A level Biology: Post your doubts here!

[darks]

This one's the 2nd example. Ans C. But this is easy to answer.

 

[Metallic9896]

What I don't understand is why Venules have such high cross sectional area ._.

You're right. It's common in both C and D. One normally imagines that venules and arterioles would be similar to each other but I guess not. o_o

 

[Thelastmoment]

Yea

View attachment 62465
This one's the 2nd example. Ans C. But this is easy to answer.

Yeah it was this one nice work.

 

[Metallic9896]

View attachment 62465
This one's the 2nd example. Ans C. But this is easy to answer.

Ah, yes, nice one. The only reason I got it is that cross sectional area = X. Your point about pressure holds here too. Nice.

 

[Thelastmoment]

You're right. It's common in both C and D. One normally imagines that venules and arterioles would be similar to each other but I guess not. o_o

Here's what I think,
Arteies- Small Lumen
Veins - Larger Lumen
Capillaries - One cell thick lumen
They talk about the cross-sectional area so assume all these have the same length,
Therefore arteries will have smallest "free" area with capillaries having the highest.

 

[darks]

As for this question:
At the bottom: Nucleus
Then (upwards) : Chloroplasts ,Mitcohondria
Then: RER and SER
Then Ribosomes at the top

Thanks!!

 

[zellyman]

You're right. It's common in both C and D. One normally imagines that venules and arterioles would be similar to each other but I guess not. o_o

then again in darks' 2nd example they've given a graph of what you suggested.CIE needs to be more careful with these things.

 

[Thelastmoment]

I think this could help you, it about those heart problems

 

[Metallic9896]

I think this could help you, it about those heart problems

Yes, this graph traumatized me since O Levels, but I did manage to get it. Thanks a lot though.

 

[Thelastmoment]

Yes, this graph traumatized me since O Levels, but I did manage to get it. Thanks a lot though.

Oh and it was taught to me by my tutor all credits to him. Else I was stuck with it too. c- closed and o-opened

 

[Metallic9896]

Interesting question and the only time in I guess 10 years where the word 'liposomes/liposome' occured.

Answer is C. I hope all get this. Do ask if any question.

 

[Thelastmoment]

Interesting question and the only time in I guess 10 years where the word 'liposomes/liposome' occured. View attachment 62467

Answer is C. I hope all get this. Do ask if any question.

Like cold on the inside and cold on the outside maybe I'm a liposome xD

 

[darks]

Good Luck guys!! sleep is necessary for focus I hope the paper is easy and we all nail it!

 

[Metallic9896]

Like cold on the inside and cold on the outside maybe I'm a liposome xD

Living on isolation island, cherry on the top. So metal. \m/

 

[Metallic9896]

Good Luck guys!! sleep is necessary for focus I hope the paper is easy and we all nail it!

Absolutely man, good luck to you too hope we all ace this!!

 

[Thelastmoment]

Good night and Sweet dreams hopefully not biology

 

[Metallic9896]

If anyone is still awake, answer is C. That's a pretty basic answer but A and D sound reasonable too. There is something known as penicillin allergy and D is also true and a known phenomenon. So why are they rejected? I have a couple of possible arguments but would love to hear from anyone else first.

 

[Roe Mir]

Guys how do you solve the microscopy question in paper 12 O/N 2016 Question 4
And summer 2015 Paper 11 Question 3?
URGENT

 

[Metallic9896]

Guys how do you solve the microscopy question in paper 12 O/N 2016 Question 4
And summer 2015 Paper 11 Question 3?
URGENT

I actually did these two for another user on here in pm. Here is the 2015 one, stay online, I'll post the other.

10 to 50 is 40 EPG units and it also happens to be equal to 0.1 mm as both 10 and 50 coincide with the lines of the stage micrometer.

40 EPG : 0.1 mm
1 EPG = 0.1/40 = 0.0025 mm

All the round dark circles are chloroplasts. Find one that's horizontal so it's easier to measure. There's one right near the EPG scale at around 40 units. It begins at around 37 EPG units and ends at 41 EPG units, so it's about 4 EPG units.

1 EPG unit = 0.0025 nm
4 EPG units = 0.0025 x 4 = 0.010 mm

0.010 mm to micrometer is multiply it by 1000 and you get 10 micrometer. Answer should be B.

 

[Metallic9896]

Guys how do you solve the microscopy question in paper 12 O/N 2016 Question 4
And summer 2015 Paper 11 Question 3?
URGENT

Here you go for the 2016 one.

You can begin by looking at the thick line at the left and then the middle one. From the thick to the middle it's one stage micrometer division. Now see if it coincides perfectly with any line on the EPG. Luckily, both lines do. The first thick line coincides at the 10 EPG mark, and the middle line coincides with the 50 EPG mark. Thus, 50 - 10 = 40 EPG units are equal to 1 stage micrometer division, and 1 stage micrometer division is 0.1 mm, so 40 EPG units are equal to 0.1 mm. Thus, 0.1/40 = 1 EPG unit is 0.0025 mm.

Knowing that, the next step is finding the area. For the area you need the radius. You can't do that with a stage micrometer (or else we wouldn't have needed an EPG in the first place) because not only is it not precise enough due to being magnified so much, it's also not in the center, and the radius is always from the edge to the center. The EPG however is. So your next step is to get the radius in terms of EPG units. Rather than estimating radius, it's better to get diameter then divide it by 2. The diameter starts at 0 and if you look closely goes all the way to 100. You can't read "100" written but if you count from 95 upwards you'll see that it's exactly 5 more divisions, so this means that the diameter is perfectly equal to 100 EPG divisions. The radius then is 100/2 = 50 EPG divisions.

1 EPG division was 0.0025 mm, so 50 EPG divisions = 0.0025 x 50 = 0.125 mm = the radius of the field of view. Answers seem to be in micrometers so let's convert this to micrometers beforehand. 0.125 x 1000 = 125 micrometers. The radius is 125 micrometers. Now it's very easy. Area is pi tiimes r squared or pi times r times r. In the format of the answers they've given us, it should be pi x 125 x 125, which is option C.