ALL CIE BIOLOGY DOUBTS HERE !!!

[Dania]

The sucrose id first loaded into the companion cell by active transport, using a protein molecule in the cell membrane as carrier or transporter. The latter pump out hydrogen ions actively. This creates a high concentration of H⁺ ions outside the companion cell.

Now the H⁺ ions diffuse back into the companion cell using a protein carrier down its concentration gradient. The latter move sucrose at the same time as the H⁺ ions. But the sucrose moves against its concentration gradient.

In other words, sucrose is being co-transported along with the H⁺ ions. The sucrose moves into the adjacent sieve tube elements through the plasmodesmata.

Hope it helps

Thank You! That's just what I need.

[Dania]

How come no one has doubts about tomorrow's exam? I'm surprised.

[Deadly_king]

How come no one has doubts about tomorrow's exam? I'm surprised.

I think there are not many members sitting for Biology this year.

[elemis]

I think there are not many members sitting for Biology this year.

Not many answer in the winter session.

[Arthur Bon Zavi]

Not many answer in the winter session.

That's a good fact.

Candidates appearing in May/June sessions are far more than candidates appearing in October/November session.

[Dania]

Does anyone have notes on this particular segment of Genetic Control?

Thanks in advance.

[Dania]

Help! Anyone?

The answer is D.

[Deadly_king]

Does anyone have notes on this particular segment of Genetic Control?

Thanks in advance.

Sickle Cell Anaemia results from a substitution of one base which in turn transform the whole amino acid from the glutamic acid to valine. More precisely an adenine has been replaced by a thymine.

So the answer is A.

I do not have the specific notes but the application booklet for Chemistry(Page 39) is very helpful. Do take a look.

Click here for more details about Sickle Cell Anaemia.

[Deadly_king]

Help! Anyone?

The answer is D.

The walls of both the alveolus and the capillary is one cell thick. Hence for gaseous exchange to occur the gas has to pass:

i) through the cell membrane of the one cell thick squamous epithelial cell of the alveoli so that it enters the cell.

ii) through the cell membrane of the same cell but in the opposite direction. The gas now leaves the cell, in other words it gets out of the alveoli.

iii) across the cell membrane of the one cell thick squamous epithelial cell of the capillary such that the gas enters the cell.

iv) across the cell membrane of the same cell but in opposite direction to get out of the cell and into the blood vessel.

v) lastly the gas needs to go through the cell membrane of the red blood cell for transport.

So in all, the gas has to pass across 5 cell membranes.

See the picture attached so that you may understand it better.

[Dania]

The walls of both the alveolus and the capillary is one cell thick. Hence for gaseous exchange to occur the gas has to pass:

i) through the cell membrane of the one cell thick squamous epithelial cell of the alveoli so that it enters the cell.

ii) through the cell membrane of the same cell but in the opposite direction. The gas now leaves the cell, in other words it gets out of the alveoli.

iii) across the cell membrane of the one cell thick squamous epithelial cell of the capillary such that the gas enters the cell.

iv) across the cell membrane of the same cell but in opposite direction to get out of the cell and into the blood vessel.

v) lastly the gas needs to go through the cell membrane of the red blood cell for transport.

So in all, the gas has to pass across 5 cell membranes.

See the picture attached so that you may understand it better.

Thank you! Very helpful. Eid Mubarak!

[Deadly_king]

Thank you! Very helpful. Eid Mubarak!

Anytime

Eid Mubarak to you too.

[Dania]

The answer to this is B. Can anyone explain why it is not A?

[Dania]

The answer to this question is A. Why is it not B?

[Dania]

The answer is D

[Dania]

Please explain why the answer is D