Biochemistry · MU Sofia

15. RESPIRATORY CHAIN

Covers the respiratory chain as the inner-membrane electron transport system that turns NADH and FADH2 energy into ATP via a proton gradient. It goes through the four protein complexes and their cofactors, proton translocation sites, the P/O coefficient with typical values, respiratory control, and inhibitors such as barbiturates, antimycin A and cyanide. It also describes the barbiturate-alcohol interaction, mitochondrial diseases such as LHON and MELAS, and ends with four multiple-choice questions and answers.

Inside: 14 sections · 6 labelled pictures · 10 flashcards · 5 min

Topic 15 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 14 sections, about 659 words (5 min of reading), with 10 flashcards.

In this note

  1. Introduction
  2. INTRODUCTION TO THE RESPIRATORY CHAIN
  3. MECHANISM OF ACTION
  4. LOCALIZATION
  5. FUNCTION
  6. MOLECULAR STRUCTURE
  7. SITES FOR PROTON TRANSLOCATION
  8. COEFFICIENT OF OXIDATIVE PHOSPHORYLATION (P/O)
  9. RESPIRATORY CONTROL
  10. INHIBITORS OF ELECTRON TRANSFER
  11. DANGEROUS COMBINATION OF BARBITURATES AND ALCOHOL
  12. MITOCHONDRIAL DISEASES
  13. MCQ
  14. ANSWERS

INTRODUCTION TO THE RESPIRATORY CHAIN

  • The respiratory chain, also known as the electron transport chain, is a crucial component of cellular respiration, the process by which cells generate energy in the form of adenosine triphosphate (ATP). Located in the inner membrane of mitochondria, the powerhouse of the cell, this chain is the final and most complex stage of metabolism in aerobic organisms.

Fundamental Role

  • The primary role of the respiratory chain is to convert the energy stored in reduced metabolic intermediates (NADH and FADH2) into ATP, which is used as a universal energy currency by cells to perform various functions. This process involves a series of redox reactions where electrons are transferred through a sequence of protein complexes and mobile carriers within the mitochondrial inner membrane.

MECHANISM OF ACTION

As electrons move through the chain, they release energy at key steps. This energy is harnessed to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating an electrochemical gradient known as the proton motive force.

The return flow of protons into the matrix through ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate.

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