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BarryIsMyName
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#1941
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#1941
(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


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BarryIsMyName
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#1942
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#1942
Also does anyone have a list of definitions to know


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sandrabondaruk
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#1943
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#1943
(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.



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Pataiiii
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#1944
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#1944
(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.
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Suzanna5678
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#1945
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#1945
(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.



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do we need to mention a water p gradient
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Razer_M
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#1946
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#1946
http://web.archive.org/web/201006020...W-QP-JUN09.PDF

Q4(a)

I don't get this at all 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?
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Suzanna5678
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#1947
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#1947
(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 ?
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Mr boombang
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#1948
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#1948
Can anyone tell me whats immunological comparision of proteins and how its done?
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Suzanna5678
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#1949
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#1949
What are people doing for revision today? Is everyone just looking over notes ?
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Suzanna5678
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#1950
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#1950
(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
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Katy1704
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#1951
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#1951
Hello 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?
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Pataiiii
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#1952
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#1952
(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.
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Katy1704
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#1953
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#1953
(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
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Suzanna5678
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#1954
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(Original post by Katy1704)
Hello 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
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Suzanna5678
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#1955
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#1955
(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
Could you link me to the paper? Wanna see which question this is
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sandrabondaruk
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#1956
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#1956
(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


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Suzanna5678
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#1957
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#1957
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 ?!
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Katy1704
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#1958
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#1958
(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.
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Katy1704
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#1959
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(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?
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Suzanna5678
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#1960
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#1960
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
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