biology paper 1 doubts

[externityxzx]

Dipeptide = 2 amino acids
You have 12 possibilities for the first amino acid
You also have 12 possibilities for the second amino acid
So you have a total of 12 x 12 = 144 possibilities for the dipeptide.

wow... i never realized that!! thank you!!

 

[♥Яαηõõşḧ♥]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s07_qp_1.pdf
can someone plz help me with question 7.... i dnt get why the answer is B
dont triglycerides have hydrogen bonds ????

 

[Irfan1995]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_qp_1.pdf
can someone plz help me with question 7.... i dnt get why the answer is B
dont triglycerides have hydrogen bonds ????

No, triglycerides do NOT have any hydrogen bonds as they don't have any sufficiently positive hydrogen atom in its structure. Even if, the molecule is too large to be affected by one or two hydrogen bonds.

 

[nelly trich]

I don't get this question ! why is it not c ?

 

[Taci12]

14 Single-celled animals that live in fresh water have a vacuole that contracts regularly to remove
excess water. Single-celled plants that live in fresh water do not have a similar vacuole.
Which statement explains why only these animals need this vacuole?
A Plant cell cytoplasm and animal cell cytoplasm both have a lower water potential than fresh
water.
B Plant cell sap has the same water potential as fresh water, animal cytoplasm has a lower
water potential than fresh water.
C Plant cell walls are impermeable to water, animal cell surface membranes are permeable to
water.
D Plant cell walls restrict the entry of water, animal cell membranes allow the free entry of
water.

The answer is D. Why isn't the answer B? How do plant cell walls restrict the entry of water?

Please help!

 

[Jevin Sanoo]

No, triglycerides do NOT have any hydrogen bonds as they don't have any sufficiently positive hydrogen atom in its structure. Even if, the molecule is too large to be affected by one or two hydrogen bonds.

If they would have hydrogen bonds lipids wouldn't float on water.

 

[♥Яαηõõşḧ♥]

No, triglycerides do NOT have any hydrogen bonds as they don't have any sufficiently positive hydrogen atom in its structure. Even if, the molecule is too large to be affected by one or two hydrogen bonds.

thanks!!! i get it now =)

 

[athaan]

Gah, I think I killed myself working on MJ2011 variant 2. I have questions about it!
http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_s11_qp_12.pdf
I have questions on number;
- 4 (answer is C) // why isn't chloroplast an essential structure? isn't the prokaryotes able to photosynthetic thus requires chloroplast?
- 38 (answer is B) // what does the anaerobic actually do? can anyone explain? why it is B, not A?

 

[nelly trich]

14 Single-celled animals that live in fresh water have a vacuole that contracts regularly to remove
excess water. Single-celled plants that live in fresh water do not have a similar vacuole.
Which statement explains why only these animals need this vacuole?
A Plant cell cytoplasm and animal cell cytoplasm both have a lower water potential than fresh
water.
B Plant cell sap has the same water potential as fresh water, animal cytoplasm has a lower
water potential than fresh water.
C Plant cell walls are impermeable to water, animal cell surface membranes are permeable to
water.
D Plant cell walls restrict the entry of water, animal cell membranes allow the free entry of
water.

The answer is D. Why isn't the answer B? How do plant cell walls restrict the entry of water?

Please help!

excuse in which exam is this question ??

 

[♥Яαηõõşḧ♥]

do T -lymphocytes form memory cells or only B-lymphocytes???
according to the older years they don't, but in june 2012 the answer to one of the questions said that they do
so whats the right answer ??

 

[Irfan1995]

do T -lymphocytes form memory cells or only B-lymphocytes???
according to the older years they don't, but in june 2012 the answer to one of the questions said that they do
so whats the right answer ??

Both form memory cells.

