Download Outline – Cellular Respiration Energy to Drive Metabolism Cellular

Fig. 9.1
Outline – Cellular Respiration
Respiration
• Cellular Energy Harvest: an Overview
• Stages of Aerobic Cellular Respiration
– Glycolysis
– Oxidation of Pyruvate
– Krebs Cycle
– Electron Transport Chain
• Anaerobic Respiration and Fermentation
• Catabolism of Protein and Fat
Energy to Drive Metabolism
• Autotrophs – use inorganic sources of energy
Photoautotrophs
– harvest sunlight
– convert radiant energy into chemical energy.
Chemoautotrophs
Cellular Respiration
Metabolic pathways Æ series of reactions
Æ oxidations – loss of electrons
Æ dehydrogenations
hydrogen atom (1 electron, 1 proton).
– harvest energy from inorganic sources
– S, NH3, NH2, H2S, Fe+2
• Heterotrophs – use organic sources of energy
– live off energy produced by autotrophs.
– extract energy from food catabolism
– Uuse cellular respiration to extract energy
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Cellular Aerobic Respiration
Cellular Respiration
• How do cells harvest energy
– cells break chemical bonds
– shift electrons from molecule to molecule
Glucose molecules broken down to CO2
Glucose loses electrons (as hydrogen atoms) to oxygen
Cells tap energy from electrons
Cells bank energy in ATP
• Where do the electrons go?
Loss of hydrogen
atoms (oxidation)
– Aerobic respiration
• final electron acceptor is oxygen
C6H12O6
– Anaerobic respiration
+
6 CO2 + 6 H2O
6 O2
+
Glucose
(ATP)
Energy
Gain of hydrogen
atoms (reduction)
• final electron acceptor is not oxygen
ΔG = -686kcal/mol
glucose
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Transferring Energy
Transferring Energy – Electron Transport Chain
Oxidation - Dehydrogenase removes electrons from substrate
1. NADH passes electrons to an electron transport chain
2. Energy is released as electrons “fall” and lose energy
Reduction - Electrons in Hydrogen Transferred to NAD+
NADH
H
Oxidation
H
O
Dehydrogenase
O + 2H
(Enzyme)
NAD
+
+ 2H
2H
+
Reduction
+ 2e−
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
NADH +
(carries
2 electrons)
NAD
+
+
H
+
ATP
2e−
Controlled release of
energy for ATP
synthesis
H+
Electron
Transport
Chain
H+
2e−
O2
H2O
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 9.6 (TEArt)
Aerobic Respiration
Oxidation of Glucose
Aerobic Respiration Stage 1: Glycolysis
1
2
3
6-carbon glucose
(Starting material)
2 ATP
Complete oxidation of glucose proceeds in 4 stages
1. glycolysis
2. pyruvate oxidation
3. Krebs cycle (citric acid cycle)
4. electron transport chain & chemiosmosis
P
P
P
6-carbon sugar diphosphate
P
6-carbon sugar diphosphate
P
P
P
3-carbon sugar 3-carbon sugar
phosphate
phosphate
P
3-carbon sugar 3-carbon sugar
phosphate
phosphate
NADH
NADH
2 ATP
2 ATP
3-carbon
pyruvate
3-carbon
pyruvate
Priming reactions.
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Fig. 9.7a (TEArt)
1. Priming
3. Energy Harvest
CH2 O
O
7. Removal of high-energy
phosphate by two ADP
molecules produces two
ATP molecules and leaves
two 3PG molecules.
P
Phosphoglucose
isomerase
CH2 O
O
P
ATP
P
3
Phosphofructokinase
P O
ADP
Electron transport
chain
CH2
O
CH2
O
P
8–9. Removal of water yields
two PEP molecules, each
with a high-energy
phosphate bond.
O CH2
C
O Dihydroxyacetone
CH2OH phosphate
2. Cleavage
Glyceraldehyde 3
-phosphate (G3P)
H
C O
CHOH
CH2 O
P
Pi
NAD+
Pi
6
3. Energy Harvest
Glyceraldehyde
NADH
NADH
3-phosphate
P O C O
dehydrogenase
CHOH
1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate
CH2 O P
(BPG)
(BPG)
NAD+
7
Phosphoglycerate
kinase
3-Phosphoglycerate
(3PG)
OC
CHOH
3-Phosphoglycerate
(3PG)
2-Phosphoglycerate
(2PG)
ADP
C O
H C O
CH2OH
2-Phosphoglycerate
(2PG)
P
OH2O
C
Phosphoenolpyruvate
(PEP)
10
Pyruvate kinase
ATP
Pyruvate
O P
CH2
O-
9
Enolase
Phosphoenolpyruvate
(PEP)
10. Removal of high-energy
phosphate by two ADP
molecules produces two
ATP molecules and two
pyruvate molecules.
ADP
ATP
8
Phosphoglyceromutase
H2O
Fructose 1,6-bisphosphate
4,5 Aldolase
Isomerase
ADP
ATP
CH2OH
Fructose 6-phosphate
Krebs
cycle
1,3-Bisphosphoglycerate
(BPG)
Glycolysis - Steps
O
Glucose 6-phosphate
2
Pyruvate
oxidation
6. Oxidation followed by
phosphorylation produces
two NADH molecules and
two molecules of BPG, each
with one high-energy
phosphate bond.
CH2OH
ADP
Glycolysis
4–5. Six-carbon molecule split
into 2 three-carbon molecules
one G3P & dhap which is
converted to G3P
Fig. 9.7b (TEArt)
Glucose
1
ATP
Hexokinase
1. Priming
Energy-harvesting
reactions.
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Glycolysis - Steps
Glucose
Cleavage reactions.
