The diagram shows an agar plate with four paper discs soaked in different antibiotics (A, B, C, D). Each disc has created a clear zone of inhibition around it.

Measure the diameter of the zone of inhibition for antibiotic B.

The actual diagram shows antibiotic B has a clear zone with a diameter that needs to be measured in millimetres.

A student investigates the effect of temperature on enzyme activity. They measure the time taken for starch to be completely broken down by amylase at different temperatures.

(a) State the temperature at which the enzyme worked FASTEST. [1]

(b) Explain why the time taken increased at 60°C. [2]

A student uses a measuring cylinder to measure the volume of oxygen produced by a plant during photosynthesis.

The measuring cylinder has graduations every 1 cm³. The student records a volume of 24 cm³.

(a) State the PRECISION of this measurement. [1]

(b) Suggest ONE way to improve the precision of the volume measurement. [1]

A student investigates osmosis using potato cylinders. They measure the length of each potato cylinder before and after placing them in different concentrations of sugar solution.

Calculate the percentage change in length. Show your working. [3]

Formula: Percentage change = (change ÷ original) × 100

A student draws a diagram of a plant cell observed under a microscope. The actual length of the cell is 0.05 mm.

In the student's drawing, the cell measures 50 mm in length.

Calculate the magnification of the drawing. Show your working. [2]

Formula: Magnification = Image size ÷ Actual size

Refer back to the antibiotic sensitivity test diagram in Question 1.

Which antibiotic (A, B, C or D) was MOST EFFECTIVE against the bacteria? [1]

In the antibiotic test, a control disc soaked in STERILE WATER (no antibiotic) was also placed on the agar plate.

Explain why this control disc is necessary. [2]

A student investigates the effect of light intensity on the rate of photosynthesis using pondweed. They count the number of oxygen bubbles produced per minute at different distances from a lamp.

(a) Describe the pattern shown in the results. [1]

(b) Explain this pattern. [2]

A student tests four food samples (A, B, C, D) for the presence of starch using iodine solution. The results are shown below:

(a) Which samples contain starch? [1]

(b) State what the yellow-brown colour indicates. [1]

A student investigates respiration in germinating seeds by measuring the temperature change in a vacuum flask.

(a) Explain why the temperature increased in Flask A. [2]

(b) Explain the purpose of Flask B. [1]

In the antibiotic sensitivity test, the agar plate is incubated at 25°C for 48 hours.

Explain why the plate is NOT incubated at 37°C (human body temperature). [1]

A student uses dilute hydrochloric acid in an experiment to investigate the effect of pH on enzyme activity.

State TWO safety precautions the student should take when using dilute hydrochloric acid. [2]

A student wants to investigate the effect of EXERCISE on breathing rate.

Design an experiment to investigate this. Your answer should include:

• The independent variable
• The dependent variable
• How to measure the dependent variable
• TWO control variables

A student investigates osmosis by placing potato cylinders in different concentrations of sugar solution. They use a potato borer to cut cylinders that are all the same size.

(a) State ONE way to ensure all potato cylinders are the same size. [1]

(b) Explain why it is important that all potato cylinders are the same size. [2]

A student carries out the iodine test for starch on three different food samples. They test each food sample only ONCE.

(a) Suggest why the student should REPEAT each test. [1]

(b) The student records their observations as "dark colour appeared."

Explain why this is not a good observation. Suggest how to improve it. [2]