 

[Irfan1995]

14 Single-celled animals that live in fresh water have a vacuole that contracts regularly to remove
excess water. Single-celled plants that live in fresh water do not have a similar vacuole.
Which statement explains why only these animals need this vacuole?
A Plant cell cytoplasm and animal cell cytoplasm both have a lower water potential than fresh
water.
B Plant cell sap has the same water potential as fresh water, animal cytoplasm has a lower
water potential than fresh water.
C Plant cell walls are impermeable to water, animal cell surface membranes are permeable to
water.
D Plant cell walls restrict the entry of water, animal cell membranes allow the free entry of
water.

The answer is D. Why isn't the answer B? How do plant cell walls restrict the entry of water?

Please help!

Plants' cell walls are fully permeable. That is, they allow anything to pass through, even water. That is, until the cell is completely turgid then it won't allow any net movement of water in to prevent bursting.

 

[athaan]

do T -lymphocytes form memory cells or only B-lymphocytes???
according to the older years they don't, but in june 2012 the answer to one of the questions said that they do
so whats the right answer ??

Uh oh, as what I remember, T-lymphocytes do create memory cells.
It is even written in the official CIE textbook, which bolded.

"In addition to the helper cells and killer cells, memory T cells are produced which remain in the body and ..."

 

[Jevin Sanoo]

Gah, I think I killed myself working on MJ2011 variant 2. I have questions about it!
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_12.pdf
I have questions on number;
- 4 (answer is C) // why isn't chloroplast an essential structure? isn't the prokaryotes able to photosynthetic thus requires chloroplast?
- 38 (answer is B) // what does the anaerobic actually do? can anyone explain? why it is B, not A?

In prokaryotes, there may be an infolding of the plasma membrane which may form a photosynthetic membrane. It is this structure which carry out photosynthesis.

 

[♥Яαηõõşḧ♥]

Gah, I think I killed myself working on MJ2011 variant 2. I have questions about it!
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_12.pdf
I have questions on number;
- 4 (answer is C) // why isn't chloroplast an essential structure? isn't the prokaryotes able to photosynthetic thus requires chloroplast?
- 38 (answer is B) // what does the anaerobic actually do? can anyone explain? why it is B, not A?

for question 38, anaerobic bacteria are denitrifying bacteria so they convert nitrates to nitrogen gas

 

[athaan]

In prokaryotes, there may be an infolding of the plasma membrane which may form a photosynthetic membrane. It is this structure which carry out photosynthesis.

Wow, I didn't know that before! thank you for the information, gotta sure to keep this in mind!

for question 38, anaerobic bacteria are denitrifying bacteria so they convert nitrates to nitrogen gas

i see, i thought they were only normal bacterias

 

[Irfan1995]

Gah, I think I killed myself working on MJ2011 variant 2. I have questions about it!
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_12.pdf
I have questions on number;
- 4 (answer is C) // why isn't chloroplast an essential structure? isn't the prokaryotes able to photosynthetic thus requires chloroplast?
- 38 (answer is B) // what does the anaerobic actually do? can anyone explain? why it is B, not A?

4) Many prokaryotes have chlorophyll which carries out photosynthesis. In plants, chlorophyll is contained within chloroplasts.
38) Nitrifying bacteria require aerobic conditions (soil with oxygen) to convert ammonium ions into nitrates.
Without oxygen (anaerobic conditions), the opposite takes place, which is denitrification (converting nitrates back to nitrogen gas)

 

[♥Яαηõõşḧ♥]

Uh oh, as what I remember, T-lymphocytes do create memory cells.
It is even written in the official CIE textbook, which bolded.

"In addition to the helper cells and killer cells, memory T cells are produced which remain in the body and ..."

so i think we should go with what the text book says and also june 2012 is more recent so that means they probably produce memory cells...
thanks for the help !!!

 

[Kumkum]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w11_qp_12.pdf
please help with question number 39

 

[♥Яαηõõşḧ♥]

can someone plz tell me the exact compositions of blood, tissue fluid and lymph ?????
i always get those questions wrong :/