Biology 2

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action spectrum

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is the rate of a physiological activity plotted against wavelength of light. It shows which wavelength of light is most effectively used in a specific chemical reaction

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active site

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is a small port in an enzyme where substrate molecules bind and undergo a chemical reaction. This chemical reaction occurs when a substrate collides with and slots into the active site of an enzyme.

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allosteric site

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is the regulation of a protein by binding an effector molecule at a site other than the protein's active site.

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ATP synthase

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is an important enzyme that provides energy for the cell to use through the synthesis of adenosine triphosphate (ATP). ATP is the most commonly used "energy currency" of cells from most organisms. It is formed from adenosine diphosphate (ADP) and inorganic phosphate (Pi), and needs energy.

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carboxylase

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is an enzyme of the ligase class that catalyzes the (depending on the species) irreversible carboxylation of pyruvate to form oxaloacetate (OAA). It is an important anaplerotic reaction that creates oxaloacetate from pyruvate.

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oxygenase

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is any enzyme that oxidizes a substrate by transferring the oxygen from molecular oxygen O2 (as in air) to it.

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catalyst

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A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up, or catalyze.

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cellular respiration

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is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. The energy released is trapped in the form of ATP for use by all the energy-consuming activities of thecell. The process occurs in two phases: glycolysis, the breakdown of glucose to pyruvic acid.

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chemical equilibrium

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is the state in which both reactants and products are present in concentrations which have no further tendency to change with time. Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction.

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coenzyme

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are small molecules. They cannot by themselves catalyze a reaction but they can help enzymes to do so. In technical terms,coenzymes are organic nonprotein molecules that bind with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme).

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cofactors

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is a non-protein chemical compound that is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations.

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cytochrome oxidase

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is a large transmembrane protein complex found in bacteria and the mitochondrion of eukaryotes. It is the last enzyme in the respiratory electron transport chain of mitochondria or bacteria located in the mitochondrial or bacterial membrane.

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electrochemical gradient

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is a gradient ofelectrochemical potential, usually for an ion that can move across a membrane. Thegradient consists of two parts, the electricalpotential and a difference in the chemical concentration across a membrane.

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electron carrier

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A molecule capable of accepting one (or more than one) electrons from another molecule (electron donor), and then ferry these electrons to donate to another during the process of electron transport.

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electron transport chain flavin adenine

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is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism. FAD can exist in three different redox states, which are the quinone, semiquinone, and hydroquinone. FAD is converted between these states by accepting or donating electrons.

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dinucleotide

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a nucleotide consisting of two units each composed of a phosphate, a pentose, and a nitrogen base

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oxidation

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is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

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reduction

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is any chemical reaction that involves the gaining of electrons. Specifically, it refers to the side that accepts electrons.

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phosphoglyceric acid

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is a biochemically significant 3-carbon molecule that is a metabolic intermediate in both glycolysis and the Calvin cycle. This chemical is often termed PGA when referring to the Calvin cycle. In the Calvin cycle,

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proton gradient

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The product of the electron transport chain. A higher concentration ofprotons outside the inner membrane of the mitochondria than inside the membrane is the driving force behind ATP synthesis.

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proton pump

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is an integral membrane protein that is capable of moving protonsacross a biological membrane. Mechanisms are based on conformational changes of the protein structure or on the Q cycle.

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endergonic

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In chemical thermodynamics, an endergonic reaction (also called a nonspontaneous reaction or an unfavorable reaction) is a chemical reaction in which the standard change in free energy is positive, and energy is absorbed.

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exergonic

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is one in which there is a positive flow of energy from the system to the surroundings. Constant pressure, constant temperature reactions are exergonic if and only if the Gibbs free energy change is negative