Hi!
1. Cholesterol is the backbone of steroids. Cholesterol is a four-ring structure, therefore the backbone of steroids is a four-ring structure.
2. Lysine, histidine and arginine are the basic amino acids. Bases are proton acceptors, and at neutral pH these amino acids accept a proton onto their R-group NH2 component, which leads to NH3+, making the amino acid positively charged. Conversely, acid amino acids are proton donors, and at neutral pH they kick off their extra proton (COOH becomes COO-), which makes the amino acid negatively charged.
3. Chiral: a molecule or ion is called chiral if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes (your hands are mirror images of each other but cannot be superimposed onto each other (ie if you attached your right hand to your left wrist it would not look the same as normal)). The Cahn-Ingold-Prelog system is a set of rules that defines the stereochemical configuration of any stereocenter, using the'R ' (from the Latin rectus, meaning right-handed) or ' S ' (from the Latin sinister, meaning left-handed). Each branch of the molecule gets assigned a priority from 1-4, and the number order determines if it is S or R.
4.The sequence of amino acids is the order in which the amino acids are bonded one after the other. For example, the order could be proline-arginine-histidine-etc. That sequence is required to make a protein (insulin for example), while a change in that sequence (ie, proline-aspartic acid-histidine) will make a different protein (glucagon, for example).
5. Yes, the tertiary structure refers to the 3-D shape of a protein. A protein's final conformation is the shape it has to be in to function properly.
6. Peptide bonds are between amino acids, and these are created in the primary structure of the protein. A polypetide refers to a chain of multiple amino acids bonded together via peptide bonds. A quaternary structure is made up of two proteins bonded by hydrogen bonds, Van der Waal forces and ionic bonds.
7. The structure of NADH contains many carbon-hydrogen bonds.
8. I am not totally sure what you are asking here, could you clarify?
9. Km is the amount of substrate needed to achieve half the Vmax. Therefore, it is independent of the enzyme concentration, because it is only dealing with substrate concentrations. Vmax is dependent of enzyme concentration because Vmax is the level at which the enzymes become saturated. If you have a higher enzyme concentration, then there is a higher number of enzymes to be saturated and Vmax will be higher.
10. As I said above, Km is the amount of substrate needed to achieve half the Vmax. Therefore, if you increase the concentration of the substrate, you are increasing the Km. Vmax is dependent on the enzyme concentration, and would not be affected by the amount of substrate added in competitive inhibition.
11. Yes
12. I will pose this question to the instructor in our next BioBiochem session
13. Yes and yes
14. Yes
15. Yes, snRNPs are enzymes that catalyze splicing.
16. A backward mutation is a change from a mutant to wild-type. A "permanent change" means that the mutation cannot be reverse, but it can be mutated again, as we see in backward mutation.
Hope that helps!
Katie (specialist moderator)