for 3R

Hi 3R

Solutions for the revision mini test.

Consultations ogay.

Dear all, if you want to see me for a consultation, please make prior appointment with me.

best is sms or write me a note.

Even those who have already made appointments with me verbally, please sms me!! Cos, I can't remember them :P bad memory

All the best to all of you out there!

Some useful online chem resources

Rod Beavon: one of the chief examiners in UK for edexcel exam. http://www.rod.beavon.clara.net/chemistry_contents.htm

Chemguide: Good for building foundation and explaining and visualizing concepts http://www.chemguide.co.uk/

More on tutorial 14b and proteins

Here's an FAQ on what you should do in terms of preparing for the proteins section for Chem H2 syllabus. What do you need to study??

I suggest you print this FAQ and append to your tutorial 14b. The FAQ also references tutorial 14b.

Q1. Is it important to know about how enzymes work (induced fit theory etc.)?

A1. No. However students must know that enzyme function depends on its structure, which means if the structure is lost through denaturation, function is lost too. The whole chunk about how enzymes work explains the structure function relationship.


Q2. So what is it that the students NEED to know?

A2. The tutorial is crafted according to SIOs of the syllabus. So its a good guide on what students need to know. Basically 4 major portions:

i) amides - hydrolysis, synthesis, and peptide sequencing. That’s tutorial qn 1,2,3

ii) Protein stucture - Mostly fact and recall. Definitions and esp FOCUS ON BONDING
involved. They also need to draw diagrams, which cannot be only memorized but must be practiced (to draw good diagrams) esp for secondary and tertiary. Tutorial Q4,5,6,10

Quaternary structure. Question 10: you notice there are only 6 marks awarded but 12 bullets in the answer key! Why?
Actually on the FIRST 6 bullets in the answer key are marking points. Those points give a DESCRIPTION of what the quaternary structure is.
The next 6 bullet points actually give the SIGNIFICANCE of the quaternary structure. SO students need to discern; the points from allosteric properties onward should be written if the question asks for SIGNIFICANCE of quaternary structure.
The specific use of haemoglobin as an example is an SIO. So students must know all these points.

iii) Denaturation - Students should know the process, how denaturation take place. They should also know the significance and explain: mainly loss of normal function such as structural strength(eg in rebonding) or catalytic property(rate of enzyme catalysed reactions) and solubility(coagulation). Tutorial questions 7,8,9

iv) Explaining observed phenomenon: examples are given in notes from pg44-45. They need to know them for experience. The examples are by no means exhaustive, and I do not know what's going to feature in the A lvls. The basic concept is that structural alteration(usually via denaturation)or structural differences alters observed function. So students should be exposed and familiar with as many examples as possible, and be able to explain when given any example. Tutorial Q7,8,9


Q3. What does allosteric properties mean?

A3. It means that the biochemical property of the protein is altered. If this word makes you feel uncomfortable feel free to expand. It should go something like "The significance of the quaternary structure is that the biochemical properties of the protein is changed; allosteric properties can arise in the quarternary complex."
A little bit more about allosteric properties: it has to do with altering enzyme active site property when something else binds to it at some other site other than its own active site.
So the haemoglobin example illustrates this... the haemoglobin sub-units are bound together by extensive side chain interaction, when an oxygen molecule bonds to one of the haem groups, its subunit's conformation alters. This forces a conformational change on the other subunits. The result is that their haem groups now have an increased tendency to bind oxygen.

For bio students you would have seen other egs of allosteric effects, eg from co-factors, co-enzymes, and allosteric inhibitors

Some exam techniques

This is with regard to time management and how extensive you need to answer your questions.

Elucidation Questions:

1) Most importantly you must give proper deduction of FG and reaction linked to observation:
eg A reacts wtih 2,4, dinitrophenylhydrazine to form hydrazone--> A has carbonyl group.
These are most important, since without proper deductions you may make mistakes in structures.

2) Give structures and label: these will be 1 mark per structure.

Normally for 10 marks, elucidating 4-6 structures plus all deductions will give full marks.

3) equations?: give these only if the question demands for them. IE the question states:" give equations for ALL reactions that take place"

If question implies that equations are optional: for eg, "deduce structures, and use eqns where appropriate", it means that the equations are used in place of deductions, so they share the same marks. IE if you are able to give full and complete deductions, equations become redundant and do not score more credit.

In these cases, I recommend especially when you are short of time not to write equations; simply do a good job with observations->deductions and structures and you will score.

But if you've got time, write the equations to secure 100% marks.

During tutorials I always demand a higher standard(120%) in order to train you up, and you need the practice to ground your foundation. But during exam, learn to discern good time management.

remember: 1 mark => 1.5 minutes. you may need to be faster than this for organic chem, because for stoichiometry, 1 mark may take a long time (calculations etc) to obtain.

That's it for now.

Something abt proteins

Hi all,

IMPORTANT CLARIFICATION: Some texts regards -S-S- disulphide link as part of primary protein sturcture. This is from definition that primary structure is made by covalent bonding. Also certain proteins exist as crosslinked polymers, hence the inclusion of -S-S- as primary structure.

BUT PLEASE TAKE NOTE: at A lvls, the primary structure is defined ONLY by the amino acid sequence joined up by peptide links. Please do not include S-S in its definition.

-S-S- link is weak and considered to be part of tertiary structure.

Please make sure you highlight this on your notes.