OCR 21st Century Biology - B4 B5 B6 - Unofficial Mark Scheme

Hey guys! This is the unofficial mark scheme created by @menna123 and I. Menna is awesome!!! :biggrin:

If you have any changes to make then feel free to type it and we'll edit it! :smile:

Also, thanks @danielwinstanley for helping to type out all the marks for each question and construct a more coherent mark scheme!!

1. what is memory? (2 marks)

the storage (1) and retrieval of information (1)

1ii. What is the part of the brain responsible for memory? (1 mark)

Cerebral Cortex

2. Why would John still want to undertake the surgery? (2 marks)

- benefits outweighs the risks
- if he does not have the surgery it can spread to the rest of his brain.
- The benefits of the surgery outweigh the consequence of losing some of his memory.
- John's perception of the risk is low because he does not mind losing his memory.

3. How does Judith remember to play the piano? (3 marks)

- First time she plays it is in short term memory, and she needs to establish new neurone pathways in the brain.
- with repetition and reinforcement moves into the long term memory and this info can be retrieved
- neurone pathways form when she learns the skill
- as she reinforces and repeats the skill the neuron pathways travel down more strengthened.

4. When do human cells respire anaerobically (1 mark)

during vigorous exercise

5. What two things are needed to make amino acids? (2 marks)

nitrates and glucose.

6. What do amino acids make when joined together? (1 mark)

Proteins

7. How does water travel through the roots? (1 mark)

Osmosis

8. Why is oil stored on top of the glucose/starch solution? (2 marks)

It means that no oxygen enters the solution as fermentation requires anaerobic respiration, and the presence of oxygen would mean that it would respire aerobically and fermentation would not be able to take place.

8ii. Conclusions (4 marks)

any valid conclusion based on the data is correct, links to respiration
- At 45 degrees the rate of respiration is high due to high rate of reaction so lots of CO2 bubbles are released but would then decrease due to high temperatures denaturing the active site of the enzyme. This means that the enzyme can no longer respire anaerobically and release CO2 as the cells have been killed.

8iii. Problem with measuring CO2 bubbles (1 mark)

- it's difficult to observe and see what qualifies as a bubble
- the bubbles of CO2 could be different volumes
- human error as not measured by a computer (such as she may miscounted, might miss a bubble)

8iiii. Another way to measure CO2 volume (1 mark)

- Measure the volume of carbon dioxide produced in a set time period
- Measure the time taken to produce a set amount of gas
- Gas syringe

9. Ticking boxing question for respiration (3 marks)

Aerobic respiration - Needs oxygen
Both aerobic and anaerobic respiration - need glucose
Anaerobic respiration - releases lactic acid
Aerobic respiration - in the mitochondria
Aerobic respiration - releases carbon dioxide

10. Graph question for limiting factor of photosynthesis (1 mark)

when graph flattened out. Plot the X anywhere when the graph plateaus (light is no longer increasing)

11. Six marker on dunes (6 marks)

transect,quadrat,identification key.
Define each and explain how it would be useful.

12. Six marker on star fish (6 marks)

- human nervous system = CNS, brain and spinal chord. Joined to body via peripheral nervous system
- motor and sensory neurons. I said that the centre of the starfish was its CNS and it too has neuron pathways and receptors.
- They both have receptors (light receptor in the starfish and receptors in humans)
- Human nervous system has a processing centre to modify reflexes and for higher thought whereas starfish rely on simple reflexes.
- Human nervous system has synapses (gaps) whereas starfish do not.
- Human nervous system is made out of billions of neurons.

13. Six marker on amino acid and proteins (6 marks)

DNA is a double helix of paired bases a-t c-g, genetic code for production of proteins. Triplet code codes for one amino acid. Amino acids joined to make proteins etc. Different base would mean different coding of amino acid, meaning different sequence of amino acid a different/faulty protein is made. (Could refer to mRNA and ribosomes but probably not necessary in gaining 6 marks).

14. Name for when a plant grows towards light (1 mark)

Phototropism (positive)

14ii. Why do plants grow towards light (1 mark)

To increase chances of survival as they can have more light energy for photosynthesis.

15. Question on child with cystic fibrosis (1 mark)

baby is unlikely to have cystic fibrosis

15i. What doctor would do with information (1 mark)

more genetic tests/monitor child

16. Calculations- 0.0012% (2 marks) and 9000 (1 mark)

17. Question on why mucus was sticker (2 marks)

faulty DNA means that chloride ions (dissolved in water) cannot move from higher to lower concentration in membrane due to the fact that cystic fibrosis is a genetic disorder of the cell membranes. Meaning that the mucus stays in the region of higher concentation, further increasing the concentation of chloride ions, making mucus stickier

18. Order for serotonin concentration (3 marks) (not confirmed)- potentially (C) A B E D
but the order was:
1)more serotonin is released from the first neuron.
2) increase in serotonin concentration
3) more serotonin binds to next membrane
4) more impulses generated

20. What can you gather from results on ecstasy from graph (1 mark)

Ecstasy with psychotherapy is more effective than just psychotherapy

20ii.Question on increasing confidence in ecstasy test results (2 marks)

- use a bigger sample
- conduct over a longer period of time
- peer review and other scientists do it to make it reproducible.

