Cell: Structure and Function question and answers class 8
A. Choose the correct option.
1. Which of these is the lowest level of organization in a multicellular organism?
a. Cell b. Organ c. Tissue d. Organ System
Answer: a. Cell
2. Which of these is the outer covering of a cell?
a. Nuclear membrane b. Endoplasmic Reticulum c. Cell membrane d. Mitochondrion.
Answer: c. Cell membrane
3. Which of these is present only in plant cells?
a. Plastids b. Cell wall c. Centrosome d. Both a and b.
Answer. d. Both a and b.
4. Which of these is found only in animal cells?
a. Cell wall b. Centrosome c. Plastids
d. All of these.
Answer. b. Centrosome
5. Which cytoplasmic organelle is known as the suicide bag of a cell?
a. Lysosome b. Ribosome c. Centrosome
d. Plastid.
Answer. a. Lysosome
B. Fill in the blanks with the correct words.
B. Fill in the blanks with the correct words.
1. __________ (Unicellular/Multicellular) organisms are made up of a single cell.
Answer: Unicellular.
2. A _________ (cell/tissue) is the lowest level of the body structure organization in multicellular organisms.
Answer: Cell.
3. The specific _________ (function/number) of a cell affects its shape.
Answer: Function.
4. _________ (Bacteria/Human nerve cells) are the smallest cells in size.
Answer: Bacteria.
5. The thin sheet of glass placed over the sample while making a slide, is called a _________ (stage/coverslip).
Answer: Coverslip.
6. To view a specimen under a microscope we have to first make a ________ (stage/slide) of the specimen.
Answer: Slide.
7. A cell has _________ (only living/both living and non-living) parts.
Answer: Both living and non-living.
8. The nucleus is filled with a substance called the _________(cytoplasm/nucleoplasm).
Answer: Nucleoplasm.
9. _________ (Centrosome/Cell wall) is present in an animal cell but not in a plant cell.
Answer: Centrosome.
10. Growth in an organism happens because of the increase in the _________ (number/size) of cells.
Answer: Number.
C. Name the following.
1. This part of the cell secretes chemical substances that help in various functions
Answer: Golgi apparatus (Golgi body).
It packages and secretes substances like enzymes and hormones and prepares materials for transport.
2. This is a fluid-filled space that stores substances in a cell
Answer: Vacuole.
Vacuoles store water, nutrients, and waste; plant cells have a large central vacuole.
3. They are called suicide bags of the cell
Answer: Lysosomes.
Lysosomes contain digestive enzymes that break down waste and worn-out parts of the cell.
4. It helps in the synthesis, storage, and transport of cell products
Answer: Golgi apparatus Golgi complex.
The Golgi modifies, stores and ships proteins and lipids produced by the ER.
5. Protein synthesis takes place here
Answer: Ribosomes.
Ribosomes are the sites where amino acids are linked to form proteins.
6. They are called the powerhouses of the cell
Answer: Mitochondria.
Mitochondria produce ATP — the energy currency that powers cellular processes.
D. Answer the following questions.
1. What is a cell?
Answer: A cell is the basic structural and functional unit of all living organisms. It contains genetic material, cytoplasm, and organelles enclosed in a membrane, and it performs life processes such as nutrition, respiration, growth and reproduction.
2. What are unicellular organisms? Give two examples.
Answer: Unicellular organisms are organisms made of a single cell that performs all life functions. Examples: Amoeba and Paramecium (also bacteria like Escherichia coli).
3. How are unicellular organisms different from multicellular organisms?
Answer:
- Unicellular: one cell does every job feeding, moving, reproducing. They are usually microscopic.
- Multicellular: many cells with specialized roles (cells → tissues → organs → systems). Multicellular organisms (like plants and humans) can be large and have tissue and organ-level functions.
4. List the levels of organization in a multicellular organism.
Answer: Cell → Tissue → Organ → Organ system → Organism.
Example: muscle cell → muscle tissue → heart → circulatory system → human.
5. What is a specimen? What do we use to view a specimen?
Answer: A specimen is a small sample or piece of material taken for study (e.g., a thin onion peel or a drop of pond water). To view a specimen we use a microscope; the specimen is placed on a glass slide and covered with a coverslip.
6. What is a coverslip? Why do we use it in preparing a slide?
Answer: A coverslip is a very thin square of glass placed over the specimen on the slide. We use it to:
- hold the specimen flat,
- protect the specimen and the microscope lens,
- reduce evaporation and prevent air bubbles, and
- allow light to pass evenly for clearer viewing.
7. Describe the stepwise process of preparing a slide.
Answer. simple step-by-step:
- Clean the glass slide.
- Place a drop of water or stain if needed on the slide.
- Using forceps, add the thin and small specimen.
- Hold the coverslip at a 45° angle to the slide touching the drop, then gently lower it to avoid air bubbles.
- Blot excess liquid with absorbent paper at the edge.
- Place the slide on the microscope stage, start with the lowest-power objective, focus using the coarse knob, then switch to higher power and use the fine focus for clear detail.
Always handle glass carefully and label the slide.
Q8.With the help of a labelled diagram, illustrate the structure of a generalized cell.
Q9.Write a short note on the three main parts of a cell.
Answer.
three main parts:
- Cell membrane (plasma membrane): A thin, flexible boundary of the cell made of a lipid–protein layer that controls what enters and leaves the cell; it protects and supports the cell.
- Cytoplasm: The jelly-like fluid (cytosol) that fills the cell and holds organelles; many chemical reactions occur here and organelles are suspended in it.
- Nucleus: The control centre containing DNA (genetic material); the nucleus regulates cell activities (growth, metabolism, reproduction) and contains the nucleolus where ribosomes are made.
Q10. Draw a labelled diagram of a plant cell.
Major organelles: large central vacuole, chloroplasts green oval, for photosynthesis, nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, and cytoplasm. Mark the cell wall, chloroplasts, and large vacuole clearly — these are plant-cell-specific.
Q11.11. Differentiate between a plant cell and an animal cell.
Answer.
| Feature | Plant Cell | Animal Cell |
| Cell wall | Present (made of cellulose) | Absent |
| Shape | Usually rectangular or fixed shape | Usually round or irregular |
| Chloroplast | Present for photosynthesis | Absent |
| Vacuole | One large central vacuole | Many small vacuoles (if present) |
| Mode of nutrition | Autotrophic (makes its own food) | Heterotrophs depend on others for food. |
| Centrioles | Absent | Present |
| Lysosomes | Rare | Common |
| Energy storage | Starch | Glycogen |