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OCR A2 Biology F214 unofficial mark scheme

(Unfinished)
These are by no means, entirely correct, they are just brief indications of what I wrote and a few points from other people.
I personally thought it was a hard paper.

Q1)
Name the pigment at the reaction centre (1)

chlorophyll a


Name an accessory pigment (1)

carotene/xanthophyll/chlorophyll b (POSSIBLY carotenoids)


Purpose of accessory pigments (1)

absorb a range of wavelengths not well absorbed by chlorophyll and pass on that energy

maybe protect chlorphyll from very intense light


Name of compound formed (1)

adenosine triphosphate (ATP)


Enzyme that fixes CO2 in calvin cycle (1)

rubisco


stable intermediate formed (1)

Glycerate-3-phosphate


Compound regenerated (1)

Ribulose bisphosphate (RuBP)


Polysaccharides that can be formed (1)

Cellulose and starch/(amylose/amlyopectin)



Q2)
Why is it a transducer? (1)

converts one form of energy to another (pressure stimulus converted to electrical energy of nerve impulse)



Suggest how membrane made more permeable to Na+ (1)

Gate of sodium ion channel forced open/ deformation by pressure


What is the all or nothing law? (1)

action potentials do not vary in size, either happens or doesn't (if reaches threshold potential (-50mV))


How intensity of stimulus signalled to brain? (2)

frequency of action potentials indicates strength

greater frequency = more intense
OR
All action potentials same magnitude but stronger stimuli produce more action potentials


Why do the impulses generated stop? (1)

acclimitisation/runs out of vesicles/fatigued


Role of synapses (3)

Ensure one direction only

Intergration (convergence/divergence)

Summation (temporal/spatial)

memory and conscious thought

Filter out low level signals


Q3)
Condition tested for (1)

diabetes mellitus


Why was he fasting? (1)

Needs to have a high blood glucose concentration so effect of insulin can be seen


Calculate % increase (2)

18.6%


Explain when a glucagon injection is needed (1)

blood glucose concentration low/hypoglacaemia


Hb complex thing why not useful after 8-12 weeks? (2)

red blood cells broken down and recycled in liver

therefore less Hb complex thing than there should be



Explain why blood glucose was higher in test than over 8 week period (1)

nervous before taking exam = increased blood glucose levels/had just been exercising


Describe role of glucagon (5)

detected by alpha cell receptors

glucaon secreted binds to complementary receptor cells in liver plasma membrane

gluconeogenesis (making glucose from fats/amino acids)

glycogenolysis(breaking down glycogen to glucose)

more fatty acids used in respiration

role of adenyl cylase/cyclic AMP

glucose leaves cells by faciliated diffusion

reference to inhibitory effect of hormone (stops insulin secretion)


Explain why concentration of NAQ thing builds up (2)

the glutathione runs out

enzymes become saturated, cannot work quickly enough


Name a neurotransmitter (1)

acetylcholine


Where are the receptors located on the neurone and explain (2)

either pre or post synaptic membrane

stop secretion/stop binding


Diagram of liver (5)

sinusoid

bile duct

hepatic portal vein (branch of)

hepatic artery (branch of)

hepatic vein (branch of)


Liver cells that divide are called and how they do (1)

hepatocytes and mitosis


Describe how respiration rate of cauliflower changes with temperature (2)

rate increases as temperature increases

figures quoted, trend (5 to 10 degrees rate doubles)


What are the best conditions from table? (1)

low temperature (0 degrees)


Which is the best fruit/vegetable to store and explain (3)

Onion as slowest rate of respiration at all temperatures

possibly potato at 0 degrees? unknown rate of respiration

really don't know what else to put for this one


Which is the worst one and why? (1)

asparagus as has highest rate at all temperatures


Why do parasites in blood respire anaerobically? (2)

oxygen tightly held to haemoglobin

no oxygen was the selection pressure for natural selection

can't kill host, so cannot use their oxygen

travel in deoxygenated areas of body (in veins) (possibly)


Why is anaerobic respiration in animals reversible? (3 + QWC)

In mammals pyruvtae turned into lactate

lactate converted back to pyruvate in liver

in yeast CO2 released

Maybe doesn't have enzymes for conversion back?
possibly lactate/ethanol dehydrogenase catalyse both directions, pryruvate carboxylase cannot


Where is glucose reabsorbed? (1)

PCT ( I think the label was Q)


Parts of the nephron in cortex (1)

All of them except the loop of henle and lower part of the collecting duct


Where are podocytes found? (1)

Renal capsule label


how long loop of henle helps desert mouse (2)

greater salt concentration in medulla

more water reabsorbed by osmosis from collecting duct

maybe ref. to mechanism, impermeable ascending walls, greater countercurrent mechanism


Substance tested for in urine (1)

anabolic steroids

(edited 9 years ago)

Scroll to see replies

The one you can't remember at the end is about podocytes :smile:

Thanks for this btw, everyone asks for but nobody bothers to make the unofficial mark schemes!!!
Wasn't it asparagus not celery?
Original post by Mule
Q1)
Name the pigment at the reaction centre (1)

chlorophyll a


Name an accessory pigment (1)

carotene/xanthophyll


Purpose of accessory pigments (1)

absorb wavelength not well absorbed by chlorophyll and pass on that energy


Name of compound formed (1)

adenosine triphosphate (ATP)


Enzyme that fixes CO2 in calvin cycle (1)

rubisco


stable intermediate formed (1)

Glycerate-3-phosphate


Compound regenerated (1)

Ribulose bisphosphate (RuBP)


Polysaccharides that can be formed (1)

Cellulose and starch



Q2)
Why is it a transducer? (1)

converts one form of energy to another (pressure stimulus converted to electrical energy of nerve impulse)



