EDEXCEL Biology Unit 2 6BIO2 21st May 2012

Thought I'd try to make somewhat an unofficial mark scheme, I know you guys have discussed most questions but just wanted to put all the answers together in one post along with the marks each question was worth

1) Identify the organelles labelled: (3)
A - Rough endoplasmic reticulum
B - Mitochondria
C - Nucleolus

What moves to opposites sides on the cell during prophase: G
What disappears during prophase: A

2) Cellulose - Can't remember the question, can someone quote me and let me know, please!

3) Why are all the fibres taken from the same plant: (1)
- So that they are all genetically identical/So genotype doesn't effect results

Two things that had to be considered when selecting 10 fibres: (2)
- Length of fibre
- Diameter of fibre
- Mass of fibre?? (this is what I wrote but I'm not so sure whether it is right, can someone confirm this for me please!)

4) Why was the experiment carried out at 37 degrees: (1)
- That's (core) human body temperature

Give a reason, for safety, for covering the beaker with clear plastic film: (2)
- Prevent contamination
- Prevent anerobis respiration

Give one reason, other than safety, for covering the beaker with clear plastic film: (1)
- To be able to see inside the beaker clearly? (This was my guess, can someone else suggest a better answer, please?)

Explain 3 ways in which the human sperm cell is adapted to it's function: (6)
- Has flagellum
= To be able to swim towards the egg cell for fertilisation to take place
- Has haploid nucelus
= So that full complement/diploid number can be restored at fertilisation
- Has acrosome in the head
= So that the zona pellucida can be digested when the sperm penetrates the egg cell.

5) Explain the term haploid nucleus: (2)
Contains half the number of chromosomes than a normal cell.

Explain the change in pH3)
- Begins at neutral
- pH decreases
- As cytoplasam becomes more acidic

Explain how happens to the amino acids from when they are made to when they are secreted as enzymes in the style: (6)
- Proteins enter rER
- They become packages into vesicles
- They assume their 3 dimensional shape
- They move to golgi apparatus/vesicles fuse with golgi
- Proteins are modified
- Become packed into vesicles, again
- Vesicles leave golgi/ fuse with cell surface membrane
- Amino acids secreted from vesicles via exocytosis

6) Tick if present in both William Withering and Current testing, cross if not: (3)
Monitor for effectiveness - Yes
Tested on animals - No
Carries out doubleblind trials - No

7) What organ is shown: (1)
C - Stem

What two structures shown in the diagram contain lignin: (1)
B - Q and R

Tissue present at U show totipotency. Explain why tissue from R would not be used instead of U. (3)
- R represents xylem vessels
- Xylem tissue is differentiated for their function
- Xylem tissue are not unspecialised and will not show totipotency
8) Size of seed: 7mm
Reason: Because it has the highest germination success

Why is it useful to store different species of seeds? (3)
- Increase genetic diversity
- Prevent inbreeding

What do seedbanks do in order to ensure long-term survival? (4)
- Reference to drying the seeds
- Reference to storing them in cold conditions
- Check seeds regularly for viability

I can't remember some of the questions and there are also a few answers that I can't remember all the points of, please quote me so I can add to it, thanks!
Oh, and tell me whether I've made any mistakes - this is all just from memory

Thought I'd try to make somewhat an unofficial mark scheme, I know you guys have discussed most questions but just wanted to put all the answers together in one post along with the marks each question was worth

1) Identify the organelles labelled: (3)
A - Rough endoplasmic reticulum
B - Mitochondria
C - Nucleolus

What moves to opposites sides on the cell during prophase: G
What disappears during prophase: A

2) Cellulose - Can't remember the question, can someone quote me and let me know, please!

3) Why are all the fibres taken from the same plant: (1)
- So that they are all genetically identical/So genotype doesn't effect results

Two things that had to be considered when selecting 10 fibres: (2)
- Length of fibre
- Diameter of fibre
- Mass of fibre?? (this is what I wrote but I'm not so sure whether it is right, can someone confirm this for me please!)

4) Why was the experiment carried out at 37 degrees: (1)
- That's (core) human body temperature

Give a reason, for safety, for covering the beaker with clear plastic film: (2)
- Prevent contamination
- Prevent anerobis respiration

Give one reason, other than safety, for covering the beaker with clear plastic film: (1)
- To be able to see inside the beaker clearly? (This was my guess, can someone else suggest a better answer, please?)

