A level Biology: Post your doubts here!

[ashcull14]

which year maybe we have to say that rubisco catalyses co2 and rubp reaction ,co2 fixation
becasue in ms we have collision between co2 and enzyme above the confusing point
i think we should say that in C more co2 is there to be fixed . more co2 collide with rubp so more enzyme substrate complex forms
this reaction is catalysed by rubisco
by the way its AVP so u can anything but related and valid not only this confusing point

thanks..its june 2006

 

[My Name]

9700/32/MJ/14

Oh you need a slide for this. -_-
Sorry I can't help you.
Just go through the MS then.

 

[Eugene99]

Why can't it be cholera? Only sickle cell anemia and tuberculosis can genetically be transferred but the answer is B when A is equally likely

 

[Eugene99]

What do they mean by reducing water potential gradient?

 

[Eugene99]

Nuclear envelope also reforms during cytokinesis, why is it C?

 

[Shah34]

Telophase consists of nuclear envelope reforming , in which cytokenesis specifically refers to division of cytoplasm and cell into two by constriction from edges of cell Only!.
Check out corsebook book mitiotic cell cycle chap.

 

[Shah34]

View attachment 59920
What do they mean by reducing water potential gradient?

They mean characteristic features of xyrophytic plants that greatly reduce water loss ie transpiration etc.

 

[mohmed ahmed soliman]

simple dilution calculation
help!

 

[Amila Suriarachchi]

View attachment 59128
Can someone please tell me why the answer is C?

We measure the size of cells, tissues or large organelles (such as mitochondria, chloroplasts) using micro metres. However, to measure small orgenelles, such as cell membrane (7nm), cell wall, ribosomes or lysosomes, we have to use nano metres.

 

[Eugene99]

Telophase consists of nuclear envelope reforming , in which cytokenesis specifically refers to division of cytoplasm and cell into two by constriction from edges of cell Only!.
Check out corsebook book mitiotic cell cycle chap.

Actually, I read that in a mark scheme of a paper 2, that nuclear envelope reforms during cytoknesis. MCQs are just soo confusing!

 

[My Name]

View attachment 59919
Why can't it be cholera? Only sickle cell anemia and tuberculosis can genetically be transferred but the answer is B when A is equally likely

Some answers fro MCQs are surprising.People here suggested that I take alook at examiners report.You should also try that maybe it can help you.

 

[Rizwan Javed]

View attachment 59921
Nuclear envelope also reforms during cytokinesis, why is it C?

It's simple, bro. Look they said what is ALWAYS true for cytokenisis. Nuclear envelop is only present in eukaryotic cells. What about prokaryots? They don't have any nuclear envelop. So this statement does not hold true for every type of cell. I think you got it now. Right?

 

[Eugene99]

It's simple, bro. Look they said what is ALWAYS true for cytokenisis. Nuclear envelop is only present in eukaryotic cells. What about prokaryots? They don't have any nuclear envelop. So this statement does not hold true for every type of cell. I think you got it now. Right?

yup. get that now

Some answers fro MCQs are surprising.People here suggested that I take alook at examiners report.You should also try that maybe it can help you.

yeah you are right, will read er n future as well, thank you

 

[qwertypoiu]

View attachment 59919
Why can't it be cholera? Only sickle cell anemia and tuberculosis can genetically be transferred but the answer is B when A is equally likely

One possible explanation I can think of is that they didn't mean by genetic transfer only. Perhaps if the parent and child live together it is possible for the cholera bacteria to be transferred through using of same food utensils or something like that.

For malaria there is isn't a direct transfer of the disease; a mosquito would have to bite one person and bite the next one.

But I agree it's a bit silly.

 

[Eugene99]

One possible explanation I can think of is that they didn't mean by genetic transfer only. Perhaps if the parent and child live together it is possible for the cholera bacteria to be transferred through using of same food utensils or something like that.

For malaria there is isn't a direct transfer of the disease; a mosquito would have to bite one person and bite the next one.

But I agree it's a bit silly.

yes exactly

 

[Rizwan Javed]

One possible explanation I can think of is that they didn't mean by genetic transfer only. Perhaps if the parent and child live together it is possible for the cholera bacteria to be transferred through using of same food utensils or something like that.

For malaria there is isn't a direct transfer of the disease; a mosquito would have to bite one person and bite the next one.

But I agree it's a bit silly.

Yeah, you're right

Sickle cell anemia is a genetically inherited disease. Cholera bacteria can also be passed on to children from parents, if they are living together. Similarly tuberclosis is transferred when a parent coughs, the vapours containing the bacteria may be inhaled by the children, thus again it's directly passed on.

For malaria, it can't be passed on directly. It requires a vector for its transfer. If there is no vector, disease can never be transferred from parent to child, no matter how severe it is.

 

[qwertypoiu]

Yeah, you're right

Sickle cell anemia is a genetically inherited disease. Cholera bacteria can also be passed on to children from parents, if they are living together. Similarly tuberclosis is transferred when a parent coughs, the vapours containing the bacteria may be inhaled by the children, thus again it's directly passed on.

For malaria, it can't be passed on directly. It requires a vector for its transfer. If there is no vector, disease can never be transferred from parent to child, no matter how severe it is.

Oh yes I forgot even TB isn't transferred genetically.
Your explanation is perfect

 

[Shah34]

guys please help with this question
???

 

[kareem22010]

can somebody help me with this confusing markscheme doubt?
The question says: Outline the differences between the apoplast and symplast pathways after the water has left the xylem?( 4 points)
My answer is: Apoplast:water moves through cell walls only and passes from one cell to another through adjacent cell walls or through airspaces between cells.
Symplast:water moves through cytoplasm and vacuole and passes from one cell to another via plasmodesta.

i think i should earn 2 marks for mentioning about plasmodesta and cell walls for apoplast somehow, the 2nd point of the markscheme says 'ref to only cytoplasmic/not including vacuoles' then at the 6th point it says '(includes) vacuolar pathway /(through) vacuoles' and according to my coursebook symplast pathway passes through both cytoplasm and vacuoles.i am confused.how many marks should i earn for mentioning both cytoplasm and vacuole in symplast?

 

[kareem22010]

View attachment 59952 View attachment 59953 guys please help with this question
???

as you can see, affinity for oxygen has decreased so, this means that red blood cells are able to dissociate oxyhaemoglobin and release oxygen more easily in respiring tissues without having to be completely saturated. can you please refer to the markscheme? i answered this question once and it was correct but i don't remember my exact answer now.