Explanation:

Electron transport chain
From the functional perspective, the electron transport chain (ETC), commonly called the respiratory chain, consists of four protein-lipid complexes (cytochromes) located in the inner membrane of the mitochondrion. The role of these complexes is to participate in the transfer of electrons to oxygen. Electrons are most commonly transferred in association with hydrogen atoms or hydride ions. In three of four complexes that make up the electron transport chain, the free energy released during electron transport is associated with photon pumping from the matrix to the cytosolic side of the inner mitochondrial membrane.

Reference: Biochemistry Primer for Exercise Science-4th Edition, Page no: 120.

Explanation:

The root meristem, like that of the shoot, is composed of an organizing centre, called the quiescent centre in roots, in which the cells divide only very rarely, and which is surrounded by stem-cell-like cells that give rise to the root tissue. The quiescent centre is essential for meristem function. The quiescent centre is a region of slow mitotic activity. It serves as a reserve for replenishment of damaged cells of the meristem.

Reference: Developmental Biology: A Very Short Introduction By Lewis Wolpert, page No: 35.