This document discusses intermediary metabolism, specifically: 1) The respiratory quotient and how it varies based on the fuel source, from 0.6 for alcohol to 1 for carbohydrates. 2) The citric acid cycle, which is both catabolic and anabolic and occurs in the mitochondrial matrix. It generates GTP and reduces NADH, FADH2, and ubiquinone. 3) Oxidative decarboxylation and substrate-level phosphorylation provide energy during the citric acid cycle.

1. Intermediary metabolism

2. Rspiratory quotient
• Alcohol  0.6
• Fat  0.7
• Protein  0.8
• Carbohydrate 1
• For a mixed diet it is between 0.7 and 1, often around 0.82–0.85.
• When the rate of utilization of fat increases in relation to carbohydrates, RQ
falls. This happens in diabetes mellitus, when utilization of carbohydrate is
reduced. The RQ is lowest when ketolysis is very active

3. Citirc acid cycle  amphibolic pathway
• BOTH CATABOLIC & ANABOLIC
• OCCURS IN MITOCHONDRIAL MATRIX
• EXCEPT SUCCINATE DEHYDROGENASE  IN MITOCHONDRIAL MEMBRANE 
PART OF ELECTRON TRANSPORT CHAIN (COMPLEX II)

4. FINAL COMMON
OXIDATIVE PATHWAY

5. AMPHIBOLIC PATHWAY

7. OXIDATIVE
DECARBOXYLATION
OXIDATIVE
DECARBOXYLATION
SUBSTRAYE
PHOSPHORYLATION

8. TCA CYCLE
4 DEHYDROGENASE
• ISOCITRATE
DEHROGENASE
• ALPHA KETO GLUTARATE
DEHYDROGENASE
• SUCCINATE
DEHYDROGENASE 
FADH2
• MALATE
DEHYDROGENASE
1 SUBSTRATE LEVEL
PHOSPHORYLATION
• SUCCINATE THIOKINASE 
PRODUCTION OF GTPOXIDATIVE
DECARBOXYLA
TION

12. ACETYL CoA IS COMPLETELY OXIDISED IN TCA
CYCLE  NOT GLUCONEOGENIC

13. OXALOACETATE IS A CATALYST
FAT IS BURNT IN FLAME OF
CARBOHYDRATE

14. FUMARATE FROM
ARGINOSUCCINATE
ENTERS IN TO TCA
CYCLE

15. 1 2 3 5 VITAMINS IN TCA CYCLE
COENZYME VITAMIN TCA CYCLE ENZYME
THIAMINE PYROPHOSPHATE (TPP) B1 α KETO GLUTARATE
DEHYDROGENASE COMPLEX
NICOTINAMIDE ADENINE
DINUCLEOTIDE
B3 • ISOCITRATE DEHYDROGENASE
• α KETOGLUTARATE
DEHYDROGENASE
• MALATE DEHYDROGENASE
FAD B2 SUCCINATE DEHYDROGENASE
CoA B5

16. AMPHIBOLIC PATHWAY

17. ANAPLEUROTIC  FILLING UP REACTIONS
INTERMEDIATE DEPLETED BY REPLENISHED BY
OXALOACETATE Aa SYNTHESIS PYRUVATE CARBOXYLASE 
MAJOR ANAPLEROTIC ENZYME
SUCCINYL CoA HEME SYNTHESIS FROM PROPIONYL CoA BY
CARBOXYLASE & METHYL
MALONYL CoA MUTASE
OXALOACETATE , FUMARATE GLUCONEOGENESIS FROM AA

18. REGULATION OF TCA CYCLE

20. Malonate is a competeitive inhibitor

22. ACETYL CoA & NADPH ARE UTILISED
FOR FA SYNTHESIS

25. FLUROACETATE ACONITASE
ARSENITE α KETOGLUTARATE DEHYDROGENASE
HIGH NH3 α KETOGLUTARATE DEHYDROGENASE
MALONATE SUCCINATE DEHYDROGENASE
MALONATE IS
COMPETETITIVE INHIBIITOR

26. • Fat in adipose tissue is largest reservoir of energy
• Glycogen is the first main provider of energy

27. Fed Fasting Starving
Brain Glucose Glucose Ketone bodies
RBC Glucose Glucose
Heart Fatty acids Fatty acids Ketone bodies
Liver Glucose Fatty acids Aa
Muscles Glucose Fatty acids Fatty acids
Ketone bodies
Adipose tissue Glucose Fatty acids Fatty acids
Ketone bodies

32. Immediate energy system Anerobic glycolytic
system
Aerobic or oxidative
system
Source of energy Stored ATP & creatine
phosphate
Glucose or glycogen Glucose /glycogen or FA
Energy production Very fast Fast Slow
Peak 0-30 sec 20-180 sec >3min
Limiting factor Depletion of ATP creatine
phosphate
Lactic acid accumulation Glycogen depletion
Used in Short sprints Longer sprints Endurance events
Ball games

33. One carbon metabolism

34. Aa One carbon group produced
Glycine Methylene
Serine Methylene
Tryptophan Formate
Histidine Formimino
Methionine ` Methyl
Folate is the carrier of one carbon grup