Transcript Cellular Respiration - Pictures only

Cellular Respiration
Getting Energy
https://www.youtube.com/watch?v=Gh2P5CmCC0M
Where Is the Energy?
Figure 9.2
Light
energy
Photosynthesis first
evolved in prokaryotic
organisms; scientific
evidence supports
that prokaryotic
photosynthesis
accounts for the
production of an
oxygenated
atmosphere.
Prokaryotic
photosynthesis
pathways were the
foundation of
eukaryotic
photosynthesis.
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2  H2O
Organic
 O2
molecules
Cellular respiration
in mitochondria
ATP
Heat
energy
ATP powers
most cellular work
ATP  Adenosine Triphosphate
(high energy storing molecule)
Adenine
Ribose
3 phosphates
THERE ARE 2 TYPES OF CELLULAR RESPIRATION:
* AEROBIC (requiring oxygen)
* ANAEROBIC (no oxygen)
Formula for Aerobic Respiration:
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy
Reactants
Products
(ATP)
The Principle of Redox
• redox reactions- Chemical reactions that
transfer electrons between reactants
• oxidation, a substance loses electrons, or is
oxidized
• reduction, a substance gains electrons, or is
reduced (the amount of positive charge is
reduced)
• During cellular respiration, the fuel (such as
glucose) is oxidized, and O2 is reduced
© 2011 Pearson Education, Inc.
Figure 9.UN03
becomes oxidized
becomes reduced
Figure 9.5
H2  1/2 O2

2H
1/
Explosive
release of
heat and light
energy
Free energy, G
Free energy, G
(from food via NADH)
Controlled
release of
+

2H  2e
energy for
synthesis of
ATP
O2
ATP
ATP
ATP
2 e
2
1/
H+
H2O
(a) Uncontrolled reaction
2
H2O
(b) Cellular respiration
2
O2
3 major steps of Cellular Respiration
1. Glycolysis
2. Krebs cycle
3. ETC: Electron Transport Chain
 Oxidative phosphorylation:
 most effective way to make ATP
Animal Cell
Cytoplasm
Nucleolus
Nucleus
Ribosomes
Cell Membrane
Mitochondria
Rough Endoplasmic
Reticulum
Golgi Bodies
Smooth Endoplasmic
Reticulum
Using Coupled Reactions to Make ATP
• Glycolysis: the pathway that converts glucose (C6H12O6)
into 2 three carbon pyruvates (CH3COCOO− + H+)
 the breaking of the bonds yields energy used to phosphorylate ADP to
ATP (subtrate-level phosphorylation – directly adding a Phosphate to
ADP)
 in addition, electrons and hydrogen atoms are donated to NAD+ to form NADH
(electron carriers)
Figure 9.6-1
Electrons
carried
via NADH
(Sugar splitting)
Glycolysis
2 Pyruvates
Glucose
CYTOSOL
ATP
Substrate-level
phosphorylation
MITOCHONDRION
How glycolysis works
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The reactions of glycolysis
Figure 9.6-2
Electrons
carried
via NADH
(Sugar splitting)
Step 1: Glycolysis
2 Pyruvates
Glucose
Electrons carried
via NADH and
FADH2
Step 2:
Krebs Cycle
Pyruvate
oxidation
Citric
acid
cycle
Acetyl CoA
(enzyme)
(matrix)
CYTOSOL
MITOCHONDRION
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Harvesting Electrons from Chemical Bonds
• Mitochondrion: Aerobic
Respiration (O2)
 Oxidation of pyruvate
(oxidative respiration) to
acetyl-CoA
 Carbon removed from CO2
 Happens before aerobic
respiration can occur
Harvesting Electrons from Chemical Bonds
• NADH and NAD+ are used by cells to carry
hydrogen atoms and energetic electrons
Figure 8.6 How NAD+ works
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Harvesting Electrons from Chemical Bonds
• The fate of acetyl-CoA depends on the
availability of ATP in the cell
 if there is insufficient ATP, then the acetylCoA heads to the Krebs cycle: make more
ATP
 If there is plentiful ATP, then the acetyl-CoA
is diverted to fat synthesis for energy
storage
Harvesting Electrons from Chemical Bonds
•
2. Krebs cycle

