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Transcript of Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings INTRODUCTION TO CELLULAR...
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
– To produce glucose and O2 from CO2 and H2O
CO2
H2O
Glucose
O2
ATP
ECOSYSTEM
Sunlight energy
Photosynthesis in chloroplasts
Cellular respiration in mitochondria
(for cellular work)
Heat energy
Figure 6.1
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 banks energy in ATP molecules
• Cellular respiration breaks down glucose molecules
– And banks 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
CONNECTION
6.4 The human body uses energy from ATP for all its activities
• ATP powers almost all cellular and body activities
Table 6.4
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
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
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 prime 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
• 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
CO2
Pyruvate
NAD NADH H
CoA
Acetyl CoA(acetyl coenzyme A)
Coenzyme A
Figure 6.8
6.8 Pyruvate is chemically groomed for the 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
6.9 The citric acid cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules
• In the citric acid cycle
– The two-carbon acetyl part of acetyl CoA is oxidized
CoACoA
CO2
NAD
NADHFAD
FADH2
ATP P
CITRIC ACID CYCLE
ADP
3
3
3 H
Acetyl CoA
2
Figure 6.9A
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
– Two CO2 molecules are released
– The energy yield is one ATP, three NADH, and one FADH2
2
2
1
1
3
3
4
4
5
5
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
• Various poisons
– Block the movement of electrons
– Block the flow of H+ through ATP synthase
– Allow H+ to leak through the membrane
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
12
Figure 6.11
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
6.12 Review: Each molecule of glucose yields many molecules of ATP
• Oxidative phosphorylation, using electron transport and chemiosmosis
– Produces up to 38 ATP molecules for each glucose molecule that enters cellular respiration
NADHNADH
NADH NADH FADH2
Cytoplasm
Electron shuttleacross membrane Mitochondrion
GLYCOLYSISGlucose Pyruvate
by substrate-level phosphorylation
by substrate-level phosphorylation
by oxidative phosphorylation
OXIDATIVE PHOSPHORYLATION
(Electron Transport and Chemiosmosis)
2 AcetylCoA
CITRIC ACIDCYCLE
2 ATP 2 ATP about 34 ATP
Maximum per glucose:About
38 ATP
2
2 6 2
2 2
(or 2 FADH2)
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
6.15 Food molecules provide raw materials for biosynthesis
• Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials
• This process of biosynthesis
– Consumes ATP
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, but not animals
– Can also make these molecules from inorganic sources by the process of photosynthesis
Figure 6.16