instance_of protoporphyrin ix
Catalase is a common ___MASK83___ found in nearly all living organisms exposed to oxygen ( such as bacteria , plants , and animals ). It catalyzes the ___MASK52___ of hydrogen peroxide to ___MASK82___ and oxygen . It is a very important ___MASK83___ in protecting the cell from oxidative damage by reactive oxygen species ( ROS ). Likewise , catalase has one of the highest turnover numbers of all enzymes ; one catalase ___MASK8___ can convert millions of hydrogen peroxide molecules to ___MASK82___ and oxygen each second . Porphyrins are a ___MASK21___ of heterocyclic macrocycle organic compounds , composed of ___MASK22___ modified pyrrole subunits interconnected at their  carbon atoms via methine bridges (= CH ). The parent porphyrin is porphin , and substituted porphines are called porphyrins . The porphyrin ___MASK94___ ___MASK28___ is aromatic , with a total of 26 electrons in the conjugated ___MASK53___ . Various analyses indicate that not all atoms of the ___MASK94___ are involved equally in the conjugation or that the ___MASK8___ ' s overall nature is substantially based on several smaller conjugated systems . One result of the large conjugated ___MASK53___ is that porphyrin molecules typically have very intense absorption bands in the visible region and may be deeply colored ; the name " porphyrin " comes from the Greek word  (" porphyra "), meaning " purple ". A macrocycle is , as defined by IUPAC , " a cyclic macromolecule or a macromolecular cyclic portion of a ___MASK8___ ". In the chemical literature , macrocycles varyingly include molecules containing rings of 8 or more atoms , or 12 or more atoms . Well - known examples are the group of drugs known as macrolides . The IUPAC definition notes that a " cyclic macromolecule has no end - groups but may nevertheless be regarded as a chain ", and that "" macrocycle " is sometimes used [ in the literature ] for molecules of low relative molecular mass that are not considered macromolecules . Many macrocycles are employed as macrocyclic ligands . Porphin , sometimes spelled porphine , is the parent ___MASK37___ for types of biochemically significant compounds called porphyrins . The chemical formula of porphin is CHN . Porphin is an organic compound that is aromatic and heterocyclic since its chemical structure , shown at right , essentially consists of four pyrrole rings joined together by four methine (= CH ) groups to form a larger macrocycle ring . The compound itself is a solid . Enzymes are macromolecular biological catalysts . Enzymes accelerate , or catalyze , ___MASK75___ reactions . The molecules at the beginning of the process upon which enzymes ___MASK49___ act are called substrates and the ___MASK83___ converts these into different molecules , called products . Almost all metabolic processes in the ___MASK10___ need enzymes in ___MASK31___ to occur at rates fast enough to sustain life . The set of enzymes made in a ___MASK10___ determines which metabolic pathways occur in that ___MASK10___ . The study of enzymes is called " enzymology ". Zinc protoporphyrin ( ZPP ) is a compound found in red blood cells when heme ___MASK100___ is inhibited by lead and / or by lack of iron . Heme or haem ( from Greek " haima " meaning blood ) is a cofactor consisting of an Fe ( ferrous ) ___MASK56___ contained in the centre of a heterocyclic macrocycle ___MASK68___ called a porphyrin , made up of four pyrrolic groups joined together by methine bridges . Not all porphyrins contain iron , but a substantial fraction of porphyrin - containing metalloproteins have heme as their prosthetic group ; these are known as hemoproteins . Hemes are most commonly recognized as components of hemoglobin , the red pigment in blood , but are also found in a number of other biologically important hemoproteins such as myoglobin , cytochrome , catalase , heme peroxidase , and endothelial nitric oxide synthase . In chemistry , a conjugated ___MASK53___ of connected p - orbitals with delocalized electrons in molecules with alternating ___MASK30___ and multiple bonds , which in general may lower the overall energy of the ___MASK8___ and increase stability . Lone pairs , radicals or carbenium ions may be part of the ___MASK53___ . The compound may be cyclic , acyclic , linear or mixed . A ___MASK27___ is a locus ( or region ) of DNA which is made up of nucleotides and is the molecular unit of heredity . The transmission of genes to an ___MASK77___ ' s offspring is the basis of the inheritance of phenotypic traits . Most biological traits are under the influence of polygenes ( many different genes ) as well as ___MASK27___  environment interactions . Some genetic traits are instantly visible , such as eye colour or number of limbs , and some are not , such as blood type , risk for specific diseases , or the thousands of basic biochemical processes that comprise life . Myoglobin ( ___MASK7___ Mb or MB ) is an iron - and oxygen - binding protein found in the muscle tissue of vertebrates in general and in almost all mammals . It is related to hemoglobin , which is the iron - and oxygen - binding protein in blood , specifically in the red blood cells . In humans , myoglobin is only found in the bloodstream after muscle injury . It is an abnormal finding , and can be diagnostically relevant when found in blood . Myoglobin is the primary oxygen - carrying ___MASK2___ of muscle tissues . High concentrations of myoglobin in muscle cells allow organisms to hold their breath for a longer period of ___MASK34___ . Diving mammals such as whales and seals have muscles with particularly high abundance of myoglobin . Myoglobin is found in Type I muscle , Type II A and Type II B , but most texts consider myoglobin not to be found in smooth muscle . Protoporphyrinogen oxidase is an ___MASK83___ that in humans is encoded by the " PPOX " ___MASK27___ . An ___MASK56___ is an atom or a ___MASK8___ in which the total number of electrons is not equal to the total number of protons , giving the atom or ___MASK8___ a net positive or negative electrical charge . Ions can be created , by either chemical or physical means , via ionization . Protoporphyrin IX , in the ___MASK61___ of porphyrin , is created by the ___MASK83___ protoporphyrinogen oxidase . Hemoglobin ; also spelled haemoglobin ( United Kingdom spelling ) and abbreviated Hb or Hgb , is the iron - containing oxygen - ___MASK54___ ___MASK66___ in the red blood cells of all vertebrates ( with the exception of the ___MASK62___ family Channichthyidae ) as well as the tissues of some invertebrates . Hemoglobin in the blood carries oxygen from the respiratory organs ( lungs or gills ) to the rest of the body ( i . e . the tissues ). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the ___MASK77___ in the process called metabolism . An ___MASK68___ is virtually any ___MASK37___ that contains carbon , although a consensus definition remains elusive and likely arbitrary . Organic compounds are rare terrestrially , but of central importance because all known life is based on organic compounds . The most basic petrochemicals are considered the building blocks of organic chemistry . Protoporphyrins are tetrapyrroles containing the following ___MASK1___ chains : Protoporphyrin IX is a biochemical widely used as a carrier ___MASK8___ for divalent cations . Together with iron ( Fe 2 +) the body of the heme - group of hemoglobin , myoglobin and many other heme - containing enzymes like cytochrome c and catalase are formed . Complexed with magnesium - ions ( Mg 2 +) the main part of the Chlorophylls are formed . Complexed with zinc - ions ( Zn 2 +) it forms Zinc protoporphyrin . In organic chemistry and biochemistry , a ___MASK1___ ___MASK25___ is a chemical group that is attached to a core part of the ___MASK8___ called " main ___MASK25___ " or backbone . A ___MASK1___ ___MASK25___ is also known as a pendant ___MASK25___ , but a pendant group ( ___MASK1___ group ) has a different definition . Pyrrole is a heterocyclic aromatic ___MASK68___ , a five - membered ring with the formula CHNH . It is a colorless volatile liquid that darkens readily upon exposure to air . Substituted derivatives are also called pyrroles , e . g ., " N "- methylpyrrole , CHNCH . Porphobilinogen , a trisubstituted pyrrole , is the biosynthetic precursor to many natural products such as heme .