39 terms

Chapter 6: Metabolism - Energy and Enzymes

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active site
The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface and where the reaction occurs
adenosine diphosphate
(ADP) a substance involved in energy metabolism formed by the breakdown of adenosine triphosphate
adenosine triphosphate
a nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions
ATP synthase complex
a special protein complex embedded in the thylakoid membrane that allows H+ ions to escape from the lumen and uses the resulting energy to generate or make ATP
chemical energy
potential to perform work due to the arrangement of atoms within molecules
chemiosmosis
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by this process.
coenzyme
An organic non-protein molecule that binds temporarily with substrate to an enzyme active site. It is essential for enzyme activity.
cofactor
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. They can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
competitive inhibition
an enzyme may encounter a substance that resembles its specific substrate, the enzyme may bind to this substance instead of the correct substrate and the desired chemical reaction will not occur; substrate and inhibitor are both able to bind to the enzyme's active site
coupled reactions
when the energy released by an exergonic reaction is used to drive an endergonic reaction
denatured
To disrupt the secondary and/or tertiary structure of a protein while leaving its amino acid sequence intact; they can no longer perform their biological functions; caused by a less than optimal pH and temperature
electron transport chain
A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions from a higher to lower energy level that release energy used to make ATP
endergonic reaction
A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings.
energy
the ability to do work or cause change
energy of activation
The amount of energy that reactants must absorb before a chemical reaction will start
entropy
A quantitative measure of disorder or randomness, symbolized by S.
enzyme
any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions
enzyme inhibition
Process by which a substance known as an inhibitor binds to an enzyme and decreases it's activity
exergonic reaction
A spontaneous chemical reaction in which there is a net release of free energy.
feedback inhibition
the inhibition of an early step in a series of events by the product of a later step in the series; this has the effect of stopping the series of events when the products are plentiful and the series is unnecesseary; it is the most common form of regulation in the body, controllin such things as enzyme reactions, hormone levels, blood pressure, body temperature, etc.
free energy
The portion of a system's energy that can perform work when temperature is uniform throughout the system.
heat
The total amount of kinetic energy due to molecular motion in a body of matter; the energy in its most random form.
induced fit model
interactions between the substrate and the enzyme that change the shape of the enzyme
kinetic energy
the energy an object has due to its motion
laws of thermodynamics
1) energy can not be created or destroyed, only converted from one form to another, 2) each time you convert one form of energy to another, some energy is converted to a non-usable form (more energy efficient to consume plants because they exist very close to the initial source of energy), 3) also called law of conservation
mechanical energy
kinetic or potential energy associated with the motion or position of an object
metabolic pathway
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).
metabolism
sum of the chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes
nicotinamide adenine dinucleotide
captures released electrons and picks up two hydrogen atoms (each with one proton and one electron); acts as a shuttle to the Electron Transport Chain in the mitochondria during cellular respiration
nicotinamide adenine dinucleotide phosphate
The co-enzyme which accepts electrons from PS I and which, in a reduced form, is an energy source for the light independent reaction.
noncompetitive inhibition
the act of binding to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
oxidation
the loss of one or more electrons from a substance involved in a redox reaction
phosphorylation
In metabolic processes, the transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.
potential energy
stored energy that is latent but available for use. A rock poised at the top of a hill or water stored behind a dam are examples.
product
a chemical substance formed as a result of a chemical reaction
reactant
a chemical substance that is present at the start of a chemical reaction
reduction
gain of electrons by an atom or molecule with a concurrent storage of energy; in biological systems, the electrons are accompanied by hydrogen ions
substrate
a substance on which an enzyme acts during a chemical reaction
vitamin
any of a group of organic substances essential in small quantities to normal metabolism; part of coenzymes