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For assistance with (but not answers to) homework problems.

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A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed.

  1. Started by dttom,

    I was told that for an allosteric enzyme regulation to work, the enzyme in account should contain at least 2 subunits, but I can't understand why this is necessary. I think enzyme regulation is different from competitive inhibition as the former just stabilize the T state shifting the equilibrium but not directly competing for active site as in the latter case. And I think enzyme regulation is also different from non-competitive inhibition as non-competitive inhibition directly bind and inhibit the R state while the former just stabilize the T state, so it is in an equilibrium, an increase in substrate concentration could shift back the equilibrium. But this is not the …

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  2. Alright so this isn't exactly a homework question, but a strange thing I encountered in my course book : using visible movement as the defining characteristic of life is not enough. Movements over very small scales will be invisible to the naked eye – movements of molecules, for example. Is this invisible molecular movement necessary for life? If we ask this question to professional biologists, they will say yes. In fact, viruses do not show any molecular movement in them (until they infect some cell), and that is partly why there is a controversy about whether they are truly alive or not. Why are molecular movements needed for life? We have seen in earlier cl…

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  3. Started by CrazCo,

    POSTED THIS IN THE WRONG FORUM. SORRY. I'm a klutz. REPOST. I did a lab and my results showed some inconsistencies. My concentration of 100 units/ml of catalase in H2O2 gave me a slower rated than the 80units/ml. I performed many tests so I don't understand where it could have gone wrong. Any ideas. The 100 units/ml concentration was obtained using 20mls of yeast and the 80 was obtained using 12mls of yeast with 3ml of distilled water. Any hypotheses? Is it because there is sufficient enzymes in both and by shear chance of the substrate getting into an enzyme the 80units/ml had better results?

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  4. Started by stads_29,

    The p-nitrophenolate ion absorbs lights at 405nm. A solution that is 74um in the p-nitrophenolate ion was diluted 1 in 2 with water.Absorbance of resulting solution at 405nm was .650. Calculate molar extinction coefficient of the p-nitrophenolate ion at 405nm. Your meant to assume water has no absorbance at 405 nm. How do you use the beer lambert law to predict the absorbance at 405nm of a solution that is 11.0mM in the p-nitrophenolate ion, how do you show absorbance has no units?

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  5. Started by mooeypoo,

    Hey guys, I'm working on a fourier transform and got stuck in a stage where I think I'm supposed to complete the square .. but.. I don't manage to do it. Here's what I have: [math]\int \exp{(\frac{-\alpha t^2}{\triangle t^2})} \exp{(-i\omega t)}=\int \exp{-(\frac{\alpha t^2}{\triangle t^2}+i\omega t)}[/math] And so from this point I want to complete the square so I can continue to solve. Here's how I started: [math]\frac{\alpha}{\triangle t^2}\left( t^2 + \frac{i\omega \triangle t^2}{\alpha}t \right) = \frac{\alpha}{\triangle t^2}\left( t^2 + \frac{i\omega \triangle t^2}{\alpha}t + (\frac{i\omega \triangle t}{2\alpha})^2 - (\frac{i\omega \triangle t}{2…

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  6. Started by CrazCo,

    You know how varying pH levels can affect the reaction rate of enzymes. Why is this from a molecular standpoint. Do they ions from the enzyme get attracted to the acidic/basic environments and leave the enzyme?

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  7. Started by blackhole123,

    1. (bunch of filler info about barium sulfate). Given the following starting compounds, write for each compound a balanced total ionic equation and a balanced net ionic equation to prepare BaSO4: Ba(OH)2, BaCl2, BaCO3. If the the rxn occurs in more than one step then write the rxn as a series of sequential reactions. Identify the type of each reaction. For this one do I just add some sort of soluble sulfate compound that reacts with the starter compound to produce an insoluble precipitate? I'm guessing the first one is some sort of acid. Would you add H2SO4 and get (for the molecular equations, I know how to do ionic equations thats not the problem): Ba(OH)2…