(edited 6 years ago)

Reply 1

According to this mark scheme, I got 51-53 in that exam. Do you guys think that warrants full UMS or is it too low?

Reply 2

For question 9, both types of respiration also release carbon dioxide because:
GLUCOSE + OXGEN -> C02 + WATER
GLUCOSE -> CO2 + LACTIC ACID

Reply 3

Original post by CandidateZero

According to this mark scheme, I got 51-53 in that exam. Do you guys think that warrants full UMS or is it too low?

A mark in the low forties is usually an a* so if the grade boundaries were to stay put, then yes quite possibly, but it depends this year as a lot of people found it easier but it's very likely to be an a*

Reply 4

Original post by ktb786

For question 9, both types of respiration also release carbon dioxide because:
GLUCOSE + OXGEN -> C02 + WATER
GLUCOSE -> CO2 + LACTIC ACID

In animal cells is does not release co2
Only lactic acid.

(edited 6 years ago)

Reply 5

Sum Ting

11

Think i got 44 :s-smilie:

Hopefully i scrape the a*

Reply 6

Original post by ktb786

For question 9, both types of respiration also release carbon dioxide because:
GLUCOSE + OXGEN -> C02 + WATER
GLUCOSE -> CO2 + LACTIC ACID

Incorrect. Anaerobic respiration produces only lactic acid; oxidation of lactic acid forms carbon dioxide which, in the context of anaerobic respiration, we know can not occur until the body has recovered.

Reply 7

Guys, I think I got 46 marks. On the starfish nervous system question I did something really thick by comparing human and nerve cells. But I did link the features to thier functions such as the light receptors. Would I still be able to pick up a couple of marks?

Reply 8

Original post by ktb786

Guys, I think I got 46 marks. On the starfish nervous system question I did something really thick by comparing human and nerve cells. But I did link the features to thier functions such as the light receptors. Would I still be able to pick up a couple of marks?

Yes, the mark scheme will be separated into different sections remember; e.g. A subheading with something like 'identifies features of starfish nervous system' etc.

Reply 9

Original post by ktb786

Guys, I think I got 46 marks. On the starfish nervous system question I did something really thick by comparing human and nerve cells. But I did link the features to thier functions such as the light receptors. Would I still be able to pick up a couple of marks?

Can you give me an example of what you put so I can better understand where you are coming from?

Reply 10

Original post by CandidateZero

Can you give me an example of what you put so I can better understand where you are coming from?

Mate, I basically said the starfish has a light receptor which is similar to the dendrites in the human nerve cell as they detect changes in stimuli and so on. I think I misread 'nervous system' and talked about individual features of nerve cells but I did say stuff like the response in a human would be quicker and slower in the starfish. Do you think I can pick up a couple of marks here?

Reply 11

Original post by ktb786

Mate, I basically said the starfish has a light receptor which is similar to the dendrites in the human nerve cell as they detect changes in stimuli and so on. I think I misread 'nervous system' and talked about individual features of nerve cells but I did say stuff like the response in a human would be quicker and slower in the starfish. Do you think I can pick up a couple of marks here?

Certainly, if you made 3-4 comparisons like such then there's no reason I don't believe that you will get at least 3 marks.

Reply 12

tanishaevans

9

for 9 i said both aerobic and anaerobic respiration release carbon dioxide because anaerobic respiration can produce ethanol and carbon dioxide in plants and microorganisms?

for 11 i wrote about transects, quadrats and light metres instead of the identification key, is it still right?

and for 20 i said PTSD decreased in patients treated w ecstasy then backed it up w numbers (decreased by 75% from 100% to 25%) will i still get the marks?

Reply 13

Original post by CandidateZero

Certainly, if you made 3-4 comparisons like such then there's no reason I don't believe that you will get at least 3 marks.

Thanks, you legend mate! It is just that whenever I come out of an exam I always get stressed out over what I wrote. Last year I took Core Science early and got a grade A so this year, IA, I really want to push for that A*.

Reply 14

tanishaevans

9

Original post by menna123

In animal cells is does not release co2
Only lactic acid.

but the question didn't specify animal cells only... did it? (i don't remember now)

Reply 15

Original post by tanishaevans

for 9 i said both aerobic and anaerobic respiration release carbon dioxide because anaerobic respiration can produce ethanol and carbon dioxide in plants and microorganisms?

for 11 i wrote about transects, quadrats and light metres instead of the identification key, is it still right?

and for 20 i said PTSD decreased in patients treated w ecstasy then backed it up w numbers (decreased by 75% from 100% to 25%) will i still get the marks?

1) the question was about animal cells, not plant cells it stated at the top 'animal'
2) yeah it's still right but I don't think you would be credited for light meter because it's not really required in that context

Reply 16