Suggest how membrane made more permeable to Na+ (1)

Gate of sodium ion channel forced open/ deformation by pressure


What is the all or nothing law? (1)

action potentials do not vary in size, either happens or doesn't (if reaches threshold potential (-50mV))


How intensity of stimulus signaleld to brain? (2)

frequency of action potentials indicates strength

greater frequency = more intense


Why do the impulses generated stop? (1)

acclimitisation/runs out of vesicles/fatigued


Role of synapses (3)

Ensure one direction only

Intergration (convergence/divergence)

Summation (temporal/spatial)

memory and conscious thought

Filter out low level signals


Q3)
Condition tested for (1)

diabetes mellitus


Why was he fasting? (1)

Needs to have a high blood glucose concentration so effect of insulin can be seen


Calculate % increase (2)

16.8%


Explain when a glucagon injection is needed (1)

blood glucose concentration low/hypoglacaemia


Hb complex thing why not useful after 8-12 weeks? (2)

red blood cells broken down and recycled in liver

therefore less Hb complex thing than there should be


Describe role of glucagon (5)

detected by alpha cell receptors

glucaon secreted binds to complementary cells in liver

gluconeogenesis

glycogenolysis

more fatty acids used in respiration

role of adenyl cylase/cyclic AMP


Name a neurotransmitter (1))

acetylcholine


Where are the receptors located on the neurone and explain ( can't remember if 2 or 1)

either pre or post synaptic membrane

stop secretion/stop binding


Diagram of liver (5)

sinusoid

bile duct

hepatic portal vein (branch of)

hepatic artery (branch of)

hepatic vein (branch of)


Liver cells that divide are called and how they do (1)

hepatocytes and mitosis


Describe how respiration rate of cauliflower changes with temperature (2)

rate increases as temperature increases

figures quoted, trend (5 to 10 degrees rate doubles)


What are the best conditions from table? (1)

low temperature (0 degrees)


Which is the best fruit/vegetable to store and explain (3)

Onion as slowest rate of respiration at all temperatures

don't know what else


Which is the worst one and why? (1)

celery as has highest rate at all temperatures


Why do parasites in blood respire anaerobically? (2)

oxygen tightly held to haemoglobin

no oxygen was the selection pressure for natural selection


Why is anaerobic respiration in animals reversible? (3 + QWC)

In mammals pyruvtae turned into lactate

lactate converted back to pyruvate in liver

in yeast CO2 released

Maybe doesn't have enzymes for conversion back?


Where is glucose reabsorbed? (1)

PCT


Parts of the nephron in cortex (1)

All of them except the loop of henle and lower collecting duct


( one more question I can't remember) (1)
how long loop of henle helps desert mouse (2)

greater salt concentration in medulla

more water reabsorbed by osmosis from collecting duct


Substance tested for in urine (1)

anabolic steroids



The one you cant remember was "which feature contains Podocytes?" It was the Bowmans Capsule.

Also, the hardest one to keep was Asparagus, NOT celery.
Am I the only one who thought the transduction question shouldn't have been asked? That's physics!
It was Asparagus
Reply 6
I'm sure the answer for the percentage increase was 18.60%.
Reply 7
Original post by basmaay
I'm sure the answer for the percentage increase was 18.60%.

Yeah... I got 18.6%
Reply 8
Using this i only got 34 ish out of 60... I'm aiming for an A fml
Original post by Bisphosphate
Am I the only one who thought the transduction question shouldn't have been asked? That's physics!


It's in the heinman book, but I don't think many people read that bit, lol I do physics and physics wouldn't of helped me with that.

Its just ocr being awkward, again.
Original post by Bisphosphate
Am I the only one who thought the transduction question shouldn't have been asked? That's physics!



"outline the roles of sensory receptors in
mammals in converting different forms of
energy into nerve impulses"

That's from the specification, nothing specifically about transducers but my book covered it.
Reply 11
Original post by 2102
Using this i only got 34 ish out of 60... I'm aiming for an A fml


I've probably missed a lot of marks, these are just off the top of my head of some things I wrote, that's why I want people to contribute.
45 If I'm lucky, which isn't an A. yay.
Is chlorophyll B classed as an accessory pigment?
Reply 14
Original post by AliBachir
45 If I'm lucky, which isn't an A. yay.


Again don't make an accurate prediction based on this rough mark scheme yet.
Also 45 could well be an A.
A* boundaries for unit 4:
June 10 - 47
Jan 11 - 51
June 11 - 45
Jan 12 - 51
June 12 - 49
Jan 13 - 49
June 13 - 50

And I personally thought this was a bad paper
Original post by RadishWadish
Is chlorophyll B classed as an accessory pigment?


yes
Reply 16
Original post by RadishWadish
Is chlorophyll B classed as an accessory pigment?


I think it is, i'm not certain though.
Reply 17
Can you say Type 2 Diabetes instead of Diabetes Mellitus?
Reply 18
Lool I know I sound like a dick but I was actually scared that I got an A/B as apposed to an A*
Could someone add the asparagus and onion question please...I put that the onion would be the most stable and that asparagus the least stable
Original post by Mule
Again don't make an accurate prediction based on this rough mark scheme yet.
Also 45 could well be an A.
A* boundaries for unit 4:
June 10 - 47
Jan 11 - 51
June 11 - 45
Jan 12 - 51
June 12 - 49
Jan 13 - 49
June 13 - 50

And I personally thought this was a bad paper



Thanks alot for that. I think you did a pretty good job on the mark scheme but I disagree with one of your answers. For the parasite question, I wrote that not all blood is oxygenated such as that found in the veins. This means the parasite cannot respire aerobically until it reaches the lungs again and so has adapted to respire anaerobically. I hope that's right at least ...

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