blazinfury

Thanks guys. It really helped. It was more of me realizing that the anomeric was special in its unique mutorotation ability. Now I also see that for the rest, if you create an epimer you change the whole sugar molecule. It's pretty crazy how one OH flip can alter the identity of a whole sugar but I guess that that's science for you. Thanks again.

If one wants to separate DNA better using a gel would they use a higher percentage of gel or lower percentage? I was thinking a higher percentage because that would make the gel more viscous and dense and thus promote better separation. Was this improper thinking?

In the case of glucose, D and L glucose are enantiomers. So can one say that all D and L sugars (of the same sugar molecule) are enantiomers of each other? Just out of curiosity, why is it that if a sugar is D and it becomes L, all of the chiral centers flip-- is this just nature at work? I ask because if one is distinguishing b/c alpha and beta of the same sugar molecule, it is deemed as an anomer (which is an epimer which is a diastereomer)? What makes the penultimate so special that the whole molecule becomes an enantiomer instead of just an epimer? Does this have to do with how the straight chain becomes a ring structure? Thank you.

I am trying to understand which of the two operons uses positive and which uses negative feedback. In addition, which of the two are an inducible and which is a repressible system. Would someone mind explaining that?

If a person is fasting, what biochemical processes occur to generate energy to get the person through this period. Since the body is low on glucose, gluconeogenesis would occur to synthesize more glucose so that it can enter glycolysis and be broken down. The body would also undergo fatty acid synthesis on the mitochondria which would enter the Krebs cycle to generate energy. Proteins would be broken down into amino acids and those amino acids would enter Krebs as well? If all of this happens, then why do Ketone bodies form and what is their purpose?

The purpose of a dielectric is to aid a capacitor in maximizing the amount of charge that it can store. However I am confused about whether the best material for a dielectric would be a polar or nonpolar? I had always thought that you wanted a vacuum or a near vaccuum between the two plates to minimize charges from flowing between the plates and thus maximizing charge storage on each plate. However it seems that the more polar a material the better the dielectric and thus the higher the capacitance. Would someone be able to clarify why a polar material is better?

Is a disapropriation reaction a reaction oxidation and reduction occurs at the same time to a single reactant species to yield 2 products (one oxidized and one reduced form) of the reactant?

If a cell were to be deprived of oxygen, what effect would this have on b-oxidation? I know that the cell would go the route of lactic acid fermentation but would/ could b-ox still occur in the mitochondria and if so, does that mean that Krebs would still occur as would the electron transport chain?

I am confused about nondisjunction and so I tried to draw it out but am not sure if it's correct. Please comment on the attached picture. From what I read, NDJ occurs in both males and females, but does it occur predominantly more in one sex than the other? For instance with regards to Kleinfelter's Syndrome (XXY), which results from Meiosis I NDJ, does it occur more in females than in males? Thanks.

I am sorry if I was not clear enough. P- product R- reactant Q- Quotient or in some cases IP (ionization product)

I have a question about Ksp and L'Chateliur's Principle. Lets says we have the following: NaCl(s) ----> Na+(aq) + Cl-(aq) If we add more NaCl(s), the equilibrium does now shift since (s) and (l) do not affect Keq. In addition, the reaction does not shift either b/c L'Chateliur's Principle shifts are not affected by (s) or (l). But what about Q. Q is the [P]/[R] at any time. If we add more solid, don't we in fact increase the value of Q. If so, can't we then compare Q and K to see which way the reaction shifts and/or if we can still dissolve more solid? Thanks.