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  8. Started by stads_29,

    Hey, have this question which i just cant wrap my head around, any help would be appreciated. Formic Acid (HCOOH) - pKa = 3.8 is a weak acid that partially dissociates to form its conjugate base (HCOO-) and releases protons into aqueous solutions. Whats the pH of a solution in which (HCOOH) = .7M and (HCOO-) = .15M? Then, if the pH of sol. of Formic acid has been titrated to a final pH of 2.8, Whats the ratio of conjugate base : Weak acid? And suppose your given stock solutions of formic acid and sodium salt of the conjugate base : (HCOOH) = 3.OM and (HCOONa) = 1.5M, How would you make a .1 M buffer(total formic acid + sodium formate concentration), 100mL tot…

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  9. Started by dcowboys107,

    a.ln(x)-ln(6-x)=3 b.log base 2 of (x+5)=log base 2 of (x-5)+log base 6 of (36)+6^(log base 6 of 3) a.ln(x) - ln(6-x) = 3 ln(x/(6-x)) = 3 x/(6-x) = e³ I've gotten this far for part a but now I can't solve for x. log[base 2] ((x+5)/(x-5)) = 2 + 3 (x+5)/(x-5) = 2^5 Part b I've gotten this far. It says not to give a decimal approximation for any of the problems rather a fraction or an exact expression. Can someone show me how to solve for x in these two problems? Thanks!

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  10. Hi everyone, I'm new to the forum and have this question on biochemistry related to a homework assignment that I can't wrap my brain around. So I'm told that a mixture containing the following two polypeptides were subjected to an isoelectric focus gel electrophoresis. Two bands were observed. I need to identify which band belonfs to each peptide, and briefly explain why. The polypeptides: Thr-Ala-Asn-Phe-Glu Pro-Gly-Thr-Cys-Met I have a diagram which shows a band at around pH of 5-7 and another at pH of 9-11. I know this procedure utilizes the isoelectric point of a protein, but so far in my study of biochemistry (1 month into the semester), I've encountere…

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  11. Started by ed84c,

    I'm trying to write a Matlab (well.. octave) code to plot the tradjectory of a satellite in orbit. Unfortunately it just keeps drawing a diagonal line, but I can't for the life of me work out why it wont do any type of "proper" orbit. I think it's nearly there as if I "drop" the satelite (no tangental velocity) it does a sort of 1D elipse. I've attatched the file anyway (renamed .m to .txt as uploader didn't like) if somebody could have a look I would be very appreciative. I'm using the following to work out trajectories (given in question); [Math] r(t + \delta t) = 2r(t) - r(t-\delta t) + \delta t^2 * F(t)/m...............and....... \\ \\ v =…

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  12. Started by DJBruce,

    While studying for the Michigan Mathematics Prize Competition, I came across this problem on an older exam: The value of [math] \frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{2006}{2007!} [/math] is A) [math]0.9999[/math] B) [math]1[/math] C) [math]\frac{2006}{2007}[/math] D) [math]1-\frac{1}{2007!}[/math] E) [math]\frac{1}{2007!}[/math] When I went to evaluate the series I did the following: [math] \frac{1}{2}+\frac{1}{3}+\frac{1}{8}....[/math] So I know it cannot be found using the summation for a geometric or arithmetic sequence. However I was easily able to eliminate answer E. I was however able to write the sequence in summation notation: [mat…

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  13. Started by CrazCo,

    e^x+e^-x=3 i tried xlne+-xlne=ln3 x(1)+-x(1) = ln3 x-x = ln3 but that doesn't work btw the answer is +- 0.96

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  14. Started by sci-nuke,

    1) i don't get the law of reflection! 2) Don't get the normal 3) Refraction... what do you mean bending to/from the normal? 4) How do i write a summary note for this quote 'Energy travels in waves (carried by carriers?)' so srry about bad english I am so noob at science plz help P.s. please provide some examples NOTE: Im trying to type up a summary for myself to study

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  15. Started by hjel0743,

    Hi all, I'm a beginning ME student and I have a project that requires me to heat a liquid (around 16 ounces) to around 120-140 degrees F. My idea is to place an electrically heated coil powered by a dynamo. My question is: what kind of voltage would i need to supply with my dynamo to achieve this kind of temperature? Also, I researched some kinds of resistive wires that I could use and most said to use the same kind of wire that is used in appliances like toasters. Is there a better way to go about this? THANKS!

