Biology Ch 5 Ground Rules Of Metabolism

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energy

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The capacity to do work

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Entropy

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Measure of how much the energy of a system is dispersed

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First Law of Thermodynamics

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Energy cannot be created or destroyed

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kinetic energy

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the energy of motion

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potential energy

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stored energy

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Second law of thermodynamics

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Energy tends to disperse spontaneously

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activation energy

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minimum amount of energy required to start a reaction

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endergonic

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Describes a reaction that requires a net input of free energy to proceed.

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Exergonic

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Describes a reaction that ends with a net release of free energy.

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product

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a molecule that remains at the end of a reaction

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reactant

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a molecule that enters a reaction

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active site

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of an enzyme, pocket in which substrates bind and a reaction occurs

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catalysis

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the acceleration of a reaction by a molecule that is unchanged by participating in the reaction

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induced-fit model

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the concept that substrate binding to an active site of an enzyme improves the fit between the two molecules

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substrate

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a molecule that is specifically acted upon by an enzyme

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transition state

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Point during a reaction at which substrate bonds reach their breaking point and the reaction will run spontaneously

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Allosteric

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describes a region of an enzyme that can bind a regulatory molecule and is not the active site

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electron transfer chain

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array of enzymes and other molecules that accept and give up electrons in sequence, thus releasing the energy of the electrons in usable increments

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feedback inhibition

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Mechanism in which a change that results from some activity decreases or stops the activity

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metabolic pathway

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series of enzyme-mediated reactions by which cells build, remodel, or break down an organic molecule

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redox reaction

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Oxidation-reduction reaction, in which one molecule accepts electrons (it becomes reduced) from another molecule (which becomes oxidized)

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antioxidant

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substance that prevents oxidation of other molecules

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ATP

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the nucleotide adenosine triphosphate

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ATP/ADP cycle

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Process by which cells regenerate ATP. ADP forms when ATP loses a phosphate group, then ATP forms again as ADP gains a phosphate group

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coenzyme

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an organic molecule that is a cofactor

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cofactor

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a metal ion or a coenzyme that associates with an enzyme and is necessary for its function

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phosphorylation

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transfer of a phosphate group from one molecule to another

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adhesion protein

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membrane protein that helps cells stick together in animal tissue

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fluid mosaic

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model of a cell membrane as a two-dimensional fluid of mixed composition

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receptor protein

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plasma membrane protein that binds to a particular substance outside of the cell

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recognition protein

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plasma membrane protein that identifies a cell as belonging to self (one's own body)

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transport protein

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protein that passively or actively assists specific ions or molecules across a membrane

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concentration

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number of molecules or ions per unit volume

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concentration gradient

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difference in concentration between adjoining regions of fluid

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diffusion

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spontaneous spreading of molecules or ions in a liquid or gas

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hypertonic

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describes a fluid that has a high overall solute concentration relative to another fluid

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hypotonic

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describes a fluid that has a low overall solute concentration relative to another fluid

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isotonic

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describes two fluids with identical solute concentrations

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osmosis

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the diffusion of water across a selectively permeable membrane in response to a concentration gradient

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osmotic pressure

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amount of turgor that prevents osmosis into cytoplasm or other hypertonic fluid

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turgor

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pressure that a fluid exerts against a wall, membrane, or other structure that contains it

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active transport

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energy-requiring mechanism in which a transport protein pumps a solute across a cell membrane against its concentration gradient

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calcium pump

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active transport protein; pumps calcium ions across a cell membrane against their concentration gradient

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passive transport

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mechanism by which a concentration gradient drives the movement of a solute across a cell membrane through a transport protein. requires no energy input

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endocytosis

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process by which a cell take in a small amount of extracellular fluid by the ballooning inward of its plasma membrane

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exocytosis

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process by which a cell expels a vesicle's contents to extracellular fluid

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phagocytosis

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"cell eating"; an endocytic pathway by which a cell engulfs particles such as microbes or cellular debris

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pinocytosis

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endocytosis of bulk materials