Microbiology Chapter Six

Adenosine diphosphate (ADP)

"Can be viewed as an acceptor of free energy. (ADP + Pi (inorganic phosphate group) = ATP, an endergonic reaction)"

Another name for Complex II

succinate dehydrogenase complex

Another name for Complex IV

cytochrome c oxidase complex

Terminal Electron Acceptor

Chemical that is ultimately accepts the electrons donated by the energy source and is reduced as a consequence of fermentation or respiration

Another name for Complex III

Cytochrome bc1 complex

Reduced

Donates Electrons

Quinones

Electron carriers that are lipid soluble organic molecules that move freely in the membrane and can therefore transfer electrons between different protein complexes in the membrane.

Cytochromes

Electron carriers that are proteins that contain heme, a molecule that holds an iron atom in its center.

Flavoproteins

Electron carriers that are proteins to which flavin is attached; synthesized from the vitamin riboflavin.

Kinetic Energy

Energy of motion such as water released from a dam.

Free Energy

Energy that is released when a chemical bond is broken. Termed in "reactants" (starting compounds) and "products."

Investment Phase

First phase of glycolysis. Two different steps each transfer high energy phosphate group to the 6 carbon sugar. The 6 carbon sugar is then split into two 3-carbon molecules, each with a phosphate molecule.

FAD

Flavin adenine dinucleotide; electron carrier; in its oxidized form, it is FAD+ + 2e- + 2H+, in its reduced form it is FADH2; used to generate a proton motive force that can drive ATP synthesis

Yeild of Glycolysis

For every glucose molecule degraded, glycolysis produces ATP, Reducing power and Precursor metabolites.

Proton Motive Force

Form of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient.

Bacteriochlorophylls

Found in anoxygenic photosynthetic baccteria.

Chlorophylls

Found in plants, algae and cyanobacteria.

Electron Transport Chain of Mitochondria

Group of membrane-embedded electron carriers that pass electrons from one to another and in the process, create a proton motive force. Comprised of 4 protein complexes.

Feedback Inhibition

Inhibition of gene activity by the end product of a biosynthetic pathway (allosteric inhibitor).

Transition Step

Links previous metabolic pathways to the TCA cycle.

Precursor Metabolites

Metabolic intermediates that can be either used to make the subunits of macromolecules or oxidized to generate ATP.

Fermentation

Metabolic process that stops short of oxidizing glucose or other organic compounds completely, using an organic intermediate as a terminal electron acceptor.

Respiration

Metabolic process that transfers electrons stripped from a chemical energy source to an electron transport chain, generating a proton motive force that is then used to sythesize ATP.

Another name for Complex I

NADH dehydrogenase complex

NADP+

Nicotinamide Adenine Dinucleotide Phosphate; electron carrier; in its oxidised form it is NADP+ + 2e- + 2H+, in its reduced form it is NADPH + H+; Biosynthesis

NAD+

Nicotinamide Adenine Dinucleotide; electron carrier; in its oxidised form it is NAD+ + 2e- + 2H+, in its reduced form it is NADH + H+ ; used to generate a proton motive force that can drive ATP synthesis

Chemoorganotrophs

Obtain energy by degrading organic compounds. They depend on the activities of photosynthetic organisms.

Coenzymes

Organic cofactors made from vitamins and other non-proteins

Photosynthetic Organisms

Organisms that harvest the energy of sunlight using it to power the synthesis of organic compounds from carbon dioxide. Converts kinetic energy of photons to potential energy of chemical bonds.

Chemiosmotic Theory

Originally proposed by British scientist Peter Mitchel; the universal name of Oxidative Phosphorylation

Antennae Pigments

Photosynthetic pigments that make up a complex that acts as a funnel, capturing the energy of light and then transferring it to the reaction-center pigment

Catabolism

Processes that harvest energy released during the breakdown of compounds such as glucose, using it to synthesize ATP.

Anabolism

Processes that synthesize and assemble the subunits of macromolecules, using energy of ATP; biosythesis.

Endergonic Reactions

Products have more free energy; Reaction requires input of energy.

Chemolithotrophs

Prokaryotes unique in their ability to use reduced inorganic compounds as sources of energy (such as hydrogen sulfide and amonia)

Enzymes

Proteins that function as biological catalysts, accelerating the conversion of one substance, the substrate, into another, the product.

