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A level Biology: Post your doubts here!

S

Shemyaa

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Deeksha Tamang said:
View attachment 64476 can anyone plz tell me the answer and why it is the answer
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The correct answer I guess is A
This is the explanation:
As you increase the temperature, the rate of enzyme working becomes more efficient as it reaches more towards the optimum temperature, therefore it will produce more enzyme-substrate complex and then product, but after the optimum temperature, the enzyme denatures and the active site is no more complementary to the shape of the substrate, less enzyme-substrate complex is formed and more substrate is left out.
you might confuse with D but the thing is the substrate concentration won't increase back because this reaction is not a reversible reaction and it's not like you can change the product back to the reactant so basically substrate concentration remains constant.
I hope you understood.
 
S

Shemyaa

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KashishV said:
HI guys, I was solving this question. The "less turgid" aspect is clear to me. However, I don't understand why it isn't "less negative" as in option D.
The mark scheme says B. The water needs to move out of the cells to ensure that final length is less than initial. and water moves from less negative value-> more negative value right? I don't know where I am messing up.
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Okay so basically while answering this I'll assume you understand why its less turgid,
water potential can either be +/-/0, when its 0 this means I have a pure water solution (isotonic), if you have more solutes it becomes more negative since now water gradient is lesser (they're less likely to lose water to a region that also has low water potential compared to pure water)(hypertonic)
Keep this in mind, negative water potential is low water potential basically, so it makes sense as more sucrose diffuses in then the cell will have less water potential than pure water, (less steep water potential gradient)
Hope it helped.
 
S

Shemyaa

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Alis alis said:
Please tell why option b is not right in question no 3?

View attachment 64446
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For active transport to occur, we need specific carrier proteins that are only found in the cell surface membrane, plasmodesmata is nothing but an empty desmotubule (tube-like structure that connects cells/companion cell and phloem sieve tube)
They have nothing with active transport,
they basically act as a pathway for diffusion of sucrose and amino acids by symplast pathway through plasmodesmata into the sieve tube element,
Also, for them to actively transport they need ATP and they can't get that
The special thing about carrier proteins is that they are attached to ATPase enzyme which will break ATP to ADP and again plasmodesmata doesn't have that too.
Hope it helped :)
 
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Clark20

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Need help understanding this. Why is the answer not B? As the chromosome does condense during prophase. (The correct answer is D).
 

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