I have several questions about the menstrual cycle and would appreciate some clarification. Thanks. 1. Upon birth, a female child is born with primary oocytes. At puberty, primary ooctyes become secondary oocytes. Now it is at menstruation that each of the secondary oocytes are released from the follicle and the whole process occurs. My quest is whether all of the primary oocytes are converted into secondary oocytes at puberty or it is only that primary oocytes start to be converted at each menstrual cycle? I think that the latter is more correct and if so, that means that a female has both secondary and primary oocytes before mensturation. Is there a time or ratio that details when a primary oocyte becomes a secondary oocyte-- is it 3 hrs b/f menstruation? 2. You only form a blastula if 2ndary oocyte is fertilized, correct? So if the secondary oocyte is not fertilized, it remains trapped in Meiosis II since it requires a sperm to tell it to finish Meiosis II. Since it takes around 10 days for the blastula to implant if egg is fertilized, but when it is not, then by Day 23,the corpus luteum starts to degrade since there is no hCG to maintain it, correct? You also have no progresterone to maintain the lining and so there is sloughing off. If that is the case, then how does the body rid itself of the secondary oocyte and where is it by Day 23-- abdominal cavity still? 3. Is there no more corpus luteum by the second trimester since the placenta takes over and makes estrogen and progesterone? 4. Before ovulation, there is a small amount of Estrogen that is secreted by the mature follicle that stimulates contraction and negative feedback to GnRH and prevents release of LH and FSH. By ovulation, you have a buildup of Estrogen and so the high levels of Estrogen go to stimulate LH and FSH release and thus you have the spike at ovulation? Is it the increased estrogen levels that stimulate the release of LH? If that is correct, then when someone is on the pill (which contains low levels of estrogen and progesterone), how does the pill prevent the increase in Estrogen levels from the mature follicle? Also how does a person on the pill menstruate but not ovulate-- is it that the follicle never pops and so the secondary oocyte is not released, but the whole follicle dies by Day 23 with the secondary oocyte within it? Thank you.

I am trying to understand exactly what the Van der Waals equation states about the Pressure and Volume of a real gas compared to an ideal gas. Based on the equation, I think that P(ideal)>P(real) because the ideal gas needs to overcome the IMF of attraction since ideal gases have no IMFs; and V(ideal)>V(real) b/c ideal gases occupy no volume and had their volume been smaller, the gas particles would succumb to IMFs. If someone could please correct me if I am wrong and my logic, I would greatly appreciate it. Thank you.

Lidocain pka 7.6 Prolocain pKa 8.4 We are told that a decrease in the amount of base facilitates removal of the local anesthetics, resulting in a shorter duration of action. Which has a more rapid onset? The answer was that it was Lidocaine because more exists in its base form at body pH. However, this seems counterintuitive since both pKa's are higher than the pH. I do remember reading a rule somewhere that if pKA>pH, then the group is considered to be in its acidic form when attached to an aa, but I don't know if that rule only applies to aa and what that rule means. Could someone please clarify it?

I am confused about what the difference is between Bond Energy, Enthalpy of Formation, Hess's Law and Enthalpy? The reason being that they all involve heat (ie enthalpy) as a measurement. Enthalpy I know is the heat present in a system. Enthalpy of Formation is the formation of a compound from elements in their most stable/standard state. Bond energy is the heat added to a system to break bonds and then heat is released when new bonds are formed. But the answer that you get in the end of the day is still in terms of enthalpy, correct? If so, then does that mean that if a reaction is exothermic, heat is released, surroundings get hotter, and the bonds formed are stronger than the bonds broken because more heat/energy is released than was used to initially break the bonds? Also, if one compares bond strength (such as in sp>sp2>sp3), does that mean that the stronger bond is more exothermic, the products are at a lower energy and are more stable than the reactants? To make this claim, we would use Hrxn = E(bonds broken) - E(bonds formed), correct? Then when do we use delt H= products - reactants? I would greatly appreciate it if someone could please clarify my confusion. Many thanks.

I was looking in a book and I found that the Bond Energy of C-C single bond= 347 KJ/mol double bond= 614 KJ/mole triple bond= 839 KJ/mole Now this shows that a triple bond is stronger than a double which is stronger than a single bond. However, when I subtracted Bond Energies b/w the double and single bond, I got 267 KJ/mole, which is a value less than the energy of a single bond. When I did the same between a double and triple bond, I got 225 KJ/mole. From this, I get the impression that the single bond is the most energetic since it is the most stable, but why is it that as you increase the # of bonds (ie single--double--->triple), the energy of the addition of an extra single bond decreases? Does this imply that a triple is less stable than a double which is less stable than a single bond? Also, since the energy difference between a triple and a double bond is 225 KJ/mole. Does this mean that if I add this amount of energy to a triple bond, it will break into a double bond, but to break the two pi bonds together, I would add 225+267 KJ/mole and convert the triple bond into a single bond? Thank you.

