inslupbanana
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Edexcel Biology B A level Unofficial mark scheme

Probably should have done this earlier as I can't remember half of it now but I assumed someone else would do it- guessing there aren't that many people doing this course.

I don't remember many of the questions and I definitely didn't get the answers right, so please just add onto this thread and we'll see if we can get most of it down and then organise it later.

First question
Table comparing DNA and mRNA (4)
DNA and mRNA both have adenine
mRNA has uracil, DNA doesn't
Google seems to think that they both have hydrogen bonding and they both have pentose sugars but there was definitely one thing that DNA was supposed to have and mRNA wasn't- i think DNA was supposed to have hydrogen bonding and mRNA not, so they both had pentose sugars.
Explain how gel electrophoresis separates fragments (2)
-negatively charged DNA molecules pulled through due to electric field, smaller molecule pulled faster than large molecules through pores in gel
Size of fragment F(1)
Think I put 4 for some reason

Electron microscope/mitochondria question

-Multiple choice (1): Matrix (?)
-Explain the difference in these pictures(2)
Idk, said something about it being on a higher magnification so easier to see the inter-membrane space
-Why were there different Protein/Lipid ratios in mitochondria membranes (6)
Not sure, said something about the outer membrane having equal protein to phospholipid mass as lots of different particles taken in while the inner membrane has a much greater relative protein content because thats where all the complex ions need to get in for specialised processes. If someone actually knows the answer that'd be great!

DNA methylation question
-What is DNA methylation (1)
-Difference between, toti, pluri and multipotent stem cells (3)
-Using graph explain why it is involved in embryonic cell divison (2)
-Why can't all cells divide to produce different ones (2)

Question on rust fungus
-Multiple choice: Which one of these refers to rust fungus(1)
Puccinia
-Why does rust fungus reduce the yield(2/3?)
I put something about it taking nutrients from the plants but I don't know.
-?? Can't remember question (3)


Plant question
-Magnification of genetically modified photograph (2)
- I put x1700
question here I can't remember
-Describe how you would measure rate of photosynthesis (3)
-Use the graph to explain the difference in photosynthetic rates between plants(3)
I put wider stomata allows for more gas exchange and so more carbon dioxide available for photosynthesis ?
-Why does GM have a higher yield/growth or something(3)
3 Multiple choice questions
Why does the guard cell open the stomata? (1)



LDL and HDL question
-how are LDLs adapted to transport fatty acids and cholesterol(3)
-Calculate volume of LDL(1) (5758 or something, pi x x^3)
-Explain why LDL has a lower density(2/3?)
-Explain why LDLs cause heart disease

Question on thyamidine/antigens and genetic culturing
-Don't really know what the questions were


Last question was the cancer one
-Dox cancer cell question, why does it stop cell dividing (5)
-Using graph, what are effects of thing on different types of amino acids (6)
-How does weak cardiac muscle effect a person (2)
The heart cannot pump enough blood out to the body, the individual would find it difficult during exercise as the heart wont be able to pump blood to the muscle and they could have difficulty breathing.

I've really gotta revise chem rn but if anyone else wants to put in the stuff I'm missing, that'd be great.
Last edited by inslupbanana; 1 year ago
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juliejoyceyao
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last question: How does weak cardiac muscle effect a person?
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aqauamarine
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There were three multiple choice questions in a row about the stomata and guard cell but don’t remember the wording
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aqauamarine
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Q: what was the genus of stem rust fungus
A: Pucinnia
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dlemuella
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I said: The heart cannot pump enough blood out to the body, the individual would find it difficult during exercise as the heart wontbe able to pump blood to the muscle and they could have difficulty inbreathing.

(Original post by juliejoyceyao)
last question: How does weak cardiac muscle effect a person?
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Declan6546
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Hi. what did you guys put for the 6 mark question on Dox with the graph? there seemed to be absolutely no difference between effect or polar and non polar amino acids?
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dpatel457
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there was one which was about the inner wall/ outer wall being more flexible as to how the guard cell opens??

(Original post by aqauamarine)
There were three multiple choice questions in a row about the stomata and guard cell but don’t remember the wording
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T-wreckz
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Dude of course they both have pentose sugars, Ribose and Deoxyribose thats simple and I think I failed. The famous hydrogen bonds between the nigrogeneos bases on the two DNA strands that RNA does not have. x1.92 faster and they wanted the answer in standard form thats 1.7 x 10^3
(Original post by inslupbanana)
Edexcel Biology B A level Unofficial mark scheme

Probably should have done this earlier as I can't remember half of it now but I assumed someone else would do it- guessing there aren't that many people doing this course.

I don't remember many of the questions and I definitely didn't get the answers right, so please just add onto this thread and we'll see if we can get most of it down and then organise it later.

