1. Introduction to METABOLISM

2. Metabolism
is the sum of all chemical changes occurring in a cell , tissue or the body
It is composed of pathways
Pathway
is a multistep sequence of reactions
in which the product of one reaction serves as the substrate of the subsequent reaction
Each reaction is catalyzed by a specific enzyme (may be with help of a coenzyme)
A B C D E F G
Different pathways can intersect forming a network of chemical reactions.
K T
A B C D E
Pathways can be classified as either : L U
catabolic (degredative)
or anabolic (synthetic) M V

3. Glycolysis, an example of a metabolic pathway

4. Metabolic map
is a map that shows components of a pathways of metabolism
It is useful in tracing connections between pathways
metabolic map of
intermediary
metabolism
Example of a
metabolic map

5. Catabolic & Anabolic Reactions
Catabolic Reactions
Catabolic reactions break down complex molecules such as proteins, polysaccharides and lipids to few simple molecules
Serve to:
yield energy in the form
of ATP from the
degradation of energy-
rich fuel molecules
Allow molecules in the
diet (or nutrient
molecules stored in the
cells) to be converted
into building blocks
needed for the synthesis
of complex molecules
Anabolic Reactions
Anabolic pathways
form complex end
products from simple
precursors
i.e. synthesis of
glycogen from glucose
& proteins from amino
acids
Requires energy
provided by
breakdown
of ATP to ADP & Pi

6. ANABOLIC CATABOLIC Biosynthetic Degradative Reductive Oxidative
large complex organic molecules are constructed from small molecules
Decomposition of large complex molecules into small molecules
Biosynthetic
Degradative
Reductive
Oxidative
Energy Required
Energy Liberated
Diverging
Converging

7. Catabolism
Anabolism
(diverging)
(converging)
Few
Many
Many
Few

8. Catabolism(oxidative, exergonic) Anabolism (reductive, endergonic)
Macromolecules
Proteins
Polysaccharides
Lipids
Nucleic acids
Nutrients
Carbohydrates
Fats
Proteins
GTP
ATP
NADPH
Catabolism(oxidative, exergonic)
Anabolism (reductive, endergonic)
NADPH
Chemical energy
NADPH
NADH
ATP
ATP
Precursor Molecules
Amino acids
Sugars
Fatty acids
Nitrogenous bases
End products
H2O, CO2, NH3
Catabolism and anabolism are always related.

9. Amphi = Dual, amphibolic: dual pathway
Amphibolic Pathway
Amphi = Dual, amphibolic: dual pathway
For example,
Krebs cycle is mainly a catabolic cycle, but with some anabolic features.
e.g. part of Krebs cycle is used for the synthesis of glucose from amino acids
Therefore, Krebs cycle is amphibolic 9

10. Stages of Catabolism Citric acid cycle produces NADH & FADH2
Electrons flow from NADH & FADH2 in the mitochondria (electron transport
chain) generates energy in the form of ATP (oxidative phosphorylation).

12. Adenosine triphosphate ATP
(carrier of energy)
ATP ADP + Pi
ADP AMP + Pi Pi Pi Pi

13. Mitochondria BATTERY OF THE CELL site for generating ATP Through
Electron Transport Chain
&
Oxidative Phosphorylation

14. In Electron Transport Chain in the mitochondria
Flow of electrons from NADH & FADH2 (through electron carriers
CoQ & cytochromes) to oxygen yields energy
This energy is used for phosphorylation of ADP to ATP
(phosphorylation)

15. Flow of electrons
NADH

16. ATP PHOSPHORYLATION OXIDATION NADH
Oxidative Phosphorylation (in mitochondria)
Oxidation: electron flow in electron transport chain (with production of energy)
Phosphorylation: phosphorylation of ADP to ATP

17. Diet Carbohydrates Glycogen (liver & Sk. Ms.)
Glucose
GLYCOLYSIS (in cytoplasm)
Lactate Pyruvate
in mitochondria
Acetyl CoA
Citric Acid Cycle
(in mitochondria)
NADH & FADH2
Electron transport chain (flow of electrons)
Formation of ATP
(oxidative phosphorylation)
CATABOLISM OF
CARBOHYDRATES

18. Triglycerides
Fatty acids
Acetyl CoA
Citric acid cycle
ATP
Energy
Lipid Catabolism

19. Protein Catabolism Protein Amino Acid amino group (a-ketoacid)
(nitrogen) (carbon skeleton)
incorporated
into
other excreted catabolised synthesis
Compounds of other compounds
(e.g. urea)
acetyl CoA
Citric Acid Cycle ATP
(energy)
DEAMINATION