Why is the conversion of ADP to ATP energetically unfavorable?
Due to the charge repulsion introduced by the third phosphate group on the molecule
If the product of a reaction is of lower free energy than the reactant, the reaction is ________
If the product of a reaction is of higher free energy than the reactant, the reaction is ________
Enzymes catalyze reactions (speed and specificity) by lowering the energy required to reach the ______ _______ of a reaction
Where is the energy for the production of ATP primarily derived from?
From a series of oxidation-reduction reactions
Conversion of sugars, fatty acids, and amino acids to _____ represents the full oxidation of carbon sources.
Muscle likes _____
Liver likes ______
What are some common reducing agents?
What are some common oxidizing agents?
The energetically favorable oxidation of carbon sources is coupled to the energetically unfavorable reduction of NAD+ and FAD+ to _______ and ______, which act as mobile electron carriers.
The net oxidation of glucose (via glycolysis in the cytosol and Krebs cycle in the mitochondria) coupled with reduction of O2 (via the ETC in the mitochondrial inner membrane) results in the production of ____ molecules of ATP
What is the carbon carrier from glycolysis to the Krebs cycle, or from the cytosol to the mitochondria?
For the Krebs cycle to maintain activity, acetyl CoA must be supplied. This is accomplished primarily within the mitochondrial matrix through the conversion of ________ (derived from glycolysis in the cytosol) and __________ (beta-oxidation) to acetyl CoA
Within the Krebs cycle, the two carbons of acetyl CoA are converted to two molecules of ______ .
What is the terminal electron acceptor in the electron transport chain?
As electrons pass through the electron transport chain, they lose electrochemical potential and the energy is utilized to pump protons from the matrix space into the inner mitochondrial space, thus creating the proton gradient for what two things?
Synthesis of ATP
Heat for maintenance of body temperature
The ETC starts with ______ energy NADH and moves to the _______ energy reaction of reducing O2 to H2O
NADH donates electrons to which complex in the ETC?
FADH2 donates electrons to which complex in the ETC?
ATP is synthesized through the action of what enzyme? Where does this enyzme reside, and where does it derive its energy for the production of ATP from?
Inner mitochondrial membrane
Proton gradient generated by the ETC
This refers to O2 consumption when only Krebs cycle intermediates are supplied
State 2 Respiration
Why does oxygen consumption increase when ADP is added to state 2 respiration? What is this called?
Because the proton gradient is being utilized to produce ATP and thus the rate of electron transport and O2 reduction must increase to maintain the proton gradient.
Stage 3 Respiration
Why does the rate of O2 consumption slow upon conversion of ADP to into ATP? What is this called
Slows due to the diminished utilization of the proton gradient and the decreased demand for electron transport
State 4 Respiration
The rate of which respiration state provides an overall indication of ATP synthase, electron transport, and Krebs cycle function?
State 3 Respiration
This state of respiration provides an index of membrane integrity and the rate at which protons leak from the inner mitochondrial membrane space to the matrix in the absence of ATP production
State 4 Respiration
A high rate of this respiration state could indicate that the membrane has been damaged or, as is the case in adipose tissue, protons are transported via uncoupling proteins in an effort to produce heat
State 4 Respiration
What is the ratio of state 3:state 4 respiration referred to as? What does this indicate when it is high? What does it indicate when it is low coupled with a high state 4 respiration rate (and what is it referred to as)?
Respiratory Control Rate (RCR)
Electron transport and ATP synthesis are tightly coupled
Indicative of a high rate of proton leak (referred to as uncoupled)
What does a high ADP/O ratio (ADP consumed relative to oxygen utilization) indicate?
A tight coupling between electron transport and ATP synthesis
Conversion of pyruvate, derived from glycolysis in the cytosol, to acetly CoA, for utilization by the Krebs cycle, is catalyzed by what multienzyme complex, which is within the mitochondrial matrix?
What is the E1 co-enzyme of pyruvate dehydrogenase?
Thiamine Pyrophosphate (TPP)
What is the prosthetic group for E2 (Dihydrolipoyl transacetylase)?
Pyruvate dehydrogenase is a mulienzyme complex. What is E1 classified as?
Pyruvate dehydrogenase is a multienzyme complex. What is E2 classified as?
Pyruvate dehydrogenase is a multienzyme complex. What is E3 classified as?
What are two co-enzymes associated with the E3 enzyme dihydrolipoyl dehydrogenase (of pyruvate dehydrogenase)?
By what two methods is pyruvate dehydrogenase regulated?
It is inhibited by its own product (Acetyle CoA)
By phosphorylation (inhibition) and dephosphorylation (activation)
____ activates (turns on) pyruvate dehydrogenase by activating phosphatase to dephosphorylate the complex
The Krebs cycle is composed of how many enzymes?
What enzyme catalyzes the formation of Citrate from Acetyl CoA + Oxaloacetate in the Krebs cycle? Is this reaction thermodynamically favorable?
Highly Thermodynamically Favorable
Within the Krebs cycle, what enzyme catalyzes the conversion of Citrate to Isocitrate? Is this reaction thermodynamically favorable?
Are thermodynamically favorable reactions highly regulated, or unregulated?
Within the Krebs cycle, what enzyme catalyzes the conversion of Isocitrate to alpha-ketoglutarate? Is this reaction thermodynamically favorable?
