CH 6 Microbial Metabolism: Fueling Cell Growth

List the structure and composition of an enzyme, describe the active site and allosteric site, and explain how they relate to the enzyme-substrate complex: ACTIVE SITE

- Critical site to which a substrate binds by weak forces - the binding of the substrate causes the shape of the flexible enzyme to change slightly, this is called ENZYME SUBSTRATE COMPLEX

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. OXIDATION-REDUCTION REACTION (REDOX REACTION)

- The substance that loses electrons is OXIDIZED by the reaction; - The substance that gains those electrons is REDUCED

Metabolism

- cells need to harvest energy and convert it to form that can power the various energy-consuming reactions, including those that make new parts sum of all chemical reactions in the body -

Make a simple diagram that integrates the central metabolic pathways, including their starting and end products.

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Compare and contrast each of the central metabolic pathways with respect to the yield of ATP, reducing power, and the number of different precursor metabolites. GLYCOLYSIS

1. 2 ATP (net) by substrate-level phosphorlation 2. NADH + 2 H+ 3. Six different precursor metabolites

8. List two environmental factors that influence enzyme activity.

1. Temperature- increase temperature of 10 degrees celcius, doubles the speed of enzyme reaction 2. pH enzymes function best at a pH just above 7 3. Salt concentration- desires low salt concentration

Compare and contrast catabolism and anabolism

1. Catabolism- (BREAKS DOWN) is the set of chemical reactions that degrade compounds, releasing their energy - cells capture that energy and use it to make ATP 2. Anabolism (biosynthesis)- (BUILDS) is the set of chemical reactions that cells use to synthesize and assemble the subunits of macromolecules, using ATP for energy ATP made during catabolism is used in anabolisms

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. ELECTRON CARRIERS

1. NAD/NADH 2. NADP/NADPH 3. FAD/FADH - Reduced electron carriers represent REDUCING POWER because they can easily transfer their electrons to another chemical that has a higher affinity for electrons - NADH and FADH2 us oxidation phosphorlation (uses proton motive force)

Compare and contrast each of the central metabolic pathways with respect to the yield of ATP, reducing power, and the number of different precursor metabolites. Pentose Phosphate cycle

1. NADPH + H+ (amount varies) 2. Two different precursor metabolites

Distinguish between respiration and fermentation.

1. Respiration - Transferring t electrons taken from glucose to the electron transport chain, which ultimately donates them to a terminal electron acceptor 2. Fermentation - Cells break down glucose through glycolysis only and then use pyruvate or derivative as a terminal electron acceptor - By transferring the electrons carried by NADH to pyruvate or a derivative, NAD+ is regenerated

Describe the roles of the three central metabolic pathways (glycolysis, pentose phosphate pathway, Tricarboxylic acid cycle (TCA cycle - Krebs cycle)): GLYCOLYSIS

1. Splits glucose and gradually oxidizes it to form two molecules of pyruvate 2. Makes small amount of ATP, some reducing power, and 6 precursor metabolites

Describe the roles of the three central metabolic pathways (glycolysis, pentose phosphate pathway, Tricarboxylic acid cycle (TCA cycle - Krebs cycle)). TRICARBOXYLIC ACID CYCLE

1. just before this cycle, a single reaction called the transition step converts the pyrubate from glycolysis into acetyl-CoA, one molecule of CO2 is released as a result combining making a total of 2

Describe the roles of the three central metabolic pathways (glycolysis, pentose phosphate pathway, Tricarboxylic acid cycle (TCA cycle - Krebs cycle)). PENTOSE PHOSPHATE PATHWAY

1. starts the oxidation of glucose 2. PRIMARY ROLE is the production of compounds used in biosynthesis (anabolism: set of chemical reactions that cells use to synthesize and assemble the subunits of macromolecules, using ATP for energy) 3. Makes two precursor metabolites, and reducing pwoer in the form of NADPH

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. PRECURSOR METABOLITES

Are intermediate molecules in catabolic and anabolic pathways that can be either oxidized to generate ATP or can be used to synthesize macromolecular subunits such as amino acids, lipids, and nucleotides - EX: E. coli can grow in glucose-salts medium. This means that the glucose serves two purposes: 1. The energy source 2. The starting point from which all cell components are made including proteins, lipids, carbohydrates, and nucleic acids

Compare and contrast cofactors and coenzymes.

COFACTOR: (magnesium, zinc, copper and other trace elements) some enzymes act with the assistance of a non-protein component. Help with binding COENZYMES: Organic cofactors that function as loosely bound carriers of molecules or electrons (FAD, NAD+, and NADP+ - all coenzymes transfer substances from one compound to another (some remain bound to the enzyme during the trsnsfer process, whereas others separate from the enzyme, carrying the substance being transferred along with them

Compare and contrast competitive enzyme inhibition and non-competitive enzyme inhibition. NON-COMPETITIVE ENZYME INHIBITION

Occurs when the inhibior binds to a site other than the active site - The binding changes the shape of the enzyme so that the substrate can no longer bind to the active site

Describe the energy sources used by photosynthetic organisms and chemoorganoheterotrophs.

