Respiration in Plants

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

Citrate is isomerized to isocitrate.



Decarboxylation of isocitrate

to a -ketoglutaric acid.



Decarboxylation

of

a-ketoglutaric

acid

to

succinyl-CoA.



Succinyl-CoA is converted

to

succinic

acid

and

a

GTP

molecule

is

synthesised

(substrate

level

phosphorylation).

In

a coupled reaction, GTP

is converted to GDP with

simultaneous synthesis of

ATP from ADP. (NEET 2020)

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Oxidation

of

succinate

to fumarate and then to

malate.



Oxidation of malate to OAA.

2

Continued oxidation of Pyruvic acid via TCA cycle

requires continued replenishment of OAA. It also

requires regeneration of NAD⁺ & FAD⁺ from NADH &

FADH2

1

At 3 points of TCA cycle, NAD⁺ is reduced to NADH

+ H⁺ . At one point, FAD⁺ is reduced to FADH2.

(NEET 2017)^.

ËLËÇTRØÑ TRÅÑSPØRT SÝSTËM (ËTS) & ØXÏDÅTÏVË PHØSPHØRÝLÅTÏØÑ



Electron transport system (ETS) is the metabolic pathway present in the

inner mitochondrial membrane through which electron passes from

one carrier to another. (Odisha NEET 2019)



This is to release and utilize energy stored in NADH + H⁺ and FADH2

(formed during TCA cycle) by oxidation.



The electrons are passed on to O2 to form H2O.



Electrons from NADH are oxidised by an NADH dehydrogenase (complex I).



Electrons are then transferred to ubiquinone (UQ) located within the

inner membrane. Ubiquinone also receives reducing equivalents via

FADH2 (complex II) that is generated during oxidation of succinate in

citric acid cycle.

Acetyl coenzyme A

(2C)

Pyruvate

(3C)

CoA

NADH + H⁺

Citrate

synthase

Isocitrate

dehydrogenase

!-ketoglutarate

dehydrogenase

Succinate

dehydrogenase

Fumarase

Malate

dehydrogenase

Succinyl-CoA

synthetase

NADH + H⁺

NADH + H⁺

NADH + H⁺

GDP

GTP

CO2