A2 Biology OCR June 2015 Revision Thread

Original post by Hilton184

Can you explain the relative concentrations of RuBP TP and GP as temperature increases (ignoring effect of oxigenase activity of RuBP)
For example from 5 degrees to 10 degrees Celsius

The rate of all the reactions would increase
But they wouldn't necessarily increase by the same factor
And it can't be RuBP TP and GP all increase in concentrations because then you've introduced atoms from nowhere, haven't you?

Any ideas?

Posted from TSR Mobile

Ah. This is a guess. Completely.
Increase in both rate of CO2 fixation and light dependent reaction, therefore more ATP and NADPH. ATP and NADPH react to convert GP to TP, and then TP to RuBP. I guess if the CO2 concentration doesn't increase as temp does it could become the limiting factor, so then there would be a build up of RuBP, and a decrease in GP and TP concentrations.

Reply 283

Ch@r10tte

6

Original post by AnnekaChan173

Ah. This is a guess. Completely.
Increase in both rate of CO2 fixation and light dependent reaction, therefore more ATP and NADPH. ATP and NADPH react to convert GP to TP, and then TP to RuBP. I guess if the CO2 concentration doesn't increase as temp does it could become the limiting factor, so then there would be a build up of RuBP, and a decrease in GP and TP concentrations.

That's pretty much it. Before temperature becomes a limiting factor and is simply increasing reaction rates, the rate of all enzyme controlled reactions is increased as substrates/enzymes have more kinetic energy, more frequent successful collisions (etc. etc. as at AS). Once temperature is high enough to become a limiting factor (above 25 degrees celcius), the oxygenase activity of Rubisco increases more than its carboxylase activity, so photorespiration exceeds photosynthesis. This means that ATP and reduced NADP from the light-dependent stage are wasted, and the overall rate decreases. At very high temperatures, protein structure would be disrupted, and enzymes would be denatured. High temperature also increases water loss by transpiration, so triggering a stress response in the plant (abscisic acid is released), to close the stomata and prevent wilting. This would also decrease the rate of photosynthesis, as carbon dioxide availability will be lower.

Reply 284

Hilton184

9

Original post by Ch@r10tte

That's pretty much it. Before temperature becomes a limiting factor and is simply increasing reaction rates, the rate of all enzyme controlled reactions is increased as substrates/enzymes have more kinetic energy, more frequent successful collisions (etc. etc. as at AS). Once temperature is high enough to become a limiting factor (above 25 degrees celcius), the oxygenase activity of Rubisco increases more than its carboxylase activity, so photorespiration exceeds photosynthesis. This means that ATP and reduced NADP from the light-dependent stage are wasted, and the overall rate decreases. At very high temperatures, protein structure would be disrupted, and enzymes would be denatured. High temperature also increases water loss by transpiration, so triggering a stress response in the plant (abscisic acid is released), to close the stomata and prevent wilting. This would also decrease the rate of photosynthesis, as carbon dioxide availability will be lower.

Thank-you both of you.

So increasing temperature:
--> increases GP concentration
--> increases TP concentration
--> decreases RUBP concentration

Providing the oxygenase activity of rubisco does not come into play.

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Reply 285

boing360

Is anyone else struggling with genomes and gene technologies i find some of the process confusing and the books that i have don't say the same stages any help?

Reply 286

O-M-Y

The drosophila melanogaster - How much do we need to know? Surely not how it develops! :confused:

Reply 287

smozsolution

9

Original post by O-M-Y

The drosophila melanogaster - How much do we need to know? Surely not how it develops! :confused:

Which part of the spec is this? Homeobox gene?

If so, then my teacher has said to familiarise ourselves with how it works with the drosophilia melanogaster example but we could potentially be asked to apply what we know about the homeobox gene to another organism. Same for the lac operon.

Reply 288

Original post by O-M-Y

The drosophila melanogaster - How much do we need to know? Surely not how it develops! :confused:

Pretty much nothing, that spread in the book is an absolute joke. We're more likely to be asked about homebox genes and another organism like the girl above me has said :smile:

know what they do and how they do it.

Reply 289

CamilleClarke

Hi, could someone please explain what primary and secondary metabolites mean, it doesn't make sense to me in the book. Thanks!

Reply 290

Original post by CamilleClarke

Hi, could someone please explain what primary and secondary metabolites mean, it doesn't make sense to me in the book. Thanks!

Primary metabolites: things that an organism usually makes in metabolic processes, like amino acids
Secondary metabolites: things an organism wouldn't usually make, or would make under certain conditions (penicillin, insulin etc)

(edited 9 years ago)

Reply 291

Hmht

2

Original post by CamilleClarke

Hi, could someone please explain what primary and secondary metabolites mean, it doesn't make sense to me in the book. Thanks!

Primary metabolites are basically things that are made during when cells are growing or products of respiration (the things required for division in the exponential phase - e.g. amino acids, ethanol (if it's yeast and no oxygen) and so on) :smile:

Secondary metabolites are compounds produced when supplies are running low and competition starts happening. One example is that antibiotics are produced to kill rival bacteria so they have more food :smile:

Reply 292

Hmht

2

Well that the first past paper i have done for the second unit in biology... They take soo long to do!! D:

Reply 293

cforcoldplay

Has everyone already finished all the modules for unit 2?
We've sill got modules 3 and 4 to do and I'm starting to panic :frown:

Reply 294

Original post by cforcoldplay

Has everyone already finished all the modules for unit 2?
We've sill got modules 3 and 4 to do and I'm starting to panic :frown:

I haven't done 4, and at school we still have a few lessons of 2 left, but I've already written my notes on it
Don't panic though, apparently module 4 is ok, and module 3 is doable

Reply 295

username911777

15

Unit 1 learnt.

Past papers here I come :colonhash:

Reply 296

frozo123

12

Original post by Solarburst

Unit 1 learnt.

Past papers here I come :colonhash:

same here man, looks like we're working on the same wavelength haha
what course are you doing?

Reply 297

ChatteringJess

Does anyone understand the different gene therapies? please :smile:

Reply 298

cforcoldplay

Original post by AnnekaChan173

I haven't done 4, and at school we still have a few lessons of 2 left, but I've already written my notes on it
Don't panic though, apparently module 4 is ok, and module 3 is doable

Module 4 seems very similar to psychology I've seen things on dopamine and types of learning (operant and classical conditioning) which I'm doing right now in psych. Its module 3 I'm worrying about especially since I'm not too fond of ecosystems etc :frown:

Reply 299

Original post by cforcoldplay

Module 4 seems very similar to psychology I've seen things on dopamine and types of learning (operant and classical conditioning) which I'm doing right now in psych. Its module 3 I'm worrying about especially since I'm not too fond of ecosystems etc :frown: