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# Tag Info

## Hot answers tagged biochemistry

41

One argument put forward has been that aluminum is very poorly bioavailable, moreso than many other elements. Aluminum oxide is very insoluble in water. In addition, any dissolved aluminum that does form in seawater is likely to be precipitated by silicic acid, forming hydroxyaluminosilicates. From Chris Exeter's 2009 article in Trends in Biochemical ...

16

The metal’s trivalency is certainly not an issue. Iron and cobalt form trivalent compounds (in the $\mathrm{+III}$ oxidation state) in many of their biologically relevant complexes. In fact, in metalloprotein surroundings the actual ‘valency’ (oxidation state) is not so much of a deciding factor; what matters is the number of ligands and the required ...

13

There are plenty of good sources online explaining the principle behind radiocarbon dating. For instance, the wikipedia explains: During its life, a plant or animal is in equilibrium with its surroundings by exchanging carbon either with the atmosphere, or through its diet. It will therefore have the same proportion of $\ce{^14C}$ as the atmosphere, or in ...

9

There is a clear explanation and figure showing this in the following reference: Anton Gorkovskiy, Kent R. Thurber, Robert Tycko, Reed B. Wickner, PNAS 2014, 111 (43) E4615-E4622. A parallel beta sheet is one where the direction from N- to C-termini on adjacent strands run in a parallel direction (rather than antiparallel). In-register means that each ...

8

Does cooling a potato change the nature of its carbohydrates? Yes, retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. Resistant Starch: There is weak evidence that resistant starch can improve fasting glucose, fasting insulin, insulin ...

8

The metabolism of living creatures keeps the dynamic equilibrium of their $\ce{^{14}C/^{12}C}$ ratio with the enviromental $\ce{^{14}C/^{12}C}$ ratio via photosynthesis, breath, food and excrements. It is not just about one time building, but also about continuous recycling of the body content. Such an equilibrium means continuous resetting of the $t=0$ ...

7

According to Wikipedia: Glucose is usually present in solid form as a monohydrate with a closed pyran ring (dextrose hydrate). In aqueous solution, on the other hand, it is an open-chain to a small extent and is present predominantly as α- or β-pyranose, which partially mutually merge by mutarotation. Glucose predominantly occurs in nature in the form of ...

6

The open chain is floppy. The relative stereochemistry between two centers is fixed and unchanging. But the existence of geometric isomers implies additional structure imposed on the molecule. In this case, in 6-member ring, one can have axial or equatorial substitution which are distinct. The relative stereochemistry is the same but the relative ...

6

This is a summary of the account by Peter Brzezinski, Professor of Biochemistry, Stockholm University, Member of the Nobel Committee for Chemistry from the Scientific Background document. [Brzezinski:] Jacques Dubochet developed methods for preparation of samples for cryo-EM studies of biomolecules in water. Joachim Frank developed methods for structural ...

6

These are not dots. They actually are single bonds though I do not know why they are printed that way. As such, they should be represented by a half-long dash (called EN DASH in Unicode). In the name N-acetylglucosamine, acetyl means that a hydrogen atom has been replaced an acetyl group (i.e. –CO–CH3) and that the replacement occurred on the nitrogen (aka "...

5

The diameter of human hair is typically 100 microns (from 17 to 181 microns: https://hypertextbook.com/facts/1999/BrianLey.shtml ). The diameter of a cellulose fiber is about 10 microns ( https://en.wikipedia.org/wiki/Paper ), and a cellulose molecule is much smaller (up to about 10,000 glucose units long: https://en.wikipedia.org/wiki/Cellulose_fiber ). ...

5

As their name imply, each amino acid has at least one amine and one acid functional group, but in most amino acids, the basicity of the amine is offset by the carboxylic acid group at physiological $\mathrm{pH}$, and hence considered neutral. Amines are basic because the nitrogen has an unshared electron pair that can accept an $\ce{H+}$ more readily than ...

5

Cysteine is a dispensable amino acid required for synthesis of protein and non-protein compounds. These non-protein compounds include pyruate (hence acetyl coenzyme A), taurine, sulfate, and glutatione (GSH). The fate of the cycteine is hence sketched in following diagram (Ref.1): As evidence from the diagram, the sulfur atom in cysteine has been converted ...

5

Chromatography is really an empirical science. The fluid mechanical side and the adsorption phenomenon is somewhat well understood but choosing mobile phases is essentially based on trials, sadly to date. If someone has given you a ratio, say 8:2, it means someone must have tried it and they found that this mobile phase works the best. The main criterion for ...

5

Who was responsible for this naming system and how can we change it? Michael Faraday was responsible for the terms anode and cathode more than hundred years ago. All the confusion regarding the nomenclature will vanish if you do not associate electrostatic signs with these two terms. One should identify the electrode labels with the redox processes rather ...

