Chapter 6.txt

  1. activation energy
    Minimum amount of energy required to start a reaction; enzyme action lowers this energy barrier. Reactions differ in the amount required.
  2. active sites
    Chemically stable crevice in an enzyme where substrates bind and a reaction can be catalyzed repeatedly.
  3. ADP
    Adenosine diphosphate. A nucleotide with an adenine base and two phosphate groups.
  4. antioxidants
    Any enzyme or cofactor that helps neutralize free radicals before they damage tissues.
  5. ATP
    Adenosine triphosphate. A type of nucleotide that functions as the main energy carrier between reaction sites in cells. Consists of the base adenine, the five-carbon sugar ribose, and three phosphate groups.
  6. ATP/ADP cycle
    How a cell regenerates its ATP supply. ADP forms when ATP gives up a phosphate group, then ATP forms as ADP binds to inorganic phosphate or a phosphate group split from a molecule.
  7. binding energy
    Energy released as weak bonds form between a substrate, enzyme, and any cofactor.
  8. bioluminescence
    Fluorescent light formed when certain organisms convert chemical bond energy to photon energy.
  9. biosynthetic pathway (anabolic)
    Any metabolic pathway by which one or more organic compounds are synthesized.
  10. chemical energy
    Potential energy in the bonds between atoms in molecules.
  11. chemical equilibrium
    No net change in concentrations of reactants and products in a reversible chemical reaction.
  12. coenzymes
    An organic molecule that is a necessary participant in some enzymatic reactions; helps catalysis by donating or accepting electrons or functional groups; e.g., a vitamin, ATP, NAD+.
  13. cofactors
    A metal ion or a coenzyme that assists an enzyme in catalysis by accepting or donating electrons or functional groups.
  14. degradative pathway (catabolic)
    Any of the stepwise series of metabolic reactions that break down organic compounds.
  15. electron transfer chains
    Array of enzymes and other molecules in a cell membrane that accept and give up electrons in sequence; operation of chain releases the energy of the electrons in small, usable increments.
  16. endergonic reaction
    A chemical reaction that requires a net energy input and converts more stable reactants into less stable products; not spontaneous.
  17. energy
    A capacity to do work.
  18. entropy
    Measure of how much and how far a concentrated form of energy has been dispersed after an energy change.
  19. enzymes
    A type of protein that catalyzes (speeds) a chemical reaction. Some RNAs also show catalytic activity.
  20. exergonic reaction
    Any chemical reaction with a net energy loss.
  21. FAD
    Flavin adenine dinucleotide. A type of nucleotide coenzyme; transfers electrons and H+ from one reaction site to another.
  22. feedback inhibition
    Mechanism by which a change that results from some cellular activity triggers responses that decrease or shut down the activity.
  23. first law of thermodynamics
    Energy cannot be created or destroyed.
  24. free radicals
    Any unbound molecular fragment with an unpaired electron.
  25. induced-fit model
    Explanation of how some enzymes work; their shape changes and fits a bound substrate more closely, and the tension destabilizes substrate bonds so that they can break.
  26. intermediates
    A substance formed between the start and end of a metabolic pathway.
  27. kilocalorie
    1,000 calories of heat energy; amount needed to raise the temperature of 1 kilogram of water by 1�C. Standard unit of measure for food�s caloric content.
  28. kinetic energy
    Energy of motion.
  29. metabolic pathways
    A stepwise sequence of enzyme-mediated reactions.
  30. metabolism
    All the controlled, enzyme-mediated chemical reactions by which cells acquire and use energy as they synthesize, store, degrade, and eliminate substances.
  31. NAD+
    Nicotinamide adenine dinucleotide. A nucleotide coenzyme; after it accepts electrons and H+, abbreviated as NADH.
  32. NADP+
    Nicotinamide adenine dinucleotide phosphate. A phosphorylated nucleotide coenzyme; after it accepts electrons and H+, abbreviated NADPH2.
  33. oxidation-reduction reactions (redox)
    Transfer of electrons between reactant molecules.
  34. phosphorylation
    Enzyme-mediated transfer of a phosphate group to an organic compound.
  35. potential energy
    A object�s capacity to do work owing to its position in space or the arrangement of its parts.
  36. products
    A substance remaining at the end of a reaction.
  37. reactants
    Substance that enters a reaction.
  38. second law of thermodynamics
    Energy tends to flow from concentrated to less concentrated forms.
  39. substrates
    A reactant molecule that is specifically acted upon by an enzyme.
  40. transport proteins
    Membrane protein that passively or actively assists specific ions or molecules into or out of a cell. The solutes move through the protein�s interior
Card Set
Chapter 6.txt
Chapter 6