Respiration (continued)
Monacia Williams, Contributor

Welcome to another in our series of lessons. I hope that those of you who will be doing exams in June have been keeping abreast of your work so that you are now feeling confident that you will get that Grade One you want so badly.

Final reports for laboratory exercises (SBAs) should have been completed and handed in. With this, there may come a sense that a great weight has been lifted from your shoulders, but do not forget that the first question on Paper Two will be based on the laboratory exercises that you have carried out during the last two years. You, therefore, need to revise not only the theory, but also your labs.

Respiration is one of the topics that is often used for this question. The question is worth 30 marks, so it is important that you get a good score if you want to earn that Grade One.

Questions are set on experiments involving both aerobic and anaerobic respiration. This week, we will look at a question on anaerobic respiration that was taken from the January sitting of the 2003 examination.

Question

A biology class was asked to carry out an investigation on respiration in yeast. The apparatus was set up as shown below (Figure 1.1). The apparatus was left at room temperature for 20 minutes.

(a) (i) What was the aim of the investigation?

(ii) What is the purpose of:

• The oil in the test tube of Apparatus Y?
• Using boiled glucose solution in Apparatus Y?
• Equal volumes of glucose solution?

(iii) State ONE other precaution that should have been taken to ensure accurate results.

(b) Table 1 above shows the number of bubbles given off by the yeast cells at intervals in the 20-minute period.

(i) What would be a better way of presenting these results AND why?

(ii) The number of bubbles was recorded over a 20-minute period. Calculate the number of bubbles produced per minute in each tube.

(iii) Explain the difference between the results in Apparatus X and Apparatus Y.

(iv) Outline the steps you would take to find out what is happening to the glucose in each test tube during the course of the investigation.

This is only a portion of the question; the other section requires you to do a drawing of the head of a fish and to answer some questions on its gaseous exchange surface, which is its gills. I leave you this week with the regular challenge. Write your answers and then compare them with those that I will provide next week. Good luck!

From left: Albert Town High School principal, Wentworth Gabbidon, and elated students of the school, are presented with a $400,000 cheque by Tamiann Young, Digicel public relations executive, on April 10. Albert Town High was the winner of TVJ's 2008 singing competition, All Together Sing, in which high school choirs vied for the title of best choir. - Contributed