A level Biology: Post your doubts here!

[lara dalal]

I need help in paper3 biology. Does anyone have any websites or anything for plan diagrams and microscope?

 

[funky brat]

Can someone explain please?

 

[saturn21]

Are there online versions of it?

Hmm..I don't think so..

 

[Serial_Ripper]

Hey, has anyone done their practical exams yet? and if you did....how did it go?

 

[Amandaissocoollike]

O/n 12 paper 33, question 2 b (i). Can someone please explain this?

 

[Abdul Hanan]

guys any guess for p34?

 

[Hamdy123elwazzer]

guys, does anyone has ir for biology p3 v 32??????????? urgently as my eam is on tuesday and i am dying for any help

 

[♣♠ Magnanimous ♣♠]

guys, does anyone has ir for biology p3 v 32??????????? urgently as my eam is on tuesday and i am dying for any help

??

 

[qwertypoiu]

Can someone explain please?

This is about catalysis of lipid breakdown. When one lipid molecule is hydrolysed, it forms one molecule of glycerol and three molecules of fatty acid molecules. Fatty acid molecules dissociate in solution to form H+ ions. (technically H3O+ is formed)
This causes the solution to become more acidic. Since the pH of solution was 8 initially, we'd expect the pH to come down.
The rate at which the pH comes down is an indication of rate at which H+ ions are being formed, and this indicates the rate of activity of the enzyme. In other words, steep line = high enzyme activity.

We're asked to explain the activity between 50 and 60 min. Over here, the graph is flat, which means the enzymes are not doing anything. (since no H+ is being produced)
So let's jump to it:

1. No. How can enzyme concentration change at all? We're neither adding nor removing enzymes from the mixture.
2. Yes! The substrate concentration becomes limiting since it is being used up by the enzyme to form products, less concentration of substrate is definitely a factor that reduces enzyme activity.
3. All enzyme active sites are saturated???? OBVIOUSLY NOT!! That would indicate a high enzyme activity. Rather, the concentration of substrate is so low at this time that most enzyme active sites are likely to be empty.
4. Denaturation of enzyme? Is it possible? YES! Since the pH is changing due to the products, the enzyme active site shape may be altered as the change in pH alters the tertiary structure of the protein that is the enzyme, by breaking or altering ionic bonds and hydrogen bonds. Denaturation slows enzyme activity.
5. By this time the answer is clearly D. However, if you think about it, this statement is probably true. The products can act as competitive inhibitors, because fatty acids were a part of the lipid itself. Therefore it would have the same shape. Perhaps three fatty acid molecules can block the active site of the lipase.

 

[qwertypoiu]

O/n 12 paper 33, question 2 b (i). Can someone please explain this?

Whenever there is a question like this, the small width lines are the eye piece graticule. The bigger lines are the stage micrometer.
Step 1: 1 eyepiece graticule unit = 0.01 divided by 4 = 0.0025mm
(this is because I know one width of stage micrometer is 0.01mm. I can SEE that there are around FOUR eyepiece graticule units that fit into one of these stage micrometer line gaps)

Step 2: 0.0025mm multiplied by 1000 = 2.5 micrometer.
(just conversion piece of cake )

 

[Kool boy]

Any ideas for paper 32

 

[Abdul Hanan]

can anyone please explain me the difference between the types of diagrams that can come in our practical exam...
low power plan diagrams, labelled diagram, annotated diagrams are there any other? and what's the difference?
thanks for your help

 

[qwertypoiu]

can anyone please explain me the difference between the types of diagrams that can come in our practical exam...
low power plan diagrams, labelled diagram, annotated diagrams are there any other? and what's the difference?
thanks for your help

There's only two types really.
Low power plan diagram - outline of tissues only
High power diagram - shows few individual cells with high magnification

Usually you have to label both.

 

[Abdul Hanan]

There's only two types really.
Low power plan diagram - outline of tissues only
High power diagram - shows few individual cells with high magnification

Usually you have to label both.

Thanks again for your help again and again

 

[Serial_Ripper]

Can anyone answer M/J 13 P31 Q2 (a)....I DON'T GET A THING!
Thnx in advance

 

[Hamdy123elwazzer]

any info about paper 32?????? urgentlyyyyyyyyyyyyyyyyyyyyyy

 

[Mohamed Ibrahim a]

What materials should we take with us for practical like lab coat or what???

 

[Hamdy123elwazzer]

white coat and the requirements in the paper school give it to you

 

[Mohamed Ibrahim a]

Hi I was asking when drawin a plant diagram should I show layers or how to draw this

 

[shazmina]

Hi I was asking when drawin a plant diagram should I show layers or how to draw this

Yes you show the induvidual layers and NOT cells