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2

The NIH RDA for vitamin B12 is 2-3µg/day. Cyanocobalamin has an $M_r$ of 1355, of which 26, or less than 2% ($CN^-$) is cyanide. Since the Minimal Risk Level for cyanide is 50µg/kg/day, your studies are correct in that 1000x the RDA of vitamin B12 in the form of cyanocobalamin is not lethal, and furthermore is expected to not cause any negative effects ...


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Potassium cyanide is added to the cobalamins produced by bacteria to give rise to cyanocobalamin. CN is strongly bonded to Co and will not dissociate, thereby making the B12 inactive. Therefore, it has been argued that cyanocobalamin is not a good vitamin supplement and other variants such as hydroxycobalamin or methylcobalamin should be used. Since CN is ...


4

Biotechnology is a gigantic field. You should have a look at the wikipedia entry for biotechnology. Because of the size of the field "biotechnology", because the word biotechnology accept different definitions and because the word interesting is extremely arbitrary it is pretty much impossible to give a good answer to this question. I am using below ...


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Not 6, but 9 molecules of Pi are formed in the Calvin cycle, from the conversion of 9 ATP to 9 ADP: Source: Columbia University


1

Some of the water that's split is regenerated when the hydroxyl radicals (reactive oxygen species) are converted to hydrogen peroxide, water, etc. by superoxide dismutases and antioxidative mechanisms in the chloroplast (peroxisomes/catalases, etc. take care of this). There's also some evidence that the presence of mannitol, ascorbate and glutathione protect ...


1

Single covalent bond is a shared pair of electrons. For stable bond there should be 2 atoms with unfilled higher orbitals and at least a pair of electrons that is "distributed" among those slots. UC Davis have hilarious page on that.


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Water is split in chloroplasts in the light reaction of photosynthesis. Chlorophyll, acting as a photopigment, captures sunlight and transfers that energy to an electron pair of a water molecule. Under the influence of a water-splitting enzyme (George et al, 1989) it is sepaated into 2 protons, molecular oxygen and a free electron pair. Reference George et ...


1

So refer to the following diagram, In the photosystem II complex, water is decomposed into oxygen and protons. That's two electrons liberated from each water molecule. Plastoquinone accepts two protons from the stroma by coupling it to the two electrons it receives from the photosystem complex. In this manner, the protons are transported to the lumen, and ...


2

As you can see on the wikipedia page you linked yourself that beta barrels have far larger diameters (in some cases up to 40 angstroms as stated in this paper) depending on the numbers of beta sheets that make up the barrel, compared to the diameter of an alpha helix (that is fixed) of 6 angstroms. (source ...


4

chemicalize.org is a good utility for predicting many molecular properties such as pKa, pI and charge. The Human Metabolome Database uses the same underlying software but tabulates some of the data (eg charge is explicitly stated). Acetyl-CoA, for example, has a pI of 1.32 and charge of -4 at pH=7.4. Your second link is to a portion of an enzyme (a ...


4

The first compound you mention is acetyl-co-enzyme A (acetyl-CoA) (first picture, left panel). The acetyl group is uncharged, but the co-enzyme A (CoA) group (Fig. 1, right panel) does carry charge through its phosphate groups. In normal physiologic environments these phosphate groups will donate one or more protons, leaving the molecule negatively charged, ...


2

If by enzyme you mean "protein" aka polypeptide, than there are such things as catalitic RNAs. Those are molecules of RNA that facilitate chemical reactions but don't change themselves (definition of catalyst). I think that, based on the discovery of such RNAs, it is now believed that life might have started from or with the help of catalytic RNAs (please ...


1

Let me start from short description of fluorescence (since we talk about it here). Fluorescence is one of the processes through which excited molecule can relax, lose its excessive energy. That is, quantum interaction between atoms in molecule (organic dye or complex GFP) create permitted energy levels. There is "ground state" $S_0$, for example, and ...


2

It depends both on structure and charge. Binding sites of proteins are essentially formed by amino acids placed in a particular conformations such that it will match the binding site of their counterpart protein or substrate. This is commonly referred to as the lock and key model of protein binding. This is similar to how two puzzle pieces fit together, the ...


2

According to the (non peer reviewed) scientific experiment found here, simply placing a piece of kiwi onto gelatin that has set will cause the gelatin to be hydrolysed by actinidain. This experiment aims to show the effects of Proteolytic enzymes on proteins and, subsequently, the effects of extreme temperatures on the proteins themselves. Petri dishes ...


3

Nice question! I've found a great article about fatty acid metabolism in heart muscle in healthy and disease conditions. As it is stated in this paper long chain fatty acids are utilized through beta-oxidation to meet the high energy need of continuous contraction. Beta-oxidation of long chain fatty acids produce far more ATPs than glucose. According to ...


1

Great question. Turns out, there is some information about it. For example, consider following resource: Membrane Protein Lipid Composition Atlas. Published by University of Michigan, it provides information on, primarily, protein content of different membranes from different species, but also has a list of lipid content. Just as an example, consider ...


4

What seems to be forming in reusable water bottles and water coolers, is a biofilm. Since it is a complicated system, after maturation, biofilm might be very hard to remove without scrubbing. There is nice article about cleaning water coolers, which might give some information. If you closer on Google Scholar search, you'll find that quite a bit of research ...


