QUESTION OF THE DAY… All E. coli look alike through a microscope; so how can E. coli O157 be differentiated?

Catabolic and Anabolic Reactions Metabolism: The sum of the chemical reactions in an organism __________: Provides energy and building blocks for anabolism. __________: Uses energy and building blocks to build large molecules

Role of ATP in Coupling Reactions QUESTION: How is ATP an intermediate between catabolism and anabolism? Figure 5.1

Catabolic and Anabolic Reactions A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell Metabolic pathways are determined by enzymes Enzymes are encoded by genes

Collision Theory The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide Activation energy is needed to disrupt electronic configurations Reaction rate is the frequency of collisions with enough energy to bring about a reaction. Reaction rate can be increased by enzymes or by increasing temperature or pressure

Energy Requirements of a Chemical Reaction Figure 5.2

Enzyme Components Biological catalysts Apoenzyme: Protein Specific for a chemical reaction; not used up in that reaction Apoenzyme: Protein Cofactor: Nonprotein component Coenzyme: Organic cofactor Important Coenzymes: NAD+, NADP+, FAD, Coenzyme A Holoenzyme: Apoenzyme plus cofactor

Components of a Holoenzyme Figure 5.3

Enzyme Specificity and Efficiency The turnover number is generally 1 to 10,000 molecules per second

The Mechanism of Enzymatic Action Figure 5.4b

Enzyme Classification Oxidoreductase: Oxidation-reduction reactions Transferase: Transfer functional groups Hydrolase: Hydrolysis Lyase: Removal of atoms without hydrolysis Isomerase: Rearrangement of atoms Ligase: Joining of molecules, uses ATP

Factors Influencing Enzyme Activity Temperature – Denatures proteins pH – Denatures proteins Substrate concentration – Specificity of enzymes Inhibitors – Prevent binding of substate/enzyme

Effect of Temperature on Enzyme Activity QUESTION: What happens to an enzyme below its optimal temperature? Figure 5.5a

Effect of pH on Enzyme Activity Figure 5.5b

Effect of Substrate Concentration on Enzyme Activity Figure 5.5c

Enzyme Inhibitors: Competitive Inhibition Figure 5.7a–b

Enzyme Inhibitors: Competitive Inhibition

Enzyme Inhibitors: Noncompetitive Inhibition Figure 5.7a, c

Enzyme Inhibitors: Feedback Inhibition QUESTION: Why is feedback inhibition noncompetitive inhibition? Figure 5.8

Ribozymes RNA that cuts and splices RNA

Oxidation-Reduction Oxidation: Removal of electrons Reduction: Gain of electrons Redox reaction: An oxidation reaction paired with a reduction reaction Figure 5.9

Oxidation-Reduction Reactions In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

The Generation of ATP ATP is generated by the phosphorylation of ADP

Substrate-Level Phosphorylation Energy from the transfer of a high-energy PO4– to ADP generates ATP

Oxidative Phosphorylation Energy released from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP in the electron transport chain

Photophosphorylation Light causes chlorophyll to give up electrons. Energy released from transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP. QUESTION: Can you outline the three ways that ATP is generated?

Metabolic Pathways of Energy Production

Carbohydrate Catabolism The breakdown of carbohydrates to release energy Glycolysis Krebs cycle Electron transport chain REVIEW THESE CONCEPTS FROM CELL BIOLOGY!!

Alternatives to Glycolysis Pentose phosphate pathway Uses pentoses and NADPH Operates with glycolysis Entner-Doudoroff pathway Produces NADPH and ATP Does not involve glycolysis Pseudomonas, Rhizobium, Agrobacterium QUESTION: What is the value of the pentose phosphate and Entner-Doudoroff pathways if they produce only one ATP molecule?

Overview of Respiration and Fermentation Figure 5.11

Chemiosmotic Generation of ATP QUESTION: How do carrier molecules function in the electron transport chain? Figure 5.16

An Overview of Chemiosmosis Figure 5.15

A Summary of Respiration Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2). Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.