5

For currents in biological systems the magnetic field is minuscule, and likely has no physiological effect. That said, magnetoencephalography is based on measuring the tiny magnetic fields created when nerves fire. Detection requires an incredibly sensitive detector, a superconducting quantum interference device (SQUID), to detect the location of the ...

4

The Biuret Test is a chemical assay that detects the presence of proteins in a sample. The test is not named after any famous scientist, but after an urea dimer called biuret ($\ce{H2NC(O)NHC(O)NH}$). However, funny thing is biuret is not a part of the test at all. The test is called Biuret Test because biuret gives a positive result to the test (See the ...

4

Glycoproteins come in O-linked and N-linked forms. For O-linked sugars, a glycosidic bond forms between the sugar and the hydroxyl of a serine or threonine side chain. For N-linked sugars, a glycosidic bond forms between the sugar and the amide of asparagine. The equilibrium for all these reactions lies on the side of hydrolysis in aqueous solution. Is it ...

4

Biologically, methane is produced by methanogens, which are Archeabacteria. They do not utilize carbohydrates such as cellulose or glucose directly. Instead, they typically consume acetate or a mixture of hydrogen gas and carbon dioxide. These stoichiometry of these two processes is $\ce{4H2 + CO2 -> CH4 + 2H2O}$ or $\ce{CH3C(O)OH -> CH4 + CO2}$. To ...

4

In sucrose molecule the glycosidic linkage is formed by the OH group on the anomeric carbon of α-D-glucose and the OH group on the anomeric carbon of β-D-fructose. source : https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(McMurry)/Chapter_25%3A_Biomolecules%3A_Carbohydrates/25.08_Disaccharides As seen, in either alpha ...

4

Taste receptors work with water (or saliva, or whatever other liquid that happens to occur in your mouth) and the things dissolved therein. Smell receptors work with air and airborne chemicals. Short of that, they are similar in that both are wide-range chemical sensors, and different in that they send different signals to our brain.

4

Proteins are almost certainly the 'detectors' for both smell and taste, so chemistry is at the heart of the process. For airborne chemicals these will have to diffuse through some form of 'mucus' before reaching the cells in your nose on the surface of which are the receptor proteins. Typically these would span the cell membrane. Interaction of the smell/...

4

Are all the biochemicals that our body uses enantiomerically pure or are racemic mixtures too? Many molecules exist in both forms in nature. One fun example are the enantiomeric terpenoids R-(–)-carvone and S-(+)-carvone. The R-form smells like spearmint while the S-form smells like caraway. The difference in smell shows that properties other than the ...

4

1) Sodium dodecyl sulfate (SDS) is a solid anionic detergent. It can solubilize proteins and lipids that frame the cell membranes by degrading the cell (the proteins from the cell membrane get damaged and cell gets broken) and nuclear membranes that protect the DNA. This will help the cell membranes to separate and expose the chromosomes that contain the DNA....

3

To start, transition metal complexes with large porphyrin-like molecules are so electronically complex that standard chemical intuition doesn't apply and you have to either do the experiment or run a (nearly impossible) calculation to determine what effect a non-physiological metal would have on the protein activities. In the case of hemoglobin, your best ...

3

You could try a different pH to get rid of secondary structure. It might change the absorbance spectra as well, though. Here is a paper where they measured spectra of DNA and its constituents: https://doi.org/10.1016/S0022-2836(61)80003-X The abstract says the following (mμ is the same as nm): The spectra of deoxyadenylic, deoxyguanylic, deoxycytidylic ...

3

Why Molybdenum is Used in the Manufacture of Ammonia? Molybdenum tubing has particularly good resistance to corrosion by mineral acids, provided oxidizing agents are not present. It is also resistant to many liquid metals and to most molten glasses. Molybdenum is relatively inert in hydrogen, ammonia, and nitrogen up to about 1100 C, but a ...

3

1) Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process? Under physiological conditions, it is a process that goes forward, i.e. the Gibbs energy is negative. As a consequence, it can happen outside of cells in the absence of ATP. When we eat, the hydrolysis of polysaccharides starts in our ...

3

So how are the cells are arranged to form a solid structure a solid body? Plant cells have cell walls, are filled with liquid, and have strong cell-cell adhesion. This gives a fairly rigid structure that may seem like a solid. Take a carrot for example, it seems solid. But if you put the carrot in a blender, you get carrot juice - not a solid. Also, when ...

3

Horseradish peroxidase is not hydrogen peroxide, $\ce{H2O2}$, but rather an enzyme that breaks $\ce{H2O2}$ into $\ce{H2O}$ and $\ce{O2}$. In general, enzymes ending in -ase are lytic enzymes, catalyzing the breakdown of a similar-sounding substance. So, if you add ground horseradish to hydrogen peroxide, bubbles of oxygen are released. BTW, horseradish roots ...

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