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Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
RespirationRespiration
How Cells Harvest Chemical Energy
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INTRODUCTION TO CELLULAR RESPIRATION
6.1 Photosynthesis and cellular respiration provide energy for life
• Cellular respiration makes ATP and consumes O2
– During the oxidation of glucose to CO2 and H2O
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Photosynthesis uses solar energy
CO2
H2O
Glucose
O2
ATP
ECOSYSTEM
Sunlight energy
Photosynthesis in chloroplasts
Cellular respiration in mitochondria
(for cellular work)
Heat energy
Figure 6.1
To produce glucose and O2 from CO2 and H2O
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.2 Breathing supplies oxygen to our cells and removes carbon dioxide
• Breathing provides for the exchange of O2 and CO2 between an organism and its environment
CO2
CO2
O2
O2Bloodstream
Muscle cells carrying out
Cellular Respiration
Breathing
Glucose O2
CO2 H2O ATP
Lungs
Figure 6.2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.3 Cellular respiration stores energy in ATP molecules
• Cellular respiration breaks down glucose molecules
– And stores their energy in ATP
C6H12O6 CO26 H2O ATPs
Glucose Oxygen gas Carbon dioxide
6
Water Energy
O2 6+ + +
Figure 6.3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.4 The human body uses energy from ATP for all its activities
Table 6.4
ATP powers almost all cellular and body activities
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen
• Electrons lose potential energy
– During their transfer from organic compounds to oxygen
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• When glucose is converted to carbon dioxide
– It loses hydrogen atoms, which are added to oxygen, producing water
C6H12O6 6 O2 6 CO2 6 H2O
Loss of hydrogen atoms (oxidation)
Gain of hydrogen atoms (reduction)
Energy
(ATP)Glucose
+ + +
Figure 6.5A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Dehydrogenase removes electrons (in hydrogen atoms) from fuel molecules (oxidation)
– And transfers them to NAD+ (reduction)
Figure 6.5B
OH H O 2H
Reduction
Dehydrogenase
(carries2 electrons)
NAD 2H
2H 2e
NADH H
Oxidation
+
+
+
+
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• NADH passes electrons to an electron transport chain
• As electrons “fall” from carrier to carrier and finally to O2
– Energy is released in small quantities
H2O
NAD
NADH
ATP
H
H
Controlled release of energy for
synthesis of ATP
Electron transport
chain
2 O2
2e
2e
1
2
Figure 6.5C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
STAGES OF CELLULAR RESPIRATION AND FERMENTATION
• 6.6 Overview: Cellular respiration occurs in three main stages
• Cellular respiration
– Occurs in three main stages
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Stage 1: Glycolysis
– Occurs in the cytoplasm
– Breaks down glucose into pyruvate, producing a small amount of ATP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Stage 2: The citric acid cycle
– Takes place in the mitochondria
– Completes the breakdown of glucose, producing a small amount of ATP
– Supplies the third stage of cellular respiration with electrons
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Stage 3: Oxidative phosphorylation
– Occurs in the mitochondria
– Uses the energy released by “falling” electrons to pump H+ across a membrane
– Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• An overview of cellular respiration
NADH
NADH FADH2
GLYCOLYSIS
Glucose Pyruvate CITRIC ACID CYCLE
OXIDATIVE PHOSPHORYLATION
(Electron Transport and Chemiosmosis)
Substrate-level phosphorylation
Oxidative phosphorylation
Mitochondrion
and
High-energy electrons
carried by NADH
ATPATPATP
CO2 CO2
Cytoplasm
Substrate-level phosphorylation
Figure 6.6
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.7 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
• In glycolysis, ATP is used to energize a glucose molecule
– Which is split into two molecules of pyruvate
NAD NADH H
Glucose2 Pyruvate
ATP2P2 ADP
22
2
2
+
+
Figure 6.7A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Glycolysis produces ATP by substrate-level phosphorylation
Figure 6.7B
In which a phosphate group is transferred from an organic molecule to ADP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The conversion of phosphoenolpyruvate to pyruvate is another example of substrate level phosphorylation.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• In the first phase of glycolysis
– ATP is used to energize a glucose molecule, which is then split in two
ATP
Glucose PREPARATORY PHASE
(energy investment)
ADP
Step
Glucose-6-phosphate
Fructose-6-phosphate
P
P
Fructose-1,6-diphosphate
ATP
ADP
PP
Steps – A fuel molecule is energized, using ATP.
Step A six-carbon intermediate splits into two three-carbon intermediates.
1
2
3
44
1 3
Figure 6.7C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Pyruvate
ATP
ADP
ATP
ADP
P
ATP ATP
ADP ADP
P
2-Phosphoglycerate
P
H2O H2O
Phosphoenolpyruvate(PEP)
Steps – ATP and pyruvate are produced.
P 3 -Phosphoglycerate
P
P
9 9
6 6
7 7
8 8
6 9 Step A redox reaction generates NADH.