Photosynthetic organisms: Harvest the energy of sunlight, using it to power the synthesis of organic compounds from CO2 -By doing so, they convert the kinetic energy of photons (particles that travel at the speed of light) to the potential energy of chemical bonds) Chemoorganoheterotrophs: Obtain energy by degrading organic compounds; they then use some of that energy to make other organic compounds; -Because chemoorganotrophs depend on a constant source of organic compounds, they generally rely on the metabolic activities of photosynthetic organisms

Describe the components of the electron transport chain and how they generate a proton motive force. CYTOCHROMES

Proteins that contain heme, a molecule that holds an iron atom in it's center

Describe the components of the electron transport chain and how they generate a proton motive force. FLAVOPROTEINS

Proteins to which a flavin is attached FAD and other flavins are synthesized from the vitamin riboflavin

Describe the components of the electron transport chain and how they generate a proton motive force.

Series of membrane embedded electron carriers; it accepts electrons from NADH and FADH2 and then passes those elctrons fro one carrier to the next The energy released allows the eTC to pump protons accross the membrane, generating the elctron chemical gradient called proton motive force

General mechanisms of Proton Pump

Some electron carriers only accept hydrogen atoms (proton-electron pair) and others only electrons

Compare and contrast each of the central metabolic pathways with respect to the yield of ATP, reducing power, and the number of different precursor metabolites. TCA CYCLE

The TCA cycle, repeated twice to incorporate two acetyl groups, generates: 1. 2 ATP by substrate-level phosphorlation (may involve conversion of GTP) 2. 6 NADH + 6 H+ 3. 2 FADH2 4. Two different precursor metabolites

10. Compare and contrast competitive enzyme inhibition and non-competitive enzyme inhibition. COMPETITIVE ENZYME

The inhibitor binds to the active site of the enzyme, blocking access of the substrate to that site (inhibitor competes with the substrate for that active site)

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. ATP

The main energy currency of cells, serving as the ready and immediate donor of free energy - You make "energy currency" by adding an inorganic phosphate group to adenosine diphosphate (ADP), forming ATP

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. METABOLIC PATHWAY

The series of chemical reactions that convert a starting compound to an end product - Pathways can be linear, branched, or cyclical

Compare and contrast each of the central metabolic pathways with respect to the yield of ATP, reducing power, and the number of different precursor metabolites. TRANSITION STEP

The transition step, repeated twice to oxidize two molecules of purubate to acetyl-CoA, generated: 1. 2 NADH + 2 H+ 2. One precursor metabolite

Feedback inhibition

This allows the cell to shut down a pathway when the product begins accumulating

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. CHEMICAL ENERGY SOURCES

To understand how cells obtain energy, it is helpful to recall from ch 2 that certain atoms are more electronegative than others, meaning they have a greater affinity (attraction) for electrons - When a molecule has a low electron affinity (tends to give up electrons) to one that has a higher electron affinity (tend to accept electrons) - The chemical that serves as the electron donor is the ENERGY SOURCE, and the one that ultimately accepts those electrons is the TERMINAL ELECTRON ACCEPTOR

Enzyme names

Usually usually reflects it's function and ends with the suffix -ase -ex: proteases degrade protein

List the structure and composition of an enzyme, describe the active site and allosteric site, and explain how they relate to the enzyme-substrate complex: ALLOSTERIC SITE/ALLOSTERIC REGULATION

When a regulatory meolecule binds to the allosteric site, the shape of the enzyme changes -in some cases the binding of the regulatory molecule enhances the affinity for the substrate, in other cases, it decreases it

Describe the components of the electron transport chain and how they generate a proton motive force. QUINONES

are lipid-soluble organic molecules that move freely in the membrane and can therefore transfer electrons between different protein complexes in the membrane. - Most common (ubiquinone)

Describe the components of metabolic pathways (enzymes, ATP, chemical energy sources, redox reactions, and electron carriers) and the role of precursor metabolites. ENZYME

is a molecule (usually a protein) that functions as biological catalyst, speeding up the conversion of one substance, the SUBSTRATE, into another, the product - An enzyme catalyzes a chemical reaction by lowering the ACTIVATION ENERGY

Chemoorganotrophs (obtain energy by degrading organic compounds, they then use that energy to make other organic compounds) use two different processes to make ATP

1. Substrate-level phosphorylation - the energy released in an exergonic reaction is used to power the addition of P1 to ADP 2. Oxidative phosphorylation - The energy of a proton motive force drives the reaction. (The form of energy that results from the electrochemical gradient established by the electron transport chain) - ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers. This process