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Irfan1995 ??
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0.5 has a higher resolution , because objects of that size can be seen get it?Can anyone explain to me about the resolution of the light/electron microscope? 0.5 or 200 nm which of this value has a higher resolution?
whyThings you have to know first:
Going back to the figure, we can see that at:
- The atrio-ventricular (AV) valves open when the pressure of the blood in the atria is greater than that in the ventricles. We all know that blood flows from high pressure to low pressure. So when the pressure in the atria is high, blood will flow to the ventricles. The opposite is also true (i.e. the AV valves close when the pressure in the atria is less than the ventricles). If they did not close, then we would have some back-leak of the blood from the ventricles to the atria, but since there are AV valves, they close to prevent this from happening.
- The semi-lunar valves open when the pressure in the ventricles is greater than that in the aorta (this is to ensure that blood gets forced out of the ventricles to the aorta. The opposite is also true.
(1) The AV valves close (point where the blood pressure of atria becomes less than pressure in the ventricles)
(2) The semilunar valves open (point where the blood pressure of the ventricles is greater than that of the aorta)
(3) The semilunar valves close (point where the blood pressure of the ventricles is less than that in the aorta)
(4) The AV valves open (point where the blood pressure of the atria is greater than that in the ventricles)
If you want to find the time that both valves are closed, that would be between (1) and (2) and between (3) and (4)
The time between (1) and (2) is about 0.03 s
The time between (3) and (4) is about 0.04 s
The total time would be 0.07 s which corresponds to answer C.
Could you please confirm the answer with the mark scheme please? If my answer is different, please say so and I'll review my work!
WHY the time between 1 and 2 and 3 and 4 is the time both the valves are closed??Things you have to know first:
Going back to the figure, we can see that at:
- The atrio-ventricular (AV) valves open when the pressure of the blood in the atria is greater than that in the ventricles. We all know that blood flows from high pressure to low pressure. So when the pressure in the atria is high, blood will flow to the ventricles. The opposite is also true (i.e. the AV valves close when the pressure in the atria is less than the ventricles). If they did not close, then we would have some back-leak of the blood from the ventricles to the atria, but since there are AV valves, they close to prevent this from happening.
- The semi-lunar valves open when the pressure in the ventricles is greater than that in the aorta (this is to ensure that blood gets forced out of the ventricles to the aorta. The opposite is also true.
(1) The AV valves close (point where the blood pressure of atria becomes less than pressure in the ventricles)
(2) The semilunar valves open (point where the blood pressure of the ventricles is greater than that of the aorta)
(3) The semilunar valves close (point where the blood pressure of the ventricles is less than that in the aorta)
(4) The AV valves open (point where the blood pressure of the atria is greater than that in the ventricles)
If you want to find the time that both valves are closed, that would be between (1) and (2) and between (3) and (4)
The time between (1) and (2) is about 0.03 s
The time between (3) and (4) is about 0.04 s
The total time would be 0.07 s which corresponds to answer C.
Could you please confirm the answer with the mark scheme please? If my answer is different, please say so and I'll review my work!
Things you have to know first:
Going back to the figure, we can see that at:
- The atrio-ventricular (AV) valves open when the pressure of the blood in the atria is greater than that in the ventricles. We all know that blood flows from high pressure to low pressure. So when the pressure in the atria is high, blood will flow to the ventricles. The opposite is also true (i.e. the AV valves close when the pressure in the atria is less than the ventricles). If they did not close, then we would have some back-leak of the blood from the ventricles to the atria, but since there are AV valves, they close to prevent this from happening.
- The semi-lunar valves open when the pressure in the ventricles is greater than that in the aorta (this is to ensure that blood gets forced out of the ventricles to the aorta. The opposite is also true.
(1) The AV valves close (point where the blood pressure of atria becomes less than pressure in the ventricles)
(2) The semilunar valves open (point where the blood pressure of the ventricles is greater than that of the aorta)
(3) The semilunar valves close (point where the blood pressure of the ventricles is less than that in the aorta)
(4) The AV valves open (point where the blood pressure of the atria is greater than that in the ventricles)
If you want to find the time that both valves are closed, that would be between (1) and (2) and between (3) and (4)
The time between (1) and (2) is about 0.03 s
The time between (3) and (4) is about 0.04 s
The total time would be 0.07 s which corresponds to answer C.
Could you please confirm the answer with the mark scheme please? If my answer is different, please say so and I'll review my work!
yeah I don't get why to add the differences too :/absloutely right !
thanks
isnt at 2 S.V O .. why to find difference at this point ..
Coul you help- I'm still not able to do Q2 can show the working pls. ?
- 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 ?
Irfan1995
Coul you help
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_12.pdf
Question 13. I have chosen D. So the concentrations of Na inside cell is low while outside is high. So Na will move against the concentration gradient through protein 2. The concentrations of K inside cell is high and outside cell is low. So K will move against the concentration gradient through active transport through protein 3. Diffusion will occur down the concentration gradient for each, so 4 for Na and 1 for K. Answer is A. I do not get it.
Question 37. How can there be 3 fragments if the heavy polypeptide chains are hydrolysed? I thought there would be 2, each having 1 heavy chain and 1 light chain.
why
WHY the time between 1 and 2 and 3 and 4 is the time both the valves are closed??
Q13:
Active transports pumps ions against a concentration gradient (from a region of low concentration to a region of high concentration). So the cell has a high concentration of potassium, but rather than going from high to low, it will go from low to high. So the low concentration of potassium outside will all be forced inside.
With sodium, the exact opposite happens.
Diffusion goes down a concentration gradient (from a region of high concentration to a region of low concentration). There is a very low concentration of sodium inside and a high concentration of sodium outside. So sodium will travel from outside the cell to inside the cell through diffusion. The opposite is true for potassium.
Q37:
We know that an antibody looks like a "Y". When it fragments, it does so in three parts. The top two are called the "fragment antigen-binding" (Fab). These are shaped like "\" and "/". Antigens can bind to those two parts. The bottom part is the constant region, or fragment crystallizable (Fc). It's the straight/vertical line shaped like "|"
Q13: That's exactly what I said. Now look at the answer and you'll see that it should be D and it's A.
can anyone explain Q 12 please?? ans: C
Now I get it thanks a lot , JAZAK ILALLAH 5AYRANI'll try to explain this as simply as possible.
At (1), the AV valves close. At (2), the semilunar valves open. Before point (2), the semilunar valves are still closed. So between (1) and (2), both valves are closed.
At (3), the semilunar valves close, and at (4), the AV valve starts to open. Before point (4), the AV valves are still closed (they were closed since point (1)).
Now I get it thanks a lot , JAZAK ILALLAH 5AYRAN
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