CHEM AND BIO HELP AND TIPS HERE

[Ivo]

can somebooooody tell me about liver cell???

Because it is only a Biology Paper 1, you won't even really need to know about functions of the cell structures, because this is extension material (for Paper 3).

What you do need to know is the differences between plant and animal cells.  From looking at many past papers, CIE seem to like the liver cell as a typical animal cell and a palisade cell as a typical plant cell.  Those two are typical, so you should have no trouble identifying which is which!  

[bashar1045]

what is meant by a limiting reagent ?
and in fermentation what is the catalyst used ??

[Ivo]

what is meant by a limiting reagent ?
and in fermentation what is the catalyst used ??

When we carry out a reaction we sometimes use an excess of one of the reactants.  The reactant that is not in excess is called the limiting reactant or limiting reagent.  Basically, the reaction stops when the limiting reactant is used up.

The bacteria and yeasts produce enzymes that catalyse fermentation reactions in organic materials.

I hope I have answered your questions. 

[CatAly$t]

what is meant by a limiting reagent ?
and in fermentation what is the catalyst used ??

they use me as a catalyst!

[CatAly$t]

Because it is only a Biology Paper 1, you won't even really need to know about functions of the cell structures, because this is extension material (for Paper 3).

What you do need to know is the differences between plant and animal cells.  From looking at many past papers, CIE seem to like the liver cell as a typical animal cell and a palisade cell as a typical plant cell.  Those two are typical, so you should have no trouble identifying which is which!  

thx man...

[mohit1234]

hmm.......
i think the answer should be D
By the way wat does the mark scheme say?

[Borat3169]

can some1 send me all they can (through message) on these subjects PLEASE  
1-Ionic, Covelent and micro structures
2-Formulae of Fats,Carbohydrates,Proteins
3-Hydrocarbon Reaction
Thank Ya'll!

[The Golden Girl =D]

can some1 send me all they can (through message) on these subjects PLEASE  
1-Ionic, Covelent and micro structures
2-Formulae of Fats,Carbohydrates,Proteins
3-Hydrocarbon Reaction
Thank Ya'll!

check this link , i hope i t helps :

https://studentforums.biz/index.php/topic,8469.0.html

[Raywin]

Question: Why might pesticides sprayed onto the fields reduce a bean crop?

Answer Choices:
A Pesticides damage plant leaves.
B Pesticides damage plant roots.
C Pesticides kill insects that feed on bean plants.
D Pesticides kill insects that pollinate bean plants.

Isn't this a badly worded question?
What would you guys pick as the answer?

The answer is D. This is cause pesticides affect ONLY the pests, and not the plant. So due to this the first two options are eliminated.. and C is true but tht ans has no reason as to WHY it affects the bean crop. AND D, makes sense cause if the insects are killed and if the plant uses insect- pollination methods, then killing the insects will have an effect on the bean crop. So D is the ans. Hope u have understood..  

[Helium]

Outline how hydrogen is manufactured from water

Do i just say electrolysis

[holtadit]

Outline how hydrogen is manufactured from water

Do i just say electrolysis

 electrolysis of CONCENTRATED AQUEOUS SODIUM CHLORIDE.

[nid404]

Electrolysis of Brine or water...anything is fine

[Helium]

Only, ok i thought electrolysis of water (voltameter) but thats
too expensive in factories. What i thought was wrong

Thanks

Ari and Nid

[Ivo]

The answer is D. This is cause pesticides affect ONLY the pests, and not the plant. So due to this the first two options are eliminated.. and C is true but tht ans has no reason as to WHY it affects the bean crop. AND D, makes sense cause if the insects are killed and if the plant uses insect- pollination methods, then killing the insects will have an effect on the bean crop. So D is the ans. Hope u have understood..  

Yes, indeed, the only answer has to be D.  For C, it will actually increase bean crops not reduce it!  Because normally pesticides kill pests, so less pests, more crops.  But the question is, what can reduce the bean crop.  So it has to be D, indeed Raywin is correct.

[Ivo]

Outline how hydrogen is manufactured from water

Do i just say electrolysis

Brine is electrolysed in a diaphragm cell.

The ions in solution are Na⁺, H⁺, Cl^- and OH^-.

At the anode: chloride ions lose electrons and are discharged as chlorine gas:

2Cl^- -> Cl₂ + 2e^-

At the cathode: hydrogen ions accept electrons and hydrogen gas is discharged rather than sodium:

2H⁺ +2e^- -> H₂

The ions remaining in solution are Na⁺ and OH^-.  So an aqueous solution of sodium hydroxide is formed.