Chapter 6 - Respiration

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Chapter 6 - Respiration
CHAPTER 6 - RESPIRATION
O2
CO2 H2O
HEAT ENERGY
Glucose
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The only reason humans need to breathe oxygen is
to accept electrons in the final stage of ATP
synthesis in the mitochondria.
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Outline
CHAPTER OUTLINE
I. OVERVIEW II. GLYCOLYSIS Getting to
glucose Mechanisms by which ATP is
synthesized Glycolysis steps in the
process Glycolysis - summary III. THE AEROBIC
PATHWAY Mitochondrion structure A preliminary
step The Krebs cycle Oxidative phosphorylation IV.
ANAEROBIC PATHWAYS V. OTHER TYPES OF
RESPIRATION
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Outline
OVERVIEW
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I. OVERVIEW
All organisms harvest energy from stored
chemicals (starch, sugars, lipids) in the same
way The metabolic pathways by which organisms
liberate stored energy are referred to as
cellular respiration
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Respiration of glucose - equation
THE OVERALL EQUATION FOR RESPIRATION OF GLUCOSE
Carbon Dioxide
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Cellular Respiration
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Cellular Respiration
Glucose ? CO2 H2O energy (ATP)
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Overview
This is the same equation for starting a fire
using glucose as a fuel. The difference is that
the reaction in living systems is tightly
controlled and energy normally lost as heat is
captured for other uses.
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Glucose is used as a source of energy for two
kinds of respiration Aerobic Anaerobic
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Overview - aerobic respiration
Aerobic Respiration - requires oxygen as the
terminal electron acceptor 1) Stages involved a)
Krebs cycle b) Oxidative phosphorylation
(synthesis of ATP) 2) Disposition of Energy a)
Some energy is stored in ATP and in other
compounds b) Other energy dissipates as heat
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Overview - anaerobic respiration
Anaerobic Respiration (without
oxygen) Fermentation Metabolic pathways by
which energy is liberated from pyruvic acid, the
end product of glycolysis, in the absence of
oxygen.
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Outline
GLYCOLYSIS Getting to Glycolysis
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Glycolysis is the breakdown of glucose to pyruvic
acid (pyruvate).
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Retrieving glucose from other molecules

• GLUCOSE IS NOT ABUNDANT IN CELLS
• CELLS OBTAIN GLUCOSE BY BREAKING DOWN
  GLUCOSE-CONTAINING STORAGE MOLECULES, OFTEN
  SUCROSE OR STARCH

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Sucrose, Starch, Fructose, etc
Fig 6-2
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Retrieving glucose from other molecules
COMMON GLUCOSE STORAGE COMPOUNDS

• SUCROSE (TABLE SUGAR), FRUCTOSE (FRUIT SUGAR) AND
  OTHER SUGARS

• STARCH

• POLYMERS OF FRUCTOSE

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GLUCOSE IS RETREIVED FROM SUCROSE BY BY HYDROLYSIS
Requires the enzyme sucrase
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Retrieving glucose from other molecules
STARCH IS A BRANCHED POLYMER MADE UP OF GLUCOSE
MOLECULES

• SEVERAL DIFFERENT KINDS OF ENZYMES ARE REQUIRED
  TO BREAKDOWN STARCH
• Amylases
• Starch phosphorylase
• Debranching enzymes