Anaerobic Respiration Electron Acceptor Products NO3– NO2–, N2 + H2O SO4– H2S + H2O CO32 – CH4 + H2O

Carbohydrate Catabolism Pathway Eukaryote Prokaryote Glycolysis Cytoplasm Intermediate step Krebs cycle Mitochondrial matrix ETC Mitochondrial inner membrane Plasma membrane

Carbohydrate Catabolism Energy produced from complete oxidation of one glucose using aerobic respiration Pathway ATP Produced NADH Produced FADH2 Produced Glycolysis 2 Intermediate step Krebs cycle 6 Total 4 10

Carbohydrate Catabolism ATP produced from complete oxidation of one glucose using aerobic respiration Pathway By Substrate-Level Phosphorylation By Oxidative Phosphorylation From NADH From FADH Glycolysis 2 6 Intermediate step Krebs cycle 18 4 Total 30

Carbohydrate Catabolism 36 ATPs are produced in eukaryotes Pathway By Substrate-Level Phosphorylation By Oxidative Phosphorylation From NADH From FADH Glycolysis 2 6 Intermediate step Krebs cycle 18 4 Total 30

Fermentation Any spoilage of food by microorganisms (general use) Any process that produces alcoholic beverages or acidic dairy products (general use) Any large-scale microbial process occurring with or without air (common definition used in industry)

Fermentation Scientific definition: Releases energy from oxidation of organic molecules Does not require oxygen Does not use the Krebs cycle or ETC Uses an organic molecule as the final electron acceptor

An Overview of Fermentation ANIMATION Fermentation Figure 5.18a

End-Products of Fermentation Figure 5.18b

Fermentation Alcohol fermentation: Produces ethanol + CO2 Lactic acid fermentation: Produces lactic acid Homolactic fermentation: Produces lactic acid only Heterolactic fermentation: Produces lactic acid and other compounds

Types of Fermentation Compare the energy yield (ATP) of aerobic and anaerobic respiration – which one is more efficient? Figure 5.19

A Fermentation Test Figure 5.23

Types of Fermentation Table 5.4

Lipid Catabolism Figure 5.20

Catabolism of Organic Food Molecules Figure 5.21

Protein Catabolism Protein Amino acids Organic acid Krebs cycle Extracellular proteases Protein Amino acids Deamination, decarboxylation, dehydrogenation, desulfurylation Organic acid Krebs cycle

Protein Catabolism Decarboxylation Figure 5.22

Protein Catabolism Desulfurylation Figure 5.24

Protein Catabolism Urease Urea NH3 + CO2 Clinical Focus Figure B

Biochemical Tests Used to identify bacteria. QUESTION: Could biochemical tests be used to differentiate between Pseudomonas and Escherichia – explain. Clinical Focus Figure A

Photosynthesis Photo: Conversion of light energy into chemical energy (ATP) Light-dependent (light) reactions Synthesis: Carbon fixation: Fixing carbon into organic molecules Light-independent (dark) reaction: Calvin-Benson cycle

Photosynthesis Oxygenic: Anoxygenic: QUESTION: How is photosynthesis important to catabolism?

Cyclic Photophosphorylation QUESTION: What is made during the light-dependent reactions? Figure 5.25a

Noncyclic Photophosphorylation QUESTION: How are oxidative phosphorylation and photophosphorylation similar? Figure 5.25b

Calvin-Benson Cycle Figure 5.26

Photosynthesis Compared Table 5.6

Requirements of ATP Production Phototrophs verses Chemotrophs Figure 5.27

A Nutritional Classification of Organisms Figure 5.28

A Nutritional Classification of Organisms Figure 5.28

A Nutritional Classification of Organisms Figure 5.28

Metabolic Diversity among Organisms Nutritional Type Energy Source Carbon Source Example Photoautotroph Light CO2 Oxygenic: Cyanobacteria plants Anoxygenic: Green, purple bacteria Photoheterotroph Organic compounds Green, purple nonsulfur bacteria Chemoautotroph Chemical Iron-oxidizing bacteria Chemoheterotroph Fermentative bacteria Animals, protozoa, fungi, bacteria. QUESTION: Almost all medically important microbes belong to which of the four aforementioned groups?

Polysaccharide Biosynthesis Figure 5.29

Lipid Biosynthesis Figure 5.30

Pathways of Amino Acid Biosynthesis Figure 5.31a

Amino Acid Biosynthesis Figure 5.31b

Purine and Pyrimidine Biosynthesis Figure 5.32

The Integration of Metabolism Amphibolic pathways: Metabolic pathways that have both catabolic and anabolic functions Glycolysis Kreb’s Cycle