How does the ELECTRON TRANSPORT CHAIN (ETC) relate to energy coupling. I know th

Question

How does the ELECTRON TRANSPORT CHAIN (ETC) relate to energy coupling.

I know the H+ pumps that the electrons hop from power their H+ pumping, and create a gradient for chemiosmosis at the atp synthase complex where the H+ move from high to low in facilitated diffusion.

So how do i relate this to energy coupling?

Also how is coupled transport and cotransport related to energy coupling?

Side note:

my teacher also said to relate this to formation of peptide bonds. I know peptide bonds are formed by the catalytic large ribosomal subunit and peptide bonds form by dehydration which is endergonic, but what provides the energy needed for a peptide bond? hydrolysis of atp?

Explanation / Answer

The electron transport chain system or ETC represents the location for transport of electrons from one complex to another until it reaches the ultimate electron acceptor, i.e. oxygen. During this process, sequential phosphorylation and dephosphorylation of various redox couples takes place. The terminal acceptance of electron by oxygen requires presence of protons in the matrix so that the reduced oxygen atoms might stabilize themselves by attaching to positively charged protons. Thus, in order to maintain an electro-chemical gradient in the matrix and the optimized functioning of ETC, it is mandatory that a proton-motive force always takes place across the mitochondria. This is called the chemi-osmosis in the mitochondria and hence is absolutely required for coupling of ETC with energy generation at the complex V.

Secondarily, the ATP generated in the mitochondria are added up to the cellular pool. This increase in ATP pool ensures that optimum amount of energy substrate is always available in the cell so that the vital bio-molecular pathways might always take place. This holds true for DNA replication, mRNA transcription and protein translation as well. Specifically, the energy required for formation of a peptide bond is derived from this cellular pool of ATP. However, the hydrolysis of ATP is usually a reversible reaction in which dephosphorylation of ATP takes place thereby releasing a high energy phosphate group.

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