Download Carbohydrate Catabolism Cellular Respiration

Oxidation and Reduction Reactions
• Electron transfer from an electron donor to an
electron acceptor
– simultaneously
• Cells use electron carriers to carry electrons
(often in H atoms)
• Two important electron carriers
– Nicotinamide adenine dinucleotide (NAD+)
– 3 ATP per Molecule
– Flavine adenine dinucleotide (FAD) → FADH2
– 2 ATP Per Molecule
© 2012 Pearson Education Inc.
Figure 5.2 Oxidation-reduction, or redox, reactions
Reduction
Electron
donor
Oxidized
donor
Electron
acceptor
Oxidation
Reduced
acceptor
Carbohydrate Catabolism
• Carbohydrate Catabolism
– Many organisms oxidize carbohydrates as
primary energy source
– Remove electrons
– Glucose most commonly used
– Glucose catabolized by two processes:
cellular respiration and fermentation
© 2012 Pearson Education Inc.
Figure 5.12 Summary of glucose catabolism
Respiration
G
L
Y
C
O
L
Y
S
I
S
Glucose
2 Pyruvic acid
Acetyl-CoA
KREBS
CYCLE
Electrons
Fermentation
Pyruvic acid
(or derivative)
Formation of
fermentation
end-products
Carbohydrate Catabolism
• Glycolysis Overview
– Occurs in cytoplasm of most cells
– Involves splitting of a six-carbon glucose into two
three-carbon sugar molecules
– Net gain of two ATP molecules
– Two molecules of NADH
– Precursor metabolite pyruvic acid
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Carbohydrate Catabolism
• Glycolysis
– Divided into three stages involving 10 total
steps
– Energy-investment stage
– 2 ATP are used to phosphorylate glucose
– Lysis stage
– Fructose, 1,6-bipohsphate is cleaved
– Energy-conserving stage
– Pyruvic acid is produced
– 4 ATP are produced
– 2 NADH are produced
© 2012 Pearson Education Inc.
Figure 5.13 Glycolysis-overview
Carbohydrate Catabolism
• Cellular Respiration
– Resultant pyruvic acid completely oxidized to
produce ATP by series of redox reactions
– Three stages of cellular respiration
1. Synthesis of acetyl-CoA
2. Krebs cycle
3. Final series of redox reactions
(electron transport chain)
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Carbohydrate Catabolism
• Cellular Respiration
• 1) Synthesis of acetyl-CoA
– Pyruvic acid is converted into acetyl-coenzyme A
(acetyl-CoA)
– Happens to both pyruvic acid molecules
– 2 molecules of acetyl-CoA
– 2 molecules of CO2
– 2 molecules of NADH
– Cytoplasm
© 2012 Pearson Education Inc.
Figure 5.15 Formation of acetyl-CoA
Respiration
Fermentation
Pyruvic acid
Decarboxylation
Acetate
Coenzyme A
Acetyl-coenzyme A
(acetyl-CoA)
Carbohydrate Catabolism
• Cellular Respiration
• 2) The Krebs cycle
– Great amount of energy remains in bonds of
acetyl-CoA
– Transfers much of this energy to coenzymes
NAD+ and FAD
– Occurs in cytosol of prokaryotes and in
matrix of mitochondria in eukaryotes
© 2012 Pearson Education Inc.
Figure 5.16 The Krebs cycle
Respiration
Fermentation
Acetyl-CoA
OOH
OOH
OOH
OOH
Oxaloacetic acid
OOH
Citric acid
OOH
OOH
OOH
Malic acid
OOH
OOH
Isocitric acid
KREBS
CYCLE
OOH
HOO
Fumaric acid
OOH
OOH
OOH
OOH
Succinic acid
Succinyl-CoA
OOH
-Ketoglutaric acid
Carbohydrate Catabolism
• Cellular Respiration
– The Krebs cycle
– Results in
– Two molecules of ATP
– Two molecules of FADH2
– Six molecules of NADH
– Four molecules of CO2
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Carbohydrate Catabolism
• Cellular Respiration
• 3) Electron transport Chain
– Most significant ATP production
– Carrier molecules pass electrons from one to
another to final electron acceptor
– Energy from electrons used to pump protons (H+)
across the membrane, establishing a proton
gradient
– Located in cristae of eukaryotes and in
cytoplasmic membrane of prokaryotes
© 2012 Pearson Education Inc.
Figure 5.17 An electron transport chain
Respiration
Fermentation
Path of
electrons
Reduced
FMN
Oxidized
Oxidized
FeS
2
Reduced
Reduced
CoQ
Oxidized
Oxidized
Cyt
2
Reduced
Reduced
Cyt
Oxidized
2
Oxidized
Cyt
2
Reduced
Final electron
acceptor
Carbohydrate Catabolism
• Cellular Respiration
– Electron transport
– Four categories of carrier molecules
– Flavoproteins- NADH enters here
– Ubiquinones- FADH2 enters here
– Metal-containing proteins
– Cytochromes
– Aerobic respiration: oxygen serves as final
electron acceptor
© 2012 Pearson Education Inc.
Figure 6.11a
Space
between
membranes
H
H
H
H
H
Electron
carrier
H
H
H
H

