advanced higher biology 2008
Posted 20 May 2008 - 05:46 PM
Posted 21 May 2008 - 09:24 PM
Posted 22 May 2008 - 11:52 AM
Posted 22 May 2008 - 01:26 PM
Energy expenditure can also be measured by indirect calorimetry.
The following information was gathered as an individual ran on a treadmill for 20 minutes:
Volume of air breathed out in 20 minutes = 600 litres
Inspired air contained 20% oxygen, while expired air contained 16% oxygen.
4.8 kcals of energy are released for every litre of oxygen used up.
How many kilocalories of energy were expended during the 20 minutes?
Posted 22 May 2008 - 10:29 PM
Volume of air breathed out=600 litres
Composition of oxygen in inspired air=20%x600=120 litres
Composition of oxygen in expired air=16%x600=96 litres
The amount of oxygen absorbed by an individual is equal to the amount of oxygen in the inspired air minus the amount of oxygen in the expired air
Volume of oxygen absorbed=120-96=24 litres
4.8 kcal of energy is released for every litre of oxygen used so:
Energy expended in 20 minutes=4.8x24=115.2 kcals of energy
Hope that helps
Posted 23 May 2008 - 05:45 PM
Posted 23 May 2008 - 07:46 PM
So for Q2 2004 there are in total 50 cells in mitosis and 450 cells in interphase so the mitotic index=50/450x100=11.1% so the answer is C
Hope this helps
Posted 24 May 2008 - 08:34 PM
interphase is not involved in mitosis ( 2 stages interphase and the mitotic phase) so what you do is you add the number of cells in total in this case there are 500 cells in total including interphase. then you divide the total of the other phases excluding interphase by the total in this case 50/500 x 100 = 10%. This also works for the other 2 questions.
Posted 25 May 2008 - 08:54 PM
Posted 26 May 2008 - 10:32 AM
The answer is C, 25% ( marking scheme)
remember interphase isn't involved in mitosis so for the 2007 paper there are 360 cells in total including interphase. Then divide the total of the other phases except interphase by the total so in this case it's 90/360 x 100 = 25%.
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