Walt Balcavage Walt Balcavage 06/27/22 06/27/22 Introduction: • Review of e - transport and H + pumps. • Structure and function of ATP synthase. • Quantitation of Chemiosmotic Potential. • ADP regulation of respiratory metabolism. • Chemical/morphologic events of respiration. • Metabolite pumps of inner mitochondrial membrane. • The Ca ++ pump, a key mitochondrial function. • Spectral properties of heme proteins. • Distinguish between Oxidases and Oxygenases • The role of Oxygen free radicals in tissues and mechanisms that protect against tissue damage
Transcript
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Introduction:• Review of e- transport and H+ pumps.
• Structure and function of ATP synthase.
• Quantitation of Chemiosmotic Potential.
• ADP regulation of respiratory metabolism.
• Chemical/morphologic events of respiration.
• Metabolite pumps of inner mitochondrial membrane.
• The Ca++ pump, a key mitochondrial function.
• Spectral properties of heme proteins.
• Distinguish between Oxidases and Oxygenases
• The role of Oxygen free radicals in tissues and mechanisms that protect against tissue damage
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Key issues revisited:
1. e- transport results in: a. increased transmembrane [H+]. Hi H+ outside. b. increased transmembrane V (+ outside).
2. Transformation of H+ energy into ATP energy requires: a. Intact membrane b. Transmembrane proton driven ATP synthase c. ADP and inorganic phosphate
IComplex
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ATP Synthase is very large and complexATP Synthase is very large and complex
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Quantification of the Chemiosmotic Potential
• The 1st term is also known as the proton motive force (pmf).• In the 2nd term is transmembrane potential in Volts.• The 3rd term represents difference in [H+] across the membrane• Any combination of values for membrane potential and pH difference that
sum to more than the free energy of synthesizing ATP will lead to ATP synthesis.
1. Free energy available from a concentration difference across a membrane:
2. In the special case where the concentration difference is due that of H+:
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Metabolic Regulation by Mass Action PrincipalsMetabolic Regulation by Mass Action Principals
1. Normally the rate of electron transport is set by the available ADP, i.e., the energy charge of the cell regulates the process.
2. When ADP is limiting: a. Flow thru ATPase slows. b. H+ accumulates in cytosol. c. proton pumps become limited by hi pmf. d. electron transport slows because pumps are slowed e. the rate of O2 utilization is minimized and reduced substrates are conserved .
E.E.T.T.S.S.
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RESPIRATORY CONTROL:RESPIRATORY CONTROL:Regulation of respiration by presence/absence of ADPRegulation of respiration by presence/absence of ADP
state 4 (resting respiration)
Electron micrographsillustrating morphological changes mitochondria undergo as they pass from resting state (top, orthodox form)to active state (bottom. condensed form)
state 3 (active respiration)
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Other inner membrane carrier systemsOther inner membrane carrier systemsMatrix SideCytosolic Side
AntiportAntiport
SymportSymport
AntiportAntiport
AntiportAntiport
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Calcium Transport, a preeminent regulator of cell Calcium Transport, a preeminent regulator of cell metabolismmetabolism
• The mitochondrial calcium carrier is one of the most active carriers of the mitochondrial inner membrane.
• Calcium transport is driven by the pmf generated by electron transport or ATP hydrolysis.
• The mitochondrial calcium carrier is an important reservoir of cellular calcium, sequestering and releasing Ca++ in response to a variety of signals, e.g., depolarizing voltage in muscle cells, IP3 in hormone sensitive cells.
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Key Spectral Properties of Heme ProteinsKey Spectral Properties of Heme Proteins
Pure Cytochrome Pure Cytochrome ccMitochondrial suspension:Mitochondrial suspension:(reduced - oxidized)(reduced - oxidized)
As apparent from the above, the red-uced form (ferrous) of cyt. c is more absorbing than is the oxidized form.
Similar spectral effects are observedwhen mitochondria are made reduced.All the cytochromes are more absorb-ing than cytochromes in aerobic or oxidized mitochondria.
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Comparison of oxidases & oxygenases
• Oxidases, (cyt. a+a3 oxidase) incorporate molecular oxygen only into water
• Dioxygenases incorporate oxygen only into organic molecule, (inter or intra molecular)
• Monooxygenase incorporate one atom of oxygen from O2 into water and one atom of oxygen into an organic molecule. Because of this dual use of oxygen these oxygenases are often called “mixed function oxygenases”. These enzymes are highly inducible, they act to detoxify and make soluble many otherwise deleterious compounds and they all contain the heme protein known as cytochrome P450.
Oxidase2SH2 + O2 2S (ox) + 2H2O
2SH2 + R + O2 2S (ox) + H2O + ROH
2SH2 + 2R (R R) + O2 2S (ox) + 2ROH ( ROH ROH)
Monooxygenase
Dioxygenase
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