Transcript SBI 4U metabolic processes 3

Metabolic Processes Part 3
Interconnections of Metabolic Pathways
and Anaerobic Respiration
Interconnections of Metabolic
Pathways
• We can use other foods for energy (carbs other than
glucose, proteins, fats)
• Most carbohydrates are broken down into glucose first,
then enter the pathway much like glucose would.
• Proteins: amino group is taken off and the rest of the amino
acids will enter the Pathway at various parts
• Fats: glycerol is converted into glyceraldehyde-3phosphate (which is in glycolysis) and the fatty acids are
transported into the mitochondria and carbon atoms are
removed 2 at a time to create acetyl groups and enter at
the Krebs Cycle.
Anaerobic Respiration
• Some organisms do not use oxygen as the final
electron acceptor. Instead they may use sulfate,
nitrate or carbon dioxide.
• Some other organisms such as methanogens will
have a different metabolic pathway (4H2 + CO2 ->
CH4 + 2H2O)
Fermentation
• Some single-celled organisms use only glycolysis
to obtain energy
• Two common fermentation pathways:
• Lactate Fermentation: pyruvate generated by glycolysis
reacts with NADH to reoxidize NAD+ and pyruvate is
converted to lactate.
• In bacteria, this lactate is secreted into the surroundings
making an acidic environment
• In animals, this process can happen when we don’t have
enough oxygen. The excess lactate will eventually be
converted back to pyruvate and oxidized.
Fermentation Continued…
• Ethanol Fermentation: Yeast and some bacteria
convert pyruvate into ethanol and CO2.
• Pyruvate changes into acetaldehyde by cleaving off
a CO2 which then changes into ethanol.
• Used to manufacture baked goods and alcoholic
beverages.
• In ethanol fermentation, ethanol is a
byproduct, but it still has a lot of energy in the
molecule. Lately, we have been using ethanol
in our gasoline (up to 10%) as a fuel.