A level Biology: Post your doubts here!

[XPFMember]

assalamoalaikum again!

another doubt..what exactly are the products of photolysis of water in the light dependent stage of photosynthesis??

In June:2004 Q:1 (b) ms mentions H+ and OH-

In June:2009 Q:8 (c)(ii) ms mentions 2e- , 2H+ and 1/2 O2

Which equation should I learn for photolysis?? :S

 

[hassam]

brother....2009 ms is correct....cos this is wat happens really....see u split or OXIDISE water to protons,electrons and molecular oxygen..........why its like that.....bcos electrons have to fill that ELECTRON HOLE created as a result of excitation of electron in chlorophyll a molecule of PSII .....and where is proton needed?? u need it essentially for forming nadph...though electron is also needed there.....so splitting water in proton and hydroxide (according to ms 2004) will be USELESS(wrong) ......

and ur second question abt effect of temperature
less photolysis ....why? well this photolysis is ENZYME-CATALYSED.......ENZYME is located on PSII.....so enzmyatic reactions are TEMPERATURE-SENSITIVE......so.... if temp. above their optimum level.....this enzymatic activity will start slowing done due to denaturation......so less PHOTOLYSIS!!!.....AND LESS PHOTLYSIS will directly effect atp production since in ATP producction , energy of electrons is harnessed as they go from a higher P.E level to a LOWER p.e level........and these electrons essentially come from water,.....other 2 points ..no idea :unknown: :unknown: :unknown:

 

[XPFMember]

brother....2009 ms is correct....cos this is wat happens really....see u split or OXIDISE water to protons,electrons and molecular oxygen..........why its like that.....bcos electrons have to fill that ELECTRON HOLE created as a result of excitation of electron in chlorophyll a molecule of PSII .....and where is proton needed?? u need it essentially for forming nadph...though electron is also needed there.....so splitting water in proton and hydroxide (according to ms 2004) will be USELESS(wrong) ......

assalamoalaikum!!

ok...thanks a lot!

and ur second question abt effect of temperature
less photolysis ....why? well this photolysis is ENZYME-CATALYSED.......ENZYME is located on PSII.....so enzmyatic reactions are TEMPERATURE-SENSITIVE......so.... if temp. above their optimum level.....this enzymatic activity will start slowing done due to denaturation......so less PHOTOLYSIS!!!.....AND LESS PHOTLYSIS will directly effect atp production since in ATP producction , energy of electrons is harnessed as they go from a higher P.E level to a LOWER p.e level........and these electrons essentially come from water,.....other 2 points ..no idea :unknown: :unknown: :unknown:

oh..i just forgot photolysis is also enzyme catalysed reaction!
I hope I don't do such mistakes in the exam! I could remember abt rubisco enzyme being affected but totally forgot about this photolysis that it also is enzyme catalysed

JazakAllah Khair!!

 

[AAestar]

Is process of gene sequencing in the syllabus?

 

[Yukified]

Somebody help me for the dilution methods!! can anyone give me some simple and last minute tips for this things!!! please help me urgent! need it for As Bio 34

 

[SHUBHAsnlnm]

can you provide the images of the slides that come in the cie exams ie:
trachea
artery
vein
alveoli
root
stem
leaves
xerophytic leaves with trichomes

 

[blablabla]

explain chromosomal number in mitosis

 

[iKhaled]

biology: biological molecules question..please help :/

why there is only hydrogen bond in cellulose and there are no hydrogen bonds in glycogen and starch? :S:S:S

 

[iKhaled]

Re: biology: biological molecules question..please help :/

answer please..

 

[AAestar]

explain chromosomal number in mitosis

Before mitosis takes place, the chromosome number is doubled. Originally, cells that practice mitosis will have 46 chromosomes. Before mitosis, they would have 92 chromosome. And the the number would be halved by the end of mitosis. In telephase, two daughter cells are formed, each having 46 chromosomes.

 

[mrpaudel]

Explain the role of synapse in the nervous system...!! can some1 xplain those highlighted points...!! how do we explain those points..i know bout the one way transmission and memory....just xplain those highlighted one ....

 

[mrpaudel]

Describe the part played by auxin in apical dominance in a plant shoot. Plz explain the highlighted one..i have not read about active transport...!! auxin moves down the shoot via auxin transporter proteins present in cell surface membrane..this is what i know....so..plz tell me, what moves by active transport?

 

[ammu2011]

Can any1 pls tell me wat is Adenovirse.. And what is the diffrence between the adenovirse used in genetecnology and dat whc is in humans..

 

[AAestar]

Describe the part played by auxin in apical dominance in a plant shoot. Plz explain the highlighted one..i have not read about active transport...!! auxin moves down the shoot via auxin transporter proteins present in cell surface membrane..this is what i know....so..plz tell me, what moves by active transport?

I think it is the chemical diffuses down the stem and passes from cell to cell via active transport to the lateral bud.

 

[mrpaudel]

Describe the part played by auxin in apical dominance in a plant shoot. Plz explain the highlighted one..i have not read about active transport...!! auxin moves down the shoot via auxin transporter proteins present in cell surface membrane..this is what i know....so..plz tell me, what moves by active transport?

I think it is the chemical diffuses down the stem and passes from cell to cell via active transport to the lateral bud.

Till now, i didnot carefully look the book...i think i read the chemicals move by diffusion...but i carefully looked at the book..and it says..it moves by active transport...and..now, the ms says..moves by diffusion...diffuses..and moves by diffusion is other thing..now i wonder what moves by diffusion?

 

[saruman]

hey, guys.. any tips for bio p43 tmr???

 

[rz123]

plz any1...1.Explain y Io(gene for blood group o) is recessive to both iA and iB(ie alleles for blood group A and B respectively)..
2.Describe how a single base deletion in the allele Io leads to the synthesis of an inactive protein?

 

[AAestar]

plz any1...1.Explain y Io(gene for blood group o) is recessive to both iA and iB(ie alleles for blood group A and B respectively)..
2.Describe how a single base deletion in the allele Io leads to the synthesis of an inactive protein?

I am not sure if I reply late but I thought O is always the recessive. It would barely shows unless it is recessive. As for a single base deletion, point mutation I'll call it. Base deletion will produce frame shift in a code. It might delete the gene coding for the shape of the active site or so, altering the tertiary structure of the protein. The substrate cannot bind to the active site and thus leading to an inactive protein. You look under cystic fibrosis. It's mostly cause by base deletion.

 

[rz123]

^Thanks a lot !

 

[hassam]

outline the behaviour of chromosomes during meiosis?
RYT now i want to essentaily kill the examiner who is preparing ms :evil: ......wat nonsense is this.....which textbook of the world says that crossing over occurs during METAPHASE.........
reference o/n 2010 p42