Pay-off Phase

This oxidizes and rearranges the 3 carbon molecules, generating 1 NADH and 2 ATP in the process and ultimately forms pyruvate.

Pentose Phosphate Pathway

A metabolic pathway that also breaks down glucose but its primary role in metabolism is the production of compounds used in biosynthesis, including reducing power in the form of NADPH and two precursor metabolites. A product of the pathway feeds into glycolysis.

Glycolysis

A metabolic pathway that splits glucose and gradually oxidizes it to form two molecules of pyruvate. It also provides the cell with a small amount of energy in the form of ATP, some reducing power,, and six precursor metabolites.

Enzyme

A protein that functions as a catalyst, speeding up a biological reaction.

Active Site

A relatively small crevice on the surface of an enzyme that will be an adaptor for the substrate to bind to by weak forces.

Substrate

A substance on which an enzyme acts to form products or a surface on which an organism will grow.

Oxidized

Accepts Electrons

Function of Complex II

Accepts Electrons from the TCA cycle, when FADH2 is formed during oxidation of succinate. The FADH2 carries electrons that enter the transport chain "downstream" of those carried by NADH which results in fewer or no protons being expelled. Electrons are then transferred to ubiquinone.

Function of Complex I

Accepts electrons from NADH, ultimately transferring them to ubiquinone (aka coenzyme Q); in the process, four protons are moved across the membrane.

Function of Complex IV

Accepts electrons from cytochrome c and pumps two protons across the membrane. Is a terminal oxidoreductase, meaning it transfers the electrons to the terminal electron acceptor, which in this case is oxygen.

Function of Complex III

Accepts electrons from ubiquinone. Pumps four protons across the membrane before transferring the electrons to cytochrome c.

Tricarboxylic Acid Cycle

Accepts the 2-carbon acetyl group ultimately oxidizing it to release two molecules of carbon dioxide. The transition step and this pathway together generate the most reducing power of all the central metabolic pathways. They also produce three precursor metabolites and ATP.

Allosteric Site

An additional binding site on the enzyme that distorts the enzymes shape and prevents or enhances binding of the substrate. Regulatory molecule is usually the end product.

Cofactors

Assist enzymes; helping the substrate bind to the enzyme

Enzymes

Biological catalysts which increase the rate at which substrates are converted into products; name usually ends with the suffix -ase

General groups of electron carriers in the Electron Transport Chain

Quinones, Cytochromes and Flavoproteins

Exergonic Reactions

Reactants have more free energy; Energy is released in the reaction.

Reducing Power

Reduced electron carriers such as NADH, NADPH, and FADH2; their bonds contain a form of usable energy.

Anaerobic Respiration

Respiration in which a molecule other than oxygen serves as a terminal electron acceptor. Microbes employ a modified version of the TCA cycle.

Aerobic Respiration

Respiration in which oxygen serves as the terminal electron acceptor.

Metabolic pathway

Sequential chemical reactions that converts a starting compound to an end product. Can be linear, branched, or cyclical.

Potential Energy

Stored energy; can be stored in various forms including chemical bonds, a rock on a hill or water behind a dam.

Oxidative Phosphorylation

Synthesis of ATP using the energy of a proton motive force created by harvesting chemical energy.

Photophosphorylation

Synthesis of ATP using the energy of a proton motive force created by harvesting radiant energy.

Substrate-Level Phosphorylation

Synthesis of ATP using the energy released in an exergonic (energy releasing) chemical reaction during the breakdown of the energy source.

Photosynthesis

The action of capturing and subsequently converting radiant energy (sunlight) into chemical energy. Can be oxygenic or anoxygenic.

Energy

The capacity to do work. It can exist as potential energy (stored) and kinetic energy (in motion).

Energy Sourcce

The chemical that serves as the electron donor

Adenosine Triphosphate (ATP)

The energy currency of cells. Hydrolysis of the bonds between its phosphate groups can be used to power endergonic (energy consuming) reactions.

Activation Energy

The energy it takes to start a reaction.

Competative inhibition

The inhibitor binds to the active site of the enzyme, blocking access of the substrate to that site. Generally the inhibitor has a chemical structure similar to the normal substrate.

Non-Competative inhibition

The inhibitor binds to the allosteric site, changing the shape of the enzyme so that the substrate can no longer bind the active site.

Metabolism

The sum total of all chemicl reactions in a cell. (Catabolism + Anabolism = Metabolism)