Occurs in the matrix
of the mitochondrion
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Harvesting Electrons from Chemical Bonds
• So far…
 the energy from glucose chemical bonds has been
transformed into
• 4 net ATP molecules
– (4 from glycolysis (-2 paid back to cell) and 2 from Krebs Cycle)
• 10 NADH electron carriers
• 2 FADH2 electron carriers
Figure 9.6-3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Step 2: Krebs Cycle
(Sugar splitting)
Step 1: Glycolysis
2 Pyruvates
Glucose
Pyruvate
oxidation
Citric
acid
cycle
Acetyl CoA
(enzyme)
Step 3: ETC
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
(matrix)
CYTOSOL
MITOCHONDRION
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Using the Electrons to Make ATP
• NADH and FADH2 transfer electrons to ETC
• Electron Transport Chain- takes place in the cristae of
the mitochondria
 Carrier Proteins: Cytochromes- alternate reduced and oxidized
states as they accept and donate electrons
• Electrons drop in free energy as they go down the chain
and are finally passed to O2, forming H2O
 some protein complexes proton pumps
 the last transport protein donates electrons to hydrogen
and oxygen in order to form water
 the supply of oxygen and its ability to accept electrons
makes oxidative respiration possible
The electron transport chain
Using the Electrons to Make ATP
• Electrons harvested from (NADH and FADH2)
 used to drive proton pumps and concentrate protons in
the intermembrane space (proton-motive force)
 The re-entry of the protons into the matrix across ATP
synthase drives the synthesis of ATP by chemiosmosis:
use of energy in a H+ gradient to drive cellular work
• ATP synthase uses the exergonic flow of H+ to drive
phosphorylation of ATP
 oxidative phosphorylation (ATP is generated from the
oxidation of NADH and FADH2 and the subsequent transfer of
electrons and pumping of protons).
 Produces about 32-34 ATP
An overview of the electron transport chain
and chemiosmosis
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Figure 9.16
Electron shuttles
span membrane
2 NADH
2 NADH
or
2 FADH2
2 NADH
Glycolysis
Pyruvate oxidation
2 Pyruvate
Glucose
MITOCHONDRION
2 Acetyl CoA
 2 ATP
Maximum ATP per glucose:
CYTOSOL
6 NADH
2 FADH2
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
 2 ATP
 about 32 or 34 ATP
About
36 or 38 ATP
Cells Can Metabolize Food Without Oxygen
• In the absence of oxygen, organisms must rely exclusively on glycolysis
to produce ATP
• Fermentation
 the hydrogen atoms from the NADH generated by glycolysis are donated to
organic molecules, and NAD+ is regenerated
• With the recycling of NAD+, glycolysis is allowed to continue
• Anaerobic respiration uses an electron transport chain with a final
electron acceptor other than O2, for example sulfate
• Fermentation uses substrate-level phosphorylation instead of an
electron transport chain to generate ATP
Cells Can Metabolize Food Without Oxygen
• Bacteria (Prokaryotes) can perform more than a dozen
different kinds of fermentation
• Eukaryotic cells are only capable of a few types of
fermentation
• Alcohol Fermentation: in yeasts (single-celled fungi),
pyruvate is converted into acetaldehyde, which then accepts
a hydrogen from NADH, producing NAD+ and ethanol
• Lactic Acid Fermentation: In animals, such as ourselves,
pyruvate accepts a hydrogen atom from NADH, producing
NAD+ and lactate (lactic acid)
Fermentation
Cellular
Respiration
produces 32 ATP
per glucose
molecule;
Fermentation
produces 2 ATP
per glucose
molecule
• Obligate anaerobes carry out fermentation or anaerobic
respiration and cannot survive in the presence of O2
• Yeast and many bacteria are facultative anaerobes,
meaning that they can survive using either fermentation
or cellular respiration
• In a facultative anaerobe, pyruvate is a fork in the
metabolic road that leads to two alternative catabolic
routes
© 2011 Pearson Education, Inc.
Glucose Is Not the Only Food Molecule
How cells obtain energy from foods
• Cells also get energy from
foods other than sugars
• The other organic building
blocks undergo chemical
modifications that permit
them to enter cellular
respiration
Figure 9.16
Electron shuttles
span membrane
2 NADH
2 NADH
or
2 FADH2
2 NADH
Glycolysis
Pyruvate oxidation
2 Pyruvate
Glucose
MITOCHONDRION
2 Acetyl CoA
 2 ATP
Maximum ATP per glucose:
CYTOSOL
6 NADH
2 FADH2
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
 2 ATP
 about 32 or 34 ATP
About
36 or 38 ATP