A level Biology: Post your doubts here!

[Deeksha Tamang]

From the table, this is the lowest magnification...lowest magnification means that the size of each cell will be the smallest and so the maximum number can be seen
The smaller the size of an object, the more of them can fit in an area of space

ohh...thank u so much

 

[Unknown202]

Can someone help why C and not B???

 

[A*****]

View attachment 62868

Can someone help why C and not B???

Just look at the y-axis... it is time taken for reaction, not the rate of reaction
It is just the opposite...at the optimum temp. where the rate is highest, the time will be the least and similarly where the rate is least, the time will be maximum...note that the line will not cross 50°C bqz the rate will be zero

 

[Dixit Unrivalled]

Re: Biology Doubt: Nervous System!

Assalamoalaikum!

Can someone please explain, what's refractory period? I am confused about it! =/

To know refractory period, you must know about hyper polarization. Once the cell fires action potential when threshold value is reached then, depolarization occurs and when the cell re-polarizes, it goes beyond the normal resting potential value i.e. hyper polarization. To bring the cell back to resting potential, the cell needs some time and this period is known as refractory period. During this period, the sodium potassium pump plays an important role by letting 3 sodium go out of the cell and 2 sodium into the cell for each time thus, bringing the cell back to resting potential. I hope I made my point.

 

[XPFMember]

To know refractory period, you must know about hyper polarization. Once the cell fires action potential when threshold value is reached then, depolarization occurs and when the cell re-polarizes, it goes beyond the normal resting potential value i.e. hyper polarization. To bring the cell back to resting potential, the cell needs some time and this period is known as refractory period. During this period, the sodium potassium pump plays an important role by letting 3 sodium go out of the cell and 2 sodium into the cell for each time thus, bringing the cell back to resting potential. I hope I made my point.

Thanks a lot!! You did.
But guess what? That's a 6 year old post. I'm almost done with uni

 

[badrobot14]

Thanks a lot!! You did.
But guess what? That's a 6 year old post. I'll almost done with uni

XD

 

[Unknown202]

 

[Unknown202]

View attachment 62926

can someone help plzzz why for 18 ans is B??

 

[Unknown202]

 

[Unknown202]

View attachment 62927

also 7 why ans is C??

 

[Okabe Rintarou]

can someone help plzzz why for 18 ans is B??

The RNA triplet UAG means that the DNA triplet is ATC. So, you just have to insert and check where there is triplet for ATC.

A: TTC CAC TCG ATG
B: TCC ATC TCG ATG
C: TCC ACT CTG ATG
D: TCC ACT CGA TTG

The only sequence which has ATC is B, so that is the correct answer.

 

[Okabe Rintarou]

9700_s14_qp_12 Q.17,21,29,30,33. Please help!!!

 

[Okabe Rintarou]

9700_s15_qp_12 Q.17.26,34 please!!!

 

[Unknown202]

can someone help why answer is C?

 

[corona]

View attachment 62972
can someone help why answer is C?

It is the point where the ratio of initial length to final length is 1, which is 0.45 moldm-3 sucrose concentration (from graph).

 

[Unknown202]

so when it is 1 the water potential is equal to sucrose plz explain in further detail

It is the point where the ratio of initial length to final length is 1, which is 0.45 moldm-3 sucrose concentration (from graph).

 

[studyingrobot457]

so when it is 1 the water potential is equal to sucrose plz explain in further detail

at one , the length after immersion, and before immersion is the saem, this means that no water was lost/ taken in, which means that the water potential of the solution= water potential of the cells,
btw you are an arab, nice to see someone relatable

 

[Unknown202]

help question b(ii)plz

 

[studyingrobot457]

help question b(ii)plz
View attachment 62997

since adult haemoglobin is produced, oxygen is transported normally I guess, maybe because person is heterozygous, so he is only a carrier

 

[studyingrobot457]

just say the ms, my answer is correct, just need to specific that more adult haemoglobin is produced (and no genetics ;P)