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Bioenergentics & Metabolism 
Mitochondria 
1
Mitochondria Structure & Function 
Generation of metabolic energy is a major activity of all cells 
Two cytoplasmic orga...
Mitochondria 
Mitochondria are 
◦Responsible for most of the useful energy derived from breakdown of carbohydrates and fa...
Structure of Mitochondria 
Mitochondria are surrounded by a double membrane system 
•Consist of inner and outer membrane ...
Mitochondria consist of two aqueous compartments 
Interior – the matrix 
Between the inner and outer membranes – interm...
Outer Membrane 
Porins – integral proteins 
Large internal channel 
 Allows free diffusion of molecules smaller than a...
Mitochondria are positioned near to locations of high energy use i-e synapses in nerve cells, muscle cells 
Continuously...
Endosymbiotic Origin 
Mitochondria contain their own genetic system 
Mitochondria are thought to have evolved from bacte...
Mitochondrial Genome 
Mitochondrial genome are usually circular DNA molecules, like bacteria 
Present in multiple copies...
Contd… 
Smallest mitochondrial genome 
◦Protist: plasmodium falciparum 6kb, codes for only 3 proteins 
Largest mitochond...
Human mitochondrial 16 Kb genome encodes 
◦Circular DNA molecule 
◦Maternal inheritance 
Map 
Origin of replication and...
Mitochondrial Genetics 
Mitochondria use a slightly different genetic code than in prokaryotic and eukaryotic cells 
 Hu...
13
Differences between the universal and Mitochondrial Genetic codes 
Codon 
Universal Code 
Human Mitochondrial code 
UGA 
S...
Mutations in mtDNA 
Mitochondrial DNA can be altered by mutations 
Germ-line mutations in mitochondrial DNA are transmit...
Mitochondrial proteins 
Contain 1000 to 5000 different proteins but nearly half of them remain unidentified (~5% of mamma...
Transport & assembly of matrix proteins 
Pre-sequence, N-terminal 20- 35 a.a target proteins to matrix 
Partially unfold...
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Bioenergentics & Metabolism

