Edexcel GCE Biology Unit 5 6BI05 June 2013

Reply 660

jojo1995

2

Original post by SKK94

Nope, you don't :smile:

thank you

Reply 661

Misedoflauren

Original post by nukethemaly

The official Edexcel textbook is so crap it actually annoys me

SNAB is no better trust me. Doesn't help that the site is down as well
2.30pm on Monday I will be the happiest girl alive at that moment :cool:

Reply 662

bubblegummer

Original post by p1234h

would be really grateful if someone could explain the stages of anaerobic respiration :s its not very clear in my textbook and the mark schemes don't really help ssince they dont connect the stages

In anaerobic respiration basically it occurs due to the lack of oxygen in our muscles. energy is needed for the contration of the muscle so small amounts of ATP is released.

To know how this happens
- initially pyruvate is converted to lactate
- the conversion causes reduced NAD to be oxidised to NAD
- NAD is regenerated so that more ATP can be produced from glycolysis

(edited 10 years ago)

Reply 663

super121

5

Original post by nukethemaly

The official Edexcel textbook is so crap it actually annoys me

:O Really? The SNAB one? What don't you like about it? I think it's quite good :smile:

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(edited 10 years ago)

Reply 664

Dhaden

13

Original post by super121

:O Really? What don't you like about it? I think it's quite good :smile:

Posted from TSR Mobile

How science works Is a load of tosh, to much irrelevant garbage which isn't the syllabus and it isn't wrote in a concise way. For those reasons I personally use the revision guide and supplement my knowledge with points from mark schemes from past papers.

Reply 665

Lgambo

The problem with biology is the mark schemes can be so specific. I never know when I mark my own past papers whether the examiners will accept something like "thus more blood is pumped out of heart" when it says on the mark scheme "so there is increased cardiac output". Do you think in a circumstance like that the mark would be awarded?

Reply 666

Ziggy_72

Original post by iwantopas19

in darkness there is more far red light than red light. therefore PFR is converted to PR. to maintain the equilibirum.

Hi - couple of corrections here:

Far red light does not really exist in usual conditions. The Pfr is converted into Pr by long periods of darkness - slowly, so the proportions change with the length of darkness. It is more or less instantly converted to Pfr - so it is uninterrupted periods of darkness that are needed. There was some experiment where a light was flashed on every two hours in a 14 hour stretch of darkness and the Pfr proportion did not reduce significantly.

Original post by iwantopas19

yeah u are right PR is inactive it inhibits flowering whereas PFR is active and causes germination and flowring

The Pfr is ALWAYS the active one - as a stimulator or as an inhibitor. The Pr being inactive does not mean it in inhibits. In short day plants for example Pfr inhibits flowering - only when lots of it has been converted to Pr do the plants flower - i.e. when the nights are long. In long day plants it stimulates flowering.

Reply 667

Tomatochuckers

18

How many of the article marks /30 would you say were comprehension?

Thanks :smile:

Reply 668

Tomatochuckers

18

Original post by super121

:O Really? The SNAB one? What don't you like about it? I think it's quite good :smile:

Posted from TSR Mobile

It's too long and packed with uselessness.

I mainly use the CGP and the official snab revision guide, though I do refer back to the big book for the larger chapters.

Reply 669

Dhaden

13

Original post by Lgambo

The problem with biology is the mark schemes can be so specific. I never know when I mark my own past papers whether the examiners will accept something like "thus more blood is pumped out of heart" when it says on the mark scheme "so there is increased cardiac output". Do you think in a circumstance like that the mark would be awarded?

Usually equivalents next to most points on the mark scheme but its up to the examiner whether they want to award you the mark penultimately. Id defo analyase past mark schemes and use the specific terminology they contain.

Reply 670

p1234h

Original post by bubblegummer

In anaerobic respiration basically it occurs due to the lack of oxygen in our muscles. energy is needed for the contration of the muscle so small amounts of ATP is released.

To know how this happens
- initially pyruvate is converted to lactate
- the conversion causes reduced NAD to be oxidised to NAD
- NAD is regenerated so that more ATP can be produced from glycolysis

thank you! afterwards, when lactate is taken to the liver to be converted back to pyruvate... why does the livers oxygen demand increase?

Reply 671

Volltorb

1

Original post by p1234h

thank you! afterwards, when lactate is taken to the liver to be converted back to pyruvate... why does the livers oxygen demand increase?

Because:
-Lactate needs to be converted into pyruvate by oxidation
-The lactate is oxidised by the Krebs cycle to give pruyate, C02 and H20
-The extra oxygen needed for this process is called the oxygen debt

(edited 10 years ago)

Reply 672

ofudge

Is this suffice for answers?:

Behavioral Adaptation: These are changes in behavior that aid survival ( The Soldiers defending for the whole colony rather than just themselves)

Anatomical Adaptation: Physical/Structural changes- (Large, curved incisor teeth that allow them to break down tough plant fibrous material)

Physiological Adaptation: Changes in the internal biochemical functioning to aid survive: (The ability of neurones to tolerate low O2 conditions)

Would these responses get me the marks? Thank you.

Reply 673

bubblegummer

Original post by p1234h

thank you! afterwards, when lactate is taken to the liver to be converted back to pyruvate... why does the livers oxygen demand increase?

When lactate is oxidised back to pyruvate, NAD is also reduced to NADH. Aerobic respiration resumes. So we need more oxygen to accept the electrons from NADH in the electron transport chain so that NAD can be regenerated. NAD is needed so that glycolysis continues and ATP can once again be produced.

you're welcome :smile:

Original post by Volltorb

Because:
-Lactate needs to be converted into pyruvate by oxidation
-The lactate is oxidised by the Krebs cycle to give pruyate, C02 and H20
-The extra oxygen needed for this process is called the oxygen debt

i think this is more accurate.

(edited 10 years ago)

Reply 674

jetb

8

Can someone tell me the definition of Oxygen Debt?
Thanks

Reply 675

Soul_Eater

Original post by jojo1995

some proteins have bonds that are more likely to be neutralised by free radials ie ioinc bonds i think

mole rats have fewer more covelant bonds and so thier structure is less likely to be disrupted by free radicals

thx!

Reply 676

nomrota95

what is/are the difference(s) between habituation and adaptation? what brings them both about?

Reply 677

Selym95

15

Original post by SKK94

Light adaptation:
- all rhodopsin in rod cells have been broken down (bleached)
- so rod cells cannot respond to dim light anymore
- example:when you switch off the lights in a bright room, you initially cannot see anything for a few seconds (because rhodopsin has already broken down, and has to be remade). Rod cells cannot respond to low light levels.

Dark adaptation:
- all rhodopsin has been reformed (with use of ATP)
- so rod cells can respond to dim light
- example: after some time being in a dark room, you can start to identify objects/shadows faintly, this is because rhodopsin has been re-synthesised and so your rod cells can respond to low light levels.

Thanks for this. Out of curiosity, where did you find this information? It's not in the CGP revision guide

Reply 678

p1234h

Original post by bubblegummer

When lactate is oxidised back to pyruvate, NAD is also reduced to NADH. Aerobic respiration resumes. So we need more oxygen to accept the electrons from NADH in the electron transport chain so that NAD can be regenerated. NAD is needed so that glycolysis continues and ATP can once again be produced.

you're welcome :smile:

Original post by Volltorb

Because:
-Lactate needs to be converted into pyruvate by oxidation
-The lactate is oxidised by the Krebs cycle to give pruyate, C02 and H20
-The extra oxygen needed for this process is called the oxygen debt

i think this is more accurate.