Edexcel A-Level Biology A2 7.7 Core Practical 15 Respiration in Yeast Questions

Design and evaluate a yeast respiration practical by using an artificial hydrogen carrier, controlled temperatures, timed colour change and repeat measurements with marked exam evidence.

Exam points

design a yeast respiration experiment using an artificial hydrogen carrier and controlled temperatures
measure timed colour change and use repeats or means to compare respiration rates

[Maximum number: 5]

Saccharomyces cerevisiae is a type of yeast. It is a single-celled organism which is widely used in brewing and baking. The photograph shows yeast cells seen through a microscope.

Figure for Question Edexcel A-Level Biology A2 7.7 Core Practical 15 Respiration in Yeast Questions question 1 — Edexcel A-Level Biology A2

Describe an experiment to investigate the effect of temperature on the rate of respiration in yeast, using an artificial hydrogen carrier (redox indicator).

A description that contains five of the following:

- range of five suitable temperatures used (1)

- use of thermostatic waterbath (1)

- incubate yeast and indicator separately to reach same temperature (1)

- suitable named indicator used (1)

- record time taken for colour to change (1)

- identification of one variable (1)

- repeats and calculate \{ means/SD's \} (to compare) (1)

Accept temperatures between 5 and $45^{\circ} \mathrm{C}$ (ignore additional temperatures outside the range)

Accept waterbath set at a stated temperature

Accept to equilibrate/acclimatise

Accept TTC / DCPIP / methylene blue ignore stated colours

Accept: pH

\{volume / conc/mass/strain/type\} of yeast suspension/ volume/conc of TTC Ignore species

Accept average

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Edexcel A-Level Biology A2 7.7 Core Practical 15 Respiration in Yeast Questions question 1