Hello 
I got a few questions i need help with...
1. heparin is an organic compound produced by the body to stop blood clotting. Structural analysis shows heparin to be a repeating disaccharide with numerous sulfonic acid groups and carboxyl groups bonded to the structure.
a) the sulfonic acid groups and carboxyl groups on the heparin molecules are completely ionised when they are in the blood. What conclusion can be made about the pH of blood?
Would it be 7? not 100% sure
Bahahah, loving the draw on knowledge here.
You're right in that blood's pH is about 7, but it's actually slightly basic. Take note of the question - it's not asking you to give a numerical value, it's asking you to make a conclusion about the pH. This means you can simply make a statement - is it acidic, basic, or neutral?
This is slightly trickier in that it's kind of like an amino acid question - what does an amino acid look like when it's in acidic, basic, and neutral pHs? At neutral, it's zwitterionic (acid protonated, base deprotonated), at acidic, both are protonated, at basic, both are deprotonated. You can use this guide to decide if regular acids or bases will be protonated or deprotonated at particular pHs.
Using this information, if your acids are completely ionised, this means that they've all donated their protons, so we have a deprotonated acid (or a conjugate base). This means that the sugar is likely in a basic environment - and so, blood must be basic. (a quick google search tells me the pH of blood is ~7.4, so we're good!)
2. The process of preventing blood clotting by the drug involves two steps.
Step 1: The drug bonds strongly to an enzyme inhibitor molecule, which then changes shape
Step 2: This new shape of the inhibitor can now attach to the active site of the enzyme, which normally catalyses the blood clotting reaction.
a) Based on the structure of the drug molecule (similar structure of heparin but contains an extra OH on the 5'), suggest which type of bonding is most likely to occur between the drug and enzyme inhibitor molecule.
hydrogen bonding?
You certainly could form hydrogen bonds - there's also the potential for ionic bonds to form, as well, since the carboxylic groups are there.
b) Outline why the attachment of the inhibitor molecule to the active site of the enzyme prevents blooding clotting.
So for blood to clot, it needs to get into the enzyme. If it can't, because there's an inhibitor in the way, it can't get into the enzyme! Remember the lock and key model - only one substrate can get in at a time. So if something blocks up the active site, no other molecules can get in, preventing blood clotting.
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