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biological oxidation
Mind map of biological oxidation. The process of oxidation and decomposition of chemical substances in living organisms is called biological oxidation. (Mainly refers to the oxidation and decomposition process of the three major nutrients: sugar, fat, and protein.)
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biological oxidation
- bacteria
This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
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biological oxidation
Mitochondrial oxidative system and respiratory chain
Biological oxidation: The process of oxidation and decomposition of chemical substances in living organisms is called biological oxidation. (Mainly refers to the oxidation and decomposition process of the three major nutrients: sugar, fat, and protein.)
Features: Enzyme catalysis is required, and it is completed step by step.
Microsomal oxidation system: The oxidation reactions that occur in microsomes, endoplasmic reticulum, etc. are mainly oxidative modification and transformation of substrates, without the generation of ATP.
The main function of the mitochondrial oxidation system is to provide energy to the body, including heat energy, ATP, etc.
Features: The reaction is mild, requires enzymes, and requires a variety of components capable of transferring hydrogen and electrons to participate in the redox reaction.
The mitochondrial oxidative system contains multiple components that transport hydrogen and electrons.
Nicotinamide adenine nucleotides transport hydrogen and electricity.
electron transmitter
direct transfer of electrons
Transfer electrons in the form of hydrogen atoms
Functional group: the change between pentavalent nitrogen and trivalent nitrogen in the aromatic ring.
Water-soluble coenzymes or prosthetic groups: NAD /NADH NADP /NADPH
Flavin nucleotide derivatives transfer hydrogen and electrons
Functional group:isoalloxazine ring
Water-soluble coenzymes or prosthetic groups: FAD/FADH2 FMN/FMNH2
The organic compound ubiquinone transports hydrogen and electrons.
Ubiquinone, also known as coenzyme Q, is a fat-soluble quinone compound.
Q in the human body is a side chain connected by 10 isoprene units, represented by Q10.
The hydrophobic nature of Q allows it to diffuse freely in the inner mitochondrial membrane.
Q can carry out the transfer of double and single electrons.
Iron-sulfur proteins and cytochrome proteins transport electrons
Cytochromes are a type of protein containing heme-like prosthetic groups.
Cytochrome proteins function as single electron transporters through the iron ions in the prosthetic group heme
Protein complexes with the ability to transfer electrons form the respiratory chain
respiratory chain
Definition: Located on the inner membrane of the mitochondria, it is composed of a series of enzyme complexes with electron transfer functions arranged in a certain order. It can transfer the hydrogen taken off by the metabolites, or the electrons taken off by the metabolites, to oxygen to generate water. reaction chain.
It is mainly composed of four protein complexes located on the inner mitochondrial membrane. Complexes I, II, III and IV respectively
Each complex is composed of multiple enzyme proteins, metal ions, coenzymes or prosthetic groups.
The respiratory chain is accompanied by the transmembrane transport of hydrogen ions during the transfer of electrons.
Complex I transfers electrons from NADH to ubiquinone
Complex I is also called NADH-Q reductase or NADH dehydrogenase
Function: Accept electrons from NADH and transfer them to Q
Complex 1 is a transmembrane protein composed of flavoprotein, iron-sulfur protein, etc., and is in an "L" shape.
The process of transferring electrons: NADH→FMN→Fe-S→Q
With proton pump function.
Complex II transfers electrons from succinate to ubiquinone.
Complex II is succinate-ubiquinone reductase.
Function: is to pass electronic city from succinic acid to Q
The process of transferring electrons: succinic acid → FAD → Fe-S → Q
No proton pump function
Complex III transfers electrons from reduced ubiquinone to cytochrome c
Complex III also known as ubiquinone-cytochrome c reductase
Function: Accept electrons from QH2 and pass them to CytC
Human complex III consists of Cytb, Cytc1 and iron-sulfur proteins. Forms a dimer, pear-shaped
The process of transferring electrons: (Q cycle) QH2→Cytb→Fe-S→Cytc1→Cytc
With proton pump function
Cytc is the only water-soluble globular protein in the respiratory chain.