First question
Table comparing DNA and mRNA (4)
DNA and mRNA both have adenine
mRNA has uracil, DNA doesn't
Google seems to think that they both have hydrogen bonding and they both have pentose sugars but there was definitely one thing that DNA was supposed to have and mRNA wasn't- i think DNA was supposed to have hydrogen bonding and mRNA not, so they both had pentose sugars.
Explain how gel electrophoresis separates fragments (2)
-negatively charged DNA molecules pulled through due to electric field, smaller molecule pulled faster than large molecules through pores in gel
Size of fragment F(1)
Think I put 4 for some reason

Electron microscope/mitochondria question

-Multiple choice (1): Matrix (?)
-Explain the difference in these pictures(2)
Idk, said something about it being on a higher magnification so easier to see the inter-membrane space
-Why were there different Protein/Lipid ratios in mitochondria membranes (6)
Not sure, said something about the outer membrane having equal protein to phospholipid mass as lots of different particles taken in while the inner membrane has a much greater relative protein content because thats where all the complex ions need to get in for specialised processes. If someone actually knows the answer that'd be great!

DNA methylation question
-What is DNA methylation (1)
-Difference between, toti, pluri and multipotent stem cells (3)
-Using graph explain why it is involved in embryonic cell divison (2)
-Why can't all cells divide to produce different ones (2)

Question on rust fungus
-Multiple choice: Which one of these refers to rust fungus(1)
Puccinia
-Why does rust fungus reduce the yield(2/3?)
I put something about it taking nutrients from the plants but I don't know.
-?? Can't remember question (3)


Plant question
-Magnification of genetically modified photograph (2)
- I put x1700
question here I can't remember
-Describe how you would measure rate of photosynthesis (3)
-Use the graph to explain the difference in photosynthetic rates between plants(3)
I put wider stomata allows for more gas exchange and so more carbon dioxide available for photosynthesis ?
-Why does GM have a higher yield/growth or something(3)
3 Multiple choice questions
Why does the guard cell open the stomata? (1)



LDL and HDL question
-how are LDLs adapted to transport fatty acids and cholesterol(3)
-Calculate volume of LDL(1) (5758 or something, pi x x^3)
-Explain why LDL has a lower density(2/3?)
-Explain why LDLs cause heart disease

Question on thyamidine/antigens and genetic culturing
-Don't really know what the questions were


Last question was the cancer one
-Dox cancer cell question, why does it stop cell dividing (5)
-Using graph, what are effects of thing on different types of amino acids (6)
-How does weak cardiac muscle effect a person (2)
The heart cannot pump enough blood out to the body, the individual would find it difficult during exercise as the heart wont be able to pump blood to the muscle and they could have difficulty breathing.

I've really gotta revise chem rn but if anyone else wants to put in the stuff I'm missing, that'd be great.
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TheOnlyIzzy
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For the protein/lipid ratio, I talked about the chemiosmotic theory of ATP synthesis, because this takes place on the inner mitocondrial membrane. the extra proteins would be the enzyme ATPase and Active Hydrogen Pumps (protein carriers in cell membrane). I checked with my biology teacher and he believes that was the right answer, so idk if that helps ??
(Original post by inslupbanana)
Edexcel Biology B A level Unofficial mark scheme


-Why were there different Protein/Lipid ratios in mitochondria membranes (6)
Not sure, said something about the outer membrane having equal protein to phospholipid mass as lots of different particles taken in while the inner membrane has a much greater relative protein content because thats where all the complex ions need to get in for specialised processes. If someone actually knows the answer that'd be great!
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TheOnlyIzzy
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it was "the stomata open because water moves into/out of the guard cells by osmosis, which causes the guard cells to be turgid/relax" (something like that), and then another being like "the guard cells open because the inner wall is more/less/ the same flexiblity as the outer wall" (you get the idea).

the answer btw was stomata open because guard cells flood with water, so they become turgid and stand up, because the outside wall is more flexible than inside
(Original post by dpatel457)
there was one which was about the inner wall/ outer wall being more flexible as to how the guard cell opens??
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TheOnlyIzzy
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(Original post by inslupbanana)
Edexcel Biology B A level Unofficial mark scheme

Please just add onto this thread and we'll see if we can get most of it down and then organise it later.


DNA methylation question
-What is DNA methylation (1)
-Difference between, toti, pluri and multipotent stem cells (3)
-Using graph explain why it is involved in embryonic cell divison (2)
-Why can't all cells divide to produce different ones (2)
What is DNA Methylation (1):
I put "the addition of a methyl group between a cytosine and guanine base pair, which closes up the chromatin structure to prevent transcription"

Difference between tori, pluri and multipoint stem cells? (3):
"tori potent has the ability to form all of the cell types needed for a new organism, pluripotent can form most of the cell types but not the placental tissue, and multipototent stem cells can form a limited range of tissues - the tissues for the organ it is found in"


Using graph explain why it is involved in embryonic cell divison? (2):
at the start of the graph, there is totipotent, as it matures (differentiations) it becomes somatic tissue, it does this because DNA methylation turns off the genes to form other cell types as the cell matures, which is why DNA methylation goes up on the graph towards the end, because it is differentiating the tissues"

Why can't all cells divide to produce different ones? (2):
"because the cells are fully differentiated and cannot differentaiate any further"

idk if thats right, but update if you know
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