H
H
H
H
Protein
complex
Inner
mitochondrial
membrane
–
–
FADH2
FAD
H
Electron
flow
1
2
–
O2

2 H
H2O
–
NAD
NADH
H
ADP
H
H
ATP
P
H
H
Matrix
Electron transport chain
ATP synthase
Figure 5.18 One possible arrangement of an electron transport chain
Bacterium
Mitochondrion
Intermembrane
space
Matrix
Exterior
Cytoplasmic
membrane
Cytoplasm
Exterior of prokaryote
or intermembrane space
of mitochondrion
FMN
Ubiquinone
Cyt b
Phospholipid
membrane
NADH
from glycolysis,
Krebs cycle,
pentose phosphate
pathway, and
Entner-Doudoroff
pathway
Cyt c
Cyt a3
Cyt a
Cyt c2
FADH2
from
Krebs cycle
Cytoplasm of prokaryote
or matrix of mitochondrion
ATP synthase
Carbohydrate Catabolism
• Cellular Respiration Summary
– In glycolysis and the Krebs cycle
– Electrons are taken from glucose and transferred to
NADH and FADH2
– NADH and FADH2 pass their electron to the ETC
– As the electron move down the chain, proton
pumps use energy to move protons across the
membrane
– Creating a proton gradient
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Cellular Respiration
– Chemiosmosis
– Use of electrochemical (ion) gradients to
generate ATP
– Create proton gradient from energy released in
redox reactions of ETC
– “Water held behind a dam”
– Protons flow down electrochemical gradient through
ATP synthases that phosphorylate ADP to ATP
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Cellular Respiration
– Chemiosmosis
– Pumps three protons per NADH
– 3 ATP per NADH
– 30 ATP
– Pumps two protons per FADH2
– FADH2 delivers electrons further down the chain
– Transfers 1/3 fewer protons
– 2 ATP per FADH2
– 4 ATP
– 34 ATP from ECT
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Cellular Respiration
– Glycolysis- net 2 ATP
– Krebs cycle- 2 ATP
– ETC- 34 ATP
• 38 ATP total
© 2012 Pearson Education Inc.
Respiration Review
• https://www.youtube.com/watch?v=Gb2EzF_XqA
Practice
• Label the diagram of respiration with the
proper terms.
Carbohydrate Catabolism
• Fermentation
– Sometimes cells cannot completely oxidize
glucose by cellular respiration
– Cells require constant source of NAD+
– Cannot be obtained simply using glycolysis and
Krebs cycle
– Fermentation pathways provide cells with source
of NAD+
– Uses organic molecule within cell as final electron
acceptor
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Fermentation
– Any spoilage of food by microorganisms
– Any process that produces alcoholic beverages
or acidic dairy products
– Scientific definition:
– Releases energy from oxidation of organic
molecules
– Does not require oxygen
– Does not use the Krebs cycle or ETC
– Uses an organic molecule as the final electron
acceptor
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Fermentation
– Allows ATP production to continue in the
absence of cellular respiration
– Not as efficient as cellular respiration
– Most of the energy remains in the bonds of the
fermentation product
– Products include: ethanol and lactic acid
– Fermentation can be used to identify mos
– Proteus ferment lactose
– E. coli ferments glucose and lactose
© 2012 Pearson Education Inc.
Carbohydrate Catabolism
• Fermentation
– Contains single carbohydrate and a source of
protein
– Used to identify what carbon source a microbe
can use
– If sugar is used, acidic end products and gas are
produced
– pH indicator changes color
© 2012 Pearson Education Inc.
Figure 5.21 Fermentation
Respiration
Fermentation
Pyruvic acid
Lactic acid
Acetaldehyde
Ethanol
Figure 5.22 Representative fermentation products and the organisms that produce them
Glucose
Pyruvic acid
Organisms
Propionibacterium
Aspergillus
Lactobacillus
Streptococcus
Saccharomyces
Clostridium
Fermentation
CO2, propionic acid
Lactic acid
CO2, ethanol
Acetone, isopropanol
Wine, beer
Nail polis remover,
rubbing alcohol
Fermentation
products
Swiss cheese
Cheddar cheese,
yogurt, soy sauce