Skip to main content

Renin Angiotensin Mechanism.

Electron transport chain (ETC) and its mechanism.

 

Definition:

  • Present in the mitochondria, Electron Transport Chain is a series of compounds where electrons from electron carriers develop a chemical gradient. 

  • It is used for oxidative phosphorylation. 

  • The molecules present in the chain are made up of enzymes that are protein complex or proteins, peptides and much more.

  • Large amounts of ATP are produced here by process of oxidative phosphorylation.

  • The electrons are transferred from electron donor to the electron acceptor leading to the production of ATP

Introduction:

  • The byproducts of most catabolic processes are NADH and [FADH2] which are the reduced form.

  • Metabolic processes use NADH and [FADH2] to transport electrons in the form of hydride ions (H-). 

  • These electrons are passed from NADH or [FADH2] to membrane bound electron carriers which are then passed on to other electron carriers until they are finally given to oxygen resulting in the production of water. 

  • As electrons are passed from one electron carrier to another hydrogen ions are transported into the intermembrane space at three specific points in the chain.

  • It happens in the aerobic environment i.e. in the presence of atmospheric oxygen.

Overview of ETC:

  • A complex could be defined as a structure that comprises a weak protein, molecule or atom that is weakly connected to a protein.

  • As shown in the Figure above, there are four protein-based complexes, referred to as complexes I through IV. 

  • When these four complexes are aggregated, along with the associated mobile electron carriers, an electron transport chain is formed. 

  1.  (NADH-ubiquinone oxidoreductase): 

    1. An integral protein that receives electrons in the form of hydride ions from NADH and passes them on to ubiquinone.

  2. II (Succinate-ubiquinone oxidoreductase also known as succinate dehydrogenase from the TCA cycle): 

    1. A peripheral protein that receives electrons from succinate (an intermediate metabolite of the TCA cycle) to yield fumarate and [FADH2]. 

    2. From succinate the electrons are received by [FAD] which then become [FADH2]. 

    3. The electrons are then passed off to ubiquinone.

  3. Q (Ubiquinone/ ubiquinol): 

    1. Ubiquinone (the oxidized form of the molecule) receives electrons from several different carriers; from I, II, Glycerol-3-phosphate dehydrogenase. 

    2. It is now the reduced form (ubiquinol) which passes its electron off to III.

  4. III (Ubiquinol-cytochrome c oxidoreductase): 

    1. An integral protein that receives electrons from ubiquinol which are then passed on to Cytochrome c

  5. IV (Cytochrome c oxidase):

    1. An integral protein that receives electrons from Cytochrome c and transfers them to oxygen to produce water within the mitochondrial matrix.

  6. ATP Synthase: 

    1. An integral protein consisting of several different subunits. 

    2. This protein is directly responsible for the production of ATP via phosphorylation.

Electron Flow

  • It can be seen in the diagram above that ubiquinone (a hydrophobic carrier that resides within the membrane) receives electrons from several different electron carriers. 

  • Cytochrome c (a hydrophilic carrier present within the intermembrane space) on the other hand only transfers electrons from III to IV. 

  • The driving force of the ETC is the fact that each electron carrier has a higher standard reduction potential than the one that it accepts electrons from. 

  • Standard reduction potential is a measure of the ability to accept or donate electrons. 

  • Oxygen has the highest (most positive) standard reduction potential hence accepting electrons from other carriers. That is why it is found at the end of the ETC.

Basic Function of ETC:

  1. To generate a vast amount of ATPs from the reduced compounds obtained from various metabolic processes, in short it acts like a bank which receives cheques and in cash them in the form of cash i.e. ATPs.

Commonly Asked Question.

  1. Write a short note on ETC.

  2. Describe ETC along with its components and significance.
Labels:

Popular posts from this blog

Heat Exchangers and Heat Interchangers.

  In pharmaceutical industries many types of equipments are used for transfer of heat, they can be classified as follows, Heat Exchangers. Heat Interchangers. Heat Exchangers: These devices are used for transferring heat from a fluid (Hot Gas or Steam) to another fluid (Liquid) through a metal wall. Heat Interchangers: These devices are used for transferring heat from a One liquid to another liquid or one gas to another gas through a metal wall. HEAT EXCHANGERS; The equipment used for heat transferring are known as heat exchangers. Some of the processes that involves heat transfer in pharmaceutical industries are: Preparation of starch paste (in steam jacketed kettle). Crystallization. Evaporation. Distillation.  Classification of heat exchangers On the basis of transfer of heat, heat exchangers are classified as: Direct transfer type:  The hot and cold fluids are separated by a metal wall through which the heat is transferred from hot fluid to cold fluid. E.g. shell and ...
Read more

Rate of Drying Curve.

  Definition Drying is defined as the removal of liquid from a product usually with application of heat. Rate of Drying Curve. Drying process can be divided into three periods Initial Adjustment Period. Constant drying rate period. First falling drying rate period. Second falling rate period. Initial Adjustment Period (A-B): Also called the “ Heating up” period . In this period the substance gets heat and increases in temperature. Drying has not yet started. Constant drying rate period (B-C): During this period the temperature of the solid and the rate of drying remain constant. The moisture evaporating from the surface is replaced by water diffusing from the interior of the solid at a rate equal t o the rate of evaporation.  The moisture content at the end of constant rate (point C) is referred to as the critical moisture content (CMC).  At CMC, dry spots start appearing and drying rate starts falling . First falling drying rate period (C-D): This period is also called ...
Read more

Glycogenesis.

  Definition: Biosynthesis of Glycogen from Glucose is called Glycogenesis. Glycogen is synthesized  Depending on the demand for glucose and ATP (energy), insulin promotes the glucose conversion into glycogen. Glycogen is the major storage form of carbohydrate in animals similar to starch in plants. It is a homopolymer made up of repeated units of α- D glucose and each molecule is linked to another by 1→4 glycosidic bonds . Once there is a chain consisting of 8 to 10 glycosidic residues in the glycogen fragment, branching begins by 1→6 linkages . Glycogen is stored in liver and skeletal muscles. Location: Cytoplasm of cells in the muscle, liver, and adipose tissue. Steps Involved in Glycogenesis: Glucose is converted into glucose-6-phosphate by the action of glucokinase or hexokinase  with conversion of ATP to ADP. Glucose-6-phosphate is converted into glucose-1-phosphate by the action of phosphoglucomutase. Glucose-1-phosphate is converted into UDP-glucose by the actio...
Read more