445 Answered Questions for the topic biochemistry


What is an irreversible reaction?

There are reactions with large Delta G negative values. Why these reactions are irreversible? As in: out of 10 steps of Glycolysis, 3 are irreversible steps. I need an explanation for why they are... more


Why restriction enzymes cut (usually) at palindromic sequences?

Restriction enzymes usually cut only at palindromic sequences. Is there any specific reason for that ? Is there any advantage for bacteria if it cuts up virus at this type of sequences ?


What is the difference between a protein and a factor?

In terms of nomenclature/semantics, why are some proteins named proteins, and some named factors?I've been revising on eukaryotic DNA, and I've come across some proteins that seem to serve roughly... more


When giving blood, what is the specific Iron measurement they take?

I went to give blood the other day, and they take an "iron" measurement prior to actually drawing the blood. My level was 16.4 -- but what specific type of iron were they measuring? I've heard of... more


Why is absorbance at 280 nm for protein solution going up when I measure repeatedly?

I have been measuring my protein solutions' concentrations by diluting them in water 20 fold with a final volume of 100 uL and then measuring the absorbances of these solutions in 96 well plates... more


Membrane Permeability to Pyruvate?

Pyruvate seems to pass easily through the outer membrane of the mitochondrion but has difficulty entering the inner membrane (and gets in by H+ symport). I have two questions: (1) what property of... more


Why are enzyme-catalysed reactions slower at lower substrate concentration?

Suppose I'm using 200 nmoles of enzyme and 2 mmoles of substrate. The enzyme should be saturated but if I use 50 mmoles of substrate, the reaction will be faster. Why?I just can't get it! Even at... more


What exactly makes bananas go brown?

I know that often oxidation processes are mentioned when referring to the color change from yellow to brown in bananas (specifically: those that you get everywhere in supermarkets, with no... more


Why do red blood cells maintain Iron in the Haem group in the +2 (ferrous) oxidation state?

A lot of sources tell me that RBCs contain a number of enzymes, and that these serve multiple functions from maintaining the structure and elasticity of the corpuscle wall, to preventing the... more


Is there a reliable source for storage and stability of reducing agents like DTT?

Reading the literature on DTT, one is confronted with a confusing mass of papers; some claim that a 1M solution in water is stable, other papers say it is not. I use the reaction with DTNB to show... more


How is respiration an unbalanced equation?

The equation for respiration is... more


What biological processes cause leaves to change colours in Autumn?

I am curious to learn what are the biological mechanisms that cause leaves of deciduous plants to change colour? What happens to the chlorophyll?What environmental phenomena (temperature/air... more


Why can't you just take a vitamin? Why you need a healthy diet on top of that?

From what I understand, your body needs certain amounts of vitamins and minerals to maintain health. Why can't we just take enough pills to obtain these vitamins and minerals?


Why is GTP, not ATP, produced in Gluconeogenesis & TCA Cycle?

In both gluconeogenesis and the TCA cycle, there is a point in each that GTP is produced instead of the usual ATP. My question is why GTP and not ATP for these 2 specific steps?


How can facultative anaerobes exist without catalase?

>Catalase-negative bacteria may be anaerobes, or they may be **facultative anaerobes** that only ferment and do not respire using oxygen as a terminal electron acceptor<br />A facultative... more


What stops messenger RNA from binding to itself?

Since mRNA is single-stranded, and (mostly) floats freely within the cytosol, what stops it from folding onto itself (like DNA) and preventing transcription?


Why is glycine considered a nonpolar amino acid but a polar molecule?

Glycine has a dipole moment, so why is it considered a nonpolar amino acid when discussing its occurrence in proteins?Also, is the backbone of a protein nonpolar?


What exactly happens if during translation, an amino acid is not present?

Lets say that the cell wants to make a particular protein. Transcription of the appropriate gene is done and the mRNA is made. mRNA attaches to the ribosome and the translation is initiated in a... more


Why does high pH result in the denaturation of DNA?

In the Southern blot method, for example, a solution of NaOH is used to denature the DNA in the sample. I find this counterintuitive since I expected that $\ ext{Na}^+$ cations would neutralize... more


Why doesn't surgical steel cause inflammation?

It seems some very specific alloys like implant surgical steel and titanium don't cause inflammation in the human body, but when I asked my doctor about it, they simply said "it just has some... more


why is AUG the initiation codon?

Is there any reason why AUG is the initiation codon ?Why is there a need for an initiation codon ? Can't translation start with different codons?


Is it possible to synthesize chiral version of an organism (incompatible with our pathogens)?

In theory, it should be possible to synthesize chiral (mirror image) version of some organism: with all molecules replaced with their enantiomers, e.g. L-sugars in place of our D-sugars.Direct... more


The Bohr Shift Changes the Affinity of Hemoglobin for Oxygen

What is the Bohr Shift and why is it significant in restoring pH levels in the blood to normal?


What are the roles of guanidine-HCl and ethanol in binding of DNA to silica?

I'm trying to understand how exactly the binding to silica gel (in kits) step works and I cannot find any papers which provide an explanation of the physics or chemistry; especially on the way that... more


How does CO₂ concentration affect photosynthesis?

I have heard the theory that with the increase of CO<sub>2</sub> in the air, the speed of the photosynthesis would increase, thereby limiting the increase of CO<sub>2</sub>... more
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