Questions from past and present

Today, I finally remembered to tell another class to come by here. The implied response was my apparent lack of life beyond school. Arrgh. Only if you realised that this place is specially 4 you and so that you can understand the subject better, otherwise I guess I wouldn't be here


1) Amino acids are supposed to have buffering abilities... even the acidic and basic ones.
But can acidic amino acids help to prevent solution from being acidic?

At physiological pH, acidic aa will have 1 NH3+ and 2 COO- so if there is more H+ ions in the bloodstream, the H+ will be attracted to COO- to form COOH and thus the buffering effect. So the concern could be what about the extra H+ released into the bloodstream upon ionization. Well, it may be removed, be contained within bldstream to maintain pH or taken up by cells for use.


2) What is the monomer in HIV protease referring to? The entire polypeptide chain?

HIV is protease is a dimer; made up of 2 monomers - 2 folded polypeptide chains.
Monomer = subunit; thus the protease has a quaternary structure.


3) Are saturated fats made from saturated fatty acids completely? OR do they have a small % of unsaturated fatty acids?

When we talked about saturated fats in food, we are referring to the presence of a high % of saturated fat. Similarly for olive oil, we say that it has unsaturated fats but we are not excluding the presence of saturated fats but in relative much lower amt.


4) How does the specificity of enzyme apply in the induced fit model?
I am going to discuss this in class. Complementary shape is applicable.


5) If the phosphate heads are polar/charged, wouldn't there be repulsion.
Yup, there will be but there is also attraction btw the hydrophobic tails so equilibrium of opposing forces will be established.

6) In facilitated diffusion, it is a passive process yet there is conformation change of carrier proteins when transport solutes across the lipid bilayer. Should there be energy expenditure for the conformation change?
There is energy involved but it is inherent when the solutes move from a region of high conc to low conc - loss of potential energy/ free energy which is utilised. This explains why the movement of solutes is bi-directional.
On the other hand, active transport goes against conc gradient and thus requires external input of energy usually in the form of ATP.

7) diagram in Enzyme notes: graph of Y never reaches zero (% of unreacted molecules)
Due to fdbk inhibition lah. With sufficient amt of product, all enzymes can be inhibited