Cellular Respiration

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Section 4.3

• Cellular Respiration

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Section objectives

• Explain how cellular respiration releases energy
  from food
• Compare aerobic and anaerobic respiration

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Key words

• Cellular Respiration
• Glycolysis
• Krebs cycle
• Electron transport
• Fermentation
• Calorie

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p.107d
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Cellular Respiration

• The process by which glucose is broken down to
  release energy
• ATP is produced

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Cellular Respiration

• Two types
• Aerobic requires O2
• Anaerobic no O2

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The End Results

• Aerobic respiration produces 36 ATP molecules
  from each glucose molecule
• Anaerobic produces only 2 ATP per glucose

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Inefficient?

• 36 ATP represent only half the energy contained
  in one molecule of glucose, so the process is
  inefficient.

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Waste products

• CO2, water and heat are wastes from cellular
  respiration

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Three stages of cellular respiration

• Glycolysis (breaking sugars)
• The Krebs cycle
• Electron Transport

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Glycolysis

• Occurs in cytoplasm
• Breaking down one glucose molecule yields
• 2 ATP (net)
• 2 NADH
• 2 molecules of pyruvate

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Pyruvate?

• How many carbon atoms are in each molecule of
  pyruvate
• See fig. 4.12 on page 92
• Answer three (3)

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The Krebs Cycle of Cellular Respiration

• Pyruvate produced in glycolysis is converted into
  acetyl-CoA
• Pyruvate has 3 carbons acetyl-CoA has 2
• Whered the other C atom go?
• Answer CO2 was given off

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Krebs Cycle cycles

• Acetyl-CoA goes through the cycle, eventually
  producing ATP and NADH, and FADH2

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The Krebs Cycle

• Occurs in the mitochondria (powerhouse of the
  cell)
• Also called the Citric Acid cycle as citric acid
  is produced during the cycle

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Acetyl-CoA Formation
pyruvate
coenzyme A
NAD
(CO2)
NADH
CoA
acetyl-CoA
Krebs Cycle
CoA
oxaloacetate
citrate
NAD
NADH
NADH
NAD
FADH2
NAD
FAD
NADH
ADP phosphate group
ATP
Fig. 7-7a, p.113
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Krebs cycle net results

• Only one ATP is produced from each pyruvate
  molecule
• This yields two from each molecule of glucose

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Overall net results

• So far
• 2 ATP were formed in glycolysis
• 2 ATP were formed in the Krebs cycle

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Still more energy?

• More energy was stored in FADH2 and NADH during
  the Krebs cycle
• It will be used in the last stage to produce more
  ATP

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Electron transport

• A system used to make
• ATP from NADH and FADH2
• Similar to carrier molecule chain in
  photosynthesis
• Occurs in the inner membrane of the mitochondira

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ETC

• Electrons are released from NADH and FADH2
• They pass down the ETC
• Their energy used to actively transport H ions
  into intermembrane space

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ETC, ETC, ETC. . .

• A H ion concentration gradient is formed
• H ions diffuse through ATP synthase, forming ATP
  (a total of 32/glucose)

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Wastes, always wastes

• Electrons at the end of the ETC are accepted by
  oxygen and join with H ions to form water
• This water is waste

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Wastes, always wastes

• The CO2 formed in the Krebs cycle is also a waste
  and must be eliminated

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Anaerobic respiration

• A process known as fermentation that releases
  energy from food without oxygen
• Some unicellular organisms and some animal cells,
  like muscle cells, can do it

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Fermentation

• Two types
• Alcoholic
• Lactic acid
• In both types, only 2 ATP are formed from each
  glucose

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Alcoholic fermentation

• Converts pyruvate to ethanol and CO2
• CO2 is used to make bread rise, and in
  manufacture of wine, beer and ethanol for adding
  to gasoline

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Alcoholic fermentation

• Animal cells DO NOT use this process
• Animals use lactic acid fermentation instead
• Still only 2 ATP produced

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Sore muscles?

• Lactic acid is produced by muscle cells when not
  enough oxygen is available for aerobic respiration

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Sunlight
Heat
O2
Photo- System I
Photo- system II
Electron Transport System
ATP
H2O
ATP
NADP ADP
NADPH
NAD
NADH
CO2
Calvin
Citric Acid
Cycle
Cycle
ATP
Glucose
Pyruvate
CHLOROPLAST
MITOCHONDRION