OCR AS Biology (F211) 21st May 2014, OFFICIAL THREAD

Topics that are going to come up are (high probability):

1. Transportation in plants learn about the apoplast/symplast/vascular pathways
2. Xylem and Phloem adaptations

If you have any questions please ask

(edited 9 years ago)

Reply 21

ThatWasHard!

7

Original post by ThatWasHard!

Topics that are going to come up are (high probability):

1. Transportation in plants learn about the apoplast/symplast/vascular pathways
2. Xylem and Phloem adaptations

Also, revise organelles. Organelles always comes up (even the grittier details such as cytoskeleton moving organelles on microtubules) etc etc

(edited 9 years ago)

Reply 22

TheLastMagnus

Original post by StartingTheParty

Does anyone know if we have to know the mechanism by which the stomata open and close? It is in the revision guide but it isn't on the specification.

What is the mechanism? I'm drawing a blank.

Reply 23

ishackm

5

can anyone explain spirometer please, the whole topic please...

Reply 24

StartingTheParty

12

Original post by TheLastMagnus

What is the mechanism? I'm drawing a blank.

1) Guard cells fill with water and become turgid which opens the stomata.
2) Active transport of K+ into cells and Cl- removed from surrounding cells.
3) Water potential in guard cell becomes more negative than surrounding cells.
4) Water moves down a water potential gradient into the guard cells by osmosis opening them more.

In the dark the active transport stops, apparently. Very bizarre.

Reply 25

milesnej

i got really paranoid i hadn't revised properly by looking at the comments then i realised im not even doing OCR, i'm doing AQA lol

Reply 26

Priya1997

I'm really worried, what topics should I go over now because i went over past papers marked then and evrything but I just don't feel that confident and I feel like I'm going to do bad :/

Reply 27

chocablocka

a spirometer consists of a chamber filled with oxygen that floats on a tank of water
A person breathes in through a disposable mouthpiece attached to a tube connected to the chamber with MEDICAL GRADE oxygen (always asks for precautions and things you should check)
Breathing in takes oxygen from the chamber which sinks down
Breathing out pushes air into the chamber which then floats up.
The movements of the chamber are recorded using a datalogger so that a spirometer trace can be produced
Precautions:
medical grade oxygen
disinfected mouthpiece
health of the person
maintain constant temperature

Reply 28

StartingTheParty

12

Original post by ishackm

can anyone explain spirometer please, the whole topic please...

A spirometer can be used to measure the tidal volume and vital capacity of an individual.

The procedure is as follows:

1) The subject should breathe through a disinfected mouthpiece whilst wearing a noseclip.
2) As the subject inhales, medical grade oxygen is drawn from the chamber of air causing it to fall.
3) As the subject exhales, air enters the system and CO2 is removed by a canister of soda lime before causing the chamber of air to rise.
4) The movements of the air chamber are recorded in a data logger or on a revolving drum.

When measuring TIDAL VOLUME - the subject should breathe normally.
When measuring VITAL CAPACITY - the subject should breathe in and out as deeply as possible.

There are several precautions you should take:

1) The person should be healthy; not asthmatic.
2) The person should wear a nose clip to ensure all air breathed in comes from the chamber and no air escapes through the nose. This increases the validity.
3) The air inside the chamber should be medical grade oxygen; normal air only contains 20% oxygen which will run out quickly.
4) The mouthpiece should be disinfected before each use to prevent the spread of disease.
5) The air breathed out should pass through a canister of soda lime to absorb and remove any CO2.

Analysing a Spirometer trace..

You could be asked how to measure and calculate the following:

1) Vital Capacity - calculate the difference in the volume of air between the peak and the trough of the deepest breath (biggest wave)
2) Tidal Volume - calculate the difference in the volume of air between the peak and trough of one normal breath.
3) Breathing Rate - count the number of peaks in 60 seconds; units are "breaths per minute".
4) Oxygen Uptake - calculate the difference in volume of air between the first peak and the last peak of normal breathing; divide by the time taken.

The height of at least three waves should be measured and a mean calculated.

Reply 29

Priya1997

Quick question , you know in the SAN and AVN, when describing the process can I use the term " waves of electrical activity" to describe the fact these are sent to the atrial wall etc.

(edited 9 years ago)

Reply 30

StartingTheParty

12

Original post by Priya1997

Quick question , you know in the SAN and AVN, when describing the process can I use waves of electrical activity to describe the fact these are sent to the atrial wall etc.

