OCR Biology F214 Communication, Homeostasis and Energy Friday 22 June 2012

Original post by corpuscallosum

Ok Jan 11 q1, Can anyone tell me why in mammals the first hydrogen acceptor after glycolysis is pyruvate? I thought it would be lactate, since pyruvate is produced during glycolysis...

Pyruvate during glycolysis doesn't accept any hydrogens. It's the product of Triose Phosphate giving away 2 hydrogens.

Pyruvate accepts hydrogens to become lactate - therefore is the hydrogen acceptor.

Reply 783

Original post by corpuscallosum

That's what I thought, but the Jan 11 mark scheme says that the Schwann cell produces the myelin and that the idea of production is needed?!

Id just add it in anyway then if it comes ip tomorrow!

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Reply 784

corpuscallosum

10

Original post by Jellybeany

Because it accepts hydrogen from nadh (from glycolysis) with they help of lactate (sp?) dehydrogenase to convert it into lactate/ lactic acid. Nad is reused

I think. Unsure about lactate/ lactic acid

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But surely the lactate accepts the hydrogen from the NADH? I don't understand how pyruvate could be the acceptor after glycolysis when pyruvate is the end product of glycolysis..?

Reply 785

_Browner_

Anyone else planning an all night revision session? Hate this exams sooo much!

Reply 786

Original post by corpuscallosum

But surely the lactate accepts the hydrogen from the NADH? I don't understand how pyruvate could be the acceptor after glycolysis when pyruvate is the end product of glycolysis..?

Not really sure. Lactate is the final product. Pyeuvate needs an extra hydrogen atom to turn it into lactate!

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Reply 787

corpuscallosum

10

Original post by CollateralElement

Pyruvate during glycolysis doesn't accept any hydrogens. It's the product of Triose Phosphate giving away 2 hydrogens.

Pyruvate accepts hydrogens to become lactate - therefore is the hydrogen acceptor.

Ohh, thank you, that explains it.

Reply 788

Original post by _Browner_

Anyone else planning an all night revision session? Hate this exams sooo much!

I was planning on doing this for law (exam in the morning :frown:

) dont thnk it's going to happen! How can you stay up?

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Reply 789

Original post by corpuscallosum

But surely the lactate accepts the hydrogen from the NADH? I don't understand how pyruvate could be the acceptor after glycolysis when pyruvate is the end product of glycolysis..?

Two reactions occur during anaerobic respiration. Glycolysis and lactate fermentation.

Reply 790

Original post by corpuscallosum

That's what I thought, but the Jan 11 mark scheme says that the Schwann cell produces the myelin and that the idea of production is needed?!

Yeah. Schwann cell is responsible for myelination so we've got to say it produces myelin. God knows if that's actually true but everywhere I look, OCR want us to say that.

Reply 791

MyselfEtAl

Original post by arvin_infinity

In where!

In link reaction it transfers a 2c compound (acetate) from pyruvate molecule into krebs cycle..so that acetate can combine with oxaloacetate to form citrate (5c)

Original post by otrivine

and this is morning exam right? to confirm

Yes.

Original post by otrivine

its to carry the acetate for the krebs cycle

But what's the point? Lol the Krebs cycle is in the matrix, so is the link reaction. :dontknow:

Also, how come glucose is "too big" to pass through the glomerulus, but it's then reabsorbed in the PCT? Where's that coming from?

EDIT: my teacher got the notes wrong :angry:

- no need to answer the above.

(edited 11 years ago)

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Original post by otrivine

adrenaline increases heart rate, cardiovascular centre in medulla oblongata , acceletor nerve decreases heart rate, venus decreases heart rate

so 4 points including QWC so 5 marks in total for this question

Yup

Reply 793

Sparkzz

4

Original post by Groat

Bile emulsifies fats and oils, increasing the surface area and allows these to be hydrolysed. Then it neutralises the acid, yes.

Cirrhosis is when the liver tissue is replaced with fibrous scar tissue. It usually occurs after a fatty liver (which may be due to excessive alcohol consumption).

I think hes actually referring to sodium hydrogen carbonate solution which is released by acinar cells in the pancreas into the pancreatic duct....this empties into the duodenum in order to neutralised the acidic contents from the stomach?

Reply 794

kishenp

Original post by corpuscallosum

Ok Jan 11 q1, Can anyone tell me why in mammals the first hydrogen acceptor after glycolysis is pyruvate? I thought it would be lactate, since pyruvate is produced during glycolysis...

This is lactate fermentation
Pyruvate is converted to Lactate by using the enzyme pyruvate dehydrogenase which causes the reduced NAD to accept hydrogen to form NAD again which can be used in glycolysis to generate ATP
Therefore Pyruvate is the hydrogen acceptor
And for alcoholic fermentation Ethanal is the Hydrogen acceptor
However, to convert Ethanal to ethanol, the enzyme ethanol dehydrogenase is used
Hope that helps :smile:

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otrivine

14

Original post by CollateralElement

Yup

Suggest what happens if the level of light intensity decreases (2)

Reply 796

Can someone explain the whole Liver thing to me and selective reabsorption in the way OCR want me to say it? :frown:

Please?

Reply 797

Original post by otrivine

Suggest what happens if the level of light intensity decreases (2)

For photosynthesis?

Light-dependent reactions won't be able to occur, therefore, Calvin Cycle won't be able to make RuBP. So, photosynthesis rate will be significantly reduced.

Reply 798