* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cell Chemistry
Amino acid synthesis wikipedia , lookup
Photosynthesis wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Biosynthesis wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Magnesium transporter wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Genetic code wikipedia , lookup
Metalloprotein wikipedia , lookup
Biochemical cascade wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Microbial metabolism wikipedia , lookup
Signal transduction wikipedia , lookup
Phosphorylation wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Proteolysis wikipedia , lookup
Western blot wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Mitochondrial replacement therapy wikipedia , lookup
Electron transport chain wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Biochemistry wikipedia , lookup
Mitochondrion wikipedia , lookup
Readings and Objectives • Reading – Russell : Chapter 6 – Cooper: Chapter 3, 11 • Objectives • • • • • Sugar metabolism Mitochondrion structure Mitochondrial genome Proteins Mitochondrial function • Krebs cycle • Oxidative Phosphorylation 2 Mitochondria: structure • Generate energy from lipids & carbohydrates • Surrounded by a double-membrane system • The inner membrane has numerous folds (cristae), which extend into the interior (matrix) 3 Mitochondria: dynamic organelles • Outer membrane: permeable to small molecules • Porins, form channels (in o.m.), allows free diffusion of small molecules • Intermembrane space: composition similar to the cytosol • Inner membrane: impermeable to most ions and small molecules • Helps maintain the proton gradient • Mitochondria positioned near locations of high-energy use, ie. synapses in nerve cells, muscle cells • Continually fusing and dividing, remodels the network of mitochondria in the cell, and affects function and morphology 4 Endosymbiotic origin • Mitochondria are thought to have evolved from bacteria that began living inside larger cells (endosymbiosis) • Living organisms that have genomes most similar to the mitochondrial genome are free-living α-proteobacteria 5 See a review paper for endosymbiosis under literature section Mitochondrial genome • Circular DNA 16 kbp, multiple copies • Maternal inheritance Map: • Origin of replication: D-loop • Code for rRNAs, tRNAs, own ribosomes • Encode 13 proteins essential for oxidative phosphorylation – Electron transfer chain complexes, including I, III, IV and V Human Mitochondrial genome map (16 kbp) 6 Mitochondrial: Genetics • mitochondrial genetic code is different from the universal code • U in the tRNA anticodon can pair with any of the four bases in the third codon position of mRNA; thus four codons are recognized by a single tRNA • Some codons specify different amino acids in mitochondria than in the universal code 7 Mitochondrial Proteins • contain 1000 to 1500 different proteins, but nearly half of them remain unidentified • mitochondria from different tissues contain different proteins • Genes for many mitochondrial proteins are in the nucleus (95% of mtProteins) • Some of these genes were transferred to the nucleus from the original prokaryotic ancestor of mitochondria • Cytosolic protein synthesis mit. Transport • All Krebs enzymes, rep/transcrip/translation • Complex because of mito. double membrane 8 Transport and Assembly of Matrix Proteins • Presequences, N-terminal 2535 positively charged a.a. targets proteins to matrix • Partially unfolded by Hsp70 chaperone – Prevent aggregation as emerge from free ribosomes • bind to receptors on Tom protein complex (translocase of outer membrane) – First to Tom20 then Tom5 – To import poreTom40 – Passage , bind intermembrane tail of Tom22 • Bind Tim complex (translocase of inner membrane) – Bind Tim21/Tim50 of Tim23 complex matrix 9 Transport and Assembly of Matrix Proteins In the Matrix • Presequence/Hsp70/Tom44 works as a ratchet • Reversible binding with short hydrophobic amino acids • Sequential ATP hydrolysis • Powers the binding & dissociation of Hsp70 • Might integrate to membrane, or • Protein is pulled into matrix • Matrix processing peptidase (MPP) cleaves presequence • Hsp70 binding assists proper folding 10 Mitochondrial Function • Oxidative catabolism of glucose and fatty acids • The matrix contains the genetic system and enzymes for oxidative metabolism • Pyruvate (from glycolysis) is transported to mitochondria, where its complete oxidation to CO2 yields the bulk of usable energy (ATP) obtained from glucose metabolism 11 Glycolysis • Universal pathway • Glucose starting substrate • sequentially broken down to pyruvate • 10 steps (all enzymes are cytosolic) – Early preparatory steps uses ATP – Later steps produces chemical energy Net yeild: • 2 ATP (4ATP-2ATP) • 2 NADH • 2 Pyruvate 12 Glycolysis Glycolysis provides substrates for mitochondrial Krebs cycle 13 Krebs Cycle • In eukaryotic cells, glycolysis takes place in the cytosol • Pyruvate is then transported into mitochondria, where it is completely oxidized • Pyruvate undergoes oxidative decarboxylation in the presence of coenzyme A (CoA-SH), forming acetyl CoA 14 Krebs Cycle • Acetyl CoA enters the citric acid cycle or Krebs cycle • The 2-carbon acetyl group combines with oxaloacetate (4C) to yield citrate (6 C) • In the remaining reactions, 2 carbons of citrate are completely oxidized to CO2 and oxaloacetate is regenerated All enzymes are in matrix 15 Krebs Cycle • The citric acid cycle completes the oxidation of glucose to six molecules of CO2 • yields one GTP, three NADH, and one reduced flavin adenine dinucleotide (FADH2), which is another electron carrier All enzymes are in matrix 16 Krebs Cycle 17 Electron Transport Chain • High-energy electrons from NADH and FADH2 are transferred through a series of carriers in the membrane • e- carriers organized in ET complexes I, II, III, IV • Low energy electrons from IV carried on O2 +2H+ to form H2O • energy from ETC is used to pump protons to intermembrane space cyt b Coenzyme Q 18 Electron Transport Chain • Electrons from FADH2 are transferred through complex II • Then carried by Coenzyme Q to complex III and IV 19 Proton gradient and Chemiosmotic coupling • proton gradient established across the inner membrane • Chemiosmotic coupling: Energy stored in H+ gradient is coupled to ATP synthesis (Peter Mitchel 1961) 20 Oxidative phosphorylation • protons can cross the membrane only through a protein channel (complex V) • complex V (ATP synthase), has two units, F0 and F1, linked by a slender stalk. • F0 spans the inner membrane and forms a channel through which the protons move • F1 catalyzes the synthesis of ATP 21 Oxidative phosphorylation • flow of protons through F0 drives the rotation of part of F1, which acts as a rotary motor to drive ATP synthesis • Four protons are required to synthesize one ATP • Oxidation of one NADH yields 3 ATP; oxidation of FADH2 yields 2 ATP • Krebs and glycolysis: total 38 ATP per molecule of glucose (ie. 2 pyruvate) 22