Year 9 Cell Biology Practice Quiz (22 questions)

1. What is a plasmid in a bacterial cell?

A. A protein structure that propels the cell forward

B. A protective layer surrounding the bacterial cell

C. A small ring of DNA that can carry useful genes

D. A large linear chromosome enclosed within a nucleus

Answer: (C)

Explanation

A plasmid is a small circular DNA molecule that may carry useful genes, including genes for antibiotic resistance. A propeller-like structure is a flagellum, a protective layer may be a slime capsule, and bacteria do not have a nucleus containing linear chromosomes.

2. Why are mitochondria essential for the energy needs of a eukaryotic cell?

A. They store cell sap and maintain the cell's internal pressure

B. They contain enzymes for respiration, where most energy is released

C. They regulate which dissolved substances cross the cell surface

D. They contain DNA that controls the activities of the cell

Answer: (B)

Explanation

Mitochondria contain the enzymes needed for respiration, the process that releases most of the cell's energy. The nucleus contains genetic material, the membrane controls transport, and the permanent vacuole stores cell sap.

3. Which combination of features enables a nerve cell to carry electrical impulses and pass them between cells?

A. Sliding fibres, glycogen stores and many mitochondria

B. Many dendrites, a long axon and synapses

C. Many chloroplasts, chlorophyll and a permanent vacuole

D. A tail, a digestive acrosome and a large nucleus

Answer: (B)

Explanation

Nerve cells are adapted for communication by having many dendrites, a long axon and synapses. Sliding fibres and glycogen are associated with muscle-cell contraction rather than impulse transmission.

4. Which set of adaptations helps a root hair cell absorb water and minerals from the soil?

A. A tail, an acrosome and a nucleus with half the genetic information

B. A large surface area, a permanent vacuole and many mitochondria

C. Many chloroplasts, thin cell walls and a long axon

D. Sliding fibres, synapses and a large glycogen store

Answer: (B)

Explanation

Root hair cells have a large surface area for absorption, a large permanent vacuole, and many mitochondria to provide energy for active transport. Chloroplasts and axons are adaptations of other specialised cells, not the root hair cell.

5. Which feature identifies a cell as eukaryotic?

A. It has a single loop of DNA in its cytoplasm

B. It contains a plasmid with antibiotic-resistance genes

C. It contains a nucleus with DNA in linear chromosomes

D. It has a protein flagellum for cellular movement

Answer: (C)

Explanation

Eukaryotic cells contain a nucleus that houses DNA arranged in large linear chromosomes. A single DNA loop, plasmids, and flagella are features associated with some prokaryotic cells.

6. When beginning a microscope practical, which sequence best describes the procedure for observing and recording cells?

A. Place the slide, focus without an objective lens, increase illumination, and record the cells from memory

B. Place the slide, use the highest-power lens, focus coarsely, reduce power, and draw unlabelled cells

C. Place the slide, use the lowest-power lens, focus, increase power, refocus finely, and draw labelled cells

D. Place the slide, increase power immediately, focus finely, switch to low power, and photograph the cells

Answer: (C)

Explanation

The practical begins with the slide on the stage and the lowest-power objective, followed by coarse and fine focusing before moving to higher power and using fine focus again. Starting at high power or omitting the staged focusing process would make observation and focusing less appropriate.

7. Which sequence correctly describes how to calculate magnification from an image and its actual size?

A. Measure the image, multiply by the actual size, then convert units.

B. Measure the image, convert units, then apply the formula.

C. Estimate the image, compare the units, then add the two sizes.

D. Convert units, calculate area, then measure the image.

Answer: (B)

Explanation

A valid calculation requires measuring the image, converting the image and actual sizes into the same unit, and then applying the appropriate formula. Measuring the image alone does not determine magnification.

8. What is differentiation in the development of specialised cells?

A. The process by which a cell loses its genetic information.

B. The process by which a cell becomes specialised for a function.

C. The process by which a cell divides to produce identical cells.

D. The process by which a cell increases in size during growth.

Answer: (B)

Explanation

Differentiation is the change that makes a cell specialised for a particular function. Cell growth increases size, but it does not describe the development of specialised cell features.

9. Why would an electron microscope be chosen instead of a light microscope to examine very small cell structures?

A. It uses visible light and is easier to operate

B. It allows living specimens to remain active during observation

C. It produces useful images at lower magnification and resolution

D. It provides much higher magnification and resolution

Answer: (D)

Explanation

Electron microscopes use a high-energy electron beam and can reach magnifications up to about $\times 2{,}000{,}000$, producing higher magnification and resolution. Light microscopes are better suited to living specimens but provide lower maximum magnification and resolution.

10. An image is $12\text{ mm}$ long and the actual object is $3\text{ mm}$ long. What is the magnification?

A. $36\times$

B. $9\times$

C. $0.25\times$

D. $4\times$

Answer: (D)

Explanation

Magnification is calculated by dividing image size by actual size, so $M = \frac{12}{3} = 4\times$. Multiplying the two lengths would not apply the magnification formula.

11. How is the main bacterial chromosome arranged inside a bacterial cell?

A. As a long protein strand extending outside the cell

B. As several linear chromosomes inside a nucleus

C. As a small DNA ring attached to the cell membrane

D. As a single loop of DNA free in the cytoplasm

Answer: (D)

Explanation

The bacterial chromosome is one loop of DNA located freely in the cytoplasm. Several linear chromosomes inside a nucleus describe eukaryotic cells, while small DNA rings are plasmids and protein strands can form flagella.

