• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

AS Biology P1 MCQs Preparation Thread

Messages
274
Reaction score
277
Points
53
hey..for question no.3 what do u mean.didin't get it clearly.plz xplain once again.how does efficiency increases at high levels....?????
From all the sunlight arriving at the plant, a lot is wasted from transpiration, the light misses the leaf, the light passes through the leaf without getting absorbed by the chloroplasts etc... so only 1% of the sunlight is actually used in photosynthesis (this is a number you must know from studying ecosystems)
Also, we know that 10% of the energy in produces is actually useful to primary consumers. This is due to several reasons. For example, the cellulose in the plant's cell walls cannot be digested, so it just passes through the feces of the herbivore. A lot of energy is also wasted in respiration, and also in chewing the plant.
Secondary consumers are more efficient because more parts of the herbivore can be digested such as flesh and meat. However, there are still parts such as bones which cannot be digested. As a result, the efficiency in secondary consumers is higher than that in primary consumers. So the only option is 20%.
All the remaining energy (from cellulose, bones, organic waste) can be digested and used by microorganisms/detrivores/decomposers, so they get the remaining 80% of the energy.
 
Messages
576
Reaction score
308
Points
73
It's not C because athletes, who have greater cardiac outputs, have a lower blood pressure. Hence it can't be C or D. Also, greater cardiac output = more oxygen supplied to muscles = more carbon dioxide taken in.
I don't know why the impulses in the vagus nerve wouldn't increase. :oops: The vagus nerve decreases the heart rate.
rather call it a Bogus nerve as it is causing confusion!:confused:
 
Messages
274
Reaction score
277
Points
53
hey..for question no.3 what do u mean.didin't get it clearly.plz xplain once again.how does efficiency increases at high levels....?????
To clarify even further, plants have a lot of material that is completely useless to herbivores such as cell walls made of cellulose and chloroplasts. Most animals cannot digest cellulose, so it passes through the animal without being used. Secondary consumers eat the herbivores. Herbivores don't have any cellulose in them, nor any chloroplasts. They have mainly flesh and meat which can be completely broken down in the carnivore's digestive system and used as energy in the carnivore. In other words, there is less "waste" in the herbivore than in the plant. Hope that helps :)
 
Messages
22
Reaction score
14
Points
3
During interphase, DNA replicates. During prophase, histones unwind the DNA so that they can be condensed.

You don't need to know what histones are, just that they allow DNA to be condensed.
THX. Btw, what does condensation and spiralisation of DNA really means ??
 

egy

Messages
292
Reaction score
66
Points
38
With adding more substrate the reaction rate increases in presence of a competitive inhibitor.
however in presence of a non competitive inhibitor does the reaction rate decrease? or remain the same??

as u add more substrate to the non competitive inhibition it remains the same rate not increasing
 

thu

Messages
14
Reaction score
0
Points
1
Why can't this be A but B? Thanks!
 

Attachments

  • w08 Q6.JPG
    w08 Q6.JPG
    37.9 KB · Views: 10
Messages
274
Reaction score
277
Points
53
Pressure potential in a plant cell is how much a plant's cell membrane pushes a cell wall. This happens in a turgid cell. If a turgid cell is placed in a solution, water will leave by osmosis. This will continue to happen until the water potentials of the solution and the cell are the same. When this happens, the cell is no longer turgid, so the cell membrane will not exert a pressure on the cell wall, so the pressure potential will be zero.
 
Messages
22
Reaction score
14
Points
3
Why can't this be A but B? Thanks!
The question says structural. A refers to aplha-glucose (1.4-glycosidic bond). So, the thing that should come across your mind is cellulose. Cellulose provides structural support :D The monomers for cellulose is beta-glucose.
 
  • Like
Reactions: thu
Messages
274
Reaction score
277
Points
53
THX. Btw, what does condensation and spiralisation of DNA really means ??
Condensation means that the DNA molecules get shorter and thicker (so that it can be viewed by a light microscope after appropriate staining)
 
Messages
63
Reaction score
87
Points
28
Pressure potential in a plant cell is how much a plant's cell membrane pushes a cell wall. This happens in a turgid cell. If a turgid cell is placed in a solution, water will leave by osmosis. This will continue to happen until the water potentials of the solution and the cell are the same. When this happens, the cell is no longer turgid, so the cell membrane will not exert a pressure on the cell wall, so the pressure potential will be zero.
but the question states that "Turgid plant tissue is placed in a solution which has the same solute potential" so thier will be net movement
 
Messages
22
Reaction score
14
Points
3
Hey, what's the difference between reducing transpiration rate and reducing water potential gradient ??? For reducing transpiration rate, rolled leaves, fleshy leaves, sunken stomata and thick cuticle are needed. As for reducing water potential gradient, only rolled leaves, hairy leaves and sunken stomata are involved. Sigh :(
 
Messages
24
Reaction score
2
Points
3
I'm pretty sure....it's C

12^2 = 144..

remember it's always x^y
x is the no. of different aminoacids available...and y is the number...which would be in one particular peptide formed...
like here there were 12 different aminoacids formed...x=12
and we had to have 2 of them...so y=2

sahania
sophiaaa
Yes its C thankssssss !!!
 
Messages
1,558
Reaction score
2,428
Points
273
Aoa!
need help with some more questions plz...
View attachment 12766
For 19th questn, visualize mitosis. focus on the spindle fibers at each stage. A is when they are forming that is during prophase. B shows no considerable change in their length so this is meta phase. C shows that the length is reduced.. this must be when chromatids are separated, the anaphase. this leaves D to be the telophase. Here centromeres are detached from spindle fibers as the fibers are now disappearing.
 
Top