Chapter 8 - Cell Membranes

• What are the key concepts covered in Chapter 8 Energy, Enzymes, and Metabolism?

  Chemical transformations involve energy and energy transfers, ATP plays a key role in biochemical energetics, enzymes speed biochemical transformations, enzymes bring substrates together, and enzyme activities can be regulated.
• What is the role of salicylic acid in aspirin?

  Salicylic acid, the basis of aspirin, blocks the synthesis of prostaglandin to reduce inflammation and pain.
• When was salicylic acid discovered?

  In 1763.
• What occurs during a chemical reaction?

  A chemical reaction occurs when atoms have enough energy to combine or change bonding partners.
• What is the equation representing the reaction of sucrose and water?

  sucrose + H$_2$O → glucose + fructose
• What is metabolism?


  Metabolism is the sum total of all chemical reactions occurring in a biological system at a given time.
• What are the two types of metabolism?

  Anabolic reactions and catabolic reactions.
• What do anabolic reactions do?

  Anabolic reactions make complex molecules from simple molecules and require energy.
• What do catabolic reactions do?

  Catabolic reactions break down complex molecules into simpler ones and release energy.
• What do the laws of thermodynamics state?

  The first law states that energy is neither created nor destroyed, and the second law states that some energy becomes unavailable to do work during transformations.
• What is entropy?


  Entropy (S) is a measure of the disorder in a system.
• What is free energy (G)?


  Free energy (G) is the usable energy that can do work.
• What is the relationship between enthalpy (H), free energy (G), and entropy (S)?


  The relationship is given by the equation H = G + TS, where T is the absolute temperature.
• What are exergonic reactions?

  Exergonic reactions release free energy (–ΔG) and generate disorder.
• What are endergonic reactions?

  Endergonic reactions consume free energy (+ΔG) and increase order.
• What determines the direction of a reversible chemical reaction?

  The concentrations of reactants A and B determine which direction is favored.
• What is chemical equilibrium?

  Chemical equilibrium is the balance between forward and reverse reactions, a state of no net change, where ΔG = 0.
• What is ATP?


  ATP (adenosine triphosphate) captures and transfers free energy.
• How is ATP hydrolyzed?

  ATP can be hydrolyzed to ADP and Pi, releasing a lot of energy for endergonic reactions.
• What is the process of ATP formation?

  The formation of ATP is endergonic: ADP + Pi + free energy → ATP + H$_2$O.
• How do ATP hydrolysis and formation relate to metabolic reactions?

  Formation and hydrolysis of ATP couple endergonic and exergonic reactions, which is very common in metabolism.
• What is the role of catalysts in chemical reactions?

  Catalysts increase the rates of chemical reactions without being altered by the reactions.
• What are enzymes?


  Most biological catalysts are enzymes (proteins) that act as a framework in which reactions can take place.
• What is activation energy (Ea)?

  Activation energy is the amount of energy required to start a reaction.
• What is the transition state in a chemical reaction?

  The transition state is the reactive mode that reactants enter after overcoming activation energy.
• How do enzymes lower the energy barrier for reactions?

  Enzymes lower the energy barrier by bringing the reactants together.
• What determines the specificity of an enzyme?

  The 3D shape of the enzyme determines its specificity for substrates.
• What is the enzyme-substrate complex (ES)?

  The enzyme-substrate complex (ES) is formed when substrate molecules bind to the active site of the enzyme.
• What are the six categories of enzymes?

  Oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
• How much can enzymes increase reaction rates?

  Enzymes can increase reaction rates by 1 million to 10$^{17}$ times.
• What mechanisms can an enzyme use to catalyze a reaction?

  An enzyme may orient substrates, induce strain, or temporarily add chemical groups to catalyze a reaction.
• What is induced fit in enzyme activity?

  Induced fit is when some enzymes change shape upon substrate binding, altering the shape of the active site.
• What are ribozymes?


  Ribozymes are RNA molecules that can act as biological catalysts.
• How does substrate concentration affect the rate of a catalyzed reaction?

  The rate of a catalyzed reaction depends on substrate concentration, with enzyme concentration usually much lower than substrate concentration.
• What happens at saturation in enzyme activity?