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Amenbreak321
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#1281
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#1281
Anyone who doesn't get a question, ask me and I will explain. It will help me revise as well.
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Areen5
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(Original post by Amenbreak321)
Anyone who doesn't get a question, ask me and I will explain. It will help me revise as well.
Hellooo, can you please help me with this question

"The time required for a cell to complete the cell cycle was 4 hours 18 minutes.
Calculate the time required in minutes for this cell to multiply to produce eight cells.
Show your working." (Unit 2 May 2011)

http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF

Thank youuu
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PR11NCE
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(Original post by Simran Mars Foster)
I'm confused. So the proteins are in the capillary?
Blood is in the capillaries. Blood contains proteins, water..etc.
Yes, they are in the capillaries, but don't confuse that with tissue fluid etc..

Large proteins are in the blood,SOME smaller ones are pushed out into tissue fluid (if any at all) by ultrafiltration.
Tissue fluid is WATER O2 Nutrients. The water is reabsorbed by osmosis back into the capillary because the WP of tissue fluid is higher than that of the capillary nearest the veins.
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PR11NCE
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(Original post by Amenbreak321)
Anyone who doesn't get a question, ask me and I will explain. It will help me revise as well.
Hi! What is the Coheshion - Tension theory...
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Jimmy20002012
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(Original post by pinpin95)
you know the 'water' mentioned in the first point is that the tissue fluid?
No that is the water in the capillary that filters out of the capillary, well actually ions, salts and water filters out, but AQA only really accepts that water filters out which produces tissue fluid.


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Scienceisgood
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#1286
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Can someone please give me the ideal answer for the formation of tissue fluid please?
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JackTheNerd
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#1287
Could someone help me with Jun09, 4 (a) (this isn't.the question just my queries on.the question)
how does the mass of DNA change without the chromosomal number changing? Also, is the number of chromosomes the same because he cell hasn't divided yet?
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Jimmy20002012
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(Original post by Scienceisgood)
Can someone please give me the ideal answer for the formation of tissue fluid please?
I have done one above?


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maryamnc
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#1289
For biol1 there are two 5 markers at the end, what is the structure for biol2? thankyou
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pinpin95
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(Original post by Jimmy20002012)
No that is the water in the capillary that filters out of the capillary, well actually ions, salts and water filters out, but AQA only really accepts that water filters out which produces tissue fluid.


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ohhh ok thank you
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Amenbreak321
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(Original post by Areen5)
Hellooo, can you please help me with this question
(Original post by Areen5)

"The time required for a cell to complete the cell cycle was 4 hours 18 minutes.
Calculate the time required in minutes for this cell to multiply to produce eight cells.
Show your working." (Unit 2 May 2011)

http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF

Thank youuu
4 hours 18 mins = 2 cells. (1 division)
8 hours 36 mins = 4 cells. (2 divisions)
12 hours 54 mins = 8 cells. (3 divisions)

12 x 60 + 54 = 774
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Amenbreak321
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(Original post by PR11NCE)
Hi! What is the Coheshion - Tension theory...
Water moves out of the leaves by transpiration. That water is replaced by water from the xylem, this creates tension and pulls water up the xylem.

Water molecules stick together because of Hydrogen bonding. (cohesion) So they join together and pull themselves up the xylem in a constant column of water.

The tension crates a negative pressure that is higher when the rate of transpiration is high e.g. 12:00 till 14:00, this makes the diameter of the trunk of the tree get smaller as its sucked in.
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PR11NCE
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(Original post by Amenbreak321)
Water moves out of the leaves by transpiration. That water is replaced by water from the xylem, this creates tension and pulls water up the xylem.

Water molecules stick together because of Hydrogen bonding. (cohesion) So they join together and pull themselves up the xylem in a constant column of water.

The tension crates a negative pressure that is higher when the rate of transpiration is high e.g. 12:00 till 14:00, this makes the diameter of the trunk of the tree get smaller as its sucked in.
Thank You
Could you please explain the whole negative pressure bit, that throws me off...
Thank you though, this really cleared it up in my mind
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pinpin95
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(Original post by Scienceisgood)
Can someone please give me the ideal answer for the formation of tissue fluid please?
1) high hydrostatic pressure at the arteriole end of capillary
2)this causes water to move out by filteration
3)protiens stay in capillary as they are too large
4)in the venule end the water potential is lower due to plasma protiens
5) water moves into capillary by osmosis
6) not all the water moves into capillary
7) so the rest is drained of by lymphatic system

(this question is from the jan 2012 paper)
'Describe how tissue fluid is formed and how it is returned to the circulatory system'

the markscheme says:
Formation
1. High blood / hydrostatic pressure /
pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return
4. Low water potential in capillary /
blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;

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Areen5
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(Original post by Amenbreak321)
[CENTER]

4 hours 18 mins = 2 cells. (1 division)
8 hours 36 mins = 4 cells. (2 divisions)
12 hours 54 mins = 8 cells. (3 divisions)

12 x 60 + 54 = 774
Thank you so much, your explanation really helped, thanks
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Amenbreak321
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(Original post by PR11NCE)
Thank You
Could you please explain the whole negative pressure bit, that throws me off...
Thank you though, this really cleared it up in my mind
Water molecules also stick to the xylem walls and pull them in (adhesion) So because the water is being pulled up and its pulling the xylem walls in, it is at a lower pressure than the outside atmosphere.
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PR11NCE
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(Original post by Amenbreak321)
Water molecules also stick to the xylem walls and pull them in (adhesion) So because the water is being pulled up and its pulling the xylem walls in, it is at a lower pressure than the outside atmosphere.
Got it, thank you so much.
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Swords N Thorns
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(Original post by Layontheland)
2^3

2 = Is the fact we want pairs of chromosomes

3 = There are 3 different types of chromosomes.

For example.
ABCD

How many different pairs can we make from ABCD

Well than it would be 2^4 = 16

AA
AB
AC
AD
BB
BA
BC
BD
CC
CA
CB
CD
DD
DA
DB
DC
Ahh right, gotcha!
Thanks so so much!
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Sum786
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Approximately how many marks are you guys getting on the past papers? Also does anyone know the average mark for an A?
Thank you
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maryamnc
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(Original post by Sum786)
Approximately how many marks are you guys getting on the past papers? Also does anyone know the average mark for an A?
Thank you
I just got 57 which was the B boundary for June 2012, an A was 63
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