12. Which statement correctly distinguishes aerobic respiration from anaerobic respiration?

A. Aerobic respiration releases energy through a reaction that occurs without oxygen

B. Aerobic respiration stores sunlight in glucose through a reaction with oxygen

C. Aerobic respiration releases energy through a reaction that occurs with oxygen

D. Aerobic respiration moves particles across membranes using energy from oxygen

Answer: (C)

Explanation

Aerobic respiration is a chemical reaction that releases energy and occurs with oxygen. A reaction without oxygen describes anaerobic respiration, while storing sunlight in glucose refers to photosynthesis.

13. Why must a microscopic measurement in nanometres be converted before it is used with a measurement in micrometres?

A. The numerical value must be increased before comparison.

B. The microscope can record measurements in one unit at a time.

C. The measurements must use compatible units for calculation.

D. The smaller measurement must be changed into a magnification value.

Answer: (C)

Explanation

Measurements must be converted into compatible units before they are compared or used in a calculation. Different units cannot be substituted directly without conversion, even when they describe the same length.

14. A researcher needs to observe living cells while magnifying them. Which instrument is suitable?

A. A light microscope using a beam of light

B. A light microscope producing only images of dead material

C. An electron microscope using a high-energy electron beam

D. An electron microscope requiring a vacuum around the specimen

Answer: (A)

Explanation

Light microscopes use light and can be used to observe living specimens, with magnification up to about $\times 2{,}000$. Electron microscopes provide greater magnification but cannot be used to observe living specimens.

15. A microscope has a 10× eyepiece and a 40× objective lens. What magnification should be written below the drawing?

A. $50\times$

B. $4\times$

C. $30\times$

D. $400\times$

Answer: (D)

Explanation

Drawing magnification is found by multiplying the objective magnification by the eyepiece magnification, so $40\times 10 = 400\times$. Adding the two values would give an incorrect result because magnification is calculated multiplicatively.

16. A microscope uses an eyepiece lens of $10\times$ and an objective lens of $40\times$. What is the overall magnification?

A. $400\times$

B. $4\times$

C. $30\times$

D. $50\times$

Answer: (A)

Explanation

Overall magnification is found by multiplying the eyepiece magnification by the objective magnification, giving $10\times 40 = 400\times$. Adding the two lens values would give a sum rather than the required product.

17. Which cell structure is a jelly-like region containing dissolved substances and organelles where many chemical reactions occur?

A. The permanent vacuole

B. The nucleus

C. The cytoplasm

D. The cell membrane

Answer: (C)

Explanation

The cytoplasm is the jelly-like material in which many chemical reactions take place and where organelles are suspended. The nucleus controls cell activities, while the membrane regulates movement and the vacuole stores cell sap.

18. A dye spreads through still water from a region where many dye particles are present toward a region where fewer are present, without added energy. What process is occurring?

A. Diffusion, because particles move passively from high to low concentration

B. Active transport, because particles move toward a region of lower concentration

C. Photosynthesis, because light energy drives particle movement through water

D. Respiration, because chemical energy is released as the dye spreads

Answer: (A)

Explanation

Diffusion is the passive movement of particles from a high concentration to a low concentration. Active transport requires energy and is not identified merely by movement toward a lower concentration.

19. What is the main function of the cell membrane?

A. Providing a rigid outer layer made of cellulose

B. Releasing most of the energy during respiration

C. Controlling which substances enter and leave the cell

D. Containing the cell's genetic material

Answer: (C)

Explanation

The cell membrane is selectively permeable and regulates movement of substances into and out of the cell. Energy release occurs in mitochondria, genetic material is contained in the nucleus, and cellulose forms a plant cell wall.

20. What does resolution mean in microscopy?

A. The brightness of the beam used to illuminate a specimen

B. The physical size of the microscope's viewing chamber

C. The ability to distinguish two objects as separate points

D. The number of times an image is enlarged

Answer: (C)

Explanation

Resolution is the ability to distinguish two nearby objects as separate points. Magnification describes image enlargement, while beam brightness and chamber size do not define resolution.

21. Which description correctly identifies bacteria as prokaryotic cells?

A. They are about 2–20 μm long and lack genetic material

B. They are about 0.2–2 μm long and contain a nucleus

C. They are about 2–20 mm long and contain a nucleus

D. They are about 0.2–2 μm long and lack a nucleus

Answer: (D)

Explanation

Bacteria are prokaryotic cells that are typically 0.2–2 μm long and do not have a nucleus. Their genetic material is present in the cell without being enclosed by a nuclear membrane.

22. How do the adaptations of muscle cells support contraction?

A. A long axon transmits impulses while synapses shorten the muscle cell.

B. Sliding fibres contract using energy supplied by many mitochondria and glycogen.

C. A tail moves the cell while acrosome enzymes release energy for contraction.

D. Chloroplasts capture light and provide energy for sliding fibres to contract.

Answer: (B)

Explanation

Muscle cells contain sliding fibres and energy supplies in the form of many mitochondria and glycogen, supporting contraction through respiration. Chloroplasts capture light for photosynthesis and are not the energy adaptation described for muscle cells.