yeah, haven't heard of a biology AS paper asking for more than 80% for an A regardless of exam board/spec
But it's hard to be certain as I felt with most of the MCQ you could get them with educated guesses and eliminating ones it couldn't be without much thought

Thanks! and yeah i thought the MCQ's were really easy, the only tricky one was the diffusion of the artificial membrane one but got that in the end

Reply 885

Jitesh

14

Original post by brodingoson

Thanks! and yeah i thought the MCQ's were really easy, the only tricky one was the diffusion of the artificial membrane one but got that in the end

Which one did yhou go for? The one where the Benedict's was positive for extracellular? (C or B I think it was)

Reply 886

User1452521

2

Original post by Jitesh

Which one did yhou go for? The one where the Benedict's was positive for extracellular? (C or B I think it was)

Yeah, I put C. I felt like on some questions towards the end you could put a lot of information down like for e.g. the question that asked why do actively respiring tissues have more oxygen going to them then resting tissues. Bc you've got a steep conc. gradient, oxygen disassociates more due to acidic conditions etc...
But dunno whether the mark scheme is going to be really specific on they want bc there were a lot of valid answers for the questions

Reply 887

User1452521

2

Original post by Jitesh

Which one did yhou go for? The one where the Benedict's was positive for extracellular? (C or B I think it was)

Most of my class think they've failed it completely, I don't know how bc it wasn't a hard paper at all was just a wee bit vague on what they wanted you to put down on some questions

Reply 888

Jitesh

14

Original post by brodingoson

Yeah, I put C. I felt like on some questions towards the end you could put a lot of information down like for e.g. the question that asked why do actively respiring tissues have more oxygen going to them then resting tissues. Bc you've got a steep conc. gradient, oxygen disassociates more due to acidic conditions etc...
But dunno whether the mark scheme is going to be really specific on they want bc there were a lot of valid answers for the questions

Yeah I had to do it by a process of elimination for that MCQ because you couldn't confirm there were any sugars in the extracellular solution but you knew there wouldn't be any in the sausage thing

A lot of questions were vague and it didn't seem like it was wanting something specific near the end

Reply 889

User1452521

2

Original post by Jitesh

Yeah I had to do it by a process of elimination for that MCQ because you couldn't confirm there were any sugars in the extracellular solution but you knew there wouldn't be any in the sausage thing

A lot of questions were vague and it didn't seem like it was wanting something specific near the end

Yeah haha that MCQ was the last question I did

Reply 890

millymolly123

2

Original post by h3rmit

Just saying there was more co2 and outlining the bohr effect

By outling bohr effect do you mean the release of hydrogencarbonate ions ect?

Reply 891

Hmb28

7

Original post by Jitesh

What did your school give you?
Did they print the spec off for you at least? :s-smilie:

We got the spec and a different textbook to what most schools got

Reply 892

User1452521

2

Original post by Hmb28

We got the spec and a different textbook to what most schools got

Did they recommend buying the new spec. book?

Reply 893

thompsonnn

6

Original post by h3rmit

I think T killer cells produce perforin, it makes more sense that the killer cells actively produce substances to kill other cells

That was just a mistake in my typing, it is the T killer cells that produce perforin

Reply 894

melissa-23

4

what did everyone say for the question that was like 'why don't erythrocytes make oxygen' something like that

Reply 895

maxross

1

Original post by melissa-23

what did everyone say for the question that was like 'why don't erythrocytes make oxygen' something like that

Was this the 'why don't erythrocytes use the oxygen they carry question?'
I didn't really have a clue about it, but put something about they undergo very little metabolic processes and therefore don't require any energy, don't need to aerobically respire, so don't need oxygen.

May be well off though! Anyone else got more of an idea?

Reply 896

User1452521

2

Original post by maxross

Was this the 'why don't erythrocytes use the oxygen they carry question?'
I didn't really have a clue about it, but put something about they undergo very little metabolic processes and therefore don't require any energy, don't need to aerobically respire, so don't need oxygen.

May be well off though! Anyone else got more of an idea?

The question asked why doesn't erythrocytes use oxygen when transporting it, so i put...

oxygen can only dissociate from the iron ions/haemoglobin sub-units when the haemoglobin is in acidic conditions which only occurs when carbon dioxide enters and causes the reactions with water etc. and the H+ ions diffusing back in, alternating the tertiary structure of haemolgobin (due to the low pH) in which oxygen is then released...
So basically erythrocytes could not even use oxygen in the first place when carrying it due to low co2 and if they could use it, they'd only be able to use it when it disassociates to respiring tissues

But i dunno, you're right as well but erythrocytes in fact they actually do use a fraction of the oxygen they carry, but very minuscule

That's the problem with breadth is that you could say loads for the answer in which all answers would be valid, but they won't accept it
(kinda rambled lol)

Reply 897

JStebz

8

Original post by brodingoson

The question asked why doesn't erythrocytes use oxygen when transporting it, so i put...

oxygen can only dissociate from the iron ions/haemoglobin sub-units when the haemoglobin is in acidic conditions which only occurs when carbon dioxide enters and causes the reactions with water etc. and the H+ ions diffusing back in, alternating the tertiary structure of haemolgobin (due to the low pH) in which oxygen is then released...
So basically erythrocytes could not even use oxygen in the first place when carrying it due to low co2 and if they could use it, they'd only be able to use it when it disassociates to respiring tissues

But i dunno, you're right as well but erythrocytes in fact they actually do use a fraction of the oxygen they carry, but very minuscule

That's the problem with breadth is that you could say loads for the answer in which all answers would be valid, but they won't accept it
(kinda rambled lol)

I think I put that erythrocytes don't need to use any ATP since they don't undergo any active processes like exocytosis, active transport etc since they rely on affinity and diffusion to carry out their function properly; hence they don't need any oxygen for aerobic respiration (which produces ATP).

Reply 898

MiracleLeaf

20

Anyone got an unofficial mark scheme?

Reply 899

oni176

7

For the zoo question, I said providing medications (ex-situ approach) to prevent the endangered animals from suffering from any illness which may contribute to the death of the species. Is that wrong? That's the first thing that came into my mind when reading it.

For the question saying ''Referring to the features of blood or whatever, explain why red blood cells needs to take blood to the capillaries'' or something related to that I said capillaries are one cell thick that contains endothelium, meaning that the diffusion distance is reduced. Is that enough for 2 marks?

For the 2 marker on ''Explain/Give two reasons why species become critically endangered''' I said;
-They do not become adapted to their environment and overcome selective pressure so the species cannot interbreed and pass on their beneficial characteristics to their offspring, and also they do not have sufficient features, such as their size, which places them into a disadvantage. Do you think I'll get 2 marks?

For the question that said ''Explain an advantage of binomial classification'' I said it is universal, so scientists abroad can communicate worldwide to avoid confusion when classifying organisms

The 3 marker about DNA; I said ''The complementary base pairs (Adenine attaching to thymine, cytosine attaches to guanine, form a double helix which are attracted together by hydrogen bonding, hence they are anti-parallel in which they are attracted in opposite direction of 5' and 3'

Joining molecules was condensation reaction, but what was the chemical where two nucleotides attach together? I said RNA/nucleic acid? Maybe that's wrong?

For the advantage/ disadvantage of red blood cells I put:
Advantage; No nucleus means more space/ larger surface area for the red blood cell to transport oxygen, reducing diffusion distance
Disadvantage; Cannot control/transmit information? Maybe that's too vague?

OCR Biology A Exam Thread (Breadth - May 26, 2016 and Depth - June 7, 2016)

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