ADP
ATP
Pyruvate
O
C O
CH2
P
OC OHarvest
3. Energy
C O
CH3
3
Glycolysis - Summary
™
™
™
Glycolysis = Catabolic pathway
10 biochemical steps
Major Stages
1. Priming
2. Cleavage
3. Energy Harvesting
Substrate-level phosphorylation
™
™
™
Nets 2 ATP molecules
Nets 2 pyruvates
Nets 2 NADH
™
Universal: All living organisms
1. Releases CO2
2. Produces NADH and acetyl Coenzyme A
3. Acetyl CoA is transferred to the mitochondrion
Pyruvate in
cytoplasm
Outer mitochondrial membrane
Inner mitochondrial membrane
Aerobic Respiration Stage 3: Krebs Cycle
Mitochondrion
Aerobic Respiration Stage 3: KREBS CYCLE
Aerobic Respiration Stage 2
Oxidation of Pyruvate
4
Krebs Cycle Summary
1.
Location: Mitochondrial matrix
2.
Loss of 2 CO2 = completion of pyruvate oxidation
3.
ATP synthesis
4.
Reduction of Coenzymes…for each turn of cycle:
¾ 3 NAD+ Æ 3 NADH… or 6 for each glucose
¾ 1 FAD Æ 1 FADH2 …or 2 for each glucose
Mitochondrion Structure
Glycolysis + Pyruvate Oxidation + Krebs Cycle
After glycolysis, pyruvate oxidation, and the Krebs
cycle, glucose has been oxidized to:
- 6 CO2
- 4 ATP
- 10 NADH
Proceed to electron transport chain.
- 2 FADH2
Stage 4: Oxidative Phosphorylation
1.Electron Flow occurs in mitochondrial membrane
2.Protons are transported across the inner mitochondrial membrane
H2O
3.ATP is synthesized by Chemiosmosis
H+ H+
H+
H+ H+
H+
H+
H+
H+
.
Outer
Membrane
Intermembrane
Space
Cristae
Inner
Membrane
H
Intermembrane
space
Inner
mitochondrial
membrane
Matrix
+
H
ee-
FADH2
NAD+
NADH
Mitochondrial
matrix
H+ H+
H+
FAD
H+
H+
H
+
H+
H+
H+
H+
+
H+
H+ +
O H
Electron Transport Chain
H2O
Figure 6.10
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
5
Stage 4: Oxidative Phosphorylation
Stage 4: Oxidative Phosphorylation
ATP Synthesis by Chemiosmosis
H+
++
H
++
H
H
H+
H+
H+
H+
H+
H+
H+
+
H+
H+
H+
H+
H+
H
H+
Electron Transport Chain
ADP
P
H+
1. Occurs in the mitochondria
2. Uses the energy released by electrons to
pump H+ across a membrane
3. Harnesses the energy of the H+ gradient
through chemiosmosis, producing ATP
ATP
H+
H+
Chemiosmosis by
ATP synthase
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 9.5 (TEArt)
Oxidation-Reduction and Aerobic Respiration
Aerobic Cellular Respiration – Overview
Cytoplasm
Glucose
1. Glycolysis
2. Pyruvate oxidation
3. Krebs (Citric Acid) Cycle
NADH
Glycolysis
ATP
4. Electron Transport Chain
Pyruvate
Pyruvate
oxidation
AcetylCoA
NADH
NADH
Krebs
cycle
CO2
Intermembrane
space
Mitochondrial matrix
CO2
ATP
FADH2
H2O
e-
ATP
NAD+ and FAD
Electron
transport chain
Inner mitochondrial membrane
Mitochondrion
6
ATP Synthesis & Oxidation of Glucose
Aerobic Respiration
Cells are able to make ATP via:
1. substrate-level phosphorylation – transferring a
phosphate directly to ADP from another molecule
2. oxidative phosphorylation – use of ATP
synthase and energy derived from a proton (H+)
gradient to make ATP
Recycling NADH
– With continuous Glycolysis
• NADH Increases
• NAD+ Decreases
– NADH must be recycled into NAD+
1. aerobic respiration Æ NADH oxidized in mitochondria
2. anaerobic respiration Æ NADH oxidized another way
Æ fermentation = use of organic molecules as final electron acceptor
Æ anaerobic respiration = use of inorganic molecule as e- acceptor
Sulfate-reducing bacteria
Methanogenic bacteria
Fate of Pyruvate
Summary: Respiration without oxygen
1. Glycolysis produces a net of 2ATP
2. Fermentation - recycles NADH to NAD+
Lactic acid fermentation
CO2 and Ethanol fermentation
3. Anaerobic Respiration
Methanogens
CO2 Æ CH4
SulfateSulfate-reducing Bacteria
SO4 Æ H2S
28
7
Fig. 9.20 (TEArt)
Respiration Efficiency
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Energy Sources for Cellular Respiration
Macromolecules
Cell
building
blocks
Nucleic Proteins Polysaccharides
acids
Nucleotides
Amino
acids
Sugars
Fats
Fatty
acids
Pyruvate
Oxidative
respiration
Acetyl-CoA
Krebs
cycle
Metabolic
Waste
products
Fig. 9.23 (TEArt)
NH3
H2O
CO2
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Fermentation
Alcohol fermentation
H
H C OH
CH3
2 Ethanol
Glucose
2 ADP
2 ATP
O–
C O
C O
CH3
G
L
Y
C
O
L
Y
S
I
S
2 NADH
CO2
2 Pyruvate
Lactic acid fermentation
Glucose
2 ADP
2 ATP
O–
C O
C O
CH3
2 NAD+
G
L
Y
C
O
L
Y
S
I
S
H
C O
CH3
2 Acetaldehyde
O–
C O
H C OH
CH3
2 NAD+ 2 Lactate
2 NADH
2 Pyruvate
8