Microbial Metabolism Flashcards
–Enzymes found within the cytosol of the cell
–Active inside the cell
•Endoenzymes
–Enzymes secreted by cell into environment
–Active outside the cells
•Exoenzymes
•Some enzymes need accessory molecules such as:
- Co-factor
- Co-enzyme
•inorganic helper, metal ions common, Mg++, Mn++
Co-factor (accessory molecule for enzyme)
•organic non-protein helper, NAD, FAD
Co-enzyme (accessory molecule for enzyme)
Oxygenic Photosynthesis
Holoenzyme
Type of Enzyme Activity Regulaton
–Competitive inhibition
–Allosteric (non-competitive) inhibition
–Allosteric activation
•Enzyme level regulation
Type of Enzyme Activity Regulation
–Transcription control (genetics lecture)
•Genetic level regulation
Competitive inhibition
Allosteric Inhibition
Allosteric Activation
Type of Metabolism Regulation
–If two energy sources are available, cells use the more energy efficient of the two first
–If glucose and lactose both available, lac operon off until glucose levels low
•Catabolite repression
Type of Metabolism Regulation
–Cells may synthesize molecules only as needed, cease synthesis if molecules readily available
–In trp biosynthesis, trp is co-repressor for trp operon, trp also is allosteric inhibitor for enzyme in biosynthesis
•Feedback inhibition
Feedback Inhibition
Sum of all chemical reactions occurring within a cell
Metabolism
–Series of chemical reactions mediated by enzymes
–Product of one reaction becomes substrate of the next
–Catabolic metabolism
–Anabolic metabolism
•Metabolic pathway
Metabolic Pathway
–Break larger molecules into smaller products (hydrolysis)
–Exergonic (release energy)
–ATP generated
•Catabolic pathways
–Synthesize large molecules from the smaller products of catabolism (dehydration synthesis)
–Endergonic (require energy)
–ATP consumed
•Anabolic pathways
•Energy stored in high energy bond in ATP
–Phosphorylation
•ADP made into ATP in three ways
–Substrate-level phosphorylation
–Oxidative phosphorylation
–Photophosphorylation
Substrate-level phosphorylation
•Four major strategies for producing ATP are
Note:
- All pathways are redox reactions
- Can be differentiated by products, final electron acceptors
–Aerobic respiration
–Anaerobic respiration
–Fermentation
–Photosynthesis
–Presence of electron transport system
–Chemiosmosis
–Aerobic respiration
–Anaerobic respiration
Cellular Respiration
–Uses oxygen as a final electron acceptor
–Glucose + ADP + O2 ATP + CO2 + H2O
–Four steps in overall pathway
- •Glycolysis
- •Acetyl CoA synthesis
- •Krebs cycle
- •Electron Transport Chain (chemiosmosis)
–Produces 34-36 ATP
Aerobic Respiration
•NAD+
–Required coenzyme for
- •Glycolysis
- •Acetyl-CoA synthesis
- •Krebs cycle
–Reduced to NADH during these processes
–Oxidized back to NAD+ at electron transport chain
Aerobic Respiration
- –Uses an electron transport system and chemiosmosis
- –Uses an inorganic oxygen containing molecule as the final electron acceptor
- –NO3-, SO4-2, CO2
- –Less efficient than aerobic respiration, produces less than 34 ATP per glucose
- •Does NOT occur in eukaryotes
•Anaerobic Respiration
–Reduction of CO2 to CH4
–Methanococcus spp.
•Carbon dioxide respiration (Anaerobic Respiration)
–Reduction of SO4 to HS
–Desulfobacter spp.
•Sulfate respiration (Anaerobic Respiration)
–Reduction of NO3 to N2
–Paracoccus denitrificans
•Nitrate respiration (Anaerobic Respiration)
–Glucose via 2 pyruvate, 2 ATP, 2 NADH
–Typical glycolysis
•Embden-Meyerof-Parnas Pathway (Glycolysis)
–Glucose via 2 pyruvate, 1 ATP, 1 NADH, 1 NADPH
•Entner-Doudoroff pathway (Glycolysis)
–Glucose via 2 NADPH, CO2, ribulose-5-phosphate
•Pentose-Phosphate pathway (Glycolysis)
- Uses organic molecule as final electron acceptor
- Oxidizes NADH to NAD+ so that metabolism can continue
- Low yields of ATP per glucose (1-2 ATP)
- End products vary by organism – due to differences in metabolic enzymes
Fermentation
–Glucose + 2 ADP yields 2ATP + CO2 + Ethanol
–Saccharomyces cerevisiae
•Alcohol fermentation
(EMP Fermentation)
–Glucose + 2 ADP 2ATP + lactate
–Many bacteria and us
•Acid fermentation (EMP Fermentation)
- Lactic acid fermentation
- Propionic acid fermentation
Other Fermentations
–Lactic acid only end product
–Glucose + 2ADP yields 2 lactate + 2 ATP
–Lactobacillus spp., Lactococcus spp.
(Lactic Acid Fermentation)
•Homolactic fermentation
Homolactic Fermentation
–Lactic acid, ethanol and CO2
–Glucose + ADP yeilds ethanol + lactate + CO2 + ATP
–Leuconostoc spp.
•Heterolactic fermentation (Lactic Acid Fermentation)
Heterolactic Fermentation
•End products include propionic acid, acetic acid, carbon dioxide
–Critical part of making Emmentaler (swiss cheese)
–Propionibacterium freudenreichii
Propionic Acid Fermentation
Propionic Acid Fermentation
Type of photosynthesis
–Use of light energy to produce ATP and reduced NADPH
–ATP and NADPH used in light independent reactions
•Light dependent reactions
Type of photosynthesis
–Autotrophs use this captured energy (ATP and NADPH) to fix inorganic carbon
•Light independent reactions
•Anoxygenic photosynthesis
(Light Dependent Reactions)
•Oxygenic photosynthesis
(Light Dependent Reactions)
