The document discusses the heme catabolism and biosynthesis of hemoglobin, detailing the structures of heme and globin, and their roles in oxygen transport and regulation of acid-base balance in blood. It also covers the functions and structures of nucleic acids, including DNA and RNA, in protein synthesis, explaining the differences between them and the types of RNA involved in the process. Key objectives are to understand the impact of these components on cellular functions and their biosynthesis mechanisms.

1. 1
Heme catabolism and
Heme Degradation Pathway
By,
Mr. Abhijit Bhoyar
Associate Professor

2. Specific Learning objectives
At the end of the lecture students will be able to
• Describe the heme structure
• Explain the structure & function of hemoglobin
• Discuss the role of nucleic acids
• Illustrate biosynthesis of proteins

3. Introduction
• Hemoglobin – red coloring matter of blood Present in RBC
• Conjugated protein – heme & globin
• Molecular weight = 64,450
• Can combine with O
• Transport of O within blood

4. • Combination of two structures
• Structure of Heme
• Structure of globin – protein
Structure of Hemoglobin

5. Structure of Heme
• An iron porphyrin – cyclic compound
• Porphyrin = tetra pyrrole ring like structure
• 4 pyrrole rings are linked through methylene or
methylidene bridges
• Outer C atoms are not linked and numbered as 1-8

6. Structure of Heme
• Iron in the ferrous state is bound to nitrogen atom of the pyrrole
rings
Structure of Globin
• Globin is protein part of hemoglobin
• Composed of 4 parallel layers of closely packed polypeptide chians
• 2 chains have identical AA composition of 141 AA
• Remaining 2 have 146 AA each
• Total no. of AA in globin is 574

7. Structure of Globin
• Alpha chains 2 chain
• Beta chains 2 chain
• Hb molecule & sub-units contain hydrophobic AA
internally & hydrophyllic AA on their surfaces
• The resulting heme pockets provide for entry of O2

8. Properties of Hemoglobin
• Oxyhemoglobin – Hb + O2 - Transport of O to different parts of
the body
• Formaton of Carbamino compound – Hb+C O2
• Reaction with CO – Forms Carboxy-hemoglobin – prevents
formation of oxyhemoglobin – dangerous to inhale even small
amounts of CO
• Buffering Action – Hb + O2

9. • Buffering Action – 1 mole of Hb contains 35 histidine
residues – exerts buffering action – Hb play imp in
regulating acid-base balance of blood
• Formation of methemoglobin – by oxidaton of Hb – cannot
carry O – methemoglobin is reduced to Hb by Vit. C

10. Biosynthesis of hemoglobin
• In bone marrow – erythroid cell during development of
erythrocyte
• Iron in Ferrous state incorporated into protoporphyrin
to form Heme
• Heme attached to newly formed Globin = Hb

11. Biosynthesis of Proteins
• 3 phases
1)Initiation
• Dissociation of ribosomes
• Formation of 40s preinitiation complex
• Formation of 40s initiation complex
• Formation of 80s initiation complex

12. 2)Elongation
• Binding of Aminoacyl - tRNA to A siter
• Peptide bond formation
• Translocation
3)Termination

13. Role of Nucleic Acids in Biosynthesis of
proteins
2 types of NA
• DNA
• Deoxyribonucleic acid
• RNA
• Ribonucleic acid

14. Functions of Nucleic acids
• DNA - chemical basis for heredity
• Reserve bank of genetic information
• Responsible for maintaining the identity of different species
• Control every cellular function
• Organized into genes – the fundamental units of genetic
information
• Control protein synthesis through mediation of RNA

15. Components of Nucleic acids
• NA – polymers of nucleotides
• Nucleotides – composed of a nitrogenous base, a
pentose sugar & a phosphate
• A nitrogenous base + a pentose sugar = nucleoside
• Nucleotide = nucleoside + phosphate
• Nitrogenous bases – aromatic, heterocyclic compounds

16. Functions of Nucleotides
• Building blocks of nucleic acids
• Structural components of several coenzymes
• Serve as carriers of high energy intermediates in the
biosynthesis of CHO, lipids & proteins

17. Functions of Nucleotides
• Involved in the energy reactions of the cell – ATP is
energy currency
• As allosteric regulators – control several metabolic
reactions
• Cyclic AMP & Cyclic GMP = second messengers in
hormonal functions

18. Structure of Nucleotides
• Nitrogenous bases – two types
• Purines
• Adenine (A)
• Guanine (G)
• Pyrimidines
• Cytosine (C) found in both DNA & RNA
• Thymine (T) in DNA
• Uracil (U) in RNA

19. Difference between DNA & RNA
DNA
1. Sugar – deoxyribose
2. Pyrimidine – thymine
3. Double stranded
structure
4. Number of Guanine
equals Number of
cytosine = Chargaff’s rule
- obeyed
5. Reservoir of genetic
information
RNA
1. Ribose sugar
2. Pyrimidine – uracil
3. Usually single stranded structure
4. Guanine content is not equal to
cytosine = Chargaff’s rule – not
obeyed
5. Identified by Orcinol color reaction
6. 3 different types – based on cellular
composition
7. Responsible for transfer of genetic
material

20. Types of RNA
• Messenger RNA = mRNA
• Synthesized in nucleus
• Enter the cytoplasm to participate in protein synthesis
• High molecular weight with short half-life
• Transfer RNA = tRNA
• Molecular wt = 25000
• 20 species of tRNA corresponding to 20AA
• Contains 4 arms
• Structure resembles clover leaf

21. • Ribosomal RNA = rRNA
• Ribosomes = factories of protein synthesis
• Play significant role in binding of mRNA to ribosomes
• Responsible for protein synthesis

22. Expected Question
• Essay /Situation Question
• Explain the structure & function of hemoglobin
• Explain Nucleic Acids in Biosynthesis of proteins
• Short Question
• Explain heme and chlorophylls.
• Describe biosynthesis of proteins in the cells and role of
nucleic acids in protein synthesis.
• Defference between DNA&RNA

23. THANK YOU