Bioenergentics & Metabolism
BS MicroBiology 1st Sem

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Bioenergentics & Metabolism

  1. 1. Bioenergentics & Metabolism Mitochondria 1
  2. 2. Mitochondria Structure & Function Generation of metabolic energy is a major activity of all cells Two cytoplasmic organelles are specifically devoted to energy metabolism and production of ATP •Mitochondria Generates useful energy derived from breakdown of lipids & carbohydrates •Chloroplast Use energy captured from sunlight to generate ATP and the reducing power needed to synthesize carbohydrates from CO2 and H2O Mitochondria Structure & Function 2
  3. 3. Mitochondria Mitochondria are ◦Responsible for most of the useful energy derived from breakdown of carbohydrates and fattyacids Converted to ATP by oxidative phosphorylation Mitochondria are unique among cytosolic organelles in that They contain their own DNA which encodes tRNA, rRNA, and some other mitochondrial proteins Assembly of mitochondria contain •Proteins encoded by their own genome •Proteins encoded by nuclear genome and imported from cytosol Mitochondria Structure & Function 3
  4. 4. Structure of Mitochondria Mitochondria are surrounded by a double membrane system •Consist of inner and outer membrane separated by intermembrane space •Innermembrane form numerous folds (cristae) which extends into matrix •Large surface area •Matrix contains mitochondrial genetic system & enzymes responsible for oxidative metabolism •Houses the machinery for aerobic respiration Mitochondria Structure & Function 4
  5. 5. Mitochondria consist of two aqueous compartments Interior – the matrix Between the inner and outer membranes – intermembrane space Inner Membrane High percentage of proteins(> 70%) Involved in oxidative phosphorylation •Transport of metabolites (pyruvate, fatty acids) Impermeable to most ions and small molecules  a property critical to determining proton gradient that drives oxidative phosphorylation 5 Mitochondria Structure & Function
  6. 6. Outer Membrane Porins – integral proteins Large internal channel  Allows free diffusion of molecules smaller than about 1000 daltons Composition of intermembrane is therefore similar to cytosol with respect to ions and small molecules Mitochondria Structure & Function 6
  7. 7. Mitochondria are positioned near to locations of high energy use i-e synapses in nerve cells, muscle cells Continuously fusing and dividing , remodel the network of mitochondria in cell, and affect function and morphology 7 Mitochondria Structure & Function
  8. 8. Endosymbiotic Origin Mitochondria contain their own genetic system Mitochondria are thought to have evolved from bacteria that developed a symbiotic relationship in which they lived within larger cells (Endosymbiosis) Genomes of living organisms that are similar to mitochondria are that of α-proteobacterium Rickettsia prowazeki It is able to reproduce only in eukaryotic cells But unlike mitochondria it transcribes most of its own genes 8 Mitochondria Structure & Function
  9. 9. Mitochondrial Genome Mitochondrial genome are usually circular DNA molecules, like bacteria Present in multiple copies per organelle Vary considerably in size between different species Genomes of human and most other animal mitochondria are only about 16kb Larger mitochondrial genome are found in yeast (approx 80kb) and plants (more than 200kb) e.g Mitochondrial DNA in Arabidopsis is 367 kb, encodes only 31 proteins 9 Mitochondria Structure & Function
  10. 10. Contd… Smallest mitochondrial genome ◦Protist: plasmodium falciparum 6kb, codes for only 3 proteins Largest mitochondrial genome ◦Protozoan Reclinomonas americana ◦69 kb and contain 67 genes Most present day mitochondrial genome encode ◦ Small number of proteins Mammalian mitochondria (1000 to 5000 different proteins) representing approx 5% of proteins encoded by mammalian genome ◦tRNA, rRNA 10 Mitochondria Structure & Function
  11. 11. Human mitochondrial 16 Kb genome encodes ◦Circular DNA molecule ◦Maternal inheritance Map Origin of replication and transcriptional promoter sequences (D loop) 16sRNA, 12sRNA, 22tRNA 13 proteins (essential for oxidative phosphorylation) Electron transfer chain complexes, including I, III, IV and V 11 Mitochondria Structure & Function The Human Mitochondrial Genome
  12. 12. Mitochondrial Genetics Mitochondria use a slightly different genetic code than in prokaryotic and eukaryotic cells  Human mitochondria encode only 22 tRNAs ,approx 30 different tRNAs are required to translate the universal code according to wobble rule Translational of mitochondrial mRNA is accomplished by extreme form of wobble U in anticodon of tRNA can pair with any of four bases in third codon position of mRNA 12 Mitochondria Structure & Function
  13. 13. 13
  14. 14. Differences between the universal and Mitochondrial Genetic codes Codon Universal Code Human Mitochondrial code UGA Stop Trp AGA Arg Stop AGG Arg Stop AUA IIe Met 14 Mitochondria Structure & Function
  15. 15. Mutations in mtDNA Mitochondrial DNA can be altered by mutations Germ-line mutations in mitochondrial DNA are transmitted from mother •Mutation in tRNA gene Metabolic syndrome; obesity, diabetes •Mutation in gene that encode components of electron transport chain Leber’s hereditary optic neuropathy; blindness •Progressive Mutations in mitochondrial DNA Aging 15
  16. 16. Mitochondrial proteins Contain 1000 to 5000 different proteins but nearly half of them remain unidentified (~5% of mammalian encoded proteins) Mitochondria from different tissues contains different proteins (tissue specific functions) Genes for mitochondrial proteins are in nucleus(95% of mt proteins) Some of these genes were transferred to mitochondria by original prokaryotic ancestor Cytosoloic protein synthesis mt transport All kerb cycle enzymes/ rep/trans/translation Complex because of mt double membrane 16 Mitochondria Structure & Function
  17. 17. Transport & assembly of matrix proteins Pre-sequence, N-terminal 20- 35 a.a target proteins to matrix Partially unfolded by Hsp70 chaperon ◦Prevent aggregation as emerge from free ribosomes Bind to receptors on Tom protein complex(translocase of outer membrane) Bind Tim complex(Translocase of inner membrane) The presequence is cleaved by a matrix protease a mitochondrial Hsp70 binds the polypeptide chain as it crosses the inner membrane, driving further protein translocation. A mitochondrial Hsp60 then facilitates folding of the imported polypeptide within the matrix 17 Mitochondria Structure & Function

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