Complex IV transfers electrons from cytochrome c to oxygen
Complex IV also known as cytochrome c oxidase
Function: Accept electrons from reduced Cytc and transfer them to oxygen to generate water
The process of transferring electrons: Cytc→CuA→Cyta→Cyta3-CuB→O2
With proton pump function
NADH and FADH2 are electron donors in the respiratory chain
A chain called NADH, with NADH as the electron donor, starts from NAFH and reduces oxygen to generate water: NADH→Complex I→Q→Complex III→Cytc→Complex IV→Q2
The other is called the FADH2 respiratory chain, also called the succinic acid oxidation respiratory chain. FADH2 is used as an electron donor and passes through complex II to oxygen to generate water: succinic acid → complex II → Q → complex III → Cytc → complex IV→O2
Oxidative phosphorylation and ATP production
There are two ways to generate ATP
One is coupled with a high-energy bond hydrolysis reaction to directly transfer the energy of high-energy metabolites to ADP to generate ATP. This process is called substrate-level phosphorylation.
90% of ATP in the human body is produced by oxidative phosphorylation in mitochondria
The oxidative phosphorylation coupling site is within complexes I, II, and IV.
P/O
It refers to the number of moles of phosphoric acid required for every 1/2 mole of oxygen consumed during oxidative phosphorylation and the number of moles of ATP that can be synthesized.
The two key processes are: one is electron transfer, and the other is using the energy released during the electron transfer process to generate ATP, so that the energy can be stored through ATP for use by the body.
free energy change
The proton pump function of the respiratory chain protein complex forms a proton gradient on both sides of the inner mitochondrial membrane to store part of the energy released during the electron transfer process.
The oxidative phosphorylation coupling mechanism generates a proton gradient across the inner mitochondrial membrane
The proton concentration, positive charge on the cytoplasmic side of the mitochondria is much higher than the mechanism.
Protons flow back along the concentration gradient to release energy for the synthesis of ATP
ATP and enzymes are mushroom-like structures composed of multi-proteins, containing F1 (the hydrophilic part F1 represents the first identified factor related to oxidative phosphorylation.) and F0 (the hydrophobic part, F0 represents oligomycin sensitivity.) functional domain.
F1 mainly consists of α3, 3β, γδε subunit complex and oligomycin-sensitive protein.
Its function is to catalyze the synthesis of ATP, and it is easily combined with oligomycin and loses its activity.
You are composed of hydrophobic a, b2, c9~12 subunits in the inner mitochondrial membrane, forming a proton channel across the inner membrane.
Functions as a channel for protons to flow back to the matrix.
The ATP synthase rotor circulates once to generate three molecules of ATP.
ATP plays a central role in energy metabolism.
Features
1. Cellular biological macromolecular systems are mostly maintained through non-covalent bonds with weak bond energy and cannot withstand chemical processes that increase energy or release large amounts of energy. Therefore, metabolic reactions proceed in sequence, and energy is gradually gained and lost.
2. Organisms cannot directly utilize the chemical energy of nutrients and need to convert it into an energy form that cells can utilize, such as the chemical energy of ATP.
ATP is a high-energy phosphate compound that can directly provide energy for various physiological activities of cells. The so-called high-energy phosphate compounds refer to those compounds containing phosphate groups that can release large free energy when hydrolyzed.
ATP is an important molecule for energy capture and release utilization
ATP is the most important high-energy phosphate compound in the body and is a form of energy that cells can directly utilize.
The most important significance of ATP is that it releases a large amount of free energy through its hydrolysis. When coupled with reactions that require energy supply, it can promote the completion of these reactions under physiological conditions.
Energy supply method
Hydrolysis of high-energy phosphate bonds releases energy.
group transfer
ATP is central to energy transfer and the interconversion of nucleotides.
The adenylate kinase present in cells can catalyze the interconversion of ATP, ADP, and AMP.
ATP provides energy by transferring its own radicals.
Creatine phosphate is also a high-energy compound that stores energy
The role of ATP synthase: The proton driving force generated by the electron transfer of ATP synthase in the inner mitochondrial membrane promotes the return of protons through the ion channel of ATP synthase, and the released energy is used to generate ATP.
Other oxidation and antioxidant systems
There are also other oxidative systems in cells, which are mainly involved in the biological oxidation of substances.
There is a single electron transfer process in the mitochondrial respiratory chain.
Microsomal cytochrome P450 monooxygenase catalyzes the hydroxylation of substrate molecules
Mechanism: One oxygen atom in the catalytic oxygen molecule is added to the substrate molecule for strengthening, and the other oxygen atom is reduced to water by NADPH H.
Cytochrome P450 monooxygenase is also called mixed function oxidase or hydroxylase.
Function
1. Involved in the production of steroids, hormones, etc.
2. Biotransformation of drugs and poisons
3 Hydroxylate the substrate
Monooxygenases are most abundant in microsomes of the liver and adrenal glands and are the most complex enzymes with hundreds of isoenzymes.
