OCR Biology F211 Exam - Tues 11'th January 2011

what did people put for the working out magnification question? i always mess them up!

Image size was 9cm, equal to 90,000um (micrometers). 90,000um divided by 20um was 4500x.

Personally, I didn't think this paper was harder than any other papers, but some of the questions were so vague. Like really vauge, and there was so many suggest questions too.

Finally. How did everyone answer the water potential of the onion cell?
Three ways people have done it
-Estimate around -1700
-Half the 100% value to get -1750
-Find the difference between percents, and water potentials to be 19.444444, then multiple that by 7. Add number to -1850? <- I did it this way, but I think it may be wrong. I ended up getting -1664

No, water travels across the cell membrane by diffusion as molecules small enough to pass right through charged area and also channel proteins and aquaporines to allow bulk movement of water, pinocytosis.

Apoplast and symplast just refers to water travelling through the root doesnt it.

How does water move between cells?
When plant cells are touching each other,water molecules pass from one cell to another. The water molecules will move from the cellwith the higher water potential to the cell with lower water potential.
What route can water take between cells?
there are three possible pathways that water molecules can take between cells:
the Apoplast pathway
the Symplast pathway
the vacuolar pathway

The 6b question, was about how water passes through the membrane. So diffusion and specially adapted channel protiens - aquasomething or another .

Also, the cutting the stem off the stem of the flower. I didn't know what it was, my teacher said (I asked afterwards) "There may be an air bubble in the xylem when you first cut off the flower from the plant, by cutting it again just before you put it in water, there is still a continuous column of water molecules" Something along that.

Personally, I didn't think this paper was harder than any other papers, but some of the questions were so vague. Like really vauge, and there was so many suggest questions too.

Finally. How did everyone answer the water potential of the onion cell?
Three ways people have done it
-Estimate around -1700
-Half the 100% value to get -1750
-Find the difference between percents, and water potentials to be 19.444444, then multiple that by 7. Add number to -1850? <- I did it this way, but I think it may be wrong. I ended up getting -1664

The tutor was just about to call time up so I just had quick look and put -1600, well it did say estimate. lol

Do you think that for plant cell wall one you needed to put about the cell membrane pushing against the wall. I just put cell wall prevents bursting but now looking back im thinking mayb that bit was required also.

what did people say for the how would you use a graph question?

what did people say for the how would you use a graph question?

that was the 2 mark one right? i just wrote:
The cell wall has pressure potential preventing the cell from bursting, when the cell becomes turgid the cell wall stops allowing water to pass through :/ easy paper but written disabledly hopefully i scrape an A

scatter graph/line graph with i fink either of the first 2 for the x-axis and %age for the y-axis.
if you did scatter u mention a line of best fit to measure the estimates tbh i did scatter graph so dno what would score marks for line im not even sure my answer for scatter graph would score me any marks hopefully someone got the same as me.

scatter graph/line graph with i fink either of the first 2 for the x-axis and %age for the y-axis.
if you did scatter u mention a line of best fit to measure the estimates tbh i did scatter graph so dno what would score marks for line im not even sure my answer for scatter graph would score me any marks hopefully someone got the same as me.

Yeah symplast and vacuolar pathway across the membrane, going through channel proteins would be wrong even if the question asked how water moved through the phospholipid bilayer i think bc water molecules are an exception to that rule as theyre small enough to travel through the hydrophobic tails. but yeah symplast and vacuolar pathway

that was the 2 mark one right? i just wrote:
The cell wall has pressure potential preventing the cell from bursting, when the cell becomes turgid the cell wall stops allowing water to pass through :/ easy paper but written disabledly hopefully i scrape an A

What did the question ask for again. I think plotting % of cells haemolysed by concentration of water would give good indication of how water potential effects onion cells. But I cant remember what question was.

I put the part where the airway split (part a I believe) as Bronchus, and part b was alveoli of course.
I think I've done relatively well on this test, but it didn't have any questions on the heart or bohr shift (if you don't include the fill in the gaps question) which is what I revised...