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Edexcel GCE Biology Unit 5 6BI05 June 2013

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Reply 540
Avatar for Nilie
Nilie
Original post by SKK94
O2 is the final electron acceptor in the electron transport chain. If there is no O2, reduced NAD and reduced FAD do not lose their electrons and hydrogen to become NAD and FAD, so less NAD and FAD are formed.
Since there is less NAD and FAD, glycolysis and the Kreb's cycle are also affected.


thats the part i don't get. Why wouldn't they lose them? O2 accepts the already "free" electrons, it does not "take" them from rNAD, does it?

sorry for being such a pain :colondollar:
In anaerobic conditions, the concentration of H+ rises and NADH and FADH2. But why does the concentration of NAD fall? Is it because NADH donates its H+ is reused in the Krebs cycle?
Reply 542
Avatar for Brad0440
Brad0440
More unit 5 questions:

Name the two antagonistic muscles that work to control the size of the eye, and state whether they contract to dilate or constrict the pupil. (2)

Spoiler



State two functions of the hypothalamus. (2)

Spoiler



*Describe and explain how an action potential is generated in the bipolar cell in the retina. (6)

Spoiler

Reply 543
Avatar for Hdizzle
Hdizzle
9
Original post by Nilie
thats the part i don't get. Why wouldn't they lose them? O2 accepts the already "free" electrons, it does not "take" them from rNAD, does it?

sorry for being such a pain :colondollar:


It's essential for electrons to be able to pass along the electron carriers through the redox reactions, to provide the energy required to pump H+ ions into the intermembrane space. Now when the electrons reach the end of the carrier chain they will combine with H+ and O2 to form water. Without any O2 present the electron carrier chains become saturated and can therefore not take anymore electrons from the reduced coenzymes therefore the electron transport chain stops functioning, and oxidative phosphorylation can no longer take place.
Reply 544
Avatar for Nilie
Nilie
Original post by Brad0440
More unit 5 questions:

Name the two antagonistic muscles that work to control the size of the eye, and state whether they contract to dilate or constrict the pupil. (2)

Spoiler



State two functions of the hypothalamus. (2)

Spoiler



*Describe and explain how an action potential is generated in the bipolar cell in the retina. (6)

Spoiler



thanks a lot <3
are these questions from past papers??
Reply 545
Avatar for Nilie
Nilie
Original post by Hdizzle
It's essential for electrons to be able to pass along the electron carriers through the redox reactions, to provide the energy required to pump H+ ions into the intermembrane space. Now when the electrons reach the end of the carrier chain they will combine with H+ and O2 to form water. Without any O2 present the electron carrier chains become saturated and can therefore not take anymore electrons from the reduced coenzymes therefore the electron transport chain stops functioning, and oxidative phosphorylation can no longer take place.


that makes sense now, thanks a lot ^___________^
Reply 546
Avatar for Brad0440
Brad0440
Original post by Nilie

are these questions from past papers??


I haven't taken them from past papers, but there might be questions like them in the past papers.
Reply 547
Avatar for Nilie
Nilie
Original post by Brad0440
I haven't taken them from past papers, but there might be questions like them in the past papers.


if they came up in the exam, that would be fantastic..your questions make so much sense and are testing the biology, not how well you can overcome tricks)
Reply 548
Avatar for Nilie
Nilie
Original post by Lastminutepanic
The specification says 'Explain the fate of lactate after a period of anaerobic respiration in animals.' I am assuming this means that we don't need to know about alcohol fermentation in yeast cells?


hopefully, not. At least, my teacher did not spend any time on it, so i assume its not going to be tested
Could someone define 'negative feedback' please and an example of it in action in homeostasis?? :smile:
Reply 550
Avatar for Nilie
Nilie
Original post by JaayBiology
Could someone define 'negative feedback' please and an example of it in action in homeostasis?? :smile:


Negative feedback is returning to the norm value in responce to deviating from it.

Example of thermoregulation:

Body temperature rises
--> thermoreceptors on skin surface detect this
--> the send an impulse to the temperature control center in the hypothalamus (more specifically - the heat loss center)
--> the TCC sends an impulse to the effectors
--> temperature falls back to normal

Effectors can be: relaxing hair erector muscles, sweat glands secreting sweat, metabolic reactions occuring at a slower rate.
Reply 551
Avatar for Qwob
Qwob
1
^ and the dilation of arterioles and the inhibition of the dilation of shunts, so that blood flows more closely to the skin's surface so more heat lost through evaporation or as radiation.
Reply 552
Avatar for SKK94
SKK94
1
Do we have to know about summation in neurones (spatial and temporal) ?
Reply 553
Avatar for Qwob
Qwob
1
Original post by SKK94
Do we have to know about summation in neurones (spatial and temporal) ?


I have seen it mentioned as a mark in some mark schemes.
Original post by SKK94
Do we have to know about summation in neurones (spatial and temporal) ?


1345834178446.jpg

lols, I don't think we do.

My teacher's never taught me that :L
Original post by Nilie
Negative feedback is returning to the norm value in responce to deviating from it.

Example of thermoregulation:

Body temperature rises
--> thermoreceptors on skin surface detect this
--> the send an impulse to the temperature control center in the hypothalamus (more specifically - the heat loss center)
--> the TCC sends an impulse to the effectors
--> temperature falls back to normal

Effectors can be: relaxing hair erector muscles, sweat glands secreting sweat, metabolic reactions occuring at a slower rate.


Thankyou :smile:
What would you put for - Compare the response of a shoot to light with hormonal coordination in animals
Reply 557
Avatar for joan2468
joan2468
1
Hey guys, quick question : I was reading the analysis of the article the Hdizzle posted, and one of the answers said telomerase speeds up cell division? Anyone know how it does that? I looked up telomerase and as far as I know it's just an enzyme that helps replace the telomeres on the ends of your chromosomes, which prevent the genes in your actual chromosomes from being damaged whenever the cell divides. I'm not seeing how it speeds up cell division :s-smilie: Any ideas?
Reply 558
Avatar for Ziggy_72
Ziggy_72
Original post by JaayBiology
What would you put for - Compare the response of a shoot to light with hormonal coordination in animals


Both chemical messages (i.e. not electrical)
Both act away from site of production
Both have long lasting effects (unlike nerve impulse)
Both in relation to external stimuli (although hormones can also be internal stimulai).

Auxin only for growth, hormones can do lots of things each.
Auxin diffuses (to near production site), hormones travel in blood to many areas (picked up and activates only cells with fitting receptors).

There is a few... I think there may be more. Our teacher was really emphasising being sure on the comparisons of plant, hormonal and nervous communication....
Reply 559
Avatar for Nilie
Nilie
Original post by SKK94
Do we have to know about summation in neurones (spatial and temporal) ?


it's very easy.... i'd learn it just in case. We need to know there are excitatory/inhibitory synapses and how they work, and summation is part of that. So you'd better learn it =)

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