The mitochondrial respiratory chain can also produce reactive oxygen species
Reactive oxygen species: oxygen-containing molecules that have not been completely reduced and are much more oxidizing than oxygen
The mitochondrial respiratory chain is the main step in producing ROS.
ROS is mainly generated from the Q cycle in complex I and complex III. QH can directly leak a single electron to oxygen to generate·O2
Pathological processes such as bacterial infection, tissue hypoxia, ionizing radiation, smoking, drugs and other foreign factors can also cause cells to produce large amounts of ROS.
The antioxidant enzyme system has the function of scavenging reactive oxygen species.
Catalase mainly exists in peroxisomes, and cytoplasmic microsomes contain 4 heme prosthetic groups. It has strong catalytic activity and can catalyze the conversion of more than 40,000 substrate molecules into products per second.
Glutathione peroxidase is also an indispensable enzyme in the body to prevent ROS damage.
Protect biofilm and hemoglobin
Other small molecule free radical scavengers in the body include vitamin C, vitamin E, β-carotene, etc., which together with the antioxidant enzymes in the body form the human body’s antioxidant system.
Factors affecting oxidative phosphorylation
The amount of ATP generated mainly depends on the rate of oxidative phosphorylation.
The body regulates ATP synthesis by regulating the rate of oxidative phosphorylation according to its own energy needs.
Energy status in the body regulates the rate of oxidative phosphorylation.
The concentration of ATP in cells and the ratio of ATP/ADP can quickly sense changes in the body's energy status.
The relative concentrations of ATP and ADP also regulate glycolysis and the tricarboxylic acid cycle pathway to meet the needs of oxidative phosphorylation for NADH and FADH2.
Inhibitors block the oxidative phosphorylation process.
Inhibitors block any link in the electron transport chain or inhibit the phosphorylation process of ADP
Respiratory chain inhibitors block the electron transport process.
Rotenone, piezomycin A, and amobarbital inhibit complex 1
Carboxin is a complex II inhibitor
Antimycin A is an inhibitor of complex III
CN-, N3- are inhibitors of complex IV
Uncoupling agents block the phosphorylation process of ADP.
The uncoupling agent can separate the coupling of oxidation and phosphorylation, and electrons can be transferred normally along the respiratory chain, but the established proton electrochemical gradient is destroyed and cannot drive ATP synthase to synthesize ATP.
The body also has endogenous uncoupling agents that prevent hydrogen ions from flowing back to the mitochondrial matrix through other pathways instead of passing through ATP synthase, thus inhibiting ATP synthesis.
The inner mitochondrial membrane of brown adipose tissue is rich in a special protein called uncoupling protein 1, which is a tissue that produces heat and protects against cold.
ATP synthase inhibitors inhibit both electron transport and ATP production
Thyroid hormones promote oxidative phosphorylation and thermogenesis
Mitochondrial DNA mutations affect oxidative phosphorylation function.
Functional proteins of mitochondria are mainly encoded by genes in the nucleus.
Hereditary mt DNA diseases are mostly maternally inherited
Selective coordinated transport of oxidative phosphorylation-related metabolites across the inner mitochondrial membrane
The outer membrane has high permeability to substances and low selectivity: it mainly depends on the transport of various substances by different transport proteins in the inner membrane.
NADH in the cytoplasm enters the mitochondrial respiratory chain through a shuttle mechanism
Alpha-glycerol phosphate shuttle.
Cytoplasmic NADH in brain and skeletal muscle cells mainly enters the mitochondrial respiratory chain for oxidation through this shuttle mechanism.
1 molecule of NADH can therefore be shuttled to produce 1.5 molecules of ATP
Malate-aspartate shuttle
This mechanism is mainly used in liver, kidney and cardiomyocytes to transport cytoplasmic NADH to the mitochondrial respiratory chain.
NADH H entering the mechanism is oxidized through the respiratory chain to generate 2.5 molecules of ATP.
NADH cannot freely pass through the mitochondrial inner membrane and must enter the mitochondrial respiratory chain through a shuttle mechanism before it can be oxidized.
ATP-ADP translocase coordinates the transport of ADP and ATP into and out of mitochondria
In tissues that consume a lot of energy, such as cardiac muscle and skeletal muscle, there is a creatine kinase isoenzyme in the mitochondrial intermembrane space.
Selective coordinated transport across the inner mitochondrial membrane is essential for normal transport of oxidative phosphorylation