Download Oxidative Phosphorylation

Introduction to
METABOLISM
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
1
2 3
4
5
6
Different pathways can intersect forming a network of chemical reactions.
K
T
A B
Pathways can be classified as either :
catabolic (degredative)
or anabolic (synthetic)
C
D
L
U
M
V
E
Glycolysis, an example of a metabolic pathway
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
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 energyrich 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
ANABOLIC
large complex organic
molecules are constructed
from small molecules
Biosynthetic
CATABOLIC
Decomposition of large
complex molecules into
small molecules
Degradative
Reductive
Oxidative
Energy Required
Energy Liberated
Diverging
Converging
Catabolism
(converging)
Many
Few
Anabolism
Few
(diverging)
Many
Macromolecules
Nutrients
Proteins
Polysaccharides
Lipids
Nucleic acids
Carbohydrates
Fats
Proteins
ATP
Catabolism
(oxidative,
exergonic)
NADPHChemical
NADPH
ATP
End products
H2O, CO2, NH3
GTP
NADPH
energy
ATP
NADH
Anabolism
(reductive,
endergonic)
Precursor Molecules
Amino acids
Sugars
Fatty acids
Nitrogenous bases
Catabolism and anabolism are always related.
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
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).
Adenosine triphosphate
ATP
(carrier of energy)
ATP
ADP + Pi
ADP
AMP + Pi
Pi
Pi
Pi
Mitochondria
BATTERY OF THE CELL
site for generating ATP
Through
Electron Transport Chain
&
Oxidative Phosphorylation
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)
Flow of electrons
NADH
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
Diet Carbohydrates
Glycogen (liver & Sk. Ms.)
Glucose
GLYCOLYSIS (in cytoplasm)
Lactate
Pyruvate
in mitochondria
CATABOLISM OF
CARBOHYDRATES
Acetyl CoA
Citric Acid Cycle
(in mitochondria)
NADH & FADH2
Electron transport chain (flow of electrons)
Formation of ATP
(oxidative phosphorylation)
Triglycerides
Fatty acids
Lipid Catabolism
Acetyl CoA
Citric acid cycle
ATP
Energy
Protein Catabolism
Amino Acid
Protein
amino group
(nitrogen)
incorporated
into
other
Compounds
(e.g. urea)
excreted
DEAMINATION
(a-ketoacid)
(carbon skeleton)
catabolised
synthesis
of other compounds
acetyl CoA
Citric Acid Cycle
ATP
(energy)