Metabolism
Catabolism-Glycolysis (Kreb Cycle) Anabolism-Photosynthesis
Metabolism
• Sum of all chemical reactions • Catabolism
– Exergonic reaction – Most of energy in ATP –last phosphate bond
Metabolism
• Anabolism
– Consume more energy than produce – Use ATP for energy
Enzymes
• • • • • • • Biological catalysts Energy of activation Specificity Primary structure Secondary structure Tertiary structure Quaternary structure
Components of Enzymes
• Apoenzyme-protein only • Cofactor-nonprotein
– Trace elements
• Coenzyme-organic cofactor
– Carriers of electrons etc – NAD+
Enzyme-substrate Complex
• • • • Active site on enzyme Transformation in substrate Products released Enzyme orients substrate
• Lowers energy of activation
Denaturation
• • • • • Structure of enzyme is disrupted No longer active Temperature pH Substrate concentration
– Enzyme becomes saturated
Inhibitors
• Competitive inhibitors • Noncompetitive inhibitors
– Allosteric site
Feedback Inhibition
• End product inhibition • Series of enzymes –end product
Energy Production
• Oxidation-reduction reactions • Generation of ATP
– Phosphorylation
– Used for metabolism, binary fission, endospore formation movement
Types of Phosphorylation
• Substrate level • Oxidative phosphorylation
• Photophosphorylation
Carbohydrate Metabolism
• Glucose as an example • Two energy processes
– Cellular respiration – Fermentation – Glycolysis
• Respiration-Krebs cycle & electron transport chain
Glucose Metabolism
C6H12O6 + 6O2 + 38 ADP +38 P 6CO2 + 6H2O + 38 ATP
Glycolysis
• • • • • • • • Summary of glycolysis 2 molecules of pyruvate (3 C) Production of 2 NADH & 2H+ Net of 2 ATP Substrate phosphorylation Takes place in cytosol of bacteria & eukaryotes No oxygen is required Alternate pathways
Cellular Respiration
• Cellular respiration
– Final electron acceptor is inorganic molecule
• Two types based on final electron acceptor
Aerobic Respiration
• • • • Krebs cycle Mitochondria of eukaryotes-matrix Cytosol in prokaryotes Intermediary step- production of acetyl CoA
– 2 CO2 & 2 NADH
Aerobic Respiration
• • • • Acetyl Co enters Krebs cycle 4 carbons of glucose released as CO2 6 NADH & 2 FADH2 produced 2 ATP by substrate phosphorylation
Electron Transport Chain
• Series of redox reactions • Stepwise release of energy • Oxygen final acceptor of electrons
• Inner membrane of mitochondria in eukaryotes • Foldings of plasma membrane or thylakoid infoldings( photosynthesis) • Occurs only in intact membranes
Carrier Molecules
• Some carry both electrons & protons (H+) • Cytochromes transfer electrons only • Oxygen is last link of chain
Chemiosmosis
• ATP generation • Proton pumps • Proton motive force • Protein channels with ATP synthases
ATP Production
• Protons release energy as rush through pore • 3 ATP per NADH • 2 ATP per FADH2 • ATP produced via oxidative phosphorylation • Damage to membrane ceases proton movement
Anaerobic Respiration
• Final electron acceptor is an inorganic molecule other than oxygen • Some use NO3 - ,SO42• Important in nitrogen and sulfur cycles • ATP varies, less than 38 • Only part of Krebs cycle & ETC used
Fermentation
• • • • Pyruvate converted to organic product NAD+ regenerated Doesn’t require oxygen Does not use Krebs cycle or ETC
– Shut down
• Organic molecule is final electron acceptor • Produces 2 ATP max
Photosynthesis
• Conversion of light energy into chemical energy • Anabolism (carbon fixation)-produce sugars from CO2 • Two stages
Overall Reaction
6CO2 + 6H2O + ATP C6H12O6 + 6O2 + ADP + P
Light Reactions
• Photophosphorylation-production of ATP
– Only in photosynthetic cells
• Light energy (electromagnetic radiation) absorbed by chlorophylls
– Chlorophyll a in plants, algae and cyanobacteria – Located in membranous thylakoids of chloroplastsplants & algae – Infoldings of plasma membrane of cyanobacteria
Light Reactions
• Electrons flow through ETC • Electron carrier is NADP+ • ATP produced by chemiosmosis
Noncyclic Photophosphorylation
• • • • Plants, algae, cyanobacteria 2 photosystems Produce both ATP via chemiosmosis Produce NADPH
– Used to reduce CO2 in dark reactions – Able to produce sugars
Summary
• ATP produced by chemiosmosis
– Uses energy released in ETC
• Oxygen produced from splitting of water
– H2O→ 2H+ +2 e + O – Replace electrons lost from chlorophyll
• NADPH produced in second photosystem
Dark Reactions
• Calvin-Benson Cycle • Requires no light • Uses energy from ATP (light reactions) to reduce CO2 to sugars • Carbon fixation
Summary
• Light H20 CO2
Photosystems & ETC Chlorophyll a Chemiosmosis
NADP+ ADP+ P Calvin Cycle
ATP NADPH
sugars
O2
Cellular respiration Organic cpds