Question: What is an example of an organic cofactor?
About the article "Biomolecule", section "Apoenzymes".

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Molybdenum cofactor guanylyltransferase (, "MobA", "MoCo guanylyltransferase") is an enzyme with system name "GTP:molybdenum cofactor guanylyltransferase".
This enzyme catalyses the following chemical reaction  GTP + molybdenum cofactor formula_1 diphosphate + guanylyl molybdenum cofactor Catalyses the guanylation of the molybdenum cofactor.  
Molybdenum cofactor cytidylyltransferase (, "MocA", "CTP:molybdopterin cytidylyltransferase", "MoCo cytidylyltransferase", "Mo-MPT cytidyltransferase") is an enzyme with system name "CTP:molybdenum cofactor cytidylyltransferase".
This enzyme catalyses the following chemical reaction  CTP + molybdenum cofactor formula_1 diphosphate + cytidylyl molybdenum cofactor Catalyses the cytidylation of the molybdenum cofactor. 
Molybdenum cofactor sulfurtransferase (, "molybdenum cofactor sulfurase", "ABA3", "HMCS", "MoCo sulfurase", "MoCo sulfurtransferase") is an enzyme with system name "L-cysteine:molybdenum cofactor sulfurtransferase".
This enzyme catalyses the following chemical reaction  molybdenum cofactor + L-cysteine + 2 H+ formula_1 thio-molybdenum cofactor + L-alanine + H2O This enzyme contains pyridoxal phosphate. 
Cofactors were discovered by Arthur Harden and William Young in 1906, when they found that the rate of alcoholic fermentation in unboiled yeast extracts increased when boiled yeast extract was added.
A few years after, Hans von Euler-Chelpin identified the cofactor in the boiled extract as NAD+.
Other cofactors, such as ATP and coenzyme A, were discovered later in the 1900s.
The mechanism of cofactor activity was discovered when, Otto Heinrich Warburg determined in 1936 that NAD+ functioned as an electron acceptor.
Well after these initial discoveries, scientists began to realize that the manipulation of cofactor concentrations could be used as tools for the improvement of metabolic pathways.
An important group of organic cofactors is the family of molecules referred to as vitamins.
Vitamin B12 (cobalamin), for example, plays a crucial role in the human body, while coenzyme B12, its derivative, is found in the metabolisms of every type of cell in our bodies.
Its presence affects the synthesis and regulation of cellular DNA as well as taking part in fatty acid synthesis and energy production.
Cofactors are required by many important metabolic pathways, and it is possible for the concentrations of a single type of cofactor to affect the fluxes of many different pathways .
Minerals and metallic ions that organisms uptake through their diet provide prime examples of inorganic cofactors.
For instance Zn2+ is needed to assist the enzyme carbonic anhydrase as it converts carbon dioxide and water to bicarbonate and protons.
A widely recognized mineral that acts as a cofactor is iron, which is essential for the proper function of hemoglobin, the oxygen transporting protein found in red blood cells.
This example in particular highlights the importance of cofactors in animal metabolism. 
 and coenzymes.
Some enzymes do not need any additional components to show full activity.
However, others require non-protein molecules called cofactors to be bound for activity.
Cofactors can be either inorganic (e.g., metal ions and iron-sulfur clusters) or organic compounds (e.g., flavin and heme).
Organic cofactors can be either prosthetic groups, which are tightly bound to an enzyme, or coenzymes, which are released from the enzyme's active site during the reaction.
Coenzymes include NADH, NADPH and adenosine triphosphate.
These molecules transfer chemical groups between enzymes.
An example of an enzyme that contains a cofactor is carbonic anhydrase, and is shown in the ribbon diagram above with a zinc cofactor bound as part of its active site.
These tightly bound molecules are usually found in the active site and are involved in catalysis.
For example, flavin and heme cofactors are often involved in redox reactions.
Enzymes that require a cofactor but do not have one bound are called "apoenzymes" or "apoproteins".
An apoenzyme together with its cofactor(s) is called a "holoenzyme" (this is the active form).
Most cofactors are not covalently attached to an enzyme, but are very tightly bound.
However, organic prosthetic groups can be covalently bound (e.g., biotin in the enzyme pyruvate carboxylase).
The term "holoenzyme" can also be applied to enzymes that contain multiple protein subunits, such as the DNA polymerases; here the holoenzyme is the complete complex containing all the subunits needed for activity.