AS Biology P1 MCQs Preparation Thread

[hmlahori]

People please help! i've been posting these questions repeatedly!!!

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w05_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w05_er.pdf
Q17 How is the answer D? shouldnt it be C? The cells dont go through lysis because water moves into them and they become turgid rite?

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w06_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w06_er.pdf
Q1 My answer was C. This is how i calculated it. One division on the graticule is ((0.1/40) into 1000)= 2.5 micrometer. then i measured the width of the chloroplast with the ruler and got 1.8 cm. i placed ruler onto the graticule and got 21 divisions in 1.8 cm. multiplied 21 by 2.5 to get 52.5 approximately 50. correect answer is B 10 micrometer. something wrong with my method maybe?

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w08_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w08_er.pdf
Q18 ????

 

[sophiaaa]

amylase will break down the amylose part of starch into its monomers, which are glucose molecules...and these are reducing sugars...this happens when the reaction takes place. The test for reducing sugars is the Benedicts test. And gives a positive result, a brick red ppt, with reducing sugars so the answer is A, hope that helps

why can't it be iodine in potassiumm iodide soln?

 

[rogue94]

thnx ill check it out. can u also tell me the different formulas to calculate tidal volume and ventilation rate and breathing rate?

One peak curve/parabola, represents one breath on a graph (with volume of air in lungs on y-axis and time on x-axis.) So you should know that the number of peak curves is equal to the number of breaths and breathing rate is equal to the no. of breaths per unit time (breaths per second or per minute). Tidal volume is the minimum volume of air in the the lungs (shown on y axis) subtracted from the maximum volume of air in the lungs (shown on the y axis). Basically, you should know the graphical interpretation. I' ll try uploading a figure from past papers relevant to this.

 

[sophiaaa]

One peak curve/parabola, represents one breath on a graph (with volume of air in lungs on y-axis and time on x-axis.) So you should know that the number of peak curves is equal to the number of breaths and breathing rate is equal to the no. of breaths per unit time (breaths per second or per minute). Tidal volume is the minimum volume of air in the the lungs (shown on y axis) subtracted from the maximum volume of air in the lungs (shown on the y axis). Basically, you should know the graphical interpretation. I' ll try uploading a figure from past papers relevant to this.

and..how to calculate volume of oxygen absorbed from the graph???

 

[sophiaaa]

nd plz help me wid this one.q.no.32

 

[sagar65265]

sagar65265....... thanx soooo much man! God bless! I'll be waiting for qn 11......thanx

Okay, Q11:
First off, let's see what these substances are:
Cellulose: Polymer of Beta Glucose units. Contain lots of microfibrils - long fibres made of beta glucose links linked together by beta 1-4 links. Straight chain, unlike starch. A very strong subtance when subjected to tensile forces. Since it is the polymer of a carbohydrate, it contains polar bonds that hydrogen bond to each other and Hydrogen bonds strengthen the structure.
http://en.wikipedia.org/wiki/Cellulose#Structure_and_properties

Collagen: A fibre made of a triple helix structure. It is a fibrous protein and is very insoluble in water. It is found in animal connective tissue, tendon, ligament and in the arteries. (The significance of this is that blood is not normally supposed to meet collagen fibres. When there is a cut/ the endothelium is damaged, the blood contacts the collagen fibres and platelets bind to the collagen becoming activated in the process (http://en.wikipedia.org/wiki/Coagulation#Platelet_activation))

Glycogen: Storage molecule that is a highly branched polymer of alpha glucose. Branch points are alpha 1-6 glycosidic bonds with normal bonds alpha1-4 glycosidic bonds. Insoluble in water, thus doesn't affect waer potential of holding cell and doesn't interfere with other chemical reactions, making it a perfect long term store of energy.

Triglyceride: This is the ester of glycerol and 3 molecules of fatty acid. Basically, this is a fat, and it is insoluble (after all, that is what the ethanol test is for) and is an extremely useful source of energy. However it can't be respired in anaerobic conditions, such as at times of vigorous activity in the muscles. A relatively small molecule.

Option C can be eliminated because Collagen does not have any branches - while glycogen surely does, Collagen doesn't have any branches (to my knowledge) so Option C is out. Option B is also eliminated because Cellulose has NO branches as it is a straight chain polymer and it is also held together by Hydrogen bonds.

Option D is also eliminated since Triglycerides are molecules that do not have hydrogen bonds between molecules.

Therefore it has to be option A!

Good luck for your exams!

 

[sophiaaa]

nd plz help me wid this one.q.no.32

nyone.help wid dis one........

 

[geek101]

why can't it be iodine in potassiumm iodide soln?

cuz the amylopectin part of starch is still not broken yet....so that wouldn't really confirm the reaction cuz a slight blue black color might appear. the best way it so check whether the amylose has broken down to reducing sugar.

 

[rogue94]

People please help! i've been posting these questions repeatedly!!!

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w05_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w05_er.pdf
Q17 How is the answer D? shouldnt it be C? The cells dont go through lysis because water moves into them and they become turgid rite?