Thank you so much for your response. It is helpful. But what is the purpose of homology arms in general during construct design. What purpose do they serve aside from them being equal? Do they convey some sort of specificity? On that same note, what are LTRs used for in construct design and are they the physical promotor? I always thought that you add the promoter at the end of the 5' LTR? Thanks again.

In Lewis A/B, an acid is an e- pair acceptor and a base is an e- pair donor. So when an acid accepts e- it becomes reduced in its charge. However, acids are usually found with high ox numbers leading one to believe that they get oxidized. I find the OIL RIG and Lewis Acid/Base definitions to be counter-intuitive. For example, if one asks which of the following is a stronger acid: Ca2+ or Li+, one would say it is the one with the higher ox number, but based on the Lewis definition, wouldn't it be the one with the lower ox number since you are gaining e- (ie - charge) and should decrease in ox #?

I am trying to understand the function and purpose of some of the parts of a plasmid. Could someone please explain the following terms: Long Terminal Repeats 5' and 3' UTR (untranslatable regions) left and right homology arms

Klinefelter’s syndrome, in which a male has an extra X chromosome (XXY), is the result of nondisjunction. The failure in spermatogenesis that could produce this would occur in: B. Anaphase II. A. Anaphase I. C. Prophase I. D. Prophase II. Answer: (B) I tried drawing out the picture and I see that Anaphase II is a possibility but why would Anaphase I be incorrect? Is there a distinction b/w males and females in where it would be Anaphase I or II? Would Klinefelter’s syndrome more affect males than females in general? Thanks.

Which of the following colors would appear as a bright band in an emission spectrum of a yellow sodium vapor lamp? B. Yellow, indicating a greater wavelength than ultraviolet light A. Yellow, indicating a lesser wavelength than ultraviolet light C. Blue, indicating a lesser wavelength than ultraviolet light D. Blue, indicating a greater wavelength than ultraviolet light The answer is (B). I just feel like it was a bad question because I did not know whether the band would appear yellow or blue. Just because Na appears yellow does that mean that yellow is the color that it emits and so on a spectrum it will appear yellow as well? I understand that this problem deals with the ideas of emission and reflection. The sodium reflects the yellow color, but does it emit it as well? If so, since light particles (photons) are constantly bombarding it, exciting it, and then when Na goes back to ground state it emits a color.

Does a chemical reaction proceed from low pKa to high pKa or high pKa to low pKa? A large Ka implies how readily a reaction goes toward the products. Now since pKa=-log(Ka), wouldn't that imply that a chemcial reaction goes from high pKa to low pKa?

Effective Nuclear Charge (Zeff) is defined as how tightly the valence e- are held. I understand that Zeff decreases down a group because there is an increase in the number of principle energy levels (PEL) and as such, the valence e- are further away from the nucleus. However, Zeff increases left to right across a period. I am trying to understand this, but am having a difficult time. I understand that the number of protons and e- increase across a period, but how is that conducive to a tighter attraction with the nucleus? Thanks.

Elements on the periodic table get both oxidized and reduced. The elements that tend to get reduced are the ones closer as you go to to the right of the periodic table. Reduction is defined as an element gaining electrons. As reduction increases from right to left, IE also increases because the elements want to hang on to their electrons. Now electron affinity (EA) is the energy of an atom to gain an electron. Elements want to have an octet and so they want to gain electron, but how is that it takes more energy to gain an electron, if gaining an electron makes the element more stable? At the same time, Lewis bases are classified as electron pair donors. What does not make sense to me is that elements to the right of the periodic table are getting reduced, meaning that they are gaining e-. Or is it that since the trend for base stability is from right to left, the Lewis base strength increases from right to left-- ie those elements are more e- donors and the ones to the right are e- acceptors which is in line with the definition of reduction? Thank you and sorry for my convoluted question.

I am confused about the principle of Ki. I understand that Ki represents the affinity of the enzyme for the inhibitor, with a large Ki showing a strong inhibitor. In competitive inhibition, Ki serves to double the slope, while in noncompetitive inhibition Ki serves to inhibit the enzymes by 50%, but what does all of this mean in terms of applying it to a problem. I understand there there is no formula for Ki, like there is for Km, expect [E]/[EI]. What is the relationship between Ki and Km and can a given Ki value describe the Km magnitude if it is not given? Thanks and sorry for the contorted wording of my question.