P
NADH NADHP
P P P P
P
+H+H
ENERGY PAYOFF PHASE
Glyceraldehyde-3-phosphate(G3P)
1,3 -Diphosphoglycerate
P
5
6 9
5 5
66
7 7
88
9 9
NAD NAD
• In the second phase of glycolysis
– ATP, NADH, and pyruvate are formed
Figure 6.7C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CO2
Pyruvate
NAD NADH H
CoA
Acetyl CoA(acetyl coenzyme A)
Coenzyme A
Figure 6.8
6.8 The Link reaction (between glycolysis and Citric acid cycle)
• Prior to the citric acid cycle
– Enzymes process pyruvate, releasing CO2 and producing NADH and acetyl CoA
1
2
3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
When pyruvate enters the matrix of mitochondria it is converted to acetylCoA. Coenzyme A (CoA) is a large molecule (and a vitamin) that acts as a coenzyme.
The conversion of pyruvate to acetylCoA is an coupled oxidation-reduction reaction in which high energy electrons are removed from pyruvate and end up in NADH. The three carbon pyruvate is split into CO2 and the two carbon acetate.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.9 The citric acid cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules
• In the citric acid cycle CoA
CoA
CO2
NAD
NADHFAD
FADH2
ATP P
CITRIC ACID CYCLE
ADP
3
3
3 H
Acetyl CoA
2
Figure 6.9A
The two-carbon acetyl part of acetyl CoA is oxidized
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• The two carbons are added to a four-carbon compound, forming citrate
– Which is then degraded back to the starting compound
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
and Steps and
CITRIC ACID CYCLE
Oxaloacetate
CoA
CoA
2 carbons enter cycle
Acetyl CoA
Citrate
leaves cycle
H
NAD
NADH
CO2
Alpha-ketoglutarate
leaves cycleCO2
ADP P
NAD
NADH H
ATP
Succinate
FAD
FADH2
Malate
H
NAD
NADH
Step
Acetyl CoA stokes the furnace.
Steps
NADH, ATP, and CO2 are generated during redox reactions.
Redox reactions generate FADH2 and NADH.
Figure 6.9B
• For each turn of the cycle
2
2
1
1
3
3
4
4
5
5
Two CO2 molecules are releasedThe energy yield is one ATP, three NADH, and one FADH2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.10 Most ATP production occurs by oxidative phosphorylation
• Electrons from NADH and FADH2
– Travel down the electron transport chain to oxygen, which picks up H+ to form water
• Energy released by the redox reactions
– Is used to pump H+ into the space between the mitochondrial membranes
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes --Driving the synthesis of ATP
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH NAD+
FADH2 FAD
H2OATPADP
ATP synthase
H+ H+ H+
H+
H+H+
H+
H+
H+
H+
H+
H+
H+
H+
P
O2
Electron Transport Chain Chemiosmosis
.
OXIDATIVE PHOSPHORYLATION
+ 212
Figure 6.10
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CONNECTION
6.11 Certain poisons interrupt critical events in cellular respiration
H+
H+
H+
H+
H+
H+ H+ H+ H+
H+
H+
H+
H+
O2
H2OP ATP
NADH NAD+
FADH2 FAD
Rotenone Cyanide, carbon monoxide
Oligomycin
DNP
ATPSynthase
2
ADP
Electron Transport Chain Chemiosmosis
1
2
Figure 6.11
Block the movement of electrons
Block the flow of H+ through ATP synthase
Allow H+ to leak through the membrane
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.12 Review: Each molecule of glucose yields many molecules of ATP (38)
Figure 6.12
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.13 Fermentation is an anaerobic alternative to cellular respiration
• Under anaerobic conditions, many kinds of cells
– Can use glycolysis alone to produce small amounts of ATP
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• In lactic acid fermentation
– NADH is oxidized to NAD+ as pyruvate is reduced to lactate
2 Lactate
NAD NADH NADH NAD2 2 22
2 ATP2 ADP 22 Pyruvate
GLYCOLYSIS
P
Glucose
Figure 6.13A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• In alcohol fermentation
– NADH is oxidized to NAD+ while converting pyruvate to CO2 and ethanol
NAD NADH NADH NAD2 2 2 2
GLYCOLYSIS
2 ADP 2 P ATP
Glucose 2 Pyruvate
releasedCO2
2 Ethanol
22
Figure 6.13B
Figure 6.13C
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS
• 6.14 Cells use many kinds of organic molecules as fuel for cellular respiration
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Carbohydrates, fats, and proteins can all fuel cellular respiration
– When they are converted to molecules that enter glycolysis or the citric acid cycle
OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)
Food, such aspeanuts
Carbohydrates Fats Proteins
Sugars Glycerol Fatty acids Amino acids
Aminogroups
Glucose G3P Pyruvate AcetylCoA
CITRICACID
CYCLE
ATP
GLYCOLYSIS
Figure 6.14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Proteins must first be digested to individual a____ acids.• Amino acids that will be catabolized must have their amino groups
removed via deamination.• The carbon skeletons are modified by enzymes and enter as
intermediaries into glycolysis or the citric acid cycle, depending on their structure.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.15 Intermediates from glycolysis and the citric acid cycle are used as raw materials for making complex organic
substances
ATP needed to drive biosynthesis
ATP
CITRICACID
CYCLE
GLUCOSE SYNTHESISAcetylCoA Pyruvate G3P Glucose
Aminogroups
Amino acidsFatty acids Glycerol Sugars
CarbohydratesFatsProteins
Cells, tissues, organisms
Figure 6.15
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.16 The fuel for respiration ultimately comes from photosynthesis
• All organisms
– Can harvest energy from organic molecules
• Plants
– make these molecules from inorganic sources by the process of photosynthesis
Figure 6.16