Key concepts in biology：练习题

Which of the following sub-cellular structures is found in prokaryotic cells but not in animal cells?

An image of a plant cell nucleus is measured to be \(12\text{ mm}\) in diameter. If the actual diameter of the nucleus is \(6\text{ μm}\), what is the magnification of the image?

In a reflex arc, what is the specific role of the relay neurone?

Calculate the percentage gain in mass for a potato chip that had an initial mass of \(2.50\text{ g}\) and a final mass of \(2.75\text{ g}\) after being placed in a solution.

In an investigation into the rate of enzyme activity, a student measures that \(15\text{ cm}^3\) of product is formed in \(2\text{ minutes}\) and \(30\text{ seconds}\). Calculate the mean rate of reaction in \(\text{cm}^3\text{ s}^{-1}\).

Identify the sub-cellular structure in a plant cell that is responsible for photosynthesis.

Explain the specific adaptation of the acrosome in a sperm cell and how it facilitates its primary function during fertilisation.

Describe the lock and key hypothesis of enzyme action, explaining why a change in the shape of the active site results in the denaturation of the enzyme.

A student uses a microscope with a \(10\times\) eyepiece lens and a \(20\times\) objective lens to observe a slide of plant cells.
(a) Calculate the total magnification of the microscope.
(b) The actual length of a plant cell is \(0.04\text{ mm}\). Calculate the length of the image of this cell in \(\text{mm}\) as seen through the microscope.

A student investigates the effect of pH on the activity of amylase. The rate of reaction is measured at different pH values.
(a) Explain why the rate of reaction decreases significantly when the pH is changed from the optimum to a highly acidic or alkaline value, referring to the active site.
(b) If at pH 7, the amylase breaks down 10 g of starch in 5 minutes, calculate the rate of reaction in \(g\text{ }dm^{-3}s^{-1}\), assuming the reaction volume is \(0.05\text{ }dm^3\).