LEC: Energy Transformations in
Living Organisms: Cellular
Respiration
Unit 3: Energy Transformations
Chapter 9, Sections 1 & 2 (Pages 220-232)
Biology
Science Department
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Review: Producers
 Producers get their
energy from the sun.
 Producers convert this
light energy into
stored chemical
energy (glucose).
 This process is called
photosynthesis.
Biology
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Deerfield High School
Review: Consumers
 Consumers get their
energy from the
producers.
 Consumers convert
stored chemical
energy (glucose) into
usable chemical
energy (ATP).
 This process is called
cellular respiration.
Biology
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Cellular Respiration (aerobic)
 Cellular respiration is the process by which
glucose (C6H12O6) is broken down to
release energy for making ATP, another
form of chemical energy.
Biology
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Deerfield High School
Aerobic Respiration – Equation
C6H12O6 + 6 O2
food
oxygen
(glucose, a carbohydrate)
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6 H2O + 6 CO2 + 36 ATP
water
carbon
dioxide
BioTheme: Interdependence!
Photosynthesis:
6 H2O + 6 CO2 + energy (sun) → C6H12O6 + 6 O2
Aerobic Cellular Respiration:
C6H12O6 + 6 O2 → 6 H2O + 6 CO2 + energy (ATP)
Biology
Science Department
Deerfield High School
Why ATP? An analogy to money…
 Glucose in our food is a great source of energy! ($100 bill)
 However, individual cell processes may only require a small
amount of energy ($1 bill)
 Analogy: most vending machines do not accept $100 bills!
We need a smaller form of “currency” for these processes.
 ATP (adenosine triphosphate) is this important cellular
“currency” for life.
 ATP releases more appropriate amounts of energy for the
individual cellular processes that require energy.
(We will study this molecule in detail in our next activity!)
Biology
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Deerfield High School
The BIG Question is…
Do only animals respire?
Or do plants respire too?
 Only plants perform photosynthesis
 Plants AND animals perform cellular
respiration!
(Can you explain why??)
Biology
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Deerfield High School
Site of Cellular Respiration
 Plant and animal cells contain mitochondria: cell
structures that transform chemical energy from
glucose to ATP.
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Significant ATP Production
 Aerobic cellular respiration releases energy
SLOWLY, using oxygen to convert ONE
molecule of glucose to 36 ATP!
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Cellular Respiration (anaerobic)
 What happens when cells don’t have enough oxygen?
 Some organisms live in an oxygen-free environment.
How do they get their energy?
Biology
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Deerfield High School
Cellular Respiration (anaerobic)
 Anaerobic respiration is also called
fermentation, or the process by which
energy is released from glucose when
oxygen is NOT available.
 This process allows organisms to continue
to produce energy until oxygen is available.
 However, this process only releases 2 ATP
per molecule of glucose.
Biology
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Deerfield High School
Alcoholic Fermentation
 Anaerobic way of converting energy for
yeast and other microorganisms
 Glucose broken down to produce alcohol,
CO2 and energy (ATP)
 C6H12O6  ethanol + CO2 + 2 ATP
 EX: baking bread with yeast
fermenting wine & beer
Biology
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Deerfield High School
Fermentation - Bread
 Source of sugar?
 DOUGH! (sugar and/or flour)
 Yeast use up the O2 and ferment sugar
 Produce CO2, which is trapped within
tiny bubbles & results in the dough rising
 Produce ethanol, which evaporates in the
baking process
Biology
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Deerfield High School
Fermentation - Wine
 Source of sugar?
 GRAPES!
 Yeast use up the O2 and ferment sugar
 Produce CO2 (kept only in champagne)
 Produce ethanol (% alcohol varies based on
sugar content of grapes and # of fermentations)
Biology
Science Department
Deerfield High School
Fermentation - Beer
 Source of sugar?
 BARLEY!
 Yeast use up the O2 and ferment sugar
 Hops are added as a preservative
and for added flavor
 Produce CO2 and ethanol also
 Various carbohydrates can be used to make
alcohol – including wheat, rice, and potatoes!
Biology
Science Department
Deerfield High School
Other side effects of fermentation?!
 “Drunken Swedish moose drowns after
fermented apple binge”
http://www.usatoday.com/news/offbeat/2006-11-24-moose_x.htm
 “Drunk Moose Invade Seniors Home”
http://www.wtopnews.com/index.php?nid=456&sid=620430
Biology
Science Department
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Lactic Acid Fermentation
 Anaerobic way of converting energy in
animal cells and some microorganisms
 Glucose broken down to produce lactic
acid, CO2 and energy (ATP)
 C6H12O6  lactic acid + CO2 + 2 ATP
 EX: muscle cells during strenuous exercise
fermenting cheese, yogurt, sour cream
Biology
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Strenuous Exercise
 Lactic acid is produced by your muscle
cells during rapid exercise when the body
cannot supply enough O2 to tissues.
 Without enough O2, the body is NOT able
to produce all of the ATP that is required.
 The buildup of lactic acid can cause painful
burning in your muscles!
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Minimal ATP Production
 In the absence of oxygen, anaerobic
respiration only releases 2 ATP for each
molecule of glucose broken down.
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Comparing ATP Production
 First, your body breaks down glucose through
aerobic respiration to produce 36 ATP per
glucose molecule; however, this is a slow process.
 When muscle cells cannot get enough O2 they
break down glucose through lactic acid
fermentation to produce 2 ATP per glucose…
 Therefore, AEROBIC RESPIRATION is much
more efficient in terms of ATP production –
36 ATP compared to 2 ATP!
Biology
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Aerobic Training
 Ex: long runs, biking, swimming
 Can increase the size and number of
mitochondria in muscle cells
 Can increase the delivery of O2 to muscles by
improving the heart and lungs
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Anaerobic Training
 Ex: sprints, strides,
quick bursts of energy
 Increase the glycogen levels in the muscles
 Increase body’s tolerance to lactic acid
Biology
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Deerfield High School