A level Biology: Post your doubts here!

[princesszahra]

waitt...i'm still confused...

what is your confusion?????

 

[XPFMember]

ermm i don't know if it's because i lack knowledge abt the topic

see..when the composition of the glomerular filtrate is always same as that of blood plasma except that it has no proteins.. then how come in this case we see that conc. of urine increases...and why in the collecting duct the water is more??

 

[princesszahra]

ermm i don't know if it's because i lack knowledge abt the topic

see..when the composition of the glomerular filtrate is always same as that of blood plasma except that it has no proteins.. then how come in this case we see that conc. of urine increases...and why in the collecting duct the water is more??

glomerular filterate will not have LARGE proteins! it can have small ones!!!

urea and protein are different!
Urea, also called carbamide, is an organic chemical compound which essentially is the waste produced when the body metabolizes protein!!!

and the conc of urea in urine is increasing!!!not of urine!!!
The walls of collecting duct respond to changes in levels of ADH!!

The wide variation in water reabsorption levels for the collecting duct system reflects its dependence on hormonal activation. The collecting ducts, in particular, the outer medullary and cortical collecting ducts, are largely impermeable to water without the presence of antidiuretic hormone (ADH, or vasopressin).

 

[XPFMember]

Jazak Allah Khairen!

so..is this correct: As the filtrate passes through the PCT , substances like glucose and amino acids are completely reabsorbed. Some of the water is also reabsorbed. Most of the urea stays in. Therefore, the concentration of urea in the urine becomes higher than that in the filtrate as seen by the values in the table!

 

[princesszahra]

Jazak Allah Khairen!

so..is this correct: As the filtrate passes through the PCT , substances like glucose and amino acids are completely reabsorbed. Some of the water is also reabsorbed. Most of the urea stays in. Therefore, the concentration of urea in the urine becomes higher than that in the filtrate as seen by the values in the table!

EXACTLY!!!!!!!!!!!!!!!!!

 

[XPFMember]

Nice to know!! :Bravo:

Jazak Allah Khairen Kaseeran!! :Rose:

 

[XPFMember]

Re: Stuck in Biology?? Post your doubts here!!

Assalamoalaikum!

Please, help me with this question:
Describe the function of vasa recta.

Mark scheme points:
-removing water;
-from/ reabsorbed by collecting ducts;
-ref. to maintain water potential gradient (in medulla)

Jazakumullah Khair..

 

[princesszahra]

Re: Stuck in Biology?? Post your doubts here!!

Assalamoalaikum!

Please, help me with this question:
Describe the function of vasa recta.

Mark scheme points:
-removing water;
-from/ reabsorbed by collecting ducts;
-ref. to maintain water potential gradient (in medulla)

Jazakumullah Khair..

Vasa recta or vasa recta renis is the blood supply of the kidney, which forms capillaries in medulla!

FUNCTION-
-vasa recta has a hairpin bend so the rate of movement of substances is slow hence exchange is efficient!
-On the descending portion of the vasa recta, NaCl and urea are reabsorbed into the blood, while water is secreted. On the ascending portion of the vasa recta, NaCl and urea are secreted into the interstitium, while water is reabsorbed.
- in the point about reabsorption by collecting ducts, u have to mention abt ADH!

 

[princesszahra]

remember*
vasa recta is not loop of henle!

 

[hassam]

the very term "vasa recta' is no more used on exams ...instead we simply call them peritubular capillaries

 

[hemant1]

that circle in the centre is the vascular bundle. and the palisade layer is the one that lies below the upper epidermis, arranged vertically, closely packed and perpendicularly to the mesophyl...

 

[hassam]

WATS B???
also tell wats its role

 

[hassam]

explain three ways in which the cell depicted above is involved in selective reabsorption?

 

[hassam]

cn any one expalin the highlighted points ....and kindly please tell what are tight junctions

 

[mrpaudel]

well..they are basal channels..!! rest idk!

 

[XPFMember]

cn any one expalin the highlighted points ....and kindly please tell what are tight junctions

Assalamoalaikum...

I need help with it too :s

I also didnt get these points...

 

[hassam]

examiners are going WILD in markschemes

 

[memyself15]

examiners are going WILD in markschemes

what do you mean? :unknown: :unknown:

 

[princesszahra]

cn any one expalin the highlighted points ....and kindly please tell what are tight junctions

junctions connect adjacent lateral walls of the cells.There are many types of junctions.
Tight junctions are formed by the transmembrane proteins present on the lateral surfaces of the cells are joined to each other!
These doesnot allow transfer of any material!
This information is enough at this level!If u need more, contact me please!
( the lateral surfaces are shown in green!)

 

[XPFMember]

Assalamoalaikum!!

http://www.xtremepapers.com/CIE/Interna ... _qp_41.pdf

Q:8 (b)
I dont get the following points mentioned in the ms...how are these related to temp changes???


less photolysis ;
less ATP produced ;
increased rate of respiration ;
respiration rate faster than photosynthesis rate / ref. compensation point