8

In short, it's because fatty acids are made from two-carbon blocks. The way that most organisms make fatty acids is by the successive addition of two-carbon units (acetyl-CoA). So we usually get even-numbered fatty acids just because the building blocks are also even. In plants and in synthetic contexts, we can have some reactions that can produce odd-...


7

Protein is polymerized amino acids. Humans do not require protein intake, but certain essential amino acids are required. These essential amino acids are usually obtained through protein intake, but intake of the free amino acids themselves would suffice. Amino acids, in free or protein form, are lost from the body due to urination (see Diverse ...


5

Correct, all but one step in pyrimidine synthesis occurs in the cytosol, and purine synthesis occurs in the cytosol only. Nucleotides freely diffuse through nuclear pores but are actively transported through mitochondrial membranes via embedded membrane transport proteins (i.e. ATP-ADP translocators, GTP transporters, and pyrimidine nucleotide transporters)...


5

Although the question shows considerable effort to achieve clarity, the way it is phrased as: How many molecules of nucleoside triphosphate… [does] it take to release enough energy still allows ambiguity, as I would not really regard the NTPs involved in protein synthesis “releasing energy”. So let us consider two reformulations of the question, as the ...


4

The differential uptake of different isotopes of carbon is covered well at: https://en.m.wikipedia.org/wiki/Fractionation_of_carbon_isotopes_in_oxygenic_photosynthesis Plants have a lower proportion of C-13 than atmospheric CO2. The two mechanisms that cause this are the reduced diffusion speed of the heavier C-13, and an energetic difference in the chemical ...


3

Regarding protein synthesis rate, here's an attempt at an estimate from bioenergetics: ATP turnover in the human body is consider to be about 100 mol / day. Protein synthesis is estimated to require about 1/4 of ATP consumption in a mammalian cell, and one amino acid elongation requires about 5 ATP, so about 5 mol amino acids are elongated per day, which ...


3

Tomato leaves have something like 184 ng/g of nicotine, in the same ballpark as tomatoes (the fruit) and not close to tobacco. I think this is not peer-reviewed, but it cites other papers that are: Nicotine Analysis in Several Non-Tobacco Plant Materials And this is a PDF of a slide deck providing a simple presentation of the results from the same article: ...


3

Okay so pyruvate carboxylase is a ligase-class enzyme, meaning it forms covalent bonds. What we see is that pyruvate is carboxylated into oxaloacetate by pyruvate carboxylase, here's our proposed reaction, What this does is replenish mitochondrial oxaloacetate levels, because when we switch into lipogenesis, TCA intermediates must be shuttled into the ...


2

It is a misconception that cats cannot synthesize taurine. Cats can synthesize taurine, just like other mammals, but not enough of it to make up for an entirely taurine-deficient diet. Cats (and other mammalian carnivores) would have consumed a taurine-rich diet in the ancestral environment. It is only when they are fed vegetable/fruit/grain-derived foods ...


2

Metabolism ≈ Anabolism + catabolism Metabolism is the set of all chemical reactions happening inside a living body. These reactions can either breaks down big molecules and build up big molecules. The set of reactions the breaks down big molecules is called catabolism. The set of reactions that build up big molecules is called anabolism. Energy Generally ...


2

The dash ("-") does not represent a negative charge or an electron. It simply indicates that the group of atoms ( -OH or -H ) are attached (covalently bonded) to other atoms in a molecule. So they are saying one monomer (molecule) contributes OH to the reaction and the other H. (A charge is indicated by a trailing superscript minus sign.)


2

The answer will not satisfy you. The truth is no protein marker will do. On one hand you seem to be looking at some individual, representative protein, which you could measure by immunoblot. But most proteins are in scant concentrations, just as many as required for their job, and go up and down depending on their specific roles, rather than on general ...


2

I take issue with the previous answerer's assertion that it is extremely unlikely that previous research on nicotine concentrations has ever been performed; in fact, it was very well established decades ago that alkaloids in Nicotiana (and other Solanaceaes) are predominantly synthesized in the roots and, in the case of grafting studies, translocated through ...


