OCR Biology F214 Communication, Homeostasis and Energy Wed 25 Jan 2012

Question regarding Examination question on page 32 of the Purple OCR textbook:

Q. 5)a)i)
My answer was:
A = 3
B = 2
C = 1

Mark scheme, which can be accessed from the CD, says:
A = 1
B = 3
C = 2

I am sure this is wrong, and that my answers should be correct? Correct me if I'm wrong please

I got the same answer as you! Because the resting potential is -60mV, hence why it has to be C...
I may ask my teacher about that (:

Question regarding Examination question on page 32 of the Purple OCR textbook:

Q. 5)a)i)
My answer was:
A = 3
B = 2
C = 1

Mark scheme, which can be accessed from the CD, says:
A = 1
B = 3
C = 2

I am sure this is wrong, and that my answers should be correct? Correct me if I'm wrong please

Photorespiration occurs in response to an increase in temperature. The increase in temperature causes the enzyme Rubisco to fix oxygen with RuBP (ribulose bisphosphate) rather than RuBP being fixed with carbon dioxide. This means that glycerate 3-phosphate is not produced and therefore no triose phosphate and ultimately no carbohydrates or RuBP being regenerated. This is highly wasteful of RuBP. Some plants such as C4 plants use the enzyme PEP-carboxylase which only fixes with carbon dioxide so this problem is avoided.

Please anyone correct me if I made a mistake so I haven't given out wrong information

Sounds right to me..what do we need to know about c3 and c4 plants !! differences ?!

PS: Maybe it helps to know RUBP= ribulose bisphosphate carboxylase oxygenase

The c3 and c4 plants isn't something that's a necessity but I saw it on a past paper once so I think its one of the stretch and challenge type questions for A* or A hopefuls.

Also RuBP is ribulose bisphosphate, its Rubisco that is ribulose bisphosphate carboxylase

Mate what was the oldest F214 paper?
I can only find Jan 10?

Question regarding Examination question on page 32 of the Purple OCR textbook:

Q. 5)a)i)
My answer was:
A = 3
B = 2
C = 1

Mark scheme, which can be accessed from the CD, says:
A = 1
B = 3
C = 2

I am sure this is wrong, and that my answers should be correct? Correct me if I'm wrong please

Anaerobic respiration can take place in mammals or in plants and fungi, I'll outline what happens in each:

Mammals

Anaerobic respiration takes place when there is no oxygen present. The fact there is no oxygen present means that oxygen cannot accept hydrogen from reduced NAD molecules at the end of the electron transport chain. This means no reduced NAD can be oxidised back to NAD. Because of this the krebs cycle and the link reaction no longer takes place. Glycolysis still takes place because the 2 pyruvate molecules formed can act as alternative hydrogen acceptors. As the pyruvate molecules accept hydrogen from the two reduced NAD molecules the enzyme lactate dehydrogenase converts them into two molecules of lactate. Lactate then diffuses from the skeletal muscle into the blood and is removed by the hepatocytes (liver cells). The hepatocytes can convert lactate back to pyruvate and then respire it in normal aerobic respiration or can convert it to glycogen as an energy store. This action by the hepatocytes however needs oxygen which is why a person breathes heavily after anaerobic respiration, they are supplying the oxygen required which is known as the oxygen debt.
Anaerobic respiration is not as efficient as aerbic respiration at producing ATP as it only produces a net gain of 2 ATP molecules (as 4 are formed in glycolysis but 2 are used)

Fungi and Plants

In fungi and plants the pyruvate molecules formed take a different pathway where ethanol is produced. Also something else produced which is different to anaerobic respiration in mammals is a molecule of carbon dioxide.
First of all the enzyme ethanal dehydrogenase converts pyruvate to ethanal which at the same time produced CO2. Then the 2 reduced NAD molecules formed in glycolysis pass there hydrogen on to ethanal and at the same time as this the enzyme ethanol dehydrogenase converts ethanal to ethanol. Ethanol is then formed. This is why this pathway is also known as alcohol fermentation

that last question on respiration experiments
Do we still need to know that stuff????

mate how do you know all this extra information for anaerobic respiration in mammals where the hepatocytes convert lactate back into pyruvate
also does anerobic respiration only occour in the skeletal muscles??? or elsewhere aswell such as the liver.

btw you made a mistake in ethanol fermentation the first enzyme is pyruvate decarboxylase which converts pyruvate to ethanal, releasing a molecule of carbon dioxide

it's mentioned in the OCR biology 2 book by Mary Jones, yeah I think that it's just another name for ethanal dehydrogenase like how the krebs cycle can be called the tricarboxylic acid cycle

by the way what does everyone think may come up because of past papers?

it's mentioned in the OCR biology 2 book by Mary Jones, yeah I think that it's just another name for ethanal dehydrogenase like how the krebs cycle can be called the tricarboxylic acid cycle

by the way what does everyone think may come up because of past papers?

any idea what dehydrogenase means???