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 pathwaysMetabolism:

- 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 moleculesglycan, 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

Aerobic metabolism Anaerobic metabolism

Tricarboxylic acid (TCA)or (Krebs)or (Citric acid cycle)

Oxidative phosphorylation

Glycolysis orEmbden-Meyerhof-Parnas (EMP)

Fermentation: ethanol, acetic acid, lactate.

Glucose CatabolismGlycolysis

• 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

Pyruvate

-D-Glucose

Glucose CatabolismGlycolysis

• http://www.gwu.edu/~mpb/glycolysis.htm

• http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

(animation)

Glycolysis (EPM)

control sites: feedback inhibition

glycogen

Amino acid Acetyl-CoAEthanolFatty acidsAmino acid

Glucose CatabolismGlycolysis

• The overall reaction in glycolysis is:

Glucose + 2ADP + 2 NAD+ + 2 Pi →2 pyruvate +

2 ATP+ 2 (NADH + H+)

Glucose Catabolism

Glucose

Aerobic metabolism Anaerobic metabolism

Tricarboxylic acid (TCA)or (Krebs)or (Citric acid cycle)

Oxidative phosphorylation

Glycolysis orEmbden-Meyerhof-Parnas (EMP)

Fermentation: ethanol, acetic acid, lactate.

Glucose CatabolismKrebs, 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 CatabolismCitric Acid Cycle

Roles:

• Provide electron (NADH) for the electron transport chain for ATP generation and biosynthesis

• Supply C skeletons for amino acids synthesis

Glucose CatabolismCitric Acid Cycle

• Entry of pyruvatepyruvate + NAD+ + CoA-SH → acetyl-CoA + CO2 + NADH + H+

CoA-SH

Glucose CatabolismCitric Acid Cycle

• One molecule of acetyl-Co-A generates:

3 (NADH+H+), FADH2, GTP, and 2CO2

Citric Acid Cycle

amino acid synthesis

amino acid synthesis

Control siteNADH generatedCO2 releasedFADH2 generated

http://www.gwu.edu/~mpb/citric.htm

http://www.science.smith.edu/departments/Biology/Bio231/krebs.html

Glucose CatabolismCitric 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

Aerobic metabolism Anaerobic metabolism

Tricarboxylic acid (TCA)or (Krebs)or (Citric acid cycle)

Respiratory chain:Oxidative phosphorylation

Glycolysis orEmbden-Meyerhof-Parnas (EMP)

Fermentation: ethanol, acetic acid, lactate.