A level Biology: Post your doubts here!

[alexkay]

i got very confused about the conclusions in the 2nd ques

The conclusions to the

repeat the same procedure for the actual solution to find the rate of the enzyme, and compare it to the values of the graph. The corresponding value on the x-axis is the concentration of the solution.

I said the as well but I also found the rate of reaction as the rate of substrate disappearing (colour disappearing) divided by time. I don't know if that is right. Then I said I looked up the optimum time needed to catalyse 100% of the protein and checked the conc on the graph x axis

 

[alexkay]

what were the difficulties in judging when to stop the stopwatch?
I wrote that it is difficult to judge when gelatin is fully gone
and the dye may dissolve in the solution, so it is difficult to judge transperancy..
was out of my league.

Mine too! I wrote more that 2 things just in case, I wrote judging the end point (when it is totally transparent) and I also said the stop watch may be broken/ not work properly and therefore inaccurate and also your personal judgement (using your eye) may be inaccurate and maybe something else but I can't remember...it was hard!

 

[alexkay]

what were the difficulties in judging when to stop the stopwatch?
I wrote that it is difficult to judge when gelatin is fully gone
and the dye may dissolve in the solution, so it is difficult to judge transperancy..
was out of my league.

Oh I also said the gelatin may be too thick n some replicates and so may take longer time

 

[Heba A.Moety]

i did a lot of stupid mistakes in p5 i knew the correct answer to 2 of them but when the invigilator said there was 15 min. left every thing just vanished ?! brain washing hah !!

 

[alexkay]

i did a lot of stupid mistakes in p5 i knew the correct answer to 2 of them but when the invigilator said there was 15 min. left every thing just vanished ?! brain washing hah !!

I know how you feel

 

[Heba A.Moety]

I know how you feel

what is bothering me the most is the control ques. i have learned how to prepare controls and even told my friends how to prepare them before entering the exam hall but still i was the one who did it wrong!! when stupidness overloads !!

 

[Komail Sabba']

The conclusions to the


I said the as well but I also found the rate of reaction as the rate of substrate disappearing (colour disappearing) divided by time. I don't know if that is right. Then I said I looked up the optimum time needed to catalyse 100% of the protein and checked the conc on the graph x axis

By the way, you should perform the experiment with the same conditions. Not using the results that they gave (in 35C), but in your standard temperature.

 

[hizirofaki]

I don't know what the correct answer is cuz I was misinterpreting the question so I immediately chose A. However one or two people told me it was B.
The fish one was the most left one. Human in middle, the mammal on most right.
Collagen one was A. Has many glycine.

r u sure abt the collagen i wrote it A too

 

[alexkay]

By the way, you should perform the experiment with the same conditions. Not using the results that they gave (in 35C), but in your standard temperature.

But wouldn't 60C denature the enzyme/protein? I never heard of that before! I used 35c but just said standardise temp using water bath?

 

[qwertypoiu]

r u sure abt the collagen i wrote it A too

I'm positive

 

[Komail Sabba']

But wouldn't 60C denature the enzyme/protein? I never heard of that before! I used 35c but just said standardise temp using water bath?

the question said
"the solution contained :
subtilisin A, and enzyme of optimum temperature of 60C and pH of about 7.0-7.2
buffer solution or so
EDTA "
something like this

 

[Komail Sabba']

But wouldn't 60C denature the enzyme/protein? I never heard of that before! I used 35c but just said standardise temp using water bath?

im not sure though if we MUST use the optimum temperature or not.

 

[alexkay]

im not sure though if we MUST use the optimum temperature or not.

Well I would assume you need to test the rate of reaction and control other variables that will affect that...so a high temp that denatures enzymes will affect the results adversely? Not sure...will I get a mark for stating 'control temp with a water bath'?

 

[Komail Sabba']

Well I would assume you need to test the rate of reaction and control other variables that will affect that...so a high temp that denatures enzymes will affect the results adversely? Not sure...will I get a mark for stating 'control temp with a water bath'?

definately bro.

 

[saturn21]

rRNA

Yasssssssss!!! i did that

 

[saturn21]

How about the first question? What did you guys pick

I did C

 

[saturn21]

I'm positive

I did B

 

[qwertypoiu]

I did B

Nah B was there to trick you.
The syllabus specifically tells us to know the difference between a collagen molecule and a collagen fiber.

 

[qwertypoiu]

I did C

Should be right insha Allah I just checked width of cell walls they're measured in nanometers. (Eg 40nm)

 

[Wolfgangs]

What about the RNA and DNA questions. RNA form hydrogen bonds between each other, right?