Download Energetics

Metabolism: The sum of the chemical reactions
in an organism
A metabolic pathway is a sequence of enzymatically
catalyzed chemical reactions in a cell
Metabolic pathways are determined by enzymes
Catabolic and Anabolic Reactions
 Catabolism: Provides energy and building blocks for
anabolism. (Break down)
 Anabolism: Uses energy and building blocks to build
large molecules. (Synthesis)
Metabolism: the sum of Catabolism and
Anabolism
Oxidation: the loss or removal of electrons
Reduction: the gain of electrons
Role of ATP in Coupling Reactions
Figure 5.1
Oxidation-Reduction Reactions
 Oxidation: Removal of electrons
 Reduction: Gain of electrons
 Redox reaction: An oxidation reaction paired with a
reduction reaction
Oxidation-Reduction Reactions
 In biological systems, the electrons are often associated
with hydrogen atoms. Biological oxidations are often
dehydrogenations
The Generation of ATP
 ATP is generated by the phosphorylation of ADP
Substrate-Level Phosphorylation
 Energy from the transfer of a high-energy PO4– to
ADP generates ATP
Oxidative Phosphorylation
 Energy released from transfer of electrons (oxidation)
of one compound to another (reduction) is used to
generate ATP in the electron transport chain
Carbohydrate Catabolism
 The breakdown of carbohydrates to release energy
 Glycolysis
 Krebs cycle
 Electron transport chain
Glycolysis
 The oxidation of glucose to pyruvic acid produces ATP
and NADH
Figure 5.11
Preparatory Stage of Glycolysis
 2 ATP are used
 Glucose is split to form 2 glyceraldehyde-3-phosphate
Figure 5.12, steps 1–5
Energy-Conserving Stage of
Glycolysis
 2 glucose-3-phosphate
oxidized to 2 pyruvic acid
 4 ATP produced
 2 NADH produced
Figure 5.12, steps 6–10
The Reactions of Glycolysis
The Krebs Cycle
 Oxidation of acetyl CoA produces NADH and FADH2
The Krebs Cycle
Figure 5.13
The Reactions of the Krebs Cycle
The Electron Transport Chain
 A series of carrier molecules that are, in turn, oxidized
and reduced as electrons are passed down the chain
 Energy released can be used to produce ATP by
chemiosmosis
Overview of Respiration and
Fermentation
Figure 5.11
Chemiosmotic Generation of ATP
Figure 5.16
An Overview of Chemiosmosis
Figure 5.15
A Summary of Respiration
 Aerobic respiration: The final electron acceptor in
the electron transport chain is molecular oxygen (O2).
 Anaerobic respiration: The final electron acceptor in
the electron transport chain is not O2. Yields less
energy than aerobic respiration because only part of
the Krebs cycles operates under anaerobic conditions.
Respiration
Figure 5.16
Carbohydrate Catabolism
 Energy produced from complete oxidation of one
glucose using aerobic respiration
ATP Produced
NADH
Produced
FADH2
Produced
Glycolysis
2
2
0
Intermediate step
0
2
0
Krebs cycle
2
6
2
Total
4
10
2
Pathway
Carbohydrate Catabolism
 ATP produced from complete oxidation of one glucose
using aerobic respiration
Pathway
By Substrate-Level
Phosphorylation
By Oxidative Phosphorylation
From NADH
From FADH
Glycolysis
2
6
0
Intermediate step
0
6
0
Krebs cycle
2
18
4
Total
4
30
4
Carbohydrate Catabolism
 36 ATPs are produced in eukaryotes
Pathway
By Substrate-Level
Phosphorylation
By Oxidative Phosphorylation
From NADH
From FADH
0
Glycolysis
2
6
Intermediate step
0
6
Krebs cycle
2
18
4
Total
4
30
4
Fermentation
 One process by which pyruvate is subsequently
metabolized in the absence of oxygen
 The result of the need to recycle the limited amount
of NAD by passing the electrons of reduced NAD to
other molecules
 Homolactic acid fermentation: pyruvate is
converted directly to lactic acid, using electrons
from reduced NAD
 Alcoholic fermentation: carbon dioxide is released
from pyruvate to form acetaldehyde, which is
reduced to ethanol
Fermentation
 Any spoilage of food by microorganisms (general use)
 Any process that produces alcoholic beverages or
acidic dairy products (general use)
 Any large-scale microbial process occurring with or
without air (common definition used in industry)
Fermentation
 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
An Overview of Fermentation
Figure 5.18a
Types of Fermentation
Figure 5.19
Requirements of ATP Production
Figure 5.27
A Nutritional Classification of
Organisms
Figure 5.28
A Nutritional Classification of
Organisms
Figure 5.28
A Nutritional Classification of
Organisms
Figure 5.28
Metabolic Diversity among
Organisms
Nutritional Type
Energy Source
Carbon Source
Example
Photoautotroph
Light
CO2
Oxygenic:
Cyanobacteria plants
Anoxygenic: Green,
purple bacteria
Photoheterotroph
Light
Organic
compounds
Green, purple nonsulfur
bacteria
Chemoautotroph
Chemical
CO2
Iron-oxidizing bacteria
Chemoheterotroph
Chemical
Organic
compounds
Fermentative bacteria
Animals, protozoa,
fungi, bacteria.