A level Biology: Post your doubts here!

[Shemyaa]

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.

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.

 

[Shemyaa]

Please tell why option b is not right in question no 3?

View attachment 64446

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

 

[readermnz]

Any paper 5 topical pastpapers? or notes?

 

[Clark20]

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

 

[blymphocytes]

Is anyone doing paper 4 on 8th?

 

[fourtris46]

Is anyone doing paper 4 on 8th?

I will

 

[A*****]

Anyone having march 19 bio paper 4?

 

[helloolo]

Is anyone doing paper 4 on 8th?

Me are you ready

 

[Ayesha_m01]

any guesses for bio paper 42 day after tomorrow?

 

[Ayesha_m01]

Anyone having march 19 bio paper 4?

https://www.facebook.com/MrHossamAttya/

here u go
just keep scrolling down.. you'll find them

 

[A*****]

https://www.facebook.com/MrHossamAttya/

here u go
just keep scrolling down.. you'll find them

This was great!! Thanks alot

 

[desterman]

Do I need need to study AS topics for paper 4

 

[blymphocytes]

No

Me are you ready

You?

 

[fourtris46]

how was paper 41?

 

[blymphocytes]

how was paper 41?

longgg....... yours??

 

[helloolo]

how was paper 41?

I found it a bit hard what about you?

 

[helloolo]

longgg....... yours??

Yeah and most of the papers was about plants.

 

[blymphocytes]

Yeah and most of the papers was about plants.

Yeaa.....which qn did you do in section B?

 

[fourtris46]

longgg....... yours??

same, for section B I chose q10.. the moment I started writing, I regret not choosing q9 .. might lose 8

 

[fourtris46]

Yeah and most of the papers was about plants.

I felt like it was all about one chapter ..