• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

A level Biology: Post your doubts here!

Midnight dream

Midnight dream

Messages
1,001
Reaction score
17,743
Points
523
S

Studydayandnight

Messages
155
Reaction score
27
Points
28
qwertypoiu said:
I personally hated this question.
You probably chose C as well, since minimum membranes CO2 passes through should be 4, (2 through capillary, 2 through squamous epithelial cell of alveolar wall). We learnt the three modes of CO2 transport, and the molecule remaining in blood plasma would be the case of minimum membrane crossing situation.
And oxygen, I thought, should be 5 since we're taught it goes into red blood cell and binds with haemoglobin. However, here's what the examiner's gotta say:

"Those candidates who realised that the question asked for the minimum number of cell membranes crossed by a molecule of oxygen and a molecule of carbon dioxide when passing to or from the alveoli to the capillary knew that 4 was correct for both. Option C was incorrectly selected by many candidates, but oxygen only passes through 5 membranes when it enters the red blood cell."

I might be over-reacting but come on! We never learnt oxygen had the choice to just not go into the RBC and choose not to bind with haemoglobin!:mad:
(Or at least I didn't...):(
Click to expand...

Ugh, I hate trick questions, they mess with my mind and make me even more confused. -_-

Anyway, thanks for the help! I really appreciate it. :)
 
S

Studydayandnight

Messages
155
Reaction score
27
Points
28
My Name said:
So you know the formula Magnification=size of image/size of object.:)

and they stated this 'The length of the chloroplast from X to Y is 5000nm.' and have given you a figure.
So if you measure that length in the figure you would get about 5cm=50mm=50,000micrometer=50,000000 nanometre.
Then this value 50000000 is the size of image and you have been given the size of object as 5000nm, just place them in the formula!
You will get the answer as 10,000. And that would be C.

I hope that helps.:D

And btw I think Bio ( as compared to others like Physics and Chem) paper is easier, just make sure that you know the chapter properly and make notes when doing MCQ's that helps you to revise important points. ( I made notes for two chapters if you want I can share :))
Click to expand...

Hey, thanks! Yeah, I find bio the least hard :p I was just confused with the conversions. :/

This helped clarify that so thank you! :) Yes, please share! That'd be even more helpful. :)
 
Last edited:
You must log in or register to reply here.
Top