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w06_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w06_er.pdf
Q1 My answer was C. This is how i calculated it. One division on the graticule is ((0.1/40) into 1000)= 2.5 micrometer. then i measured the width of the chloroplast with the ruler and got 1.8 cm. i placed ruler onto the graticule and got 21 divisions in 1.8 cm. multiplied 21 by 2.5 to get 52.5 approximately 50. correect answer is B 10 micrometer. something wrong with my method maybe?

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w08_qp_1.pdf
http://www.xtremepapers.com/papers/...A and AS Level/Biology (9700)/9700_w08_er.pdf
Q18 ????

For Q17, red blood cells are animal cells and therefore, do not have a cell wall. Cell wall is present in plant cells and withstands the turgor pressure to make the plant cell turgid. In red blood cells, there is no cell wall to withstand the pressure due to the water that moves in, so the cell bursts (known as lysis/haemolysis/cytolysis). Remember turgidity is only for plant cells, not animals cells. Also, haemoglobin is a large protein so it won't be able to pass through the transport/channel proteins. Only small molecules such as water soluble vitamins, glucose and amino acids can pass through these integral proteins.
For Q1, you calibrated the gracticule correctly (1 division is equal to 2.5 um), but you measured the chloroplast incorrectly! You need to align the ends of one of the chloroplasts with the scale given below the picture of the cell. One chloroplast is approximately equal to 4 divisions. (since 1 division is equal to 2.5 um so 4 divisions are equal to 2.5 x 4 = 10um). Also 1.8 cm is too large for a chloroplast (although you dont need to measure it, perhaps you are measuring another structure; chloroplasts are the small circular structures within the cell that are densely stained and most in number.)
For Q18, The telomeres are reduced in the replicated DNA since they are not completely replaced. With substance X the telomere quantity in replicated DNA remains the same as that in the DNA which was replicated (telomeres are completely replaced), so promotion of DNA replication (in interphase of cell cycle) is not reduced and the cell divides continually . Without substance X telomeres are not completely replaced so their amount in replicated DNA decreases, which in turn reduces promotion so the finally no DNA is replicated and cell division stops as a result (If there is no DNA replication, the cell cannot divide and reproduce). Don't confuse replacement of telomeres. Substance X does not take the place of the telormers, it simply causes them to be completely replaced in replicated DNA. The Answer is A.

 

[rogue94]

and..how to calculate volume of oxygen absorbed from the graph???

volume of air absorbed into 0.21% i guess, but that gives you the volume of oxygen inhaled during one breath.

 

[sophiaaa]

cuz the amylopectin part of starch is still not broken yet....so that wouldn't really confirm the reaction cuz a slight blue black color might appear. the best way it so check whether the amylose has broken down to reducing sugar.

hey is the solute potential of phloem sieve tube high or low?why?
http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s08_qp_1.pdf.q.no.27

 

[sophiaaa]

volume of air absorbed into 0.21% i guess, but that gives you the volume of oxygen inhaled during one breath.

i mean in general how do u calculate volume of oxygen absorbed from graph?

 

[rogue94]

i mean in general how do u calculate volume of oxygen absorbed from graph?

i don't know, which graph? I mean what would be the axis of the graph?

 

[sophiaaa]

like a normal graph.volume of air absorbed in y axis and time in x axis????

 

[sophiaaa]

like a normal graph.volume of air absorbed in y axis and time in x axis????

if u could help wid dis one also........http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s08_qp_1.pdf.q.no.27

 

[rogue94]

like a normal graph.volume of air absorbed in y axis and time in x axis????

Hmmm, then to find volume of oxygen absorbed in a given time simply multiply the volume of air absorbed in the given time with .20, since there is 20% oxygen in air.

 

[rogue94]

if u could help wid dis one also........http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s08_qp_1.pdf.q.no.27

The Answer is C. Solute potential is the same as water potential, so a low solute potential means a low water potential. The phloem sap has low water potential, since it contains a significant quantity of assimilates such as sucrose and amino acids (phloem transports assimilates). Also, the cell walls are not lignified (only the walls of the xylem vessels are lignified).

 

[sophiaaa]

The Answer is C. Solute potential is the same as water potential, so a low solute potential means a low water potential. The phloem sap has low water potential, since it contains a significant quantity of assimilates such as sucrose and amino acids (phloem transports assimilates). Also, the cell walls are not lignified (only the walls of the xylem vessels are lignified).

are u sure solute potential and water potential are same???????solute potential mean concn of solute bt water potential means potential of water nt solute.isn't it???

 

[sahania]

The answer is C ... Can anyone explain it please ????

 

[geek101]

if u could help wid dis one also........http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s08_qp_1.pdf.q.no.27

for a plant cell the water potential = solute potential + pressure potential
since pressure potential = 0
so water potential = solute potential
(remember thats not the case always)
so due to the high conc of assimilates the water potential decreases and so the solute potential also decreases.