2

Aromatics that stem from the Shikimat Pathway result in a structure like this Whilst aromatics originating from the Polyketide Pathway have an alternativ structure in the distribution of the OH groups.


2

It sounds like we're mainly interested in phospholipids here, as they're the main component of cell membranes. Since your question didn't specify, we'll talk about Bacteria/Archaea and Eukarya separately Bacteria/Archaea Here, the answer is fairly intuitive. Bacteria and Archaea don't have endoplasmic reticulum, so they can't synthesize phospholipids in it....


2

A fully grown organism is subject to senescence and on a narrow perspective one of the signs of aging is the accumulation of large amount of lipofuschin. In unstressed situations protein homeostasis is balanced by folding and stabilization of proteins by chaperones of the Hsp family [1] and the controlled degradation of proteins by the proteasomal system.[...


2

It's just the nomenclature: Bacteria: Gene symbols are typically composed of three lower-case, italicized letters that serve as an abbreviation of the process or pathway in which the gene product is involved (e.g., rpo genes encode RNA polymerase). To distinguish among different [but related genes], the abbreviation is followed by an upper-case letter (e....


1

After further checking, I found that HMG-CoA synthase rather than HMG-CoA lyase is the enzyme which is regulated. This enzyme also plays a vital role in cholesterol synthesis. HMG so produced can either form mevalonate, which leads to cholesterol synthesis, or form acetoacetate. Therefore if acetoacetyl CoA were directly hydrolyzed, it would short circuit ...


1

I believe it is related to the fact that the enzyme HMG-CoA lyase is regulated by glucagon (activates) and insulin (inactivates). It appears that this extra step was added so the pathway can be hormonally regulated.


1

According to the homonymous article of Wikipedia Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA. As shown by this picture, ...


1

Probably a mistake in your notes, or in the lecture notes for the class, but not a very important error in either case aside from the confusion it has caused you. See the wikipedia article on Synthase and on wikipedia article on Ligase for a note on the terminology: historically synthetases use ATP, synthases do not, but this terminology is not adhered to ...


1

For your first question I think @Michael_A has explained why this question can't be answered. And for the second one, I quote from bscb.org : Ribosomes are found ‘free’ in the cytoplasm or bound to the endoplasmic reticulum (ER) to form rough ER. In a mammalian cell there can be as many as 10 million ribosomes (A single cell of E. Coli contains about 20,...


1

Preamble I don’t know where you read the statement “NADPH is... the main agent necessary for anabolic reactions”, but out of context it is very misleading, and it is difficult to envisage circumstances in which it would be helpful for students of metabolism. Put simply, NAPH is only used in anabolic pathways which involve chemical reduction. You ask ...


1

Bacteria and plants are able to synthesize all amino acids, as they are capable of nitrogen fixation. If animals eat plants, they get the essential amino acids needed for their proteins. Humans get the essential amino acids by eating these animals or directly by consuming plants. So yes, it is a never-ending cycle of passing.


1

.. I'm not aware of large nicotine levels in other parts of plants. I assume tobacco will still have the highest nicotine levels, because that's what people have been selecting for for centuries. .. - user137 That logic seems compellingly sound. Based on that, why would a researcher even bother to measure the nicotine content of the other parts of non-...


1

Seemingly the enzyme uses molecular oxygen in the reaction and one of the end products is water. This reaction scheme is more detailed and presumably accurate. http://www.hmdb.ca/reactions/3063 In addition there is also a set of papers detailing coproporphyrinogen oxidase which was also on the website, hopefully one goes into more detail on the reaction. ...


1

According to one study: It was calculated that if the excretory percentage of niacin metabolites in the urine were 60%, of the tryptophan ingested, the conversion factor would be a value of 67, meaning that is 67 mg of tryptophan is equal to 1 mg of niacin. However, the study has a pretty low power with only 10 participants and an indirect measure of ...


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