(i) Phosphorylation - Hexokinase, Phospho fructokinase and glyceraldehyde - 3 phosphate dehydrogenase
(ii) De-Phosphorylation - Phospho glycerate Kinase and Pyruvate Kinase

Stages	ATP	NADH2	FADH2	Total ATPs
Glycolysis Link reaction Kreb's cycle	2 - 2	2 \(\times\) 2.5 2 \(\times\) 2.5 6 \(\times\) 2.5	0 - 2 \(\times\) 1.5	7 5 20
	4 ATPs	25 ATPs	3 ATPs	32 ATPs

Because carbohydrates are partially oxidised to organic acid, particularly malic acid without corresponding release of CO₂ but O₂ is consumed. Hence the RQ value will be zero.
\(\underset { Glucose }{ 2{ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }+3{ O }_{ 2 }\rightarrow } \underset { malic\quad acid }{ 3{ C }_{ 4 }{ H }_{ 6 }{ O }_{ 5 }+3{ H }_{ 2 }O+Energy } \)
RQ of glucose in succulents = \(\frac { Zero \ molecule \ of \ { CO }_{ 2 } }{ 3 \ molecules \ of \ { CO }_{ 2 } } \) = 0 (Zero)

Electron Transport Chain (ETC) (Terminal oxidation)
(i) During glycolysis, link reaction and Krebs cycle the respiratory substrates are oxidized at several steps and as a result many reduced coenzymes NADH + H⁺ and FADH₂ are produced.
(ii) These reduced coenzymes are transported to inner membrane of mitochondria and are converted back to their oxidized forms produce electrons and protons.
(iii) In mitochondria, the inner membrane is folded in the form of finger projections towards the matrix called cristae.
(iv) In cristae many oxysomes (F₁ particles) are present which have electron transport carriers are present.
(v) According to Peter Mitchell's Chemiosmotic theory this electron transport is coupled to ATP synthesis. Electron and hydrogen(proton) transport takes place across four multiprotein complexes(I-IV). They are:
a) Complex-I (NADH dehydrogenase)
(i) It contains a flavoprotein(FMN) and associated with non-heme iron Sulphur protein (Fe-S). This complex is responsible for passing electrons and protons from mitochondrial NADH (Internal) to Ubiquinone(UQ).
\(\mathrm{NADH}+\mathrm{H}^{+}+\mathrm{UQ} \rightleftharpoons \mathrm{NAD}^{+}+\mathrm{UQH}_{2}\)
(ii) In plants, an additional NADH dehydrogenase (External) complex is present on the outer surface of inner membrane of mitochondria which can oxidise cytosolic NADH + H⁺.
(iii) Because mitochondrial inner membrane cannot allow NADH molecules directly in to the matrix. Ubiquinone (UQ) or Coenzyme Quinone (CoQ) is a small, lipid soluble electron, proton carrier located within the inner membrane of mitochondria.
b) Complex-II (Succinic dehydrogenase)
(i) It contains FAD flavoprotein is associated with non-heme iron Sulphur (Fe-S) protein.
(ii) This complex receives electrons and protons from succinate in Krebs cycle and is converted into fumarate and passes to ubiquinone.

c) Complex-III (Cytochrome bc₁ complex)
(i) This complex oxidises reduced ubiquinone (ubiquinol) and transfers the electrons through Cytochrome bc₁ Complex (Iron Sulphur center bc₁ complex) to cytochrome c.
(ii) Cytochrome c is a small protein attached to the outer surface of inner membrane and act as a mobile carrier to transfer electrons between complex III to complex IV.
\(\mathrm{UQH}_{2}+2 \mathrm{CytC}_{\text {oxidised }} \rightleftharpoons \mathrm{UQ}+2 \mathrm{Cytc}_{\text {reduced }}+2 \mathrm{H}^{+}\)
d) Complex IV (Cytochrome c oxidase)
(i) This complex contains two copper centers (A and B) and cytochromes a and a₃. Complex IV is the terminal oxidase and brings about the reduction of 1/2 O₂ to H₂O.Two protons are needed to form a molecule of H₂O (terminal oxidation).
\(2 \mathrm{CytC}_{\text {oxidised }}+2 \mathrm{H}^{+}+1 / 2 \mathrm{O}_{2} \rightleftharpoons 2 \mathrm{CytC}_{\text {reduced }}+\mathrm{H}_{2} \mathrm{O}\)
(ii) The transfer of electrons from reduced coenzyme NADH to oxygen via complexes I to IV is coupled to the synthesis of ATP from ADP and inorganic phosphate (Pi) which is called Oxidative phosphorylation.
(iii) The F₀F₁- ATP synthase (also called complex V) consists of F₀ and F₁. F₁ converts ADP and Pi to ATP and is attached to the matrix side of the inner membrane.
(iv) F₀ is present in inner membrane and acts as a channel through which protons come into matrix.