I think you should be okay with that. I always stick with "wave of depolarisation" just to be safe.

Reply 31

Priya1997

Original post by StartingTheParty

I think you should be okay with that. I always stick with "wave of depolarisation" just to be safe.

Thanks, wat topics you reckon will come up in tomorrow exam?

Reply 32

StartingTheParty

12

Original post by Priya1997

Thanks, wat topics you reckon will come up in tomorrow exam?

Mitosis, movement up the xylem vessel; maths regarding spirometers.

There's going to be maths and apart from magnification spirometers is pretty much the only other option.

Reply 33

R-123

Does anyone know a year that lots of heart questions came up please?! I want to practice before tomorrow!!

Thanks :smile:

Posted from TSR Mobile

Reply 34

cuppa

18

Even though I love plants very very much, the biology of them is honestly something I have a hard time with, lol. Can anyone give me a brief outline of transport in plants? :puppyeyes:

Also, goodluck to everyone tomorrow :smile:

Reply 35

StartingTheParty

12

Original post by cuppa

Even though I love plants very very much, the biology of them is honestly something I have a hard time with, lol. Can anyone give me a brief outline of transport in plants? :puppyeyes:

Also, goodluck to everyone tomorrow :smile:

There are some key areas you need to know:

1) Transport of water in the root
2) Transport of water in the xylem vessel

1. Transport of water in the root
- Root hair cells take up water by osmosis
- It then travels to the xylem vessel at the base of the stem by three key routes:
- Apoplast pathway; through cellulose fibres in the cell walls
- Symplast pathway; through the cytoplasm; plasmodesmata
- Vacuolar pathway; through the vacuoles and cytoplasm of cells
- Casparian strip blocks the apoplast pathway; all water must go through symplast pathway

2. Transport of water UP the xylem vessel:
- Transpiration pull created by water evaporating from surface of cells into the leaf air spaces where it diffuses through open stomata; the loss of water creates low hydrostatic pressure at the top of the xylem so water pulled up along pressure gradient.
- Cohesion, created by hydrogen bonds between water molecules, means water moves up the stem as a continuous, unbroken column of water due to tension created by loss of water vapour.
- Adhesion, attractive forces between water molecules and the cellulose cell walls of xylem; allows water to 'creep' up the vessel by capillary action.

Hope this is helpful to you!!

Reply 36

techno836

20

Original post by Priya1997

Quick question , you know in the SAN and AVN, when describing the process can I use the term " waves of electrical activity" to describe the fact these are sent to the atrial wall etc.

Original post by StartingTheParty

I think you should be okay with that. I always stick with "wave of depolarisation" just to be safe.

I write wave of excitation everytime? I've always credited it though :smile:

Reply 37

ishackm

5

Original post by StartingTheParty

A spirometer can be used to measure the tidal volume and vital capacity of an individual.

The procedure is as follows:

1) The subject should breathe through a disinfected mouthpiece whilst wearing a noseclip.
2) As the subject inhales, medical grade oxygen is drawn from the chamber of air causing it to fall.
3) As the subject exhales, air enters the system and CO2 is removed by a canister of soda lime before causing the chamber of air to rise.
4) The movements of the air chamber are recorded in a data logger or on a revolving drum.

When measuring TIDAL VOLUME - the subject should breathe normally.
When measuring VITAL CAPACITY - the subject should breathe in and out as deeply as possible.

There are several precautions you should take:

1) The person should be healthy; not asthmatic.
2) The person should wear a nose clip to ensure all air breathed in comes from the chamber and no air escapes through the nose. This increases the validity.
3) The air inside the chamber should be medical grade oxygen; normal air only contains 20% oxygen which will run out quickly.
4) The mouthpiece should be disinfected before each use to prevent the spread of disease.
5) The air breathed out should pass through a canister of soda lime to absorb and remove any CO2.

Analysing a Spirometer trace..

You could be asked how to measure and calculate the following:

1) Vital Capacity - calculate the difference in the volume of air between the peak and the trough of the deepest breath (biggest wave)
2) Tidal Volume - calculate the difference in the volume of air between the peak and trough of one normal breath.
3) Breathing Rate - count the number of peaks in 60 seconds; units are "breaths per minute".
4) Oxygen Uptake - calculate the difference in volume of air between the first peak and the last peak of normal breathing; divide by the time taken.

The height of at least three waves should be measured and a mean calculated.