10 metabolism lecture
DESCRIPTION
dr.ehabTRANSCRIPT
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• No longer active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 - ,SO4
2-
• 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 chloroplasts-
plants & 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
Calvin Cycle
NADP+
ADP+ P
ATP
NADPH
O2 sugars Cellular respiration
Organic cpds