms are made up of cells.

2. The cell wall provides rigidity and protection to the plant cell.

3. All cellular activities are controlled by the nucleus.

4. The mitochondria is known as the powerhouse of the cell.

5. Tissue is a group of cells performing a specific function.

6. It was Robert hook who observed cells for the first time.

B. Match the following.

1. Golgi Complex- Packaging center

2. Ribosomes- Protein synthesis

3. Chromosomes- Genes

4. Dead cells- Cork

5. Photosynthesis- Chloroplasts

C. Tick the correct options.

1. The cell organelle, which acts as a storage bag for a cell, is known as the-----

Ans- vacuole

2. Hen's egg is-----

Ans- a single cell

3. The nucleus is separated from the cytoplasm by the-----

Ans- nuclear membrane

4. Which of the following will not be found in an egg cell, human liver cell, and an amoeba?

Ans- cell wall

5. Which of the following represents the correct sequence?

Ans- cell ---> tissue ---> organ ---> organ system

6. Which among the following pairs, can be found only in a plant cell but not in an animal cell?

Ans- cell wall and plastids

D. Answer the following questions in brief.

1. List the (main) factors that determine the shape of a cell.

Ans- Location in different body organs and functions performed by a cell determine the shape and size of a cell.

2. Distinguish between unicellular and multicellular organisms. Give two examples of each.

Ans- Unicellular organisms - The organisms made up of a single cell are called unicellular organisms. For ex- Amoeba, Paramecium, etc.

Multicellular organisms- The organisms made up of more than one cell are called multicellular organisms. For ex- Human beings, cow, etc.

3. Give reasons for the following:

(a) The cell is called the structural and functional unit of life.

Ans- All living organisms are made up of cells. So, it is called a structural unit. Each cell performs all basic functions that are essential for life. So, it is called a functional unit.

(b) Plant cells are more rigid than the animal cells.

Ans- Plant cells are more rigid than animal cells due to the presence of cell wall.

4. Which cell organelle is known as the 'Powerhouse of the cell'? Why is it so called?

Ans- Mitochondria is known as the 'Powerhouse of the cell' because it is a site for cellular respiration and produces energy in the form of ATP.

5. Name the cell organelles responsible for imparting colour to the leaves and fruits of the plants.

Ans- Plastids imparts colour to the plants.

         Chloroplast imparts colour to the leaves.

         Chromoplasts imparts cour to the fruits.  

6. What are cilia and flagella? Write one similarity and one dissimilarity between the two of them.

Ans- Cilia and flagella are both cytoplasmic extensions on the cell membrane. 

Similarity- Both are locomotory organs.

Dissimilatory- Cilia is short hair-like structure while flagella is a long whip-like structure.

7. If onion peel cells and cheek cells are observed through a microscope, state the two major difference that the observer is likely to find.

Ans- Onion pell cells

i- Cells are arranged in rows.

ii- Nucleus is towards the periphery.

Cheek cells

i- Polygonal isolated cells or cells are in clusters.

ii- Nucleus is in the centre.

 

8. Classify the following into cells, tissue and organ.

skin, fat cell, RBCs, blood, ear, muscle.

Ans- Cell - Fat cell, RBCs 

         Tissue- Blood, Muscles 

         Organ- Skin, Ear

E. Answer the following question.

1. 'All cells in an organism do not have the same shape.' Justify the above statement by drawing at least three different cell types found in human beings.

Ans- Actually shape of the cell depends upon location in different body organs and upon the function that they perform.

2. Where, and how, are chromosomes formed? State their significance.

Ans- Chromosomes formed in the nucleus when the cell is ready to divide, the chromatin condenses to form thicker, thread-like structure called chromosomes.

                                                    It helps in the inheritance of characters from one generation to other generations.

3. With the help of well-labelled diagrams, highlight three differences between a plant cell and an animal cell.

Plastids, cell wall and vacuoles are only present in plant cell not in an animal cell.

4. Write the functions performed by the following cell organelles.

(a) Endoplasmic Reticulum- Transport of materials. 

(b) Golgi Complex- Processing and packaging of materials. 

(c) Nucleus- Control different activities of the cell.                    

(d) Chromoplast- Provide colour to fruit and flower.

(e) Vacuoles- Store excess water and waste product.

(f) Mitochondria- The powerhouse of the cell and site for cellular respiration.

5. The cell membrane is a very important component of a cell. How is damage to the cell membrane likely to impact the functions of a cell?

Ans- The cell membrane is a selectively permeable membrane. It controls the entry and exit of substances as per the requirement of the cell. So, if it is damaged then the cell will lose the ability of permeability. It will harmful to the cell.

6. Define the term cell for plants/ animals. Name the different organelles that make a cell. Explain why none of these called the structural and functional unit of life?

Ans- Cell is the structural and functional unit of a living body.

                                                   The cell membrane, nucleus, cytoplasm, plastid, mitochondria, Golgi complex, endoplasmic reticulum and vacuoles make a cell.

                                                            All the organelles perform a specific function. So, single organelle can't be the structural and functional unit. Combination of all these organelles called structural and functional unit.