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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

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Reply 260
Original post by Jorgeyy
My graph was messy because I had to change it...

I'm pretty sure the one I changed it too was right though and if it's right im gonna get full marks even though it's an ugly looking thing lol !

I used Relative Rate (1/time) sec^-1 I think?

I remember some dodgy questions as well lol like why did you rotate the tube and all I could think of was to allow enzyme and substrate to be mixed properly or something and so you could identify when a curd appeared.

Stupid stuff -.-

Yeah I used the units as s-1
My graph was okay..
Oh yeah i think i wrote for that one, allows more collisions, thus e-s complexes but there were 2points so i just woffled. Also I couldnt think of alternative rate of reaction measures. I hope the gb are low.
Reply 261
Original post by EffKayy
Yeah I used the units as s-1
My graph was okay..
Oh yeah i think i wrote for that one, allows more collisions, thus e-s complexes but there were 2points so i just woffled. Also I couldnt think of alternative rate of reaction measures. I hope the gb are low.


Sorry to interrupt, but which graph is this that you guys are talkin' bout?:confused:
Heyy can anyone clarify if this is right? i'm having a tough time remembering mitosis and meiosis

For mitosis:
Interphase - Dna is replicated
Prophase - Spindle forms
Metaphase - Chromosomes line up at the centromere of the cell
Anaphase - Spindle fibres shorten and pull chromatids to opposite poles
Telophase - 2 identical cells are formed

& mitosis is needed for Growth, Repair and Differentiation?
Original post by xkate1019x
Heyy can anyone clarify if this is right? i'm having a tough time remembering mitosis and meiosis

For mitosis:
Interphase - Dna is replicated
Prophase - Spindle forms
Metaphase - Chromosomes line up at the centromere of the cell
Anaphase - Spindle fibres shorten and pull chromatids to opposite poles
Telophase - 2 identical cells are formed

& mitosis is needed for Growth, Repair and Differentiation?


:mad:Ooh... you are quite out of track there as some of it wrong.

Just follow this:cool:, (Copied from notes):

Interphase
The cell carries out normal functions but also prepares to divide. The cell’s DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so it has spare ones, and its ATP content is increased (ATP provides the energy needed for cell division).

1)Prophase
The chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle. The nuclear envelope (the membrane around the nucleus) breaks down and chromosomes lie free in the cytoplasm.

2)Metaphase
The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.

3)Anaphase
The centromeres divide, separating each pair of sister chromatids. The spindle fibres contract, pulling chromatids to opposite ends of the cell, centromere first.

4)Telophase
The chromatids reach the opposite poles of the cell on the spindle. They uncoil and become long and thin again. They’re now called chromosomes again. A nuclear envelope forms around each group of chromosomes, so there are now two nuclei. The cytoplasm divides and there are now two daughter cells that are genetically identical to the original cell and to each other. Mitosis is finished and each daughter cell starts the interphase part of the cell cycle to get ready for the next round of mitosis.
Reply 264
Guys could somebody help me out please...

What is the actual difference between Lymph and Tissue Fluid and how exactly is Plymph formed because I'm really confused :/
Original post by Carter787
Guys could somebody help me out please...

What is the actual difference between Lymph and Tissue Fluid and how exactly is Plymph formed because I'm really confused :/


Copied from notes::cool:


Tissue fluid is the fluid that surrounds cells in tissues. It’s made from substances that leave the blood, e.g. oxygen, water and nutrients. Cell stake in oxygen and nutrients from the tissue fluid, and release metabolic waste into it. Substances move out of blood capillaries, into the tissue fluid, by pressure filtration.

1. At the start of the capillary bed, nearest the arteries, the pressure inside the capillaries is greater than the pressure in the tissue fluid. This difference in pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid.

2. As fluid leaves, the pressure reduces In the capillaries- so the pressure is much lower at the end of the capillary bed that’s nearest to the veins.

3. Due to the fluid loss, the water potential at the end of the capillaries nearest the veins is lower than the water potential in the tissue fluid – so some water re-enters the capillaries from the tissue fluid at the vein end by osmosis.

Unlike blood, tissue fluid doesn’t contain red blood cells or big proteins, because they’re too large to be pushed out through the capillary walls. Any excess tissue fluid is drained into the lymphatic system (a network of tubes that acts a bit like a drain), which transports this excess fluid called lymph form the tissues and dumps it back into the circulatory system.

Summary::rolleyes:

So basically tissue fluid surrounds cells around the capillary and when its is in excess it get drained out into a lymph vessel, as soon as it enters the lymphatic system it becomes lymph.
Reply 266
Original post by Elliekate1
Firstly, HUGE thank for the explanation. That totally makes sense now. It's just one of those things I needed to get straight in my head.

Secondly, my teacher said that we essentially had the right idea between us:

1. The leaves are thin so that all the cells within the leaf have some contact with air and therefore 02 all the time.
2. They are large so that ther is a large underside (that will have many stomata) to allow air in and to increase SA for photosynthesis (see point four)
3. Also, the Mesophyll spongy layer, the cells are loosely packerd and irregular to increase S.A further.
4. Finally, respiration and Photsynthesis (obvs depending on whether it's day or night) help to maitin a concentation gradient and so lots of movement of 02 and Co2 in and out of the cells.

