Roland
  • Member for 6 years, 8 months
  • Last seen more than a month ago
How do we know that our genetic similarities to other species is actually due to common ancestry?
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34 votes

We don't know, and we never will. Science doesn't work that way. But evolution is the simplest hypothesis that is both falsifiable and consistent with lots of experimental data. Therefore it is the ...

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120-year-old gene regulation problem independently solved by a computer. How?
21 votes

The paper by Lobo and Levin is an attempt to learn a model that represents the inner workings of a biological system by fitting parameters to data. This is a common topic in "systems biology", a model-...

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Are humans capable of both anaerobic respiration, and lactic acid fermentation?
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14 votes

Humans have no anaerobic respiration, if we define this as oxidation of a substrate with an external electron acceptor other than oxygen. In humans, the terminal electron acceptor in respiration is ...

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If red blood cells have no mitochondria how are they able to metabolize glucose?
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12 votes

In humans (and all mammals), red blood cells lack mitochondria and therefore has no functional TCA cycle. They metabolize glucose mainly via glycolysis, forming lactate which is released from the ...

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Can any enzyme be produced?
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11 votes

No, not all enzymes (or other proteins for that matter) can be obtained in functional form by recombinant expression with today's methods. As you suspect, problems arise when complex post-...

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How is vitamin B12 stored in the body although it is water-soluble?
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10 votes

Vitamin B12 (cobalamin) is a cofactor required by the enzymes methionine synthase (MTR) and methylmalonyl-CoA mutase (MUT). These are the only known enzymes that use B12 in humans, and are abundant in ...

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How does membrane potential vary between intraceullar membranes and the cellular membrane?
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9 votes

Yes, various intracellular membranes do have potential differences, but as you can imagine they are more difficult to measure experimentally, so in general data on this is scarce. Summary ...

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Is palmitic acid really that dangerous?
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9 votes

Let's first clarify some concepts. Free fatty acids, including palmitic acid, are not present in animal tissues (or in the diet) to any large extent; they are esterified with glycerol to from ...

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How are colors outside the standard RGB color scheme perceived?
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8 votes

This question is both biology and physics I think (I guess it's biophysics! :) so I feel it's worth answering here. First, we must recognize the difference between wavelength, which is just a ...

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Why are the human knees and elbows bent in an opposite direction
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8 votes

I am no expert on comparative anatomy, but I will give this a shot. Please edit if you know more about this subject! The configuration of opposing elbow and knee joints is a feature we humans share ...

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Why do animals have more heavy nitrogen and carbon than plants?
8 votes

Organisms accumulate certain isotopes because their metabolic enzymes have a slight preference for molecules containing that isotope. A well-known example is ribulose-1,5-bisphosphate carboxylase (...

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Why can't we use plasmids to add genes to ourselves?
7 votes

First, plasmids do not usually integrate into the chromosomes of human cells. In the laboratory, plasmids can be introduced into the cytosol of cells, and plasmid DNA will then be "read" by the host ...

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Are trees the only source of large amounts of oxygen?
7 votes

Trees are definitely not the only source of oxygen. First, all green plants do photosynthesis, not only trees. Moreover, about half of all photosynthesis on earth is done by microorganisms in the ...

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Confusion on polarity and hydrophobicity of Proline, Tyrosine and Cysteine?
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6 votes

TL/DR: these are borderline, complicated cases. There is no broad consensus on whether cysteine and tyrosine should be considered hydrophobic or polar. Proline is clearly nonpolar though. The reason ...

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Explain a gene network to a first year undergrad
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6 votes

There is no single answer, because networks (or graphs, as they are called in discrete mathematics) are flexible tools that can be used to model all sorts of relationships between genes, transcripts, ...

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Are there any primary structure sequences that strongly suggest b-sheet or alpha helix?
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6 votes

Yes, there are certain amino acid sequences that tend to form alpha-helices, and others that prefer to form beta-sheets. There is no perfect correspondence between sequence and structure, but there is ...

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How do stem cells produce 200 billion new blood cells every day? Does 1 stem cell division result in production of just 1 blood cell or many?
6 votes

The hematopoietic stem cells are quite rare, and each progenitor cell produced by a stem cell gives rise to a large number of red blood cells (and other blood cell types). I'm not sure if the precise ...

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In a tumor, why hypoxic regions have access to glucose?
6 votes

I think this is a difficult question for which the answer is not clear --- to my knowledge there is little data on metabolism in solid tumors, and no clear consensus in the scientific community. So I'...

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How is AMP "recharged" to become ATP in a cell?
6 votes

AMP is first converted to ADP in the reaction AMP + ATP $\leftrightarrow$ 2 ADP catalyzed by adenylate kinase. So one phophate group is transfered from ATP to AMP, resulting in two ADP molecules. ...

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Is there a database of cell images?
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5 votes

There is a yearly contest on cell tracking organized by the IEEE International Symposium on Biomedical Imaging, and the associated data sets are freely available. See for example: http://www....

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How is a substance classified as a vitamin?
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5 votes

1) Vitamin D is a bit of an umbrella term that actually refers to a whole group of related molecules. One of these, vitamin D$_3$ (cholecalciferol) is formed spontaneously from ergosterol in the ...

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Cancer biology: Can tumors form from cells that are genetically identical to non-cancerous cells?
5 votes

This is a very interesting question, and one that has been at the heart of cancer research for a long time. I think it separates into three issues. Are there non-genetic mechanisms that can induce ...

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How allele is related to trait that is more complex than two cases (ex. height)?
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5 votes

You are absolutely correct that many traits are not "digital", but "analog". In genetics, these are usually called quantitative traits. Such traits generally do not follow Mendel's laws of inheritance,...

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Does the formation of water inside the mitochondrial matrix help contribute to the proton gradient during the electron transport chain?
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5 votes

Your description of it is largely correct, but the electron transport chain does not simply "dump" charged oxygen ions in the mitochondrial matrix. Instead, cytochrome C oxidase (complex IV) binds the ...

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Why do asparagine and glutamine have two different abbreviations?
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5 votes

The abbreviation Asx (B) is used if it is uncertain whether the amino acid at a given position in a peptide sequence is Asparagine or Aspartate. Similarly, Glx (Z) is used when there is uncertainty ...

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What product of cellular respiration creates an acid when in solution with water?
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5 votes

Cellular respiration itself, defined as the activity of the respiratory chain complexes I -- V (including ATP synthase), is not acidifying. On the contrary, free protons are captured during ATP ...

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Why is it often the case that an enzyme is favorable only towards one direction of a reaction and not both directions?
5 votes

Reactions have their set equilibrium constants, which are determined by the free energy of the reactants involved, and this cannot be changed by catalysts, including enzymes. Let's look at your ...

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Energy released during the production of ATP?
5 votes

This is difficult to answer exactly since the thermodynamics of cellular metabolism are not well understood. These are spontaneous reactions, so there is certainly a loss of Gibbs' energy $\Delta G &...

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Does the energy from ATP hydrolysis vary among different cells?
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4 votes

Yes, the energy from ATP hydrolysis can vary between different cell types and condition, because it depends on several factors. Hence, you will find different values in various textbooks. First, like ...

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Roughly at least, how many types of cells comprise human blood?
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4 votes

I think any answer to this question will be subjective, depending on what you consider to be distinct cell types --- how detailed the classification should be. As you mentioned, if you consider all ...

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