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OCR Biology AS Jan Wed 14th

Reply 60

conorf199

Its hardcore revision here on in to the end of AS for me :P

Reply 61

Poshtotty

8

aimz08

*Gulps* Well using the CGP revision guide - I've only just got through the first uni. I'm off tsr good luck everyone

Is the CGP revision guide any good? I was wary of using CGP for A-level. I have the Physics one and it's actually good. Not sure about biology though?

conorf199

Its hardcore revision here on in to the end of AS for me :P

Yeah same. I just wished I'd done so from day 1 of year 12.

Reply 62

Tinkerbelle ♥

Poshtotty

Is the CGP revision guide any good? I was wary of using CGP for A-level. I have the Physics one and it's actually good. Not sure about biology though?

i brought it through our college as i thought for £4 you can't go wrong but i was pleasentley suprised :smile:

it sums up everything really well, at least, i think it does.

Reply 63

Xerophelistica

9

Hey I've got this on wednesday too.

I spent all of my christmas break revising for maths and chemistry, so I've got some crazy amounts of biology to do in such a short amount of time.

I'm finding the parts of water potential the hardest, especially having to explain exactly how the xylem, phloem and root hairs load their water, minerals and sugars. Oh also the bit on the heart is pretty hard too, lots of memorising.

Anyway, back to revision.

Reply 64

liz17

6

Wednesday- Im taking Foundation...retake!
Am on an A overall for AS biology however I got a B in this paper..what a fool.

Anybody got any questions or anything they want to ask on the foundation bit?

Reply 65

v1oXx-

12

Xerophelistica

Hey I've got this on wednesday too.

I spent all of my christmas break revising for maths and chemistry, so I've got some crazy amounts of biology to do in such a short amount of time.

I'm finding the parts of water potential the hardest, especially having to explain exactly how the xylem, phloem and root hairs load their water, minerals and sugars. Oh also the bit on the heart is pretty hard too, lots of memorising.

Anyway, back to revision.

Right.

Mineral ions are taken up by the root hair cells, which creates a water potential gradient. Water moves into the plant by osmosis. The minerals are moved through the cortex, then the endodermis, then into the xylem. The water follows by osmosis through the following pathways: Apoplast (through the cell walls and in between the cell walls), Symplast (through the cell cytoplasm) and the vacuolar pathway (through the cytoplasm and vacuole). When the water gets to the endodermis, the casparian strip blocks the apoplast pathway forcing the water through the endodermis cells, and thus into the xylem.

When water is forced into the xylem by osmosis, root pressure causes some of the water up the xylem (but can't account for all the movement in large trees). Water also moves up the xylem by adhesion. Water is attracted to the walls of the xylem, which pulsl the water up. But the main way water moves up the xylem, is through the cohesion. The water molecules are attracted to each other and thus creates a column of water. When water evapourates from the leaf, a transpiration stream is created and water moves up the plant by cohesion. This is called the cohesion-tension theory.

The water then enters the leaf, and the water evapourates in the gaps between the spongey mesophyll whic creates a water vapour gradient. Water vapour leaves the leaf.

That's the route taken by water in a plant :cool:

Reply 66

v1oXx-

12

A few typos, cba to edit it.

Reply 67

KipperSlapper

aimz08

well im using the CGP revision guide and that has two values. Heres a useful table :p:

(well kind of a table)

Light - max Res: 0.2 max mag: x1500
SEM - max Res: 0.005 max mag: x less than 1000 000
TEM - max Res: 0.0001 max mag: x more than 1000 000

another thing - for the cytoskeleton bit - do we just need to know the functions? or e.g. how it stregthens the cell

The OCR endorsed Heinemann book im using for this says:
SEM - 0.2nm res and x100 000 mag
TEM - 0.2nm res and x500 000 mag

:s-smilie:

And these are new books this year for the new spec.

Reply 68

aimz08

13

KipperSlapper

The OCR endorsed Heinemann book im using for this says:
SEM - 0.2nm res and x100 000 mag
TEM - 0.2nm res and x500 000 mag

:s-smilie:

And these are new books this year for the new spec.

the figures I posted are in micrometres

Reply 69

KipperSlapper

aimz08

the figures I posted are in micrometres

I know, I was commenting more on the magnification.

Reply 70

Banu_Hashim

2

anyone doing Foundation Biology on Wednesday???

Reply 71

aimz08

13

KipperSlapper

I know, I was commenting more on the magnification.

hmm the only thing I can think of is that in the heineman it doesnt say max magnification . I dont know all the books seem to have different figures?

