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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

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hi ,everyone i have an question regarding the jAN 2013 paper the magnification question 1d i measured the lenght of the arrow and i got 11 mm which is wrong ? can anyone helpppppp pls lol

Reply 1021

Suzanna5678

Original post by Jimmy20002012

How haemoglobin loads oxygen in the lungs and unloads in a tissue cell?:

Firstly you a low partial pressure in the lungs, so haemoglobin will have a high affinity for oxygen, so oxygen therefore binds to the haemoglobin molecule by alosteric inhibition. Oxyhemoglobin is now formed, when it reaches the reaches the respiring tissues, you have a high partial pressure, therefore you have a low affinity of oxygen. Consequently, oxyhemoglobin unload the oxygen to the respiring tissues which means cellular respiration occurs. This means that carbon dioxide is produced, which happens to lower the ph of the blood, causing a higher partial pressure, so the cells would rapidly need oxygen to be unloaded from haemoglobin, in order to compensate for this production of carbon dioxide.

This should get you 6 marks, probably need to put half of what I put :smile:

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Thank you !

Reply 1022

Suzanna5678

Does Independent segregation occur in the first division and second?

Reply 1023

homefind

Original post by Hayley-27

do we need to know the process of ventilation in fish? or just gas exchange in fish?

I'm also confused about this because we did learn the whole process of ventilation in class and the gas exchange/countercurrent mechanism, however it isn't in the CGP revision guide (the process) and the spec just says - "across the gills of a fish (gill lamellae and filaments including the countercurrent principle)"

Reply 1024

homefind

Original post by Suzanna5678

Does Independent segregation occur in the first division and second?

first, i think :confused:

Reply 1025

kingster123

Original post by Hayley-27

11mm isn't the correct length, it should be in the region of 23mm, which you then multiple by 1000 to convert it to micrometres, then you divide your length by the actual length of 48um. And i got an answer of 479.2 times (using 23000)

hey thank ,but dont you just measure the arrow

Reply 1026

Tee Logan x

Can someone explain formation of tissue fluid to me please? i've read it a couple of times and i don't understand it. Thank you :smile:

Reply 1027

homefind

Original post by Tee Logan x

Can someone explain formation of tissue fluid to me please? i've read it a couple of times and i don't understand it. Thank you :smile:

at the arteriole end the pressure inside the capillaries is greater than the pressure in the tissue fluid, the difference in pressure forces fluid out of the capillaries and into the spaces surrounding the cells (this is tissue fluid)

as the fluid leaves capillaries the pressure reduces, so at the venule end pressure is much lower. Also the WP is lower than the WP in tissue fluid and so water moves back into the capillary by osmosis.

Reply 1028

chelley2

Can you say "haemoglobin unloads where there's higher pCO2 "or is it "higher concentration of CO2"?

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Reply 1029

Suzanna5678

Original post by homefind

first, i think :confused:

Ahhh everyone is saying different things :frown:

Reply 1030

OllieWolly

Right, for question 5ci) on the June 2010 paper, could anyone possibly explain to me why it's only crossing over? I thought it was independent segregation, but apparently the mark scheme says that stating this negates the mark! Thanks in advance!

Reply 1031

Simran Mars Foster

Guys is it just me or is the Jan 11 paper particularly nasty :s-smilie:

Reply 1032

homefind

Original post by OllieWolly

isn't it just because crossing over gives rise to different alleles?

(edited 10 years ago)

Reply 1033

OllieWolly

Original post by homefind

isn't it just because crossing gives rise to different alleles?

Oh... I thought independent segregation did too? As both are responsible for variation? I'm slightly confused to say the least :frown:

Reply 1034

homefind

Original post by OllieWolly

Oh... I thought independent segregation did too? As both are responsible for variation? I'm slightly confused to say the least :frown:

ye i know they both cause variation, im not sure now!!! haha oh god :confused:

Reply 1035

username984585

Hey guys!

Can someone help me out on the Jan 2013 paper on question 8ci?

Thanks! :smile:

Reply 1036

homefind

Original post by OllieWolly

Oh... I thought independent segregation did too? As both are responsible for variation? I'm slightly confused to say the least :frown:

i think it is just because the two chromosomes at the top would not be able to produce the four gametes by independent segregation, it could only be from crossing over