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Metabolic Pathways
- Overview of metabolism pathways
- Bioenergetics
- Metabolism:
- Glucose catabolism
- aerobic pathway
- anaerobic pathway
- Hydrocarbon
- Nitrogen compounds
- Photosynthesis
- Overview of biosynthesis
Metabolic Pathways
- Overview of metabolism pathways
Metabolism:
- Catabolism: The intracellular process of
degrading a compound into smaller and simpler
products and generating energy.
Glucose to CO2, and H2O, protein to amino
acids.
- Anabolism: the synthesis of more complex
compounds and requires energy.
Synthesis of glycan (polysaccharide), DNA,
RNA, and lipid.
Metabolic Pathways
- Overview of metabolism pathways
- Categories:
Degradation of nutrients:
carbohydrate, nitrogen compounds, lipids and
nucleic acids.
Biosynthesis of small molecules, such as
building blocks for biopolymers.
amino acids, nucleotides, fatty acids and
sugars
Biosynthesis of large molecules
glycan, glycogen, lipids and nucleic acids.
Major Metabolic Pathways
- Overview of metabolism pathways
Metabolic Pathways
- Overview of metabolism pathways
End products are formed and released from the
cells through these reactions,
which are often valuable products for human or
animal consumption.
ethanol, amino acids, enzymes, fatty acids,
antibodies.
Metabolic Pathways
- Bioenergetics
- Energy is mainly stored or transferred by
adenosine triphosphate (ATP).
Other energy carrying compounds include
GTP, UTP and CTP.
Metabolic Pathways
- Bioenergetics
- Transfer of biological energy from high-energy
to low energy compounds via ATP or its analog
compounds.
Metabolic Pathways
- Bioenergetics
- Reducing power: supply hydrogen atom in
biosynthesis.
Nicotinamide Adenine Dinucleotide (NADH)
Flavin Adenine Dinucleotide (FADH2)
NADH and FADH2 are major electron carriers in the
oxidation of fuel molecules and for ATP generation.
Nicotinamide Adenine Dinucleotide Phosphate
(NADPH).
major electron donor in reductive biosynthesis
Nicotinamide Adenine Dinucleotide
(NAD+)
2e- , H+
Nicotinamide Adenine Dinucleotide
Phosphate (NADP+)
Flavin Adenine Dinucleotide (FAD)
2 electrons
Isoalloxazine ring
Review of Metabolism Pathways
http://www.genome.jp/kegg/pathway/map/map01100.html
Glucose metabolism is the centre of the cell metabolism
pathways
Glucose Catabolism
Glucose
Glycolysis or
Embden-Meyerhof-Parnas (EMP)
Aerobic metabolism
Anaerobic metabolism
Fermentation: ethanol,
acetic acid, lactate.
Tricarboxylic acid (TCA)
or (Krebs)
or (Citric acid cycle)
Oxidative phosphorylation
Glucose Catabolism
Glycolysis
• Glycolysis or Embden-Meyerhof-Parnas
(EMP)
Breakdown of a molecule of glucose to two
pyruvate molecules.
- Each pathway is catalyzed by particular
enzyme(s)
- Generating 2 ATP, 2 NADH and
2 pyruvate (Key Metabolite).
- Taking place in cytoplasm
a-D-Glucose
Pyruvate
Glucose Catabolism
Glycolysis
• http://www.gwu.edu/~mpb/glycolysis.htm
• http://www.science.smith.edu/departments/Biology/Bio231/glycolysis
.html
(animation)
Glycolysis (EPM)
glycogen
Amino acid
Acetyl-CoA
Ethanol
Fatty acids
Amino acid
control sites:
feedback inhibition
Glucose Catabolism
Glycolysis
• The overall reaction in glycolysis is:
Glucose + 2ADP + 2 NAD+ + 2 Pi →2 pyruvate +
2 ATP+ 2 (NADH + H+)
Glucose Catabolism
Glucose
Glycolysis or
Embden-Meyerhof-Parnas (EMP)
Aerobic metabolism
Anaerobic metabolism
Fermentation: ethanol,
acetic acid, lactate.
Tricarboxylic acid (TCA)
or (Krebs)
or (Citric acid cycle)
Oxidative phosphorylation
Glucose Catabolism
Krebs, Tricarboxylic Acid (TCA), or Citric
Acid Cycle
• Under aerobic conditions
• Taking place
- in mitochondria in eucaryotes
- associated with membrane-bound
enzymes in procaryotes
• Pyruvate produced in glycolysis (EMP) pathway
transfer its reducing power to NAD+.
Glucose Catabolism
Citric Acid Cycle
Roles:
• Provide electron (NADH) for the electron
transport chain for ATP generation and
biosynthesis
• Supply C skeletons for amino acids synthesis
Glucose Catabolism
Citric Acid Cycle
• Entry of pyruvate
pyruvate + NAD+ + CoA-SH → acetyl-CoA + CO2 + NADH + H+
CoA-SH
Glucose Catabolism
Citric Acid Cycle
• One molecule of acetyl-Co-A generates:
3 (NADH+H+), FADH2, GTP, and 2CO2
amino acid synthesis
Control site
NADH generated
CO2 released
FADH2 generated
Citric Acid Cycle
amino acid synthesis
http://www.gwu.edu/~mpb/citric.htm
http://www.science.smith.edu/departments/Biology/Bio231/krebs.html
Glucose Catabolism
Citric Acid Cycle
The overall reaction of TCA cycle:
acetyl-CoA + 3 NAD + FAD + Pi + 2H2O → CoA + 3(NADH + H+)
+FADH2+GTP+ 2CO2
• Intermediate products such as oxylacetate and
α–ketoglutarate are used as precursors for the
synthesis of certain amino acids.
• The reducing power (NADH + H+ and FADH2) is used
for biosynthesis pathway or for ATP generation
through the electron transport chain.
Glucose Catabolism
Glucose
Glycolysis or
Embden-Meyerhof-Parnas (EMP)
Aerobic metabolism
Anaerobic metabolism
Fermentation: ethanol,
acetic acid, lactate.
Tricarboxylic acid (TCA)
or (Krebs)
or (Citric acid cycle)
Respiratory chain:
Oxidative phosphorylation