How Cells Harvest Chemical Energy

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Lecture 12

• Chapter 6
• How Cells Harvest Chemical Energy

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Learning Objectives

• Recall
• Balanced chemical equation for respiration
• The answers to questions in this lecture
• Define
• Ethanol, lactic acid
• Discuss
• Both types of fermentation

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Question

• In cellular respiration, oxygen is the ultimate
  electron acceptor
• What happens to oxygen, once it has accepted the
  electrons?

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Balanced Respiration Equation

• Follow the 12 oxygen atoms to
• CO2
• H20

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Fermentation

• Like cellular respiration, produces ATP
• Unlike respiration
• Its anaerobic (Needs no oxygen)
• Produces fewer ATPs per glucose (inefficient)

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Fermentation Two Basic Types

• Alcoholic fermentation
• Lactic acid fermentation

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Alcoholic Fermentation

• Used by yeasts, when oxygen not available
• Uses only glycolysis
• (This was the 1st step in cellular respiration)
• Glucose broken down
• Produces ethanol and carbon dioxide
• (remember E for edible)
• Note methanol kills

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Wines vs. Champagne

• Both wine and champagne are yeast fermentation
  products
• Wine has alcohol but no bubbles
• Champagne has both
• Why?

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Inefficiency

• Ethanol is a waste product of yeast
• But, still has much energy left in it!
• Can even burn!

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Lactic Acid Fermentation

• Produces lactic acid
• Many cells use this
• Molds
• Bacteria
• Our muscle cells (short term)

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Fermentation Dairy Products

• Cheese produced by mold
• Blue cheese very much so
• Yogurt produced by bacteria

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Lactic Acid in You

• Your cells can use fermentation
• For limited time only-typically for burst or
  strength testing activities
• Why? Excess lactic acid poisonous
• Build-up causes fatigue
• Enemy of long-distance runners

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Other Energy Sources

• Glucose not the only one
• Proteins
• Fats
• Make twice the ATP of starches!!!

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Outta Your Seats!