Cellular Respiration

1
Cellular Respiration

• Chapter 6

2
Autotrophs

• Autotrophs are organisms that can use basic
  energy sources (i.e. sunlight) to make energy
  containing organic molecules from inorganic raw
  materials.
• 2 Types
• Photosynthetic autotrophs
• Chemosynthetic autotrophs

3
Chemosynthesis

• Chemosynthesis is a process used by prokaryotic
  organisms to use inorganic chemical reactions as
  a source of energy to make larger organic
  molecules.

4
Heterotrophs

• Heterotrophs require organic molecules as food.
• They get their energy from the chemical bonds in
  food molecules such as carbohydrates, fats, and
  proteins.

5
Prokaryotic Cells
6
Prokaryotic Cells

• Prokaryotic cells have no nuclei.
• Prokaryotic cells lack mitochondria and
  chloroplasts.
• They carry out photosynthesis and cellular
  respiration within the cytoplasm or on the inner
  surfaces of the membranes.

7
Eukaryotic Cells
8
Eukaryotic Cells

• Eukaryotic cells contain nuclei, mitochondria,
  and in the case of plant cells chloroplasts.
• Plant cells, animal cells, fungi and protists are
  all eukaryotic.

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Cellular Respiration

• Cellular respiration is the controlled release of
  chemical-bond energy from large, organic
  molecules.
• This energy is utilized for many activities to
  sustain life.
• Both autotrophs and heterotrophs carry out
  cellular respiration.

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Aerobic Vs. Anaerobic

• Aerobic respiration requires oxygen.
• Anaerobic respiration does not require oxygen.

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Aerobic Respiration

• Aerobic cellular respiration is a specific series
  of enzyme controlled chemical reactions in which
  oxygen is involved in the breakdown of glucose
  into carbon-dioxide and water.
• The chemical-bond energy is released in the form
  of ATP.
• Sugar Oxygen ? carbon dioxide water energy
  (ATP)

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Aerobic Respiration

• Simplified Reaction
• C6H12O6 (aq) 6O2 (g) ? 6CO2 (g) 6H2O (l) ?Hc
  -2880 kJ
• Covalent bonds in glucose contain large amounts
  of chemical potential energy.
• The potential energy is released and utilized to
  create ATP.

13
Glycolysis

• Glycolysis is a series of enzyme controlled
  anaerobic reactions that result in the breakdown
  of glucose and the formation of ATP.
• A 6-carbon sugar glucose molecule is split into
  two smaller 3-carbon molecules which are further
  broken down into pyruvic acid or pyruvate.
• 2 ATP molecules are created during glycolysis and
  electrons are released during the process.

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Krebs Cycle

• The Krebs cycle is a series of enzyme-controlled
  reactions that take place inside the
  mitochondrion.
• Pyruvic acid formed during glycolysis is broken
  down further.
• Carbon dioxide, electrons, and 2 molecules of ATP
  are produced in this reaction.

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Electron Transport System

• The electrons released from glycolysis and the
  Krebs cycle are carried to the electron-transport
  system (ETS) by NADH and FADH2.
• The electrons are transferred through a series of
  oxidation-reduction reactions until they are
  ultimately accepted by oxygen atoms forming
  oxygen ions.
• 32 molecules of ATP are produced.

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Aerobic Respiration Summary

• Glucose enters glycolysis.
• Broken down into pyruvic acid.
• Pyruvic acid enters the Krebs cycle.
• Pyruvic acid is further broken down and
  carbon-dioxide is released.
• Electrons and hydrogen ions from glycolysis and
  the Krebs cycle are transferred by NADH and FADH2
  to the ETS.
• Electrons are transferred to oxygen to form
  oxygen ions.
• Hydrogen ions and oxygen ions combine to form
  water.

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Anaerobic Cellular Respiration

• Anaerobic respiration does not require oxygen as
  the final electron acceptor.
• Some organisms do not have the necessary enzymes
  to carry out the Krebs cycle and ETS.
• Many prokaryotic organisms fall into this
  category.
• Yeast is a eukaryotic organism that performs
  anaerobic respiration.

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Fermentation

• Fermentation describes anaerobic pathways that
  oxidize glucose to produce ATP.
• An organic molecule is the ultimate electron
  acceptor as opposed to oxygen.
• Fermentation often begins with glycolysis to
  produce pyruvic acid.

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Alcoholic Fermentation

• Alcoholic fermentation is the anaerobic pathway
  followed by yeast cells when oxygen is not
  present
• Pyruvic acid is converted to ethanol and
  carbon-dioxide.
• 4 ATPS are generated from this process, but
  glycolysis costs 2 ATPs yielding a net gain of 2
  ATPs.

20
Lactic Acid Fermentation

• In Lactic acid fermentation, the pyruvic acid
  from glycolysis is converted to lactic acid.
• The entire process yields a net gain of 2 ATP
  molecules per glucose molecule.
• The lactic acid waste products from these types
  of anaerobic bacteria are used to make fermented
  dairy products such as yogurt, sour cream, and
  cheese.

21
Lactic Acid Fermentation

• Lactic acid fermentation occurs in the human body
  in RBCs and muscle cells.
• Muscle cells will function aerobically as long as
  oxygen is available, but will function
  anaerobically once the oxygen runs out.
• Nerve cells always require oxygen for
  respiration.
• RBCs lack a nucleus and mitochondria and
  therefore must always perform anaerobic, lactic
  acid fermentation.

22
Fat Respiration

• A triglyceride (neutral fat) consists of a
  glycerol molecule with 3 fatty acids attached to
  it.
• A molecule of fat stores several times the amount
  of energy as a molecule of glucose.
• Fat is an excellent long-term energy storage
  material.
• Other molecules such as glucose can be converted
  to fat for storage.

23
Protein Respiration

• Protein molecules must first be broken down into
  amino acids.
• The amino acids must then have their amino group
  (-NH2) removed (deamination).
• The amino group is then converted to ammonia. In
  the human body ammonia is converted to urea or
  uric acid which can then be excreted.