OCR AS Biology F211 May 2013 POLL

Here's a poll for how you think you did for the OCR Bio exam. Out of 60.

Unofficial Mark Scheme:F211 May 2013 Unofficial Mark Scheme (1).pdf (Credit: Uckerman)

Another Mark Scheme! Make suggestions for correction and add more if you'd like! Credit: Niceguy

1 a i)
A was nucleus
B was chloroplast [2]

ii) C was site of aerobic respiration to produce ATP
D process and package of lipids [2]

b)
Light has a longer wavelength; maximum magnification (x1500) and maximum resolution (200nm); Light microscopes can only view general cell features and mitochondria is too small;unclear/detail cannot be seen [2]

c) Compare and contrast
Distinguish different features [2]

2ai) 0.6:1 show working: SA/Volume [2]

ii) the greater the surface area: volume ratio, the faster the rate of diffusion (or reverse argument). Give examples (uneccesary?) [2]

iii) small surface are a to volume ratio, therefore slow rate of diffusion [2]

bi) Lentgh divided by time [1]

ii) length divided by time / 2 [1]

C)
Squamous epithelium - very thin allows for short diffusion distance
Large number of alveoli- increase surface are for faster diffusion
Good supply of blood- removal and picking up of o2 so steep concentration gradient of co2 and O2
Good ventilation- refreshment of air mean it cause steep concentration/ diffusion gradient [4]

3ai) mitosis [1]

ii) 4 chromosomes or sister chromatids side by side with centromere attached spindle fibres at equator [2]

iii) -800 to -950 to -1050 and -800 to -1050 [2]

b) Ring of vascular (xylem and phloem) under the bark. Cambium has meristem cells that can undergo mitosis and differentiate (for growth) [2]

C) tips of roots or shoots[1]

d) multicellular organisms have a small surface area to volume ratio so slower rate of diffusion and greater diffusion distance, animals don't need Lentices as they already have a specialised gas exchange system (confirmation needed) [2]

4a i) Fetal haemoglobin has a higher affinity for oxygen;can absorb or associate with oxygen at lower tension; adult haemoglobin releases oxygen at low tension which the fetal haemoglobin associates with. [3]

ii) Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, meaning it can absorb oxygen at low partial pressure. [2]

b) High hydrostatic pressure at the arteriole end of capillary than the tissue fluid; dissolved substances move down the hydrostatic gradient through the tiny holes in capillaries; glucose and oxygen small enough to pass through tiny holes [4]

5a i) Seperate organelles from each other; form vesicles to transport materials (proteins etc); [2]

b) any two of the following components with description and functions: phospholipid bilayer, glycoproteins, channel proteins, carrier proteins, glycolipids or cholesterol [5]

ci) phospholipid (bilayer) [1]

ii) proteins (accept named protein i.e Glycoprotein) [1]

iii) either ice pierces membrane when frosted and then thaws causing permeability to increase or proteins denature/not working at cold temperature and permeability explanation [2]

6ai)
Transpiration is loss of water vapour from surface of leaves by evaporation whilst for transpiration stream is a result of transpiration, tension forces water up leaves, cohesion of water molecules due to H bonds form column of water, adhesion of water cause it stick on xylem wall and help the stream of water to rise up [3]

b) mean number of stomata-13000
Mean surface are - 0.2
Thickness of cuticle- 8.50 [3]

C) complete table( blanks as follows)
Ions/minerals; sucrose; No cross/ end Walls; Lignin;Pits;Plasmodesmata. [4]

(edited 10 years ago)

Reply 1

OP

Not looking good for the mark boundary right now... :s-smilie:

Reply 2

Original post by MrJiggly

Here's a poll for how you think you did for the OCR Bio exam. Out of 60.

Unofficial Mark Scheme:F211 May 2013 Unofficial Mark Scheme (1).pdf (Credit: Uckerman)

The resolution for light microscope is not 0.2 ITS 200 and in nano metres.

Reply 3

OP

Original post by Legal drugdealer

The resolution for light microscope is not 0.2 ITS 200 and in nano metres.

Didn't notice hah! Thanks for pointing it out.

the mark scheme says 0.1 micrometres, and it should be 0.2 micrometers or 200 nm.

Reply 4

OP

Original post by Legal drugdealer

Sorry but there are loads of errors in the mark scheme.

let me know, I'll post an editable one. Uckerman made this mark scheme, I've noticed a few errors as well.

Reply 5

Original post by MrJiggly

let me know, I'll post an editable one. Uckerman made this mark scheme, I've noticed a few errors as well.

Question 2 bii im pretty sure its somthing to do with surface are i dont really understand what he done.

Reply 6

Question 5 shouldn't be talking about the cell surface membrane

Reply 7

OP

Original post by Legal drugdealer

Question 2 bii im pretty sure its somthing to do with surface are i dont really understand what he done.

That's correct. The question was what the student has done wrong to calculate diffusion rate. Diffusion rate= distance travelled/ time taken

Distance travelled is to the centre as HCL is coming from all sides. Therefore half the side for distance and divide by time taken.

So what the student has done wrong is not divide the distance by 2.

Reply 8

OP

Original post by Legal drugdealer

Question 5 shouldn't be talking about the cell surface membrane

He's not talking about the CSM... o_O

Reply 9

Original post by MrJiggly

That's correct. The question was what the student has done wrong to calculate diffusion rate. Diffusion rate= distance travelled/ time taken

Distance travelled is to the centre as HCL is coming from all sides. Therefore half the side for distance and divide by time taken.

So what the student has done wrong is not divide the distance by 2.

I see this makes a lot more sense.

Reply 10

Original post by MrJiggly

He's not talking about the CSM... o_O

sorry my bad read it wrong i think i should be off to bed lol yh its just the light microscope but come to think of it some text books may say what he said.

Reply 11

OP

Original post by Legal drugdealer

sorry my bad read it wrong i think i should be off to bed lol yh its just the light microscope but come to think of it some text books may say what he said.

alright lol, good night bro :smile:

Reply 12

johnabc123

complete table( blanks as follows)
Ions/minerals

can you write nutrients as well ?

Reply 13

OP