Centre No.
Paper Reference Surname Initial(s)
Candidate No. 7 0 4 0
0 2 Signature
Paper Reference(s)
7040/02
Examiner s use only
London Examinations GCE Team Leader s use only
Biology Ordinary Level Paper 2
Wednesday 9 May 2007 – Afternoon
Time: 2 hours
...
Biology
Ordinary Level Question Leave
Number Blank
Paper 2 1
Wednesday 9 May 2007 – Afternoon 2
Time: 2 hours 3
4
5
Materials required for examination Items included with question papers 6
Nil Nil
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Instructions to Candidates
The paper is arranged in three sections, A, B and C
In Section A, answer ALL questions in the spaces provided in this book 10
In Section B, answer any TWO questions in the spaces provided in this book 11
In Section C, answer any TWO questions in the spaces provided in this book
In the boxes above, write your centre number, candidate number, your surname, initial(s) and 12
signature Indicate which question you are answering by marking the box ( ) If you change your
mind, put a line through the box ( ) and then indicate your new question with a cross ( )
Information for Candidates
Calculators may be used
The total mark for this paper is 100
The mark allocation is indicated at the end of each question
The marks for parts of questions are shown in round brackets: e g (2)
This paper has 12 questions Any blank pages are indicated
Advice to Candidates
Write your answers neatly and in good English
In calculations, show all the steps in your working Total
1. Read the passage below. Use the information in the passage and your own knowledge to
answer the questions that follow.
Athletes and their respiration
Adam is an athlete. When he starts to run quickly, his muscles contract and stores
of available energy in his muscle cells are used up. In order to continue using his
muscles, Adam must release more energy as fast as he requires it. This energy is
released by aerobic respiration. How fast the energy is released depends upon how
5 fast his muscles are supplied with oxygen. A fit athlete can absorb about 4 dm 3 (litres)
of oxygen per minute and release about 80 kJ of energy. However, only about 20%
of this energy is available for movement.
The energy released by using the 4 dm3 of oxygen would enable a fit athlete to run
at a speed of about 20 km per hour. If this athlete could keep up this speed for over
10 two hours, he would have a good chance of winning a medal in an Olympic marathon
race. To win a short sprint event, however, he would need to run nearly twice as fast.
He obtains the energy for this extra speed from anaerobic respiration. This more than
doubles the energy available to the athlete, but anaerobic respiration cannot continue
at this rate for more than a short time.
15 In a 100 m race, most of the energy required is released by anaerobic respiration.
The same is true of jumping and throwing events. In middle distance races, such
as the 800 m and 1500 m, athletes obtain about half the energy they require from
aerobic respiration and the other half from anaerobic respiration. A good middle
distance runner judges his speed so that the combined energy supplied by aerobic
and
20 anaerobic respiration is enough to get him to the finish before the build up of lactic
acid affects his muscles.
After an event involving anaerobic respiration, the athlete continues to breathe
heavily so that he can obtain oxygen to convert lactic acid to harmless products. This
extra amount of oxygen is called the ‘oxygen debt’. The maximum oxygen debt
that an
25 athlete can build up is about 17 dm 3. It may take an athlete up to 45 minutes to repay
this debt and his breathing to return to normal.
(a) Which substance found in muscle cells acts as an energy store?
(f) In a long distance race, such as a marathon, suggest what proportion of the total
energy needed would come from anaerobic respiration. Give a reason for your
answer.
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