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Groups of bugs based on energy capture and carbon source
• AUTOTROPHY: Use carbon dioxide to synthesize organic molecules
• Two types:
1. Photoautotrophs: obtain energy from light
2. Chemoautotrophs: obtain energy from oxidizing simple inorganic substance
Groups of bugs based on energy capture and carbon source cont’d
• HETEROTROPHY: Get carbon dioxide from ready made organic molecules
• Two types:
1. Photoheterotrophs: obtain chemical energy from light
2. Chemoheterotrophs: obtain energy from breaking down ready-made organic compounds
The main types of energy capturing Metabolism
All microorganisms
Inorganic CO2 = carbon source AUTOTROPH
(Self feeders)
Making own food by reducing CO2
Photoautotrophs Chemoautotrophs
Organic compound = carbon source HETEROTROPH
Using ready-made organic molecules for food
Photoheterotrophs Chemoheterotrophs
Examples of Energy SourceType Energy Source Carbon Source Examples
Photolithotrophs Light CO2 Algae,Purple sulphur bacteri,green sulphur bacteria
Photoorganotrophs Light Organic Compounds Purple non sulphur bacteria
Chemolithotrophs Oxidation of inorganic compounds
Nitrifying bacteria,iron bacteria,H2 bacteria
Chemoorganotrophs Oxidation of organic compounds
Organic Compounds Most bacteria, fungi,protozoa
Photosynthesis and Respiration
Metabolism• The sum of all chemical processes carried out by living
organisms
• Anabolism: rxn that requires energy in order to synthesize complex molecules from the simpler ones
- (use energy and building blocks to build large molecules)
• Catabolism: rxn that releases energy by breaking complex molecules into simpler ones which can be reused as building blocks
- (provides energy and building blocks for anabolism)
Metabolism: The sum of catabolism and anabolism
Larger molecules
Smaller Molecules
Catabolism
Anabolism
Energy
Metabolic Pathway
• Glycolisis, fermentation, aerobic respiration and photosynthesis each consists of a series of chemical reaction
• The product of one reaction serves as the substrate for the next: ABCD
• Such chain of reactions is called a metabolic pathway:
- Anabolic pathways make the complex molecules that form structure of cells, enzymes and molecules that control cells
- Catabolic pathways capture energy in a form a cell can use
Oxidation-Reduction Reactions
• All catabolic reactions involve electron transfer which is directly related to oxidation and reduction (redox potential)
• Redox reaction: An oxidation reaction paired with a reduction reaction
- Oxidation: the loss of removal of electrons
-Reduction: the gain of electrons
Oxidation-Reduction Reactions
Representative Biological Oxidations
Acronyms for oxidation and reduction: •Oxidation Is Losing Electrons, Reduction Is Gaining Electrons: OIL RIG •Losing Electrons Oxidation, Gaining Electrons Reduction: LEO the lion. GER! or LEO says GER•Electron Loss Means Oxidation: ELMO
In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenation.
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Metabolic Pathways of Energy Production
Metabolic Pathways of Energy Production
(b)
• Carrier molecules such as Cytochrome (cyt) and some coenzymes carry energy in the form of electrons in many biochemical reactions
• Coenzymes such as FAD carry whole hydrogen atoms (electrons together with protons); NAD carries one hydrogen atom and one “naked” electron
• When co-enzymes are reduced, they increase in energy, when they are oxidized, they decrease in energy.
Energy Transfer by Carrier Molecules
Energy Generation of ATP
• ATP is generated by the phosphorylation of ADP
ADP + Pi + Energy ATP • In cells, energy is provided by the hydrolysis of
ATP
ATP ADP + Pi + Energy
Energy
Energy
Generation of ATP
1. Substrate level Phosphorylation: Energy from the transfer of a high energy PO4 to ADP generates ATP
C-C-C-P + ADP C-C-C + ATP
2. Oxidative Phosphorylation: Energy relseased from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate Atp in the electron transport chain
3. Photophosporylation: Light causes chlorophyll to give up electrons. Energy released from transfer of electrons (oxidation) of chlorophyll trough a system of carrier molecules is used to generate ATP
Overview of Respiration vs Fermentation
Carbohydrate Catabolism
• The breakdown of carbohydrate to release energy involves
1. Glycolisis (cytoplasm)
2. Krebs cycle (mitochondrion)
3. Electron transport chain
Glycolysis
• Glycolysis (Embden Meyerhof pathway) is the metabolic pathway used by most autotrophic and heterotrophic organismsm to begin breakdown of glucose
• Does not require oxygen, but occur in precense or absence of oxygen
• Overall chemical reaction of Glycolysis
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Glycolysis: Oxidation of Glucose
2ATP2 NAD+
2ADP 2NADH + 2H+
4 ADP
4 ATP
Glucose
two Glyceraldehyde-3-PO4
two Pyruvate
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Glycolysis: Oxidation of Glucose
2 glyceraldehyde-3-phosphate
O
CH2HO
OH
OH
OH
OH PO4O
CH2O
OH
CH2 O PP
OHHO
glucosefructose-1,6-diphosphate
CHO
C OHH
CH2O P
2
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Glycolysis: Oxidation of Glucose
2 NAD+ 2 NADH + 2 H+
2 glyceraldehyde-3-phosphate
CHO
C OHH
CH2O P
2 2
CHO
CH O
CH3
2 pyruvate
2 ADP + 2 Pi 2 ATP
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Glycolysis: Oxidation of Glucose
Glycolysis generates 2 ATP molecules and 2 NADH + 2 H+
Two ATP used in adding phosphate groups to glucose and fructose-6-phosphate (- 2 ATP)
Four ATP generated in direct transfer to ADP by two 3-C molecules (+ 4 ATP)
Glucose + 2 ADP + 2 Pi + 2 NAD+ 2pyruvate + 2 ATP + 2 NADH + 2 H+
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Pathways for Pyruvate
Aerobic conditions O
||
CH3–C –COO- + NAD+ + CoA
pyruvate
O
||
CH3–C –CoA + CO2 + NADH + H+
acetyl CoA
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Pathways for Pyruvate
Anaerobic conditions (No O2 available)
Reduce to lactate to replenish NAD+ for glycolysis
O OH
|| |
CH3–C –COO- + NADH + H+ CH3–CH –COO- + NAD+
pyruvate lactate
enzyme: lactate dehydrogenase
Glycolysis
Alternative to Glycolysis
• Pentose phosphate pathway
a. Uses pentoses and NADPH
b. Operates with glycolisis
• Entner-Doudoroff pathway
a. Produces NADPH and ATP
b. Does not involve glycolisis
c. Pseudomonas, Rhizobium, Agrobacterium
Intermediate step
• Pyruvic acid (from glycolysis) is oxidized and decarboxylated
The Krebs Cycle/ The Citric acid cycle (TCA cycle)
• Oxidation of acetyl Co-A produces NADH and FADH2 (mitochondrion)
The Electron Transport Chain
• An electron transport chain (ETC) couples electron transfer between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer of H+ ions (protons) across a membrane.
• A series of oxidation-reduction reactions, the electron transport chain (ETC) performs 2 basic functions:
1. Accepting electrons from an electron donor and transferring them to an electron acceptor
2. Conserving for ATP synthesis some of the energy released during the electron transfer
• 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
The Electron Transport Chain
The Electron Transport Chain
Chemiosmosis
• Electrons from the hydrogen atoms removed from the reactions of the Krebs cycle are transferred through the electron transport system
• Electron transport creates the H potential across the membrane
• Combination of hydrogen/electron carriers
Chemiosmosis
Chemiosmosis
Questions?