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  16. Started by bouma,

    Just wrote an essay on this topic just wondering what people thought? Only a rough copy but seeing of there may be any other ideas or evidence to suggest? -------------------------------------------------------------------------- Coherent Thought co·her·ent (kō hir′ənt, -her′-) adjective sticking together; having cohesion having coherence; logically connected; consistent; clearly articulated capable of logical, intelligible speech, thought, etc. Physics exhibiting coherence Many believe that what separates us from the rest of the animal kingdom is coherent thought, simply we got it and they ain’t! Yet without coherence in its basic form I fail to see…

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  17. Started by CrazCo,

    For example 1 kg of water is heated from 5 degrees C to 100 degrees C to make steam. What's the total energy. I tried q = mc delta t and adding it with delta H = nH but I keep getting it wrong, can someone just show me how to do this one example so I can apply it to my questions.

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  18. Started by boshdosh,

    my science teacher has asked us to come up with 4 common indicators and i havent got a clue, i know about red cabbage but what else??? plz help

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  19. Started by anthropos,

    How do you find this limit? I tried the sin x/x limit, L'Hopital Rule, Taylor Series, but it just kept giving me more sin x and x, so I couldn't get the limit. Can somebody give a clue?

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  20. Started by Marconis,

    For my bio class, we had to analyze a scientific article on an ant species in the Amazonian rain forest that poisons non-host plants. We were to follow a guideline in this mini book that we got, and the last question bothers me. To me, it is worded oddly. Maybe you could help? The main point(s) of view presented in this scientific article is (are)_____ Then under it it says, (The main question you are trying to answer here is: What is the author looking at, and how is s/he seeing it?) So, I took it quite literally, I guess, and responded the following:The main point of view presented in the scientific article is that the author is looking at a rather puzzling …

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  21. Started by blackhole123,

    In a car engine, gasoline (represented by C8H18) does not burn completely, and some CO forms along with CO2 and H20. If 5.0% of the gasoline forms CO: A) What is the ratio of CO2 to CO molecules in the exhaust? B) What is the mass ratio of CO2 to CO? C) What percentage of the gasoline must form CO for the mass ratio of CO2 to CO to be exactly 1/1? I literally have no clue what to do with this problem. Can someone point me in the right direction? All I have is the unbalanced equation: C8H18+ O2 --> CO2+H20+CO

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  22. Started by MSharma,

    If anyone is able to help with these questions please let me know and able to explain how they got the answer as well!!! 3. Suppose you wish to rescan the image 8 by 10 in colour and you have two possible scanner settings; one to scan 8 bit colour and a second setting to scan 16 bit colour. 8 bit colour means that the image requires1 byte per pixel in each of the three colours of red, green, blue. 16 bit colour means that the image requires 2 bytes per pixel in each of the three colours of red, green, blue. 1. How many bytes are required to store the image in 8 bit and 16 bit colour respectively?. 2. If your USB flash memory key has 16 GB of storage space. How many …

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  23. Started by computerbum,

    I am trying to understand what how to use two's complement. If I have the number 128, I know that I can find the number by converting 128 to binary such as: 0000 0000 1000 0000 Then invert the digits like so: 1111 1111 0111 1111 Then add one to it like so: 1111 1111 1000 0000 which will give me -128 but what about if I want to find 2's complement of -128 would I still do it the same way as above which would give me the value of 128? I am new at this please help?

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  24. Started by SinJunior,

    Q: What are the characteristics of a bacteria that is contagious?

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  25. Started by DJBruce,

    For a warm up in my math class we were told to find the exact domain and exact range for the following function: [math]y=\frac{-1}{15\sqrt{36-x^{2}}}[/math] Find the domain of [math]\left(-6,6\right)[/math] easily. However the range was harder to find. I realized that the upper range is going to be: [math]\frac{-1}{15\sqrt{36-0^{2}}}=\frac{-1}{90}[/math]. It's the lowest value that I am struggling to find. I think it might be negative infinity because as x approaches 6 I will get -1 over 15 times the square root of a ridiculously small number, which will be a huge negative number. However I am not sure can anyone point me in the right direction.

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