Within the Krebs cycle, what enzyme catalyzes the conversion of alpha-Ketoglutarate to Succinyl CoA? Is this reaction thermodynamically favorable?
Within the Krebs cycle, what enzyme catalyzes the conversion of Succinyl CoA to Succinate? What is unique about this step?
Generates GTP or ATP from GDP + Pi (substrate level phosphorylation)
Within the Krebs cycle, what enzyme catalyzes the conversion of Succinate to Fumarate? What is unique about this step?
FAD is oxidized to FADH2, with the electron being donated to complex II of the ETC
Within the Krebs cycle, what enzyme catalyzes the conversion of Fumarate to L- Malate?
Within the Krebs cycle, what enzyme catalyzes the conversion of L- Malate to Oxaloacetate? Is this reaction thermodynamically favorable?
The enzyme responsible for converting L- Malate to Oxaloacetate (Malate Dehydrogenase) is highly endergonic, and thermodynamically unfavorable. How is this chemical reaction driven to completion?
Driven by linking the unfavorable reaction to a favorable one (Citrate Synthase -- first step in Krebs cycle).
What are the four regulation steps of the Krebs cycle?
Entry Point (PDH -- pyruvate dehydrogenase complex)
Exergonic Steps (CS, ISDH, KGDH)
What is the major regulator of the Krebs cycle?
Protons are pumped from the matrix to the intermembrane space at which complexes in the ETC?
Complex I, III, and IV
What co-enzyme serves as the carrier of electrons to complex III?
Ubiquinone (Coenzyme Q)
What is responsible for electron transfer from complexes III to IV?
What is the complex I inhibitor, and where does this occur?
Inhibits between NADH and Q
What is the complex III inhibitor, and where does this occur?
Inhibits between Cyt B and Cyt C1
What are the complex IV inhibitors, and where do they inhibit?
CN or CO
Inhibit between Cyt (a + a3) and O2
When electron flow is blocked, all upstream redox centers should be in the _______ state while downstream of the inhibition components should be ________.
Reduced (electron rich)
Oxidized (electron poor)
Another pathway by which electrons are transferred to the ETC is when the first enzyme in beta-oxidation, ____________, transfers electrons (reduces) to the electron transfer flavoprotein (ETF). The ETF then reduces ETF:Q oxidoreductase which subsequently transfers electrons to coenzyme Q.
Acyl CoA dehydrogenase
_________ formed in the cytosol during glycolysis can also pass electrons directly to coenzyme Q (into the ETC) via the action of ____________.
Glycerol 3-phosphate Dehydrogenase
ATP synthase has numerous subunits that make up two domains, the F0 and F1 domains. The F0 domain is submerged in the lipid bilayer while the F1 domain protrudes into the mitochondrial matrix. Which domain is the site of ATP synthesis?
Uncoupling agents act by carrying electrons from the intermembrane space to the matrix, thus collapsing the proton gradient. What is an example of an uncoupling agent?
2,4 - dinitrophenol
Uncoupling agents in the mitochondria _____ O2 consumption and ______ ATP synthesis. What is this termed?
Uncoupling of Oxidative Phosphorylation
Where are uncoupling proteins particularly abundant, which serves to utilize electron transport to generate heat.
Brown Adipose Tissue
What are the four regulators of Oxidative Phosphorylation?
Thermodynamic: favorable electron transport is limited by unfavorable proton translocation. Thus, the electrical and chemical potential are limited
Acceptor Control Ratio: regulation of availability of ADP relative to ATP in the matrix
Protein Inhibitor IF1 (84 aa): prevents reverse operation of ATP synthase in ischemia.
Thermogenin: uncouples ATP synthesis from oxidation by providing a channel for return of protons to the matrix
Ischemia leads to ____ O2, ____ ATP, _____ pH, and ____ Ca2+. This in turn leads to reprefusion, with ____ free radical generation, which then leads to alterations in mitochondrial function.
Decreased O2Decreased ATP
Increased free radical generation
What are two reasons that pH drops in ischemia?
Glycolysis and Krebs cycle function results in the production of acid (H+)
The ETC consumes H+ resulting in maintenance of pH
Thus, in the absence of O2 metabolic acidosis occurs
When oxygen is limited (such as during strenuous exercise or ischemia) and electron transport activity cannot be maintained, pyruvate is converted to ________ within the cytosol by the enzyme _________ _________.
When the rate of electron transport through the ETC is reduced due to diminished requirements for ATP or when components of the chain are inhibited, the half-life of reduced components of the chain increases as does the likelihood that electrons will interact with O2 resulting in the incomplete reduction of O2 to ________ _______.
Superoxide anion can be converted to hydrogen peroxide through the action of what enzyme? Metal ions can subsequently be oxidized by _______ ______ resulting in the production of hydroxyl radical. These free radical species and pro-oxidants are highly reactive and can cause damage to lipid, protein, DNA, and RNA
Superoxide dismutase (SOD)
Within the mitochondria, what two Krebs cycle enzymes are particularly sensitive to oxidative modification? These have been reported to decline in function during numerous neurodegenerative, neuromuscular, and cardiovascular diseases.
What enzyme is a key regulatory site within the Krebs cycle?