A2 Biology OCR June 2015 Revision Thread

No It did come up in a paper once as a "outside the spec" topic but it will explain everything you need to know. Knowing the term wont hurt and the fact it is a bad thing for plants and stems from the awful structure of RuBisCO being able to accept oxygen. It might be good to know that C4 and CAM plants have mechanisms to stop photorespiration but bar that very basic amount of information I wouldn't worry about it.

For the spec point:

"Describe the formation of urea in the liver, including an outline of the ornithine cycle."

What do we need to know about in relation to the Ornithine cycle?

I know:

amino acid + oxygen = keto acid + ammonia

ammonia + carbon dioxide = urea + water

Is that enough?

Is this correct?
Type one diabetes is when beta cells are attacked by the boy's own immune system so cannot sufficiently produce insulin and so glucose cannot be converted to glycogen stores. This means when blood glucose concentrations are low, there is no glucose store to bring it back up to the ideal, and when blood glucose concentrations are high, the body isn't capable of storing the glucose as glycogen so glucose levels remain dangerously high.
Is that a decent explanation of type one diabetes?

Could someone please explain the difference between NAD and FAD aswell as Reduces NAD and FAD??

Is one for CO2 and the other for hydrogen or something?
thanks

FAD and NAD are both coenzymes- FAD is only involved in Krebs but NAD is involved in all stages of respiration. They're both reduced to form reduced NAD/FAD (or NADH/FADH) and then oxidised to form NAD/FAD.

In glycolysis, NAD is reduced to form NADH when the triose phosphate is oxidised to form pyruvate.
In Link NAD again forms NADH when 3C pyruvate is decarboxylated to 2C pyruvate.
In Krebs, NAD is reduced to form NADH when 6C citrate is dehydrogenated and decarboxylated to form 5C + CO2 + NADH. Then next in Krebs is that 5C being again decarboxylated and dehydrogenated to form 4C (oxaloacetate) + NADH + CO2 + ATP + reduced FAD. This part of the reaction reduces FAD--> reduced FAD.
In oxidative phosphorylation, the NADH made in all the other steps is transported to the inner mitochondrial membrane and releases its H for it to split into H+ (proton) and e-, meaning the electron transport chain and chemiosmosis can occur to generate ATP. The NADH has been oxidised as it's lost its H, so it's NAD again. The NAD then goes back to the other reaction stages to be reduced again and a cycle occurs.

I'm not sure of the fate of FAD, but I can't find it in the textbook so am not sure if it's relevant? But someone correct me if I'm wrong.

Lol what the heck. Just doing a few past papers and this 'question' comes up:


(ii). Penguins living in cold climates have shunt blood vessels. These shunt vessels link arterioles carrying blood towards their feet with small veins that carry blood away from their feet (1 mark).


Like okay? What do you want me to write? lol There isn't even a question? Did it want me to comment on that statement? Describe something? Lol wtf.

I wish we don't get a question like this, tomorrow o.o

Lol what the heck. Just doing a few past papers and this 'question' comes up:


(ii). Penguins living in cold climates have shunt blood vessels. These shunt vessels link arterioles carrying blood towards their feet with small veins that carry blood away from their feet (1 mark).


Like okay? What do you want me to write? lol There isn't even a question? Did it want me to comment on that statement? Describe something? Lol wtf.

I wish we don't get a question like this, tomorrow o.o

C6H12O6 + 6O2 --> 6H2O + 6CO2

Therefore a carboyhydrates have an RQ of 1, so they're equal.

Higher than 1 would be anaerobic

Lower than 1 would be fats/proteins which indivate more CO2 given off than O2 consumed

I thought so, but then i saw this ppq http://www.ocr.org.uk/Images/63306-question-paper-unit-f214-communication-homeostasis-and-energy.pdf (question 2b), where we would need to know it in more detail

Read the first part of the question. "Explain how each of the following adaptations help the animal to control its body temperature."

In anaerobic respiration of yeast, what enzyme is used to break Pyruvate into Ethanal? Carbon dioxide is released in this reaction, and I have seen two different enzymes mentioned by two different sources; Ethanal Dehydrogenase in my textbook and Pyruvate Decarboxylase on an online resource??

Thanks if you can help!!

In anaerobic respiration of yeast, what enzyme is used to break Pyruvate into Ethanal? Carbon dioxide is released in this reaction, and I have seen two different enzymes mentioned by two different sources; Ethanal Dehydrogenase in my textbook and Pyruvate Decarboxylase on an online resource??

Thanks if you can help!!

pyruvate decarboxylase is used to produce ethanal from pyruvate which produces CO2. Ethanol dehydrogenase is used to reduce ethanal to ethanol.

I believe it's pyruvate decarboxylase, as pyruvate has 3 carbons and ethanal has 2. So it must be decarboxylated.