Edexcel AS Biology - 6B101 + 6B102 - Unit 1 and Unit 2 Exam Discussion Thread

I'm so scared for this exam! I'm retaking this too :frown:

Reply 183

lizmoo0721

13

Original post by Maronite

I'm so scared for this exam! I'm retaking this too :frown:

Me too! How are you revising? I'm just doing past papers, I dont know if it's effective to learn the markscheme or not because edexcel are probably the most fussy with specific answers :frown:

Reply 184

Original post by lizmoo0721

Me too! How are you revising? I'm just doing past papers, I dont know if it's effective to learn the markscheme or not because edexcel are probably the most fussy with specific answers :frown:

I've made a set of notes which are really detailed because I'm essentially teaching myself. After doing my notes I went through all the questions and added the mark scheme answers to my notes if that makes sense?

I'm planning on redoing the past papers tomorrow... will you be revising on the day of the exam too?

Reply 185

lizmoo0721

13

Original post by Maronite

I've made a set of notes which are really detailed because I'm essentially teaching myself. After doing my notes I went through all the questions and added the mark scheme answers to my notes if that makes sense?

I'm planning on redoing the past papers tomorrow... will you be revising on the day of the exam too?

Your method sounds good. I dont even have all my notes in one place :')
I think I'm going to summarise all my notes today, along with past papers. :smile:

What experiment do you think they will ask?? I really hope its not the enzyme catalase one!!

Reply 186

Original post by lizmoo0721

Your method sounds good. I dont even have all my notes in one place :' :wink:

I think I'm going to summarise all my notes today, along with past papers. :smile:

What experiment do you think they will ask?? I really hope its not the enzyme catalase one!!

Haha thanks! To be honest I have no idea, I haven't even looked at the experiments yet hahahaha :'(

Reply 187

DK 96

Can anyone explain the shape of the graph of initial rate of reaction with increasing enzyme concentration in terms of active sites occupied & enzyme-substrate complex ?

Reply 188

shooting_stars

5

Original post by DK 96

Can anyone explain the shape of the graph of initial rate of reaction with increasing enzyme concentration in terms of active sites occupied & enzyme-substrate complex ?

Firstly, as the enzyme concentration increases the initial rate of reaction increases at a steady rate. This is because, as the enzyme concentration increases there are more successful collisions between the enzymes and the substrates and more enzyme-substrate complexes are formed, therefore more products are formed.

After a while the graph plateaus and the rate of reaction slows down. This is because, now the enzyme concentration is not the limiting factor anymore. The substrate concentration is now the limiting factor. So, there are not enough substrate molecules to bind to the vacant active site of the enzymes. This explains why the rate of reaction slows down at this point.

Hope its useful :smile:

Reply 189

kdizzle97

15

Is Cystic Fibrosis the only disease we need to know in detail, or are there others? Thalassemia comes to mind for some reason! Thanks :smile:

Reply 190

shooting_stars

5

Original post by kdizzle97

Is Cystic Fibrosis the only disease we need to know in detail, or are there others? Thalassemia comes to mind for some reason! Thanks :smile:

Yeah, for other diseases like Thalassemia you just have to interpret the information they provide you with in the question. :smile:

Reply 191

DK 96

Original post by shooting_stars

Firstly, as the enzyme concentration increases the initial rate of reaction increases at a steady rate. This is because, as the enzyme concentration increases there are more successful collisions between the enzymes and the substrates and more enzyme-substrate complexes are formed, therefore more products are formed.

After a while the graph plateaus and the rate of reaction slows down. This is because, now the enzyme concentration is not the limiting factor anymore. The substrate concentration is now the limiting factor. So, there are not enough substrate molecules to bind to the vacant active site of the enzymes. This explains why the rate of reaction slows down at this point.

Hope its useful :smile:

Thank you so much :smile:

that's exactly what I wanted to know :smile:

Reply 192

shooting_stars

5

Original post by DK 96

Thank you so much :smile:

that's exactly what I wanted to know :smile:

No worries.. If you have any other Qs just let me know :smile:

Reply 193

kdizzle97

15

Original post by shooting_stars

Yeah, for other diseases like Thalassemia you just have to interpret the information they provide you with in the question. :smile:

Thank you! Hope revision is going well :smile:

Reply 194

rory58824

Weirdly looking forward to this exam, anyone want to ask each other questions?

Reply 195

ashsohal

could someone just outline the points we should make about the enzyme/substrate practical to get the marks? cheers

Reply 196

username1884577

19

Original post by ashsohal

could someone just outline the points we should make about the enzyme/substrate practical to get the marks? cheers

Taken from the summer 2012 exam:

1. reference to use of a range of substrate(triglyceride) concentrations ;
2. idea of mixing (enzyme and substrate) ;
3. identification of a suitable dependent variablee.g. pH ;
4. description of how to measure the dependentvariable e.g. use of pH indicator ;5. reference to measuring time ;
6. description of how to calculate (initial) rate ofreaction ;
7. idea of repeating experiment without theenzyme ;
8. idea of control of enzyme (lipase) concentration;
9. reference to one other named controlledvariable (e.g. temperature, type of triglyceride,volume of solutions) ;
10. reference to {replicates / repeats} (usingthe same triglyceride concentration)

This was using lipase and triglyceride as a substrate

Reply 197

What determines alpha helix or beta sheet? Like what is it that determines how the hydrogen bonds between the carboxylic and amine group form?

Reply 198

Also do we need to know the evidence for the fluid mosaic model in depth or can we just summarise it? Like can they ask a 5 marker on it?

I hope we get a 5 marker on something like the cardiovascular system

Reply 199

rory58824