The Biology AS-level Thread Watch

DCMed96
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#641
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#641
(Original post by PriyaPaul)
Oh yh there is only one EMPA exam... but what about the Task 1 and Task 2 Questions ?
He said it might be on either enzymes or something.. hasn't confirmed it..
the questions are all based on the empa exams!
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PriyaPaul
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#642
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#642
(Original post by JackTeh96)
the questions are all based on the empa exams!
Ah right cool
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Hudl
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#643
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#643
Has anyone actually done the AQA EMPA tasks yet?
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DCMed96
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#644
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#644
(Original post by AhmedDavid)
Has anyone actually done the AQA EMPA tasks yet?
have you?? we havent
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phaseshift
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#645
How's it going guys?
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Kvothe the Arcane
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#646
(Original post by HarryMWilliams)
How's it going guys?
You're quite the helpful mod aren't you!
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phaseshift
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#647
(Original post by keromedic)
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Yes, I am.
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Kvothe the Arcane
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#648
(Original post by HarryMWilliams)
Yes, I am.
I read that back and I realised I sounded sarcastic. I was being genuine, I just type things in a weird way sometimes. Are u a uni student?
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phaseshift
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(Original post by keromedic)
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Yep, studying Biomedical Science.
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king101
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Hey guys so I’m quite confused on the understanding of ‘valves in the control of blood flow’. From the text book it states:
The design of all valves is basically the same. They are made up of a number of tough, but flexible, fibrous tissue, which are cusp shaped. When pressure is greater on the convex side of these cusps, rather than on the concave side, they move apart to let blood pass between the cusps. However, when pressure is greater on the concave side that on the convex side, blood collects within the bowl of the cusps. This pushes them together to form a tight fit that prevents the passage of blood.

So I’m confused with this bit in bold ‘Cusp Shaped’. What does that mean? So I ‘googled it’ and it showed this:

https://www.google.com/search?site=i...2F%3B304%3B323

i.e. I guess the cusp is this sort of thing: \/ -It would be this direction for the atrioventricular valves as the image shows and for the semi lunar valves it looks like this /\. Is this right?
--------------------------------------------------------------
Okay next bit: When pressure is greater on convex side of these cusps, they move apart to let blood pass between the cusps.
THIS IS WHERE I AM CONFUSED: IF THIS IS THE CASE LOOK AT THE ATRIOVENTRICULAR VALVES I.E. \/. I.e. they are concave. When pressure is greater on the CONVEX side i.e. ventricle from the TEXT BOOK it says they move apart so wouldn’t that therefore cause blood to flow into the atrium???
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Hudl
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(Original post by king101)
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Always remember the side with greater pressure is what is pushing the valve. (In most cases to open)


. During Diastole as the blood enters the atria from the pulmonary vein and vena cava pressure builds up in the atria as it fills which pushes open the atrioventricular valves.


. The semi lunar valves are shut at this time as the muscles in the ventricles are relaxed which helps in reducing the pressure in the ventricles causing the pressure to be lower here than in the aorta and pulmonary artery. The semi lunar valve is thus shut which causes the first dub sound of the heart.



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king101
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(Original post by AhmedDavid)
Always remember the side with greater pressure is what is pushing the valve. (In most cases to open)


. During Diastole as the blood enters the atria from the pulmonary vein and vena cava pressure builds up in the atria as it fills which pushes open the atrioventricular valves.


. The semi lunar valves are shut at this time as the muscles in the ventricles are relaxed which helps in reducing the pressure in the ventricles causing the pressure to be lower here than in the aorta and pulmonary artery. The semi lunar valve is thus shut which causes the first dub sound of the heart.



Name:  Heart question.png
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This is what I do not get. Thanks so much for the diagram and explanation it makes sense. BUT not with what the text book says. It says: Valves are made up of a number of flaps of tough but flexible fibrous tissue which are cusp shaped. It then says when pressure is greater on the CONVEX side it causes the cusps to move apart and blood to flow though them. And then when pressure is greater on the CONCAVE side it causes blood to fill up in the bowl of the cusps pusshing them together preventing backflow of blood.

