Biologically important heterocycles
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Biologically important heterocycles. Alice Skoumalová. Heme complexed with protein in hemoglobin 4 pyrrole rings coordinated with Fe 2+ side chains: methyl, propionyl, vinyl carries oxygen to the tissues. Bilirubin degradation product of heme (cleavage and reduction)

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Biologically important heterocycles

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Biologically important heterocycles

Biologically important heterocycles

Alice Skoumalová


Biologically important heterocycles

  • Heme

  • complexed with protein in hemoglobin

  • 4 pyrrole rings coordinated with Fe2+

  • side chains: methyl, propionyl, vinyl

  • carries oxygen to the tissues

  • Bilirubin

  • degradation product of heme (cleavage and reduction)

  • excreted in the bile

  • jaundice


Biologically important heterocycles

  • Tryptophan

  • an amino acid (serotonin and melatonin precursor)

  • Serotonin

  • a neurotransmitter (mood control)

  • many antidepressant drugs increase the level of serotonin in the brain

  • Melatonin

  • a hormone (produced in response to the light-dark cycle → regulates circadian rhythms)

  • an antioxidant → protective effects


Biologically important heterocycles

  • Histidine

  • an amino acid (histamine precursor)

  • Histamine

  • a neurotransmitter (the major mediator of the allergic response → vasodilation, bronchoconstriction)

  • antihistamines (block histamine from binding to its receptor)

  • Biotin (vit. H)

  • in liver, egg yolk, yeast products, legumes, nuts

  • function: carboxylation (the coenzyme of the carboxylases)


Biologically important heterocycles

  • Thiamine (vit. B1)

  • contains two heterocyclic rings

  • in grain, yeast products, pork

  • its deficiency (beriberi → neurological disturbances, cardiac insufficiency, and muscular atrophy)

  • function: oxidative decarboxylation

  • Tocopherol (vit. E)

  • in cereals, liver, eggs, seed oil

  • function: antioxidant in membranes


Biologically important heterocycles

  • Nicotinamide (niacin)

  • in meat, yeast products, fruit, vegetables

  • its deficiency (pellagra → skin damage, digestive disturbances, depression)

  • function: in the coenzymes NADH and NADPH (dehydrogenases)

NAD+

NADH

  • Pyridoxal (vit. B6)

  • in meat, vegetables, grain products

  • function: the coenzyme in the amino acid metabolism


Biologically important heterocycles

  • Nucleotide bases derived from pyrimidine

  • in nucleic acids

Cytosine

Uracil

Thymine

(in both RNA and DNA)

(in RNA)

(in DNA)

  • a nucleic acid base is N-glycosidically linked to ribose or 2-deoxyribose

  • the sugar is esterified with phosphoric acid


Biologically important heterocycles

  • Nucleotide bases derived from purine

  • in nucleic acids , ATP, NADP, FAD, CoA

  • degradation of purine nucleotides → uric acid (excreted)

Guanine

Adenine

Uric acid

(in both RNA and DNA)

(in both RNA and DNA)

anhydride bonds

an ester bond

  • the most important form of chemical energy in cells

ATP


Biologically important heterocycles

  • Folic acid

  • in fresh green vegetables, liver

  • its deficiency (megaloblastic anemia)

  • function: coenzyme in C1 metabolism (nucleotide biosynthesis)

  • Riboflavin

  • in milk, eggs

  • function: in the coenzymes FMN and FAD (oxidation and reduction)

riboflavin

FAD

FADH2


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