Respiration in Plants: Key Values, Cofactors, and Disorders

Parameter	Value	Context
Net ATP from glycolysis	2 ATP	Per glucose; substrate-level phosphorylation
NADH from glycolysis	2 NADH	→ 6 ATP in ETS
NADH from link reaction	2 NADH	→ 6 ATP in ETS
NADH from TCA cycle	6 NADH	Per glucose (2 turns × 3 NADH) → 18 ATP
$FADH_{2}$ from TCA cycle	2 $FADH_{2}$	Per glucose (2 turns × 1 $FADH_{2}$ ) → 4 ATP
GTP from TCA cycle	2 GTP	Per glucose (2 turns × 1 GTP) → 2 ATP equivalents
Total ATP (aerobic)	38 ATP	Theoretical maximum per glucose
Total ATP (anaerobic)	2 ATP	Fermentation only
ATP per NADH	3 ATP	Enters ETS at Complex I
ATP per $FADH_{2}$	2 ATP	Enters ETS at Complex II
$CO_{2}$ from link reaction	2 $CO_{2}$	Per glucose (1 per pyruvate × 2)
$CO_{2}$ from TCA cycle	4 $CO_{2}$	Per glucose (2 per turn × 2 turns)
Total $CO_{2}$ released	6 $CO_{2}$	Matches overall equation
RQ — Carbohydrates	1.0	$CO_{2}$ / $O_{2}$ = 1
RQ — Fats	~0.7	More $O_{2}$ consumed
RQ — Proteins	~0.8	Intermediate
RQ — Malic acid	~1.33	4 $CO_{2}$ /3 $O_{2}$
RQ — CAM plants (night)	∞	No external $CO_{2}$ exchange

Cofactor	Enzyme	Vitamin Source
TPP (thiamine pyrophosphate)	Pyruvate dehydrogenase complex; α-KG dehydrogenase	Vitamin $B_{1}$ (thiamine)
N $AD^{+}$	Glycolysis (G3P DH); link reaction; TCA (multiple steps)	Vitamin $B_{3}$ (niacin)
FAD	Succinate dehydrogenase (Complex II, TCA)	Vitamin $B_{2}$ (riboflavin)
CoA	Pyruvate dehydrogenase complex; succinyl CoA synthetase	Pantothenic acid ( $B_{5}$ )

Disorder	Biochemical Basis
Beriberi	Thiamine ( $B_{1}$ ) deficiency → impaired pyruvate dehydrogenase → pyruvate accumulation
Lactic acidosis	Excess anaerobic respiration → lactate accumulation → metabolic acidosis
Cyanide poisoning	Inhibition of Complex IV (cytochrome c oxidase) → ETS arrest → ATP depletion