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OCR Biology F211 Exam - Tues 11'th January 2011

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are their any predicted questions that will defo come up lol if only i had the exam paper b4 hand sum hw :-)
Original post by VetApplicant
I have a 50 slide revision powerpoint for OCR AS Biology last year
If anyone wants it, just tell me how to send it and I will :biggrin:


Could you send me this too? Please, please, please. please ? ;D
Original post by qasidb
Aren't 7 and 8 the wrong way round?
I thought the ventricles begin to contract pushing blood in the atrioventricular valve falps causing them to close.


if the ventricles contracted while the valves was open the blood would return to the atria instead of going through the aorta to the body
Original post by qasidb
Aren't 7 and 8 the wrong way round?
I thought the ventricles begin to contract pushing blood in the atrioventricular valve falps causing them to close.


AV valves shut at the end of atrial systole, just before ventricular systole. because at the end of atrial systole, blood has poured into ventricles, so volume of blood and pressure in atria starts to decrease, and the blood that has just flown into the ventricles starts to flow back into the atria, filling the AV valve pockets with blood and therefore closing them. the closing of the AV valves makes a sound, and after they are shut, ventricular systole begins. :smile:
Original post by giraffegiraffe
AV shut at the end of atrial systole, just before ventricular systole. because at the end of atrial systole, blood has poured into ventricles, so volume of blood and pressure in atria starts to decrease, and the blood that has just flown into the ventricles starts to flow back into the atria, filling the AV valve pockets with blood and therefore closing them. the closing of the AV valves makes a sound, and after they are shut, ventricular systole begins. :smile:

yh thts right:smile:
what do you think your going to get in the exam
Original post by billy_h786
no coz u do tht in a2 i think lol


the spec says you need to know it. breathing rate=number of peaks per minute
oxygen uptake=decrease in peaks over a period of 1 minute
Reply 287
Avatar for fahimak
fahimak
translocation- the movement of assimilates along the phloem
sink- removal of sucrose in the phloem
source- releases sucrose in the phloem

HOW DOES SUCROSE ENTER THE PHLOEM?
basically the companion cells actively pump H+ ions form their cytoplasm using ATP energy into the surrounding cells. This produces a diffusion gradient. therefore the h+ will diffuse in to the companion cells with sucrose from a rgion of high concentration to a region of low concentration down a diffusion gradient through cotransporter proteins. this increases the concentration of sucrose in the companion cells which then diffuse into the seive tube elements via the plasmodesmata.
Can anyone describe the function of the chordae tendineae in the heart and how they carry out the function
do we need to know specific stains for the microscopes topic? they arent really mentioned in the book..
or just the fact that stains help some features of the image stand out, and dyes are used for light microscopes and metal particles are used for electron microscope stains to create contrast in the image?
Original post by The Smeezington
Can anyone describe the function of the chordae tendineae in the heart and how they carry out the function


i'm not sure that we need to know this in detail, just that the cords are on the inside of the valves and stop the valves from turning inside out therefore stop blood flowing the wrong way?
correct me if i'm wrong someone! :smile:
there's a thread on phloem/translocation etc here
:smile:

http://www.thestudentroom.co.uk/showthread.php?p=29294540&highlight=phloem
Original post by The Smeezington
Can anyone describe the function of the chordae tendineae in the heart and how they carry out the function


they are connected to the walls of the inside cardiac muscle. The have a small piece of tissue which contracts the same one of the atria or ventricles contract to open or close the valve e.g. when the ventricles contract it also contracts to close the valve and when the atria contracts it relaxes
ok.....i'm stealing notes from this thread....the Edexcel one sucks !
Original post by giraffegiraffe
do we need to know specific stains for the microscopes topic? they arent really mentioned in the book..
or just the fact that stains help some features of the image stand out, and dyes are used for light microscopes and metal particles are used for electron microscope stains to create contrast in the image?


in light microscopes colour stains chemicaly bind to parts of the cellular structure to show e.g. organelles. Different stains bind to different structures in a cell.

A lead or salt stain must be used in a electron microscope to scatter the electrons and create contrast
hope it helps
Reply 295
Avatar for ayesha00
ayesha00
can anyone describe what happens during G1,G2 and S1 during interphase?
can sum1 explain microtubules please
Look at graph:
http://www.enotes.com/w/images/thumb/5/5b/Cardiac_Cycle_Left_Ventricle.PNG/400px-Cardiac_Cycle_Left_Ventricle.PNG


does this show that the electrical activity of the heart is directly related to the cardiac cycle. how.
Original post by billy_h786

Original post by billy_h786
in light microscopes colour stains chemicaly bind to parts of the cellular structure to show e.g. organelles. Different stains bind to different structures in a cell.

A lead or salt stain must be used in a electron microscope to scatter the electrons and create contrast
hope it helps


perfect thankyou!
Original post by ayesha00
can anyone describe what happens during G1,G2 and S1 during interphase?


G1 - protein syntheis and the groth of proteins and organells
S1 - is the replication of chromosomes
G2 - is the growth of the cell and the growth of the spindle fibres

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