The Student Room Group

This discussion is now closed.

Check out other Related discussions

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

Scroll to see replies

Original post by Nav_Mallhi
Do we need to know this? I'm asking because I haven't seen it on the spec.


We do not need to know this, all we need to know about is helicase unzipping the strand, DNA polymerase essentially making a new strand on the template of each old one. There is 6 mark q on this in the jan 2013 paper all about replication, so you can see what the mark scheme wanted from you


Posted from TSR Mobile
Also does anyone have a list of definitions to know


Posted from TSR Mobile
Original post by Suzanna5678
Can someone write a 4 mark response on how antibiotics kills bacteria please


Bacteria kill bacteria by osmotic lysis.
1.The antibiotic inhibits the synthesis of protein links between the peptidoglycan molecules in the bacterial cell walls.
2.This prevents the cell from growing and weakens the cell wall.
3. Water moves in by osmosis.
4. The weakened cell wall cannot withstand the increased pressure and bursts.



Posted from TSR Mobile
(edited 10 years ago)
Reply 1943
Avatar for Pataiiii
Pataiiii
Original post by Suzanna5678
Can someone write a 4 mark response on how antibiotics kills bacteria please

The antibiotic acts as a competitive inhibitor and prevents enzyme substrate complexes forming that link the peptidoglycan chains forming in the cell wall of the bacteria. This weakens the cell wall and when water enters by osmosis down a water potential gradient, the pressure exerted on the cell wall, it is too large so osmotic lysis occurs. Some enzymes may also affect the cell cycle. Eg by preventing spindle fibres forming during prophase/ anaphase or by preventing DNA replication during s phase.
Original post by sandrabondaruk
Bacteria kill bacteria by osmotic lysis.
1.The antibiotic inhibits the synthesis of protein links between the peptidoglycan molecules in the bacterial cell walls.
2.This prevents the cell from growing and weakens the cell wall.
3. Water moves in my osmosis.
4. The weakened cell wall cannot withstand the increased pressure and bursts.



Posted from TSR Mobile
do we need to mention a water p gradient
Reply 1945
Avatar for Razer_M
Razer_M
5
http://web.archive.org/web/20100602033349/http://store.aqa.org.uk/qual/gce/pdf/AQA-BIOL2-W-QP-JUN09.PDF

Q4(a)

I don't get this at all :frown: Can someone please not only fill in the table values but also do it for the other stages of mitosis - metaphase and anaphase - which aren't asked?

And also the same table ..but for each stage of meiosis as well?
Original post by Pataiiii
The antibiotic acts as a competitive inhibitor and prevents enzyme substrate complexes forming that link the peptidoglycan chains forming in the cell wall of the bacteria. This weakens the cell wall and when water enters by osmosis down a water potential gradient, the pressure exerted on the cell wall, it is too large so osmotic lysis occurs. Some enzymes may also affect the cell cycle. Eg by preventing spindle fibres forming during prophase/ anaphase or by preventing DNA replication during s phase.

Thanks! Could it potentially be a 6 marker ?
Can anyone tell me whats immunological comparision of proteins and how its done?
What are people doing for revision today? Is everyone just looking over notes ?
Original post by Mr boombang
Can anyone tell me whats immunological comparision of proteins and how its done?

Serum A is obtained from Species 1
its then put into Species 2 and serum B is obtained (from species 2)
Serum B is put into species 3. If similar it will produce antibodies to the antigens of species 1. The more precipitate the more closely related
Reply 1950
Avatar for Katy1704
Katy1704
Hello :smile: when I did the January 2013 unit 2 exam for a mock the question on the potometer completely threw me, so does anyone know what 'how science works' questions could come up?
Reply 1951
Avatar for Pataiiii
Pataiiii
Original post by Suzanna5678
Thanks! Could it potentially be a 6 marker ?

Probably not, it's likely to be a 4 marker if it comes up but I just thought that I would give all the info.
Reply 1952
Avatar for Katy1704
Katy1704
Original post by neelam123h
Could someone help me with the Jan 13 - Q 1 d.

Thanks


Magnification = size of image / size of actual object

So you measure the starch grain in millimetres , then times this value by 1000 to get it in micrometers - this is the size of the image. Therefore, you divide this by the actual length of the starch grain (48micrometres) .

I hope this helps :smile:
Original post by Katy1704
Hello :smile: when I did the January 2013 unit 2 exam for a mock the question on the potometer completely threw me, so does anyone know what 'how science works' questions could come up?

All I've got down is that to find the rate of water you need distance moved by air bubble and surface area of lleaves. Why you cut the shoot under water is to prevent an air bubble which could disrupt the cohesion column of water in the xylem which would not be representative of the xylem
Original post by Katy1704
Magnification = size of image / size of actual object

So you measure the starch grain in millimetres , then times this value by 1000 to get it in micrometers - this is the size of the image. Therefore, you divide this by the actual length of the starch grain (48micrometres) .

I hope this helps :smile:

Could you link me to the paper? Wanna see which question this is
Original post by Suzanna5678
do we need to mention a water p gradient


I'm not convinced that it's essential, you probably wouldn't lose a mark if you didn't, however when mentioning osmosis it's probably a safe bet just to mention it in case


Posted from TSR Mobile
Right for the potometer in 2 papers its asked what's needed to calculate the water up take. In one markscheme it says 'distance and time' and 'diameter of tube' then in another markscheme it's 'distance moved by air bubble' and 'surface area of leaves' soooo what answer do I go with ?!
Reply 1957
Avatar for Katy1704
Katy1704
Original post by Suzanna5678
Could you link me to the paper? Wanna see which question this is


Sorry I can't, it's the January 2013 paper Q1d, I'm on my phone and I don't know where to find the paper on the Internet.
Reply 1958
Avatar for Katy1704
Katy1704
Original post by Suzanna5678
Right for the potometer in 2 papers its asked what's needed to calculate the water up take. In one markscheme it says 'distance and time' and 'diameter of tube' then in another markscheme it's 'distance moved by air bubble' and 'surface area of leaves' soooo what answer do I go with ?!


The most recent paper? What did the markscheme say for the most recent paper?
Sorry I know this has been asked so many times but can someone link me to the 2013 paper and markscheme or tell me what page it's on PLEASE

Related discussions

Latest

Trending

Trending

Articles for you