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Edexcel 6BIO1 ~ 9th January 2013 ~ AS Biology

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Original post by jojo1995
hi guys, I'm have forgotten the stages of meiosis, could someone help me out please

i know its
interphase,prophase,metaphase ananphase, telophase and then what omg ....
im a2 btw, i jsut cant remember :frown:
thanks


Cytoplasmic division?
Original post by The Assassin
How much of the DNA Helicase/Ligase stuff do we need to know? I don't think I've revised that :s-smilie:


Not a lot to be honest.
Just remember the names of some of them, that usually suffices. Although, its worth briefly knowing what each one does
(edited 11 years ago)
Original post by Kingboss
DNA helicase breaks the hydrogen bonds. DNA polymerase and Ligase join them up from what i remember


I've never heard of DNA helicase but that sounds right
As far as the hearts electrical system thingy goes, how much do we need to know?

Just S.A node initiating contraction by wave of depolarisation and being the hearts pacemaker, AV Node, Purkyne fibres?
^Do we even need to know about the electrical heart system thing? I haven't seen it any recent papers or in the CGP book.

Here's a mark scheme answer from AQA:

Role of SA Node
Sends out electrical activity/ impulses;
Initiates the heartbeat / acts as a pacemaker / (stimulates) contraction of atria;

Role of AV Node
AVN delays (electrical activity / impulses);
(Allowing) atria to empty before ventricles contract / ventricles to fill before they contract;
(AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne fibres;
(Causing) ventricles to contract (from base up) / ventricular systole;

Original post by mynameisntbobk
Cytoplasmic division?


Not a lot to be honest.
Just remember the names of some of them, that usually suffices. Although, its worth briefly knowing what each one does


Cheers.
(edited 11 years ago)
Reply 204
Avatar for Phteven
Phteven
15
Original post by d_94


You wonderful, wonderful person :biggrin:
Original post by The Assassin
^Do we even need to know about the electrical heart system thing? I haven't seen it any recent papers or in the CGP book.

Here's a mark scheme answer from AQA:

Role of SA Node
Sends out electrical activity/ impulses;
Initiates the heartbeat / acts as a pacemaker / (stimulates) contraction of atria;

Role of AV Node
AVN delays (electrical activity / impulses);
(Allowing) atria to empty before ventricles contract / ventricles to fill before they contract;
(AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne fibres;
(Causing) ventricles to contract (from base up) / ventricular systole;



Cheers.


Assassin, stuff on AV node and SAN are not in our spec for unit 1. However, candidates from the old spec that written jan 09 included them in the markscheme as it was so common. (for description of structure.)
Original post by letsbehonest
As far as the hearts electrical system thingy goes, how much do we need to know?

Just S.A node initiating contraction by wave of depolarisation and being the hearts pacemaker, AV Node, Purkyne fibres?


None of it. Thats the old spec, not the new one we are doing.
Original post by CoolRunner
None of it. Thats the old spec, not the new one we are doing.


Oh yay! One less thing to worry about!

What about the role of the CFTR channel? Its confusing me. My teacher skipped that whole section.
Just to get this clear:

HELICASE AND RNA POLYMERASE separate DNA strands by breaking the hydrogen bonds between complementary bases DURING PROTEIN SYNTHESIS

DNA POLYMERASE AND LIGASE joins DNA during semi conservative replication.
Reply 209
Avatar for jojo1995
jojo1995
2
Original post by mynameisntbobk
Cytoplasmic division?
isnt that for mitosis?, i thought there were more stages for meiosis.... its so confusing lol :smile: thank you
Not a lot to be honest.
Just remember the names of some of them, that usually suffices. Although, its worth briefly knowing what each one does



isnt that for mitosis?, i thought there were more stages for meiosis.... its so confusing lol :smile: thank you
Original post by letsbehonest
Oh yay! One less thing to worry about!

What about the role of the CFTR channel? Its confusing me. My teacher skipped that whole section.


Role of CFTR Channel:

1. In a CF sufferer, the CFTR channel is missing or non functional

2. Na+ move into the epithelial cell and cannot move back out, causing water to be drawn from the surrounding mucus by the process of osmosis.

3. This causes the mucus to become sticky.

4. Beating ciliae struggle to move the mucus out of the lung because it's too sticky, causing it to remain in the lungs, trapping bacteria and blocking alveoli.

5. Therefore less alveoli are available for gas exchange and so less oxygen is taken into the lungs.
Original post by jojo1995
isnt that for mitosis?, i thought there were more stages for meiosis.... its so confusing lol :smile: thank you


I'm not sure tbh. That's all unit 2 content, which I haven't gone through.
Reply 212
Avatar for jojo1995
jojo1995
2
Original post by mynameisntbobk
I'm not sure tbh. That's all unit 2 content, which I haven't gone through.


aww, thank you anyways :smile:
i got it taught this way that helicase unzips the DNA, and DNA polymerase links the adjacent nucleotides together? :/ is that right?

Posted from TSR Mobile
hey guys,
can someone explain the effect of cf on the gas exchange (respiretory system)? [4]


Posted from TSR Mobile
12 Explain the nature of the genetic code (triplet code only; non-overlapping and degenerate not required at AS).

That is just the triplet code, so 3 adjacent bases code for 1 amino acid. Several triplet codes can code for 1 amino acid. There are start and stop signals .. Is that it for that part of the spec?
Original post by Rubyturner94
hey guys,
can someone explain the effect of cf on the gas exchange (respiretory system)? [4]


Posted from TSR Mobile


Sticky mucus in bronchioles, reducing number of alveoli available for gas exchange so less surface area for gas exchange. This means that the rate of diffusion is slow, so less oxygen available. I think
Original post by Rubyturner94
hey guys,
can someone explain the effect of cf on the gas exchange (respiretory system)? [4]


Posted from TSR Mobile


- Mucus in sufferers of CF is thick and sticky
- Thickened mucus can't be moved by cilia/coughing
- Mucus blocks airways
- Gas exchange reduced
- because surface area is reduced
- so diffusion decreases
thank you :biggrin:
when they ask to ''describe the structure of enzymes'' do we descibe the 3-dimensional structure? eg chemical bond between R groupa etc?

Posted from TSR Mobile
Original post by Rubyturner94
thank you :biggrin:
when they ask to ''describe the structure of enzymes'' do we descibe the 3-dimensional structure? eg chemical bond between R groupa etc?

Posted from TSR Mobile


Yes and no. The mark scheme says this.

globular / eq ; (NOT 3D.)
2. reference to active site ;
3. reference to specific shape of active site ;
4. reference to {bonds /named bond / interaction / eq} between R groups ;
5. credit correctly named {bond/interaction} e.g. disulphide bond, hydrogen bonds, hydrophobic interactions (between R groups) ;

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