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• No longer active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

• 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– 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 & ETCChlorophyll a

Chemiosmosis

Calvin Cycle

NADP+

ADP+ P

ATPNADPH

O2sugars Cellular respiration

Organic cpds