O Level Biology Animal and Plant Cells Questions and Answers

Subject: Biology

Level: O Level

Topic: Animal and Plant Cells

This comprehensive set of O Level Biology Animal and Plant Cells Questions and Answers will help you master the differences and similarities between these two fundamental cell types. Each question is based on international syllabus standards (Cambridge, Edexcel, etc.) and includes a detailed answer, explanation, and an exam tip to boost your confidence.

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Topic Overview

Animal and plant cells share common organelles such as the nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. However, plant cells possess additional structures: a rigid cellulose cell wall, chloroplasts for photosynthesis, and a large permanent vacuole. Understanding these differences is essential for O Level Biology examinations, where you are often asked to identify, compare, and explain the functions of cell components.

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Exam Questions and Answers

Question 1

Question:
Name three structures that are found in a plant cell but are absent in an animal cell.

Answer:
Cell wall, chloroplasts, and a large permanent vacuole.

Explanation:
Plant cells have a rigid cell wall made of cellulose for support and protection. Chloroplasts contain chlorophyll and are the sites of photosynthesis. The large permanent vacuole stores cell sap and helps maintain turgor pressure. Animal cells lack these structures.

Exam Tip:
Memorise the “plant‑only trio” – cell wall, chloroplast, vacuole. In diagrams, always label them clearly; examiners often ask for two or three differences.

Question 2

Question:
Describe the function of the cell membrane and explain why it is essential for both animal and plant cells.

Answer:
The cell membrane is a partially permeable barrier that controls the movement of substances into and out of the cell. It allows essential nutrients (e.g., glucose, oxygen) to enter and waste products (e.g., carbon dioxide, urea) to leave. It also maintains the cell’s internal environment.

Explanation:
Without a functioning cell membrane, the cell could not obtain materials for metabolism nor remove toxic wastes. It also plays a role in cell signalling and recognition.

Exam Tip:
Use the term “partially permeable” (or “selectively permeable”) in your answer. Avoid simply saying “it lets things in and out” – be specific about control and examples.

Question 3

Question:
State two differences between the vacuole of a plant cell and that of an animal cell.

Answer:
In a plant cell, there is a single large central vacuole that occupies most of the cell’s volume, while animal cells contain many small temporary vacuoles (or none). The plant vacuole stores cell sap (water, sugars, ions) and helps maintain turgor pressure; animal vacuoles are mainly involved in phagocytosis or excretion.

Explanation:
The plant’s large vacuole provides structural support; when full of water it pushes the cytoplasm against the cell wall, making the cell turgid. Animal vacuoles are smaller, often used for storing food or engulfing particles.

Exam Tip:
When comparing, use comparative language: “plant cells have a large permanent vacuole; animal cells have many small temporary vacuoles.”

Question 4

Question:
Explain why a plant cell placed in distilled water does not burst, whereas an animal cell would.

Answer:
The plant cell has a strong, rigid cell wall made of cellulose that resists expansion. When water enters by osmosis, the cell becomes turgid (swollen) but the cell wall prevents bursting. Animal cells lack a cell wall, so they continue to take up water until they lyse (burst).

Explanation:
Osmosis causes water to move from a dilute solution (distilled water) into the cell’s concentrated cytoplasm. The plant’s cell wall withstands internal pressure; animal cells have only the cell membrane, which cannot withstand high pressure.

Exam Tip:
Use the term “turgid” for plant cells. Contrast with “lysis” for animal cells. A diagram of both situations often scores extra marks.

Question 5

Question:
Compare the roles of mitochondria in animal and plant cells.

Answer:
In both cell types, mitochondria carry out aerobic respiration, releasing energy (in the form of ATP) for cellular activities. Plant cells also use some of this energy for photosynthesis and for active transport; animal cells use energy for movement, synthesis, and maintaining body temperature.

Explanation:
Mitochondria are the “powerhouses” of the cell. Although plants can produce glucose by photosynthesis, they still need mitochondria to convert that glucose into usable energy. The number of mitochondria varies with the cell’s energy demand.

Exam Tip:
Emphasise that mitochondria are present in both cell types – a common misconception is that only animal cells have mitochondria. Mention “aerobic respiration” and “ATP” for top marks.

Question 6

Question:
Identify the organelle responsible for protein synthesis and state where it is found in the cell.

Answer:
Ribosomes are the organelles responsible for protein synthesis. They are found free in the cytoplasm and also attached to the rough endoplasmic reticulum (RER) in both animal and plant cells.

Explanation:
Ribosomes assemble amino acids into polypeptide chains using instructions from mRNA. Free ribosomes make proteins for use within the cell; those on RER synthesise proteins for secretion or membrane insertion.

Exam Tip:
Be precise: “ribosomes” (not “ribosome”). Know that both plant and animal cells contain ribosomes – they are not a difference between them.

Question 7

Question:
A student observed cells under a microscope and noted the presence of a cell wall and chloroplasts. Which type of cell (animal or plant) was being observed, and why?

Answer:
The cells were plant cells because they possessed a cell wall (which provides structural support) and chloroplasts (which contain chlorophyll for photosynthesis). Animal cells do not have either structure.

Explanation:
Cell walls are characteristic of plants, fungi, and bacteria, but only plant cells have chloroplasts. Observing both confirms the cells are plant cells.

Exam Tip:
When given observations, always mention the “absent” features as well. For instance, “no cell wall in animal cells” reinforces the identification.

Question 8

Question:
Describe how the structure of a palisade mesophyll cell in a leaf is adapted to its function.

Answer:
Palisade mesophyll cells are packed with chloroplasts to maximise light absorption for photosynthesis. They are column‑shaped and arranged closely together, forming a layer near the leaf’s upper surface. Their thin cell walls allow carbon dioxide to diffuse quickly.

Explanation:
These cells are specialised plant cells. Their chloroplast density and position capture light efficiently. The large surface area of the cell layer facilitates gas exchange.

Exam Tip:
Connect structure to function: “many chloroplasts → more photosynthesis”; “columnar shape → allows light to reach lower cells”. Always include a specific adaptation and why it helps.

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Key Concepts Summary

• Animal and plant cells share a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.
• Plant cells have a cellulose cell wall, chloroplasts, and a large permanent vacuole.
• Cell membrane is partially permeable and controls substance movement.
• Mitochondria carry out aerobic respiration in both cell types.
• Ribosomes are the site of protein synthesis in all cells.

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Frequently Asked Questions

Can plant cells carry out aerobic respiration without mitochondria?

No. Plant cells contain mitochondria and rely on them for aerobic respiration, just like animal cells. Even though they produce glucose via photosynthesis, they still need to break it down in mitochondria to release energy for cellular work.

Do all plant cells have chloroplasts?

No. Only green parts of plants (e.g., leaves, stems) contain chloroplasts. Root cells, for example, lack chloroplasts because they are underground and do not photosynthesise. However, they still have cell walls and a large vacuole.

What is the main difference between a plant cell and a bacterial cell?

Plant cells are eukaryotic (have a true nucleus, membrane‑bound organelles). Bacterial cells are prokaryotic (no nucleus; DNA is free in the cytoplasm). Both have cell walls, but plant cell walls are made of cellulose while bacterial walls contain peptidoglycan.

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Conclusion

Mastering O Level Biology Animal and Plant Cells Questions and Answers is essential for exam success. By understanding the unique features of each cell type, their functions, and how to apply this knowledge in exam questions, you will be well prepared. Practice these questions, review the key concepts, and use the exam tips to boost your marks. Keep revisiting the material until you can confidently explain every organelle’s role.