0

So cryopreservation would be the long-term mode of storage, and you'd do something like store your sample in a cryonic freezer supplied w/ liquid nitrogen at -196C. Cellgro provides some recommendations for cryopreservation here. Keep in mind, cryonic freezers are typically pricey, but broady, the idea is you need to keep your cells at the right temperature, ...


1

Basic sigmoidal curve looks like that: zero at $-\inf$ and one at $+\inf$. All in between should look like an integral of gaussian distribution. Take a look on this wiki page for more information. Now, the question, why sigmoidal curve is integral of gaussian function, I will leave out for now. My understanding is that gaussian distribution tells you how ...


1

Most likely, you can't assume that $h/k$ might be constant. Reason is that those parameters are characteristics of two very separate systems. Thermal conductivity shows how fast heat can be propagated through material. That is, it answers question: if block of metal has $T_0$ temperature on its surface A, and you apply temperature $T_1$ (higher) to opposite ...


1

From this post. The IC50 is the concentration of inhibitor required to reduce the activity of a molecule/protein by one-half. It is the inverse of EC50. Usually inhibition curves looks sigmoidal so the IC50 is the middle point of the S curve. Here an example. (Note that the Y-axis can be pretty much anything, like enzyme activity and the X-axis is the ...


4

The energy transfer is achieved by a process called "resonance energy transfer". It needs the positioning of the donor and the acceptor in very close proximity to each other - the light harvesting complexes are optimized for this. This allows the collection of small amounts of light energy and still enables photosynthesis. The figure shows how this works ...


1

I believe your textbook is referring to the fact that you only perform the complete beta oxidation eight times. Because there's a carboxylic acid at the terminus of a fatty acid chain, the cell takes a slightly different route and reacts it with ATP, which generates a fatty acyl adenylate and pyrophosphate (PPi). This AMP can subsequently be displaced in ...


3

First, there are three ketone bodies: Acetone (top), acetoacetic acid (middle), and beta-hydroxybutyric acid (bottom), see the illustration from the Wikipedia: The second and the third are taken up by heart and brain cells and then converted into Acetyl-CoA which is fed into the citric acid cycle where it is further metabolized. Acetone is mostly ...


10

Gluconeogenesis is not the reversal of the glycolysis, but the generation of glucose from non-carbohydrate precursors (like odd chain fatty acids and proteins). The reason why we have this process is because some organs and tissues can only use glucose as their energy source. These include the brain (although ketone bodies can be used here as well), ...


2

The electrons for shuttling are mainly generated in the cytosol from glycolysis. NADH can easily pass the outer membrane, but must be shuttled over the inner membrane. It is important to consider that the electrons must be fed to oxidative phosphorylation from the matrix of the mitochondrion, and not the intermembrane space.


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It might be due to livor mortis, also called postmortem lividity, which is the settling of the blood in the lower parts of the body which in your case might have been the limbs. By time the color can be interpreted as either blue or purple, but given, that not much time has passed it can very well be the reddish color you might have asked, as stated here on ...


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A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step ...


0

Clarify, when you say "antibody" do you mean a monoclonal antibody (where every antibody is identical, and therefore a pure population), or do you mean a polyclonal antibody (which is a mixture of antibodies that all recognize the same antigen, but may each be recognizing different epitopes on the antigen)? A monoclonal Ab (mAb) recognizes a single epitope. ...


0

TL;DR Specificity of antibody can be not superb. It can give false-positive results in up to 90% of experiments. However, some essay are 90% specific. That is an interesting question and there sure a lot of research done to understand specificity and strength of binding of antibody to its target. First of all, let me say that antibody-epitope interaction ...


7

This question really belongs at Chemistry.SE, but I'll give you a quick answer. A substance is soluble in water when its solid form (such as a sugar cube) completely dissolves in water to become a sugar solution. The sugar molecules themselves are unaffected, essentially - instead of all being bound to one another in a crystal, they are now floating around ...


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There is one main reason: Amplification of the signal. You can start a signal downwards the cascade with relatively few receptors which need to be activated which allows even for weak signals to be translated into the nucleus. This figure shows this for G protein coupled receptors (from here): For example one molecule of cAMP can activate many molecules ...


-1

Membrane potential The membrane potential in cells can be determined by the distribution of lipophilic ionic molecules between the cells and the suspending medium according to the Nernst equation: Where: ∆ ψ is Membrane potential, R is the gas constant (in J K−1), n is the number of electrons per mole, F is the Faraday constant (in C mol−1), [X]i ...


2

So, when they subjected "ready to drink" beetroot juice to thermal pasteurization, they found the betacyanin and betaxanthin (our major antioxidants, and pigment molecules) content to be 39.9 and 42.28% degraded, respectively (1). Their conclusion was as follows: Standardization of process condition and quality degradation of beetroot juice due to ...


0

I assume it has an analogous function in ligation buffers. There it apparently takes up a large proportion of the volume and thereby increases the chance of interaction between bits of DNA. In a transformation buffer it should increase the chance of DNA getting into a cell. Unfortunately the only reference I found for this was at Bitesizebio: ...


1

To get to the membrane of these species you first need to get past a formidable cell wall. The methods listed below are therefore more aimed at making cells permeable but the membranes must sustain some damage in the process. At our lab we regularly use glass bead transformation for microalgae transformation. The microabrasion allows DNA to go in so I ...


4

Either the gene is present in multiple copies (especially possible if it is in a plasmid) or multiple RNA polymerases are transcribing it, each beginning from the start site one after the other with some amount of time delay, much like multiple ribosomes translate the same mRNA to increase rate of protein production.



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