Do you get where I'm confused?
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RoyalBlue7
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(Original post by king101)
This is what I do not get. Thanks so much for the diagram and explanation it makes sense. BUT not with what the text book says. It says: Valves are made up of a number of flaps of tough but flexible fibrous tissue which are cusp shaped. It then says when pressure is greater on the CONVEX side it causes the cusps to move apart and blood to flow though them. And then when pressure is greater on the CONCAVE side it causes blood to fill up in the bowl of the cusps pusshing them together preventing backflow of blood.

Do you get where I'm confused?
Could you say what exactly the textbook says (not with your own words)

Well if you look at the diagram above the side labelled convex has the cusps concave and the concave side has the cusps convex

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Hudl
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(Original post by king101)
This is what I do not get. Thanks so much for the diagram and explanation it makes sense. BUT not with what the text book says. It says: Valves are made up of a number of flaps of tough but flexible fibrous tissue which are cusp shaped. It then says when pressure is greater on the CONVEX side it causes the cusps to move apart and blood to flow though them. And then when pressure is greater on the CONCAVE side it causes blood to fill up in the bowl of the cusps pusshing them together preventing backflow of blood.

Do you get where I'm confused?
Yes if you could write the exact words of the book, it will help me understand the description of the book better. Also what book is this?



[EDIT]---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Ive finally go it...well I think I now understand it....we were taught Meiosis the other day in college but not to much detail and I didnt understand it. Just read the book. Im going to try and explain what I think it is, if I make any mistakes I would appreciate if someone points it out.


Meiosis occurs in order to divide a diploid cell to form 4 haploid cells.In interphase the DNA is being replicated to make an exact copy of the DNA. The chromosomes can not be seen at this stage. After this stage is Prophase I where the DNA & the replicated DNA join up and are in conjunction with proteins to form chromosomes. Homologous pairs of chromosomes then partner up and 2 things happen which are important to how each haploid cell differs. Crossing and homologous recombination. The homologous chromosomes interlink and wind certain sections of the chromosomes creating tension. This tension causes a parts of the chromosomes to come off which is attached unto the other same section of the partnered homologous chromosome. The next step is metaphase I where the centresome and microtubicles in the cell help to align the homologous pair of chromosome in a line in the middle of the cell and then Anaphase I occurs where a chromosome is pulled from each pair of chromosomes. Then in telephase I the nuclear membrane reforms and nucleoli within them as the chromosomes frail back into chromatids. The increased froce between the 2 new cells called cleavage separates the nuclei and forms 2 cells in a process called cytokineses.


Prophase II occurs where the DNA join back together to form chromosomes and these chromosomes. Then it is metaphase II where the chromosomes are moved and arranged in a line by structures called the microtubicles and centresomes. Anaphase II then occurs as the chromosome is split into 2 chromatids which in are separated. The nuclear membrane then reforms in Telephase II and 2 nuclei are formed due to the increasing force causing a cleavage. The 2 cells are then formed through a process called cytokineses.
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king101
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(Original post by RoyalBlue7)
Could you say what exactly the textbook says (not with your own words)

Well if you look at the diagram above the side labelled convex has the cusps concave and the concave side has the cusps convex

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Hahaa yes my own words are confusing . Okay straight from the text book:

" The design of all the valves is basically the same. They are made up of a number of flaps of tough, but flexible fibrous tissue, which are cusp shaped. When pressure is greater on the convex side of these cusps rather than the concave side they move apart to let blood pass between these cusps. However, when pressure is greater on the concave side, than on the convex side, blood collects within the bowls of the cusps. This pushes them together to form a tight fit that prevents the passage of blood."

And that's word to word from the text book.
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king101
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(Original post by AhmedDavid)
Yes if you could write the exact words of the book, it will help me understand the description of the book better. Also what book is this?



[EDIT]---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Ive finally go it...well I think I now understand it....we were taught Meiosis the other day in college but not to much detail and I didnt understand it. Just read the book. Im going to try and explain what I think it is, if I make any mistakes I would appreciate if someone points it out.


Meiosis occurs in order to divide a diploid cell to form 4 haploid cells.In interphase the DNA is being replicated to make an exact copy of the DNA. The chromosomes can not be seen at this stage. After this stage is Prophase I where the DNA & the replicated DNA join up and are in conjunction with proteins to form chromosomes. Homologous pairs of chromosomes then partner up and 2 things happen which are important to how each haploid cell differs. Crossing and homologous recombination. The homologous chromosomes interlink and wind certain sections of the chromosomes creating tension. This tension causes a parts of the chromosomes to come off which is attached unto the other same section of the partnered homologous chromosome. The next step is metaphase I where the centresome and microtubicles in the cell help to align the homologous pair of chromosome in a line in the middle of the cell and then Anaphase I occurs where a chromosome is pulled from each pair of chromosomes. Then in telephase I the nuclear membrane reforms and nucleoli within them as the chromosomes frail back into chromatids. The increased froce between the 2 new cells called cleavage separates the nuclei and forms 2 cells in a process called cytokineses.


