Enzyme kinetics + photosynthesis + protein singalling

• What are enzymes?


  Enzymes are biological catalysts that speed up chemical reactions.
• How do enzymes function as catalysts?


  They increase the rate of a chemical reaction without being chemically changed.
• What is the primary composition of most enzymes?


  Almost all enzymes are proteins.
• Why must living organisms catalyze chemical reactions efficiently?


  To ensure that biochemical processes occur in a timely and selective manner.
• What significant contributions did Eduard Buchner and Moses Kunitz make to enzyme research?


  • Eduard Buchner showed that yeast extracts could ferment sugar.
  • Moses Kunitz crystallized digestive enzymes like pepsin and trypsin.
• What role do enzymes play in biochemical processes?


  They catalyze ordered sequences of chemical reactions known as biochemical pathways.
• How do enzymes contribute to nutrient degradation and energy transformation?


  Enzymes catalyze stepwise reactions to degrade nutrients and transform chemical energy.
• What is a genetic disease related to enzyme deficiency?

  Krabbe disease is caused by a deficiency in galactosylceramidase.
• How are purified enzymes utilized in the food industry?


  They are used to enhance food processing and preservation.
• What structural levels do enzymes contain?


  Enzymes contain secondary, tertiary, and quaternary structures.
• What are cofactors in relation to enzymes?


  Cofactors are additional chemical groups required by some enzymes for activity.
• What is a holoenzyme?


  A holoenzyme is a catalytically active enzyme with its bound metal ion and/or coenzyme.
• What is the difference between an apoprotein and a holoenzyme?


  An apoprotein is the protein part of a holoenzyme without its cofactors.
• How are enzymes classified?


  • Enzymes are classified by the reaction they catalyze.
  • The Enzyme Commission (E.C) assigns a unique 4-part number to each enzyme.
• What is the systematic name of an enzyme?


  It identifies the reaction that the enzyme catalyzes.
• What is the active site of an enzyme?


  The active site is the pocket where the substrate binds and the reaction occurs.
• How does the active site interact with the substrate?


  The active site is lined with amino acid residues that bind the substrate.
• What is the relationship between enzymes and reaction rates?


  Enzymes increase the rate of a reaction but do not affect the equilibrium.
• What does a negative $\Delta G'$ indicate about a reaction?


  A negative $\Delta G'$ means the reaction is favorable but does not guarantee a detectable rate.
• What is the transition state in a reaction coordinate diagram?


  The transition state is the peak of the reaction coordinate diagram and is not a chemical species.
• What are reaction intermediates in enzyme-catalyzed reactions?


  Reaction intermediates are chemical species that have a lifetime longer than a molecular vibration.
• What determines the rate of a reaction?


  The overall rate is determined by the reaction step with the highest activation energy, known as the rate-limiting step.
• How is the equilibrium constant $K$ related to a reaction?


  The equilibrium constant $K$ describes the ratio of concentrations of products to reactants at equilibrium.
• What is the relationship between the rate of a reaction and its rate constant?


  The rate of a reaction is proportional to its rate constant and the concentration of reactants.
• How does the transition state theory relate to rate constants?


  The transition state theory relates the magnitude of a rate constant to the activation energy of the reaction.
• How much do enzymes speed up reactions?


  Enzymes speed up reactions by 5-17 orders of magnitude.
• What types of interactions occur in enzyme-catalyzed reactions?


  Covalent and non-covalent interactions occur between substrates and functional groups of enzymes.
• How do covalent interactions affect $\Delta G$ in enzyme reactions?


  Covalent interactions lower $\Delta G$ by providing an alternative lower energy reaction path.
• What is binding energy in the context of enzyme catalysis?


  Binding energy is the major source of free energy used by enzymes to lower the $\Delta G$ of reactions.
• How much energy does a single weak interaction provide in enzyme catalysis?


  A single weak interaction provides 4-30 kJ/mol of energy.
• How does binding energy contribute to enzyme specificity?


  Binding energy helps distinguish between substrates based on weak interactions.
• What physical factors contribute to $\Delta G$ in enzyme reactions?


  Factors include entropy, solvation shells, substrate distortion, and alignment of catalytic groups.
• What is the induced fit model in enzyme-substrate interactions?


  The induced fit model describes how enzymes change conformation upon substrate binding.
• What types of catalysis are involved in enzyme reactions?


  General acid-base catalysis, covalent catalysis, and metal ion catalysis are involved.
• How does general acid-base catalysis stabilize charged intermediates?

  It stabilizes charged intermediates by transferring protons to or from the substrate.
• What is the role of covalent catalysis in enzyme reactions?


  Covalent catalysis involves a transient covalent bond between the enzyme and substrate.
• How does hexokinase demonstrate induced fit upon substrate binding?


  Hexokinase changes conformation when glucose binds, favoring the reaction with glucose over water.
• What happens when xylose is presented to hexokinase?

  Xylose cannot be phosphorylated, but it increases the rate of ATP hydrolysis.
• What is the role of metal ions in the enolase reaction mechanism?

  Metal ions stabilize the transition state during the enolase reaction.
• What is lysozyme and its function?


  Lysozyme is an antibacterial agent that cleaves glycosidic bonds in peptidoglycan.