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Retrieving glucose from other molecules
Debranching enzymes hydrolize starch at branch
points
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Outline
GLYCOLYSIS Mechanisms by which ATP is synthesized
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Synthesis of ATP
ATP is synthesized during respiration by - 1.
Substrate-level phosphorylation 2. ATP synthase
complexes in mitochondrial and chloroplast
membranes (Oxidative Phosphorylation)
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Substrate-level phosphorylation
PHOSPHOENOLPYRUVIC ACID
Transfer of a phosphate directly from an organic
molecule to ADP to make ATP
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ATP synthase complex
Oxidative Phosphorylation Coupling energy from
an electron donor with an electrochemical
gradient that spans a membrane to phosphorylate
ADP
Fig 6-15
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Outline
GLYCOLYSIS Steps in the process
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This is glycolysis
Fig 6-2
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Glycolysis occurs in the cytoplasm!!!!
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Uses 1 ATP
Fig 6-4
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Uses 2nd ATP
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We will follow what happens to glyceraldehyde
3-phosphate only. Note-all products are from this
point on are doubled
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2 molecules
Generates 2 NADH
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Generates 2 ATP
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2 molecules
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2 molecules
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Generates 2 ATP
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Total yield of energy-transport molecules from
glycolysis
Fig 6-17
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Outline
AEROBIC RESPIRATION Mitochondrion structure
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Pyruvic acid is imported into mitochondria
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The Krebs cycle occurs in the matrix of the
mitochondria
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Outline
AEROBIC RESPIRATION Oxidative decarboxylation of
pyruvate
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Pyruvate is transported into the mitochondria
Fig 6-7
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Fig 6-17
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Outline
AEROBIC RESPIRATION Krebs Cycle
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Fig 6-2
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Krebs cycle TCA cycle
The Krebs cycle is also called the TCA cycle
(tricarbocylic acid cycle) because citric acid
has three carboxyl groups) or The citric acid
cycle
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Krebs cycles X 2
The chemical reaction repeatedly recycles, taking
in two carbons and producing two CO2 molecules
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Two carbons enter
Fig 6-8
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Two CO2 molecules are produced (4/molecule of
glucose)
Fig 6-8
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Three molecules of NADH are produced (6/molecule
of glucose)
Fig 6-8
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One molecule of ATP is produced (2/molecule of
glucose)
Fig 6-8
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One molecules of FADH2 is produced (2/molecule of
glucose)
Fig 6-8
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Fig 6-17
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Outline
AEROBIC RESPIRATION Oxidative phosphorylation
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Fig 6-2
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Electron transport
NADH and ubiquinol from the Krebs cycle start a
series of oxidation reduction reactions that move
electrons through a series of carriers. The
electron carriers together are called an
electron transport chain
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See next slide for oxidation-reduction of CoQ
Fig 6-10
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Fig 6-13
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See next slide for cytochrome structure
Fig 6-10
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Fig 6-11
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Electron transport
ELECTRON TRANSPORT
Energy from the flow of electrons maintains a
proton gradient across the inner mitochondrial
membrane This proton gradient drives the
synthesis of ATP. This process is called
oxidative phosphorylation
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H
H
H
H
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ATP synthesis
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Fig 6-17
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Outline
ANAROBIC RESPIRATION
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Anaerobic respiration
Glycolysis works in an oxygen free environment
and can occur in either anaerobic or aerobic
respiration The Krebs cycle and electron
transport are inhibited by a lack of oxygen
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Inhibited
Not Inhibited
Fig 6-2
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If NADH from glycolysis builds up (because its
not being used in oxidative phosphorylation),
NAD will become depleted NAD is required to
oxidize glyceraldehyde-3 -phosphate Therefore,
glycolysis will stop
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Excess NADH can be removed by conversion of
pyruvic acid to acetaldehyde
Fig 6-18
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Lactic acid
In some animals (you), in some fungi and
bacteria, pyruvic acid is reduced to lactic acid
instead of alcohol
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Respiration overview
Aerobic respiration
Anaerobic respiration
Aerobic respiration
Glycolysis
Pyruvic acid
Krebs cycle
Alcohol or lactic acid
2ATP
36ATP
Electron transport
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Outline
OTHER TYPES OF RESPIRATION Lipids, proteins, etc
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Fig 6-19
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Respiration of lipids
Lipids are important storage compounds. They can
be metabolized to yield acetyl Co-A for aerobic
respiration
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Outline
OTHER TYPES OF RESPIRATION Cyanide resistant
respiration
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Cyanide-resistant electron transport
Cyanide
Fig 6-10
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Cyanide-resistant respiration
CYANIDE RESISTANT RESPIRATION
Aerobic respiration is inhibited when the
terminal electron carrier combines with cyanide,
azide or certain other negatively charged
ions This poisons the enzyme and stops electron
transport
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Cyanide-resistant respiration
Some plants, fungi and bacteria This pathway
produces heat rather than ATPs but is aerobic
(i.e., oxygen is the terminal electron acceptor)
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Cyanide-resistant respiration
Energy is captured from light by Philodendron
leaves and used for life processes and growth
When it flowers, the Philodendron flower heats to
as high as 46 C (115 F). The heat protects the
flowers from freezing at night and disperses
compound that attract polinators Light energy gt
Heat
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