Prophase II occurs where the DNA join back together to form chromosomes and these chromosomes. Then it is metaphase II where the chromosomes are moved and arranged in a line by structures called the microtubicles and centresomes. Anaphase II then occurs as the chromosome is split into 2 chromatids which in are separated. The nuclear membrane then reforms in Telephase II and 2 nuclei are formed due to the increasing force causing a cleavage. The 2 cells are then formed through a process called cytokineses.

I wrote the words of the text book in my post above and its the Nelson Thornes AQA text book. Thanks for the meiosis thingy by the way but I finally got my head around that haaha!
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RoyalBlue7
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(Original post by king101)
Hahaa yes my own words are confusing . Okay straight from the text book:

" The design of all the valves is basically the same. They are made up of a number of flaps of tough, but flexible fibrous tissue, which are cusp shaped. When pressure is greater on the convex side of these cusps rather than the concave side they move apart to let blood pass between these cusps. However, when pressure is greater on the concave side, than on the convex side, blood collects within the bowls of the cusps. This pushes them together to form a tight fit that prevents the passage of blood."

And that's word to word from the text book.
There should be no confusion here...

If you look at the diagram and what the textbook is saying you'll find no contradiction. The textbook refers to the shape of the cusps that is the valves while if you take the whole side it'll be different...

I think this explains it, doesn't it?



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Hudl
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(Original post by king101)
Hahaa yes my own words are confusing . Okay straight from the text book:

" The design of all the valves is basically the same. They are made up of a number of flaps of tough, but flexible fibrous tissue, which are cusp shaped. When pressure is greater on the convex side of these cusps rather than the concave side they move apart to let blood pass between these cusps. However, when pressure is greater on the concave side, than on the convex side, blood collects within the bowls of the cusps. This pushes them together to form a tight fit that prevents the passage of blood."

And that's word to word from the text book.
I have seen the section of the book you're talking about Page 91 on the nelson thornes book

Just to remind you, it also says further up in the book that "Valves in the cardiovascular system are designed so that they open whenever the difference in blood pressure either side of them favours movement of blood in the required direction. When pressure differences are reveresed ie when blood would tend to flow in the opposite direction to that which is desirable, the valves are designed to close."The part of the book you're querying is poorly worded in my opinion but if you read the sentence to the end they also said "...This pushes them together to form a tight fit that prevents the passage of blood (Figure 2). So great are the pressures created within the ventricles of the heart that the atrioventricular valves are at risk of being inverted" This is why the cusps are closed as although the beginning explanation is rather poor pressure is still however greater in the Ventricles.

The book could be possibly wrong in the wording of the top part, however I will confirm with someone if I was you. Besides all you need to know is that the valves open if the pressure is greater in the atria than ventricles as closes vice cersa. Same with the ventricles and aorta/pulmonary artery.

I hope I've been clear and you understand this, if there is still anything you dont understand please do say.

(Original post by king101)
I wrote the words of the text book in my post above and its the Nelson Thornes AQA text book. Thanks for the meiosis thingy by the way but I finally got my head around that haaha!
Oh great, glad to hear it helped you understand


----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


[EDIT] I also think I found a mistake in the book, it says in the nelson thornes book "In prokaryotic cells such as bacteria, the DNA molecules are smaller, form a circle and are not associated with protein molecules. Prokaryotic cells therefore do not have chromosomes." However on the answers to summary questions on the same book it says that In prokaryotic cells the DNA is smaller, linear and is not associated with proteins "In the mark scheme to one of the exam questions at the end of chapter 8 it says "A Palaside leaf cell is linear, larger and associated with proteins"So what is it really meant to be here as Its confusing!
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king101
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Cheers guys! Book had terrible wording is my verdict lol
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king101
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Does the formation of like carbohydrates via glysodic bonds require energy in the form of ATP for the condensation reaction to occur? I know it does for proteins but unsure about carbohydrates?
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