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

Reply 2740

2013leaver

5

Original post by 2013leaver

Jan 2011 question 6b, the penciilin question for is too confusing.

this is the mark scheme answer answer 2.png

I thought penicillin works by inhibiting the active site of enzymes, it even says in the text book. Why is the markscheme saying the opposite happens? would be grateful if someone can explain.

Anyone?

Reply 2741

Manni

Original post by Nav_Mallhi

Soon

Absolutely fantastic

Reply 2742

username984585

20

Original post by Manni

Absolutely fantastic

Get back to revision. :tongue:

Reply 2743

Aidn

6

Original post by Zebrajess

Water evaporates from the leaves of the upper branches, so the water movement starts there (as opposed to starting in the trunk). This creates tension which pulls water up the tree.

Ok, and what does 'negative pressure mean' the mark scheme in june 2012 said something about the pressure in the xylem being lower than in the atmosphere but that doesn't make sense to me :frown:

Thanks for answering btw! Especially tonight of all nights haha ^_^

Reply 2744

annaelizabet

6

Original post by BioMaths

Can somebody help me with June 2009 Q2 part (b) - I thought this would code for 8 amino acids :s-smilie:

but the MS says 4

I am guessing you know the every 3 bases codes for 1 amino acid. So count the base sequence of the top row and it is 4? I understand where you have got 8 from, it is because you have also counted the bottom row too? DO NOT do that, you only need to count the top row, as the bottom row is complimentary to the top and so it's coding for the same amino acids, no need to count this twice!

Reply 2745

daniel1005

4

Original post by hali123

Anybody got any how science works notes?

Explain why volunteers similar age.
• Age affects named disease
• Keep confounding variable constant* (tedious)

Why Sherlock calculated %change etc.
• The starting/ending mass varies
• So it makes the data comparable

Why student carried out several repeats/the students could improve the reliability by doing additional reading, explain how.
• To ensure more reliable mean
• To identify anomalies

Students could improve their graph by taking additional readings. Explain how.
• Additional reading improves precision/reliability of the line of best fit.
• So improving the precision/reliability of estimating intermediate points.

What factors would you have to consider to collect a reliable sample.
• Random sampling
• Divide study area into grid
- use random number generator
- take samples at intersection of co-ordinates
- use a large sample
- at different times of day/year
- conduct statistical test to determine validity

Bit more specific hsw questions

The student wanted to calculate rate of water uptake by the shoot in cm3 per minute. What measurements did she need to make?
• Distance and Time
• Radius of capillary tube
Why might the water uptake not be the equivalent to transpiration.
• (used to provide) turgidity/support/description of;
• (used in) photosynthesis / (produced in) respiration;
• Apparatus not sealed/’leaks’;
Suggest how the reservoir allows repeats to be made.
• Returns bubble to start

More specific hsw questions from the past

Suggest how adding antibiotics to Livestock X has improved profit for the farmer.
• Kills pathogenic/harmful bacteria/pathogens;
• Disease less likely/improves health/animals healthier/reduces spread of infection;
• Faster growth/more productive animals/more food converted to meat/greater survival/lower vet’s bills/increased yield/less energy (for „fighting infection‟);

Give ways to reduce transmission of bacteria X in hospitals
• Isolation
• Screening/Testing
• Sterilisation of wards/cleaning hands between patients/using gloves

(edited 10 years ago)

Reply 2746

PoorLoser

2

can someone explain potometer to me? i really don't understand anything about it!

Reply 2747

Zebrajess

9

Original post by marseille_h

Hello, for the questions on magnification i always get 1 mark for putting = size of image/actual size of specimen

But not the right result on the mark scheme. For the January 2010 exam can someone tell me how they did question 1(b)(ii). Maybe its the units or something else i dont understand. And more recently the question 1(d) in the January 2013 paper.

Thanks in advance :smile:

For the magnification question, the image length is 50mm.
convert this to micrometres = 50x1000 = 50000
magnification = image/actual = 50000/20 = 2500
Just make sure you convert everything to micrometres.

Reply 2748

goblins took me

7

Original post by ibmb24

does anyone have a mnemonic for learning the taxonomy groups

we werent given mnemonics but this... http://www.youtube.com/watch?v=6jAGOibTMuU&feature=youtube_gdata_player kinda cheesey but listen to it a couple of times and it sticks better then any wordplay :-D

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Reply 2749

Aardvark1998

18

Kinky Pigeons Crap On Fat Girls Shoes

That is all.

Reply 2750

liv12345

1

anyone predict the 6 mark question pls???? :biggrin:

Reply 2751

iLoveMyCatsx

11

Can someone summarize gas exchange in insects?

Reply 2752

BioMaths

Original post by annaelizabet

I am guessing you know the every 3 bases codes for 1 amino acid. So count the base sequence of the top row and it is 4? I understand where you have got 8 from, it is because you have also counted the bottom row too? DO NOT do that, you only need to count the top row, as the bottom row is complimentary to the top and so it's coding for the same amino acids, no need to count this twice!

Oh wow, thanks alot :smile:

Reply 2753

Thebest786

2

Original post by 2013leaver

Rolling up leaves traps a layer of stiil air, reducing the water potential gradient between the stomata and surrounding air, reducing transpiration.

Light only causes stomata to open, nothing else. stomata must be open for transpiration

So light causes stomata to open, the heat heats up the water, the water gains K.E and evaporates? Seen marks given in the mark scheme for the K.E part :sexface:

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Reply 2754

FatHeadedKing

Original post by 2013leaver

Anyone?

Okay, bacteria stops penicillin from working by producing enzymes which break down the penicillin.

A different penicillin will have a different Group X which isn't complementary to that bacteria's enzyme's active site so that enzyme can't break it down. So the penicillin can do it's job.

:-)

Reply 2755

_iiGEO

5

Original post by marseille_h

Hello, for the questions on magnification i always get 1 mark for putting = size of image/actual size of specimen

But not the right result on the mark scheme. For the January 2010 exam can someone tell me how they did question 1(b)(ii). Maybe its the units or something else i dont understand. And more recently the question 1(d) in the January 2013 paper.

Thanks in advance :smile:

hey there i was just doing the 2010 paper.. so you know the equation:
mag=size of image/ size of object

when you measure the size of image x-y using your ruler in cm, convert it into um by x10000 then for the size of object use the 20um provided and divide that by size of image e.g

mag= 4.9cm x 10000 / 20
= 2450um

and the answer is anything between 2350 - 2500... hope ive helped!! :biggrin:

D

Reply 2756

Manni

Original post by Nav_Mallhi

Get back to revision. :tongue:

Ooo feisty one :tongue:

Reply 2757

Suzanna5678

Do hepatic veins take blood from the liver and hepatic arterys take blood to the liver or the other way round?!