Cellular Respiration:

1
Chapter 6

• Cellular Respiration
• Obtaining Energy from Food

2
Feeling the Burn

• Aerobic metabolism is the breaking down of
  glucose using O2
• Aerobic capacity maximum rate that you can
  bring in O2 in for use
• exceed this and you enter anaerobic metabolism
  which makes lactic acid causing the burn
• not efficient mechanism for energy and so you
  colapse

3
Energy Flow and Chemical Cycling

• Indirectly all fuel molecules in food comes from
  the sun
• Sunlight energy is converted by plants to usable
  energy and fibers for clothes and wood etc

4
Terms

• Autotrophs self-seeders
• make organic matter using inorganic nutrients to
  create sugars, lipids, proteins and nucleic acids
• producers
• Heterotrophs other feeders
• must eat autotrophs or other heterotrophs for
  organic molecules
• consumers

5
Chemical Cycling

• Moves between cell respiration and photosynthesis
• Waste (H2O and CO2) from cell respiration are
  used in photosynthesis to make sugar in
  chloroplast
• sunlight is energy source
• Waste (sugar and O2) from photosynthesis are used
  in cellular respiration in mitochondria
• generate ATP and heat

6
Cellular Respiration and Breathing

• Motors require O2 to burn gas and move the car,
  so do cells to accomplish cell work
• Not the same but cells require O2 and release CO2
  just like the process of breathing

7
Cellular Respiration

• The arrows indicate that there are many steps to
  this process
• H2O comes from the H being transported to O2
• Creates about 38 ATP overall
• You should know the overall reaction!!!

8
Role of O2

• Must follow the electron transfer as they move
  with the H from sugar to O2
• Redox reactions oxidation and reduction
• transfer of electrons to another substance
• oxidation loose electron during reaction
• glucose is oxidized
• reduction gain electron during reaction
• O2 is reduced

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Redox Reaction
10
Falling Electrons

• When H or electrons change partners they give off
  energy as they are attracted to the O
• energy in the form of heat
• Cellular respiration is more controlled
• release energy in small steps that are useful
• generates NADH which is the reduced form of NAD
  that picks up 2 electrons and 1 H

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Electron Transport Chain (ETC)

• NAD (nicotinamide adenine dinucleotide) carries
  the energy from the Krebs cycle to the ETC as
  NADH
• Harvest energy in the electron in steps of the
  ETC
• generates majority of ATP and H2O

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Metabolic Pathway of Cellular Respiration

• Series of reaction in 3 metabolic stages
• glycolysis breaks glucose into 2 3C molecules
  of pyruvatic acid in the cytosol
• citric acid or Krebs cycle breaks pyruvate to
  CO2 in the mitochondria matrix
• ETC harvests energy from NADH formed in
  glycolysis and Krebs cycle into ATP energy
• Small amount of ATP formed in glycolysis and
  Krebs cycle

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Stage 1 Gylcolysis (in cytoplasm)

• Needs an input of 2 ATP to get the process
  started
• During the creation of pyruvic acid energy
  (electron and H) is stored in NADH
• Make 4 ATP overall in this stage but need to pay
  back the 2 input at the beginning
• Net reaction 2 ATP, 2 NADH, 2 pyruvates
• most energy still in the pyruvate

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Intermediate Step

• Pyruvate needs to be modified to enter Citric
  Acid cycle
• remove 1 C as CO2 and add to coenzyme A to make
  acetyl CoA
• Generate NADH in this process

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Stage 2 Citric Acid Cycle (in mitochondrial
matrix)

• Acetyl CoA enters Citric Acid cycle
• made 2 Acetyl CoA so cycle goes twice around for
  each sugar
• Removes most of the energy left in the carbons
  from the sugar and makes CO2 total of 4
• 2 for each Acetyl CoA entering the cycle
• Energy trapped in 3 NADH and 1 FADH2 and 1 ATP
  for each cycle

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Stage 3 ETC (in inner mitochondrial membrane)

• A chemical machine that take energy from the
  electrons on NADH and moves a H across the
  membrane
• increases the H in the intermembrane space
  that acts as potential energy
• functions as water behind the dam
• Use the potential energy to make ATP as the H
  moves thru ATP synthase, also in the inner
  membrane
• just like dam can make electrical energy

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ETC

• Electrons move down a series of proteins to get
  less energy to make H2O and pumps H across
  membrane
• H come back thru ATP synthase to generate ATP
• Poisons usually block the ETC and cells die
  because of the lack of energy

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Cellular Respiration Versatility

• Krebs cycle and ETC can use molecules other than
  glucose for energy
• fatty acids
• glycerol
• proteins and amino acids

20
Adding Up ATP
21
Fermentation

• Anaerobic harvest of food energy
• No or little O2 available
• See in muscle cells that are being pushed
• usually only aerobic but when you are not
  breathing properly or working more than breathing
  can bring in
• fermentation kicks in about 15 sec after O2
  levels drop
• Get ATP from glycolysis but cannot do ETC because
  no O2 to accept electrons and regenerate NAD

22
Pyruvate to Lactic Acid

• Lactic acid builds up and leads to sore muscles
• After burst of exercise breath heavily to
  replace O2 and convert lactic acid back to
  pyruvate in the liver

23
Fermentation in Microorganisms

• Certain bacteria and fungi produce lactic acid in
  fermentation makes yogurt, cheese, sour cream,
  soy sauce and many others
• Yeast can do both fermentation and cellular
  respiration
• produce ethyl alchol rather than lactic acid

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Yeast Beer and Bread
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Microorganisms Energy Source

• Facultative anaerobes do both cellular
  respiration and fermentation depending on the
  level of O2
• Obligate anaerobes only do fermentation, O2 is
  poisonous to them
• Obligate aerobes need O2 and cellular
  respiration but can do small bursts of
  fermentation