Reply 72

PrettyRainbows

steph_v

Also, how did everyone find the specimen paper? As in, the only one there is for this topic. I found it really easy, but I bet it's misleading, as always.

i found it ok, it sort of reassured me a little bit, but knowing me im going to completely fail the real one...

Reply 73

liz17

6

Banu_Hashim

anyone doing Foundation Biology on Wednesday???

Yes Yes I am!
You need any help on anything?

Reply 74

Xerophelistica

9

Okay I guess I'm going to write these notes down anyway, and I might as well put them in here for you guys to read if you need to:

The Heart;

The 3 Stages of the Cardiac Cycle:

Diastole - When the atria and the ventricles are both relaxed. Blood flows into the atria, from the Vena Cava and Pulmonary Vein, through the atrio-ventricular valves, and into the ventricles. Both the atria and ventricles begin to fill up at this point.

Atrial Systole - The atria contract, raising the pressure in them, causeing the blood already in them to be pumped through the atrio-ventricular valves and into the ventricles, fully filling them. The increase in pressure in the ventricles means that once the atria have empied all of their blood, the atrio-ventricular valves snap shut preventing backflow.

Ventricular Systole - The ventricles now contract, increasing their blood pressure, and the atrio-ventricular valves stay shut. This time, the semi-lunar valves are opened, forcing blood through the Aorta and the Pulmonary Artery. Once the ventricles are empty of bood, the pressure is lower in the ventricles than in the Aorta/Pulmonary Artery, so the semi-lunar valves shut, and the cycle repeats.

SAN/AVN:

The SAN (aka the Pacemaker) is a group of cells situated in the top right of the right atrium, which give off an electrical signal to the atria to begin contracting (atrial systole). Once the signal has travelled through the atria, it reaches the AVN, situated in the centre of the heart, which carries the signal down the Perkyne tissue (which is present in the septum and ventricle muscle), causing the ventricles to contract (ventricular systole).

And I think thats about right? Just off the top of my head so probably some mistakes in there.

Reply 75

skatealexia

14

Xerophelistica

Okay I guess I'm going to write these notes down anyway, and I might as well put them in here for you guys to read if you need to:

The Heart;

The 3 Stages of the Cardiac Cycle:

Diastole - When the atria and the ventricles are both relaxed. Blood flows into the atria, from the Vena Cava and Pulmonary Vein, through the atrio-ventricular valves, and into the ventricles. Both the atria and ventricles begin to fill up at this point.

Atrial Systole - The atria contract, raising the pressure in them, causeing the blood already in them to be pumped through the atrio-ventricular valves and into the ventricles, fully filling them. The increase in pressure in the ventricles means that once the atria have empied all of their blood, the atrio-ventricular valves snap shut preventing backflow.

Ventricular Systole - The ventricles now contract, increasing their blood pressure, and the atrio-ventricular valves stay shut. This time, the semi-lunar valves are opened, forcing blood through the Aorta and the Pulmonary Artery. Once the ventricles are empty of bood, the pressure is lower in the ventricles than in the Aorta/Pulmonary Artery, so the semi-lunar valves shut, and the cycle repeats.

SAN/AVN:

The SAN (aka the Pacemaker) is a group of cells situated in the top right of the right atrium, which give off an electrical signal to the atria to begin contracting (atrial systole). Once the signal has travelled through the atria, it reaches the AVN, situated in the centre of the heart, which carries the signal down the Perkyne tissue (which is present in the septum and ventricle muscle), causing the ventricles to contract (ventricular systole).

And I think thats about right? Just off the top of my head so probably some mistakes in there.

electrical signal = excitation wave. Remember the AVN delays the impulse slightly so there is a bit of time between atrial contraction and ventricular contraction.

Reply 76

steph_v

13

PrettyRainbows

i found it ok, it sort of reassured me a little bit, but knowing me im going to completely fail the real one...

Yes, it reassured me as well. But specimens are usually very different. I was just glad there was that massive potometer question. I messed up the bit about haemoglobin though. Too many different names of things that sound the same!
I got a very good grade in the specimen (like 94% or something) but I fall to pieces in exams, so I'm scared :frown:

Reply 77

poweroftheyouth

Biology is the BEST, it is the easiest exam in the sciences.
I do all Sciences.
Hey does anyone know how to interpret graphs probably- i hate them, lol require to much thinking especially vital capacity and tidal volume section