Cell structure：練習題

A specific type of bacterium divides by binary fission every \(20\text{ minutes}\).

If there are \(10\) bacteria at the start of an experiment, how many bacteria will be present after \(2\text{ hours}\)? Give your answer in standard form.

A scientist measures the diameter of a circular colony of bacteria on an agar plate as \(14\text{ mm}\).

Calculate the cross-sectional area of the bacterial colony. (Use \(\pi = \frac{22}{7}\))

How is a root hair cell in a plant adapted to its function?

A student uses a microscope to observe a chloroplast. The image of the chloroplast is measured as \( 15 \text{ mm} \) long. If the actual length of the chloroplast is \( 6 \text{ μm} \), calculate the magnification used.

(\( 1 \text{ mm} = 1,000 \text{ μm} \))

Xylem cells are specialised to transport water and mineral ions from the roots to the leaves. Which substance is used to strengthen the walls of these cells, allowing them to withstand the pressure of the transpiration stream?

The cytoplasm is a sub-cellular structure found in both eukaryotic and prokaryotic cells. State the primary function of the cytoplasm.

A student uses a light microscope to observe a cheek cell. The image of the cell is measured as \( 45 \text{ mm} \) wide using a ruler. The student used a magnification of \( \times 1,500 \).

Calculate the actual width of the cheek cell in micrometres (\( \mu\text{m} \)).

(Note: \( 1 \text{ mm} = 1,000 \mu\text{m} \))

A student used a light microscope to study the clear zone around an antibiotic disc on an agar plate. The radius of the clear zone was measured to be \(1.4\text{ cm}\).

a) Calculate the cross-sectional area of the clear zone in \(\text{mm}^2\). Use \(\pi = 3.14\).

b) Explain two aseptic techniques the student should have used when preparing the agar plate to ensure the culture remained uncontaminated.

a) Name the sub-cellular structure in plant cells that contains cell sap and explain its function in the cell.

b) Describe the chemical composition of the cell wall in plant and algal cells and state its primary role in maintaining cell integrity.

A student investigates cell structures using a light microscope.

a) Name the sub-cellular structure in a plant cell where aerobic respiration takes place. (1 mark)

b) Name the sub-cellular structure in a plant cell that contains cell sap to keep the cell turgid. (1 mark)

c) State the main chemical component of a plant cell wall. (1 mark)