Explain 3 ways in which the human sperm cell is adapted to it's function: (6)
- Has flagellum
= To be able to swim towards the egg cell for fertilisation to take place
- Has haploid nucelus
= So that full complement/diploid number can be restored at fertilisation
- Has acrosome in the head
= So that the zona pellucida can be digested when the sperm penetrates the egg cell.

5) Explain the term haploid nucleus: (2)
Contains half the number of chromosomes than a normal cell.

Explain the change in pH3)
- Begins at neutral
- pH decreases
- As cytoplasam becomes more acidic

Explain how happens to the amino acids from when they are made to when they are secreted as enzymes in the style: (6)
- Proteins enter rER
- They become packages into vesicles
- They assume their 3 dimensional shape
- They move to golgi apparatus/vesicles fuse with golgi
- Proteins are modified
- Become packed into vesicles, again
- Vesicles leave golgi/ fuse with cell surface membrane
- Amino acids secreted from vesicles via exocytosis

6) Tick if present in both William Withering and Current testing, cross if not: (3)
Monitor for effectiveness - Yes
Tested on animals - No
Carries out doubleblind trials - No

7) What organ is shown: (1)
C - Stem

What two structures shown in the diagram contain lignin: (1)
B - Q and R

Tissue present at U show totipotency. Explain why tissue from R would not be used instead of U. (3)
- R represents xylem vessels
- Xylem tissue is differentiated for their function
- Xylem tissue are not unspecialised and will not show totipotency
8) Size of seed: 7mm
Reason: Because it has the highest germination success

Why is it useful to store different species of seeds? (3)
- Increase genetic diversity
- Prevent inbreeding

What do seedbanks do in order to ensure long-term survival? (4)
- Reference to drying the seeds
- Reference to storing them in cold conditions
- Check seeds regularly for viability

I can't remember some of the questions and there are also a few answers that I can't remember all the points of, please quote me so I can add to it, thanks!
Oh, and tell me whether I've made any mistakes - this is all just from memory

.

Hm, for q1 the bit about what disappears, why is it A (rER)? I put nucleolus because that potentially disappears during prophase?

A few things to add, for the sperm one, I think you can also say that the middle section is packed full of mitochondria to produce energy in the form of ATP. And something on drug testing which you missed out, I believe it was phase 2, then phase 1 (tick box ones)

For the cellulose it was filling in the blanks
1) beta glucose monomers
2)hydrogen bonds
Dont remember the rest sorry

----
There was another question after the ticking boxes mentioned above where there was a pie chart and they asked you to identify which one was the correct amount for phase 3
I chose C which was the largest segment
And you had to give a reason why for the second mark
Think it was because The testing was done on a large scale (?)



This was posted from The Student Room's iPhone/iPad App

In question 1, what was G and A?

for question 2 it was, B-glucose, hydrogen bonding, pits, plasmodesmata. (I think it was only 4 marks?)

Also for the amino acid question the last sentence should be, PROTEINS secreted from vesicles via exocytosis

Unofficial Mark Scheme

Explain the change in pH: (3)
- Begins at neutral
- pH decreases
- As cytoplasam becomes more acidic

Very impressed you managed to remember all of this
But this question was a "describe question" and it was only worth 2 marks. It started neutral but it increased then decreased. You weren't required to explain anything.

It wasn't A, it was supposed to be C - typo, sorry

Thanks, I've added them now!

Haha

I've changed it now, thanks

And was there an increase and then decrease?!
I thought it just decreased

How far are we with the unofficial mark scheme - I can help.

I thought the paper was alright but made a few silly mistakes (like the percentage increase question )

Haha

I've changed it now, thanks

And was there an increase and then decrease?!
I thought it just decreased

Just remembered another one which was definition of a tissue: A group of similar cells which work together to carry out a function. And for q2 there were 5 marks...I just can't remember the 5th point. It was before pits though

the pH increased up to a peak value and then started to decrease. The net effect was a decrease of pH of 0.2 iirc.

Yes i wrote that initially too but when I was checking the paper I realised it went from 7.0 to 7.6 then down to 6.8. As long as you said a general decrease you will be fine