- Messages
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- I'm still not able to do Q2 can show the working pls. ?Oct/Nov '09:
2) 1 million nanometers = 1 millimeter. You can continue from there.
22) A tRNA molecule can bind to one type of amino acid. After it 'uses up' its amino acid, it goes back to the cytoplasm to bind with another one. After that, it returns to the ribosome to 'use it up' again.
The question tells you that there are only 4 types of amino acids, so you only need 4 different tRNA to translate the polypeptide.
17) Remember that active transport works against a concentration gradient (moving solutes from a region of low concentration to a region of high concentration). So potassium will move inside the cell and sodium moves out.
26) The solute potential is always negative, and the pressure potential is always positive. The water potential is the sum of the other two potentials, so it will be found somewhere in between them.
29) You are looking for the greatest CHANGE. So you're looking for the region where the slope is the highest. That's going to be region B
14) 20) 22) Are you sure you copied the right question paper?
Oct/Nov '08:
4) I think you just have to measure the distance with a ruler and calculate it from the magnification.
24) Actually, D is an adaptation. I'm pretty sure that option B is the right answer.
Water uptake is done through osmosis (a passive process which does not require energy). So mitochondria are not needed as energy is not required.
28) I mean, option C is correct while the others are wrong. Here are the corrections:
A: blood flows into the aorta when the LEFT ventricle contracts
B: blood flows into the left atrium through the pulmonary VEIN ...
D: blood flows into the left ventricle through the AV VALVE...
Oct/Nov '07:
6) Measure it by a ruler and calculate it using the magnification equation
25) Water flows from the roots to the xylem vessels. So the roots must have a higher water potential than the xylem vessels. That makes options C and D wrong. The soil water must contain some salts, so it's impossible to have a water potential of 0. It has to be less than that. So option A is wrong. Option B is the only one left.
28) They're asking for how many oxygen ATOMS are carried. Each oxygen molecule contains two atoms (O2). 4 molecules are carried by one haemoglobin molecule which is equivalent to 8 oxygen atoms.
May/June '07:
1) Simply divide the values to get a ratio of their sizes. Remember to convert 750 nm to 0.75 micrometers (or convert 15 micrometers to 15,000 nanometers)
So 15/0.75 = 20
Or, 15000/750 = 20
You get the same answer both ways.
4) The first figure tells you that 0.1 mm is equivalent to 50 divisions. So each division is 2 micrometers long.
By looking at the horizontal pollen tube, you can see that it grew from the 25th division to the 35th one. So it grew by 10 divisions which is equal to 20 micrometers. But, they also say that it grew 20 micrometers in 4 hours, so in 1 hour, it gre 20/4 = 5 micrometers. So the rate is 5 micrometers per hour.
15) Air contains oxygen, which is required for active transport (it's needed to produce ATP). Nitrogen cannot be used for active transport.
If you bubble air or nitrogen through the solution, the rate of the 3-carbon sugar doesn't change. This tells you that it doesn't involve active transport, which implies that it travels through diffusion.
The rate of the 6-carbon sugar was high when air was bubbled, but it completely stopped when nitrogen was bubbled. This tells you that air (hence oxygen) was necessary for uptake, so it must have been done through active transport.
- Yes the paper was may/june http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s09_qp_1.pdf Q 14 A, 20 B, 22C
- For Oct/nov 2008 Q4 From where to where do i hv to measure useing the ruler.. wheres the rbc ? - in the same paper Could u explain Q26 ?