# AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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why cant antibiotics treat viral infections? is it because viruses have no cell wall so will not be made permeable?
they have a different type of cell wall
2. Hellooo

I know this is a really simple question but my teacher managed to confuse me!

What is the definition of transpiration??

In the textbook, it says it the evaporation of water from the surface of a plant... but apparently this doesnt get you the marks?? You have to say something to do with the movement of water through a plant??

Does anyone have a defintion that is sure to get you marks??
(even with AQA being very pedantic with their keywords )
3. Evapouration of water moving out the surface of the leaf by osmosis?
Tricky!!
Evapouration of water moving out the surface of the leaf by osmosis?
Tricky!!
Thats what I thought, but apparently that doesnt get you any marks...

(although my teacher may have been talking rubbish... )
5. (Original post by spoinkytheduck)
Hellooo

I know this is a really simple question but my teacher managed to confuse me!

What is the definition of transpiration??

In the textbook, it says it the evaporation of water from the surface of a plant... but apparently this doesnt get you the marks?? You have to say something to do with the movement of water through a plant??

Does anyone have a defintion that is sure to get you marks??
(even with AQA being very pedantic with their keywords )
Transpiration is just the uptake of water through the plant.
6. (Original post by awais590)
Transpiration is just the uptake of water through the plant.
So it is the definition is talking about the uptake of water rather than the water leaving the plant...?

Okey doke

Ha, I feel so simple
7. I have two questions
What is meant by the term 'hierarchy'? and how do you work out the image size, as in whats the formula and do you convert micrometers in mm, I am rather confused :L thanks in advance
8. (Original post by spoinkytheduck)
So it is the definition is talking about the uptake of water rather than the water leaving the plant...?

Okey doke

Ha, I feel so simple
Lol,

Definition of Transpiration:

Uptake of water through the plant.
9. (Original post by PumbaWiggles)
I have two questions
What is meant by the term 'hierarchy'? and how do you work out the image size, as in whats the formula and do you convert micrometers in mm, I am rather confused :L thanks in advance
Heirachy is just 'a group within groups', it represents the classification groups of 'Kingdom, Phylum, Class etc'.

'A big group containing smaller groups'

10. (Original post by Insanity514)
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?
There are three chromosomes in the question. On lining up during meiosis metaphase 1, any chromosome in given particular position could either be one of two: paternal or maternal. The number of combinations possible therefore is 2 to the power of 3, which is 8.
Similarly you can apply combinations to why DNA is a triplet code. There are 4 possible bases to choose from, if we want a code of 3 out the 4 we can have 4^3=64 combinations. This gives a surplus of codes which can accommodate all 20 amino acids known to exist.
Basically, take your base as what a thing can be, e.g. maternal or paternal = 2, A C G or T = 4 and have your index as how many things there are.
11. (Original post by awais590)
Heirachy is just 'a group within groups', it represents the classification groups of 'Kingdom, Phylum, Class etc'.

'A big group containing smaller groups'

haha it made sense, thank you
12. (Original post by awais590)
Heirachy is just 'a group within groups', it represents the classification groups of 'Kingdom, Phylum, Class etc'.

'A big group containing smaller groups'

1 mark, with no overlap = 2nd mark
13. (Original post by LifeIsGood)
1 mark, with no overlap = 2nd mark
Ah, thank you

"Explain how the venous return of the blood to the heart is maintained?" (5 marks)

Thanks
15. Can someone help me with this?

Explain why the oxygen dissociation curve is Sigma shaped (s-shaped) 2 Marks
16. (Original post by Nuss)
Can someone help me with this?

Explain why the oxygen dissociation curve is Sigma shaped (s-shaped) 2 Marks
It's in the CGP guide but what I remember roughly was that as haemoglobin becomes saturated, it's not able to bind more easily than when it was unsaturated producing a sigma shape. That's the idea of how I remember it but it is definitley in the CGP guide.
17. (Original post by STARMissyB)

"Explain how the venous return of the blood to the heart is maintained?" (5 marks)

Thanks
I've never seen a question along those lines unless you're talking about tissue fluid?
18. (Original post by STARMissyB)

"Explain how the venous return of the blood to the heart is maintained?" (5 marks)

Thanks
veins are flattened due to muscle contractions, giving pressure in the veins
veins have valves to prevent backflow

Don't know where five marks come from....
19. What is a tissue?

We've been taught that it's and aggregation of similar cells grouped together to carry out one specific task.

But the mark scheme says that they are of "common origin"

So is the definition we've been taught still correct?

Also what does it mean by switching on genes?
Apparently when cells differentiate their genes are "switched on"???
20. (Original post by Insanity514)
What is a tissue?

We've been taught that it's and aggregation of similar cells grouped together to carry out one specific task.

But the mark scheme says that they are of "common origin"

So is the definition we've been taught still correct?

Also what does it mean by switching on genes?
Apparently when cells differentiate their genes are "switched on"???
Yes you are correct. The mark scheme varies every year, but the answers remain the same, and the examiners will acknowledge this.

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