445 Answered Questions for the topic biochemistry

07/10/19

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

07/10/19

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 ?

07/10/19

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

07/09/19

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

07/09/19

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

07/09/19

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

07/08/19

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

07/08/19

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

07/08/19

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

07/05/19

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

07/05/19

How is respiration an unbalanced equation?

The equation for respiration is... more

07/05/19

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

07/03/19

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?

07/03/19

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?

07/02/19

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

07/02/19

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?

07/02/19

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?

07/01/19

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

07/01/19

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

06/30/19

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

06/28/19

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?

06/27/19

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

06/27/19

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?

06/26/19

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

06/25/19

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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