Hope that helps.
:smile:


thankyou!:biggrin:
and you're welcome! i'm glad my explanation actually made sense :')
Original post by therapist_1
:mad:Ooh... you are quite out of track there as some of it wrong.

Just follow this:cool:, (Copied from notes):

Interphase
The cell carries out normal functions but also prepares to divide. The cell’s DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so it has spare ones, and its ATP content is increased (ATP provides the energy needed for cell division).

1)Prophase
The chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle. The nuclear envelope (the membrane around the nucleus) breaks down and chromosomes lie free in the cytoplasm.

2)Metaphase
The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.

3)Anaphase
The centromeres divide, separating each pair of sister chromatids. The spindle fibres contract, pulling chromatids to opposite ends of the cell, centromere first.

4)Telophase
The chromatids reach the opposite poles of the cell on the spindle. They uncoil and become long and thin again. They’re now called chromosomes again. A nuclear envelope forms around each group of chromosomes, so there are now two nuclei. The cytoplasm divides and there are now two daughter cells that are genetically identical to the original cell and to each other. Mitosis is finished and each daughter cell starts the interphase part of the cell cycle to get ready for the next round of mitosis.




maybe it's just me but seems your explanation is exactly the same as the first one only in more detail?

What's wrong with the first one? :s-smilie:
Original post by xkate1019x
Heyy can anyone clarify if this is right? i'm having a tough time remembering mitosis and meiosis

For mitosis:
Interphase - Dna is replicated
Prophase - Spindle forms
Metaphase - Chromosomes line up at the centromere of the cell
Anaphase - Spindle fibres shorten and pull chromatids to opposite poles
Telophase - 2 identical cells are formed

& mitosis is needed for Growth, Repair and Differentiation?


Only slightly more detail and more specific naming:smile:

Interphase- DNA replicates, protein synthesis, replication of organelles, replication of centrioles.

Prophase- Nucleolus + nuclear envelope disintegrates, chromosomes visible.

Metaphase- Chromosomes line up at equator, spindle fibres attach to centromere.

Anaphase- Spindle fibres contract, Pull chromatids towards poles.

Telephase- Cytoplasm replicates, Nucleolus and nuclear envelope re appear, become two seperate cells.
Reply 269
Does anyone have or know how to get hold of the old specification past papers for unit two?????
Reply 270
Original post by Robert McGeachan
Does anyone have or know how to get hold of the old specification past papers for unit two?????


http://freeexampapers.com/past_papers.php?l=Past_Papers%2FA+Level%2F
Original post by xkate1019x
Heyy can anyone clarify if this is right? i'm having a

Interphase - Dna is replicated
Prophase - Spindle forms
**Metaphase - Chromosomes line up at the centromere of the cell
**Anaphase - Spindle fibres shorten and pull chromatids to opposite poles
Telophase - 2 identical cells are formed

& mitosis is needed for Growth, Repair and Differentiation?


:ff2:
In metaphase chromosomes do not line up at the centromere of the cell they line up at the equator of the cell. Then the centromere of the chromosome is attached to a spindle fibre.

In anaphase the spindle fibres contract and not shorten, you could have lost marks for incorrect terminology.

Its just that, that made me think alot, you were quite right after all.:rolleyes:
Original post by therapist_1
:ff2:
In metaphase chromosomes do not line up at the centromere of the cell they line up at the equator of the cell. Then the centromere of the chromosome is attached to a spindle fibre.

In anaphase the spindle fibres contract and not shorten, you could have lost marks for incorrect terminology.

Its just that, that made me think alot, you were quite right after all.:rolleyes:


Thankyou :smile: gosh i'm dreading this exam lol!
Original post by al_habib
hows revision,,


Going good for bio not other subjects wa bou u?
u prepared for this thursdaii
Haemoglobin

Are my Facts correct? I'm a bit unsure on my termonology...

- Haemoglobin is a protein
- It is made up of 4 polypeptide chains (quartenary structure)
- Each polypeptide has a haem group (non protein ), which contains iron
- It is hard for oxygen to bind with haemoglobin but when the first haem binds to oxygen, the structure of the polypeptides change to make the haemoglobin have a high affinity for oxygen.
- A haemoglobin with a high affinity for oxygen takes up oxygen more easily, but released it more readily. (e.g. in the lungs)
- when one oxygen molecule is released from the haem group, it changes the shape of the haemoglobin structure, and makes it easier for the other 3 to be released, giving it a low affinity for oxygen
- a low affinity for oxygen means the haemoglobin takes oxygen up less easily but released it more readily easily (e.g. in a quickly respiring muscle)

Thanks in advance :smile:
Original post by Limitless
I don't know if you are just chatting ****. I never sat the exam so I don't know, I would need to ask somebody who sat the exam and does not talk out of his ass like you.


I took the unit 4 exam in January and there was nothing on there that we hadnt done :smile:
Reply 277
Original post by SurfingGirl
I took the unit 4 exam in January and there was nothing on there that we hadnt done :smile:


I think he was trying to make everybody revise the wrong thing so everybody gets **** marks and the grade boundaries are lower and he has a chance of getting a decent grade. This is just a theory I would need to test this experiment out and repeat it several times to make it reliable and to reduce the affect of anomalous results. :cool:
Can someone please explain 5dii on Biology June 2010 paper??
Reply 279
Can anyone explain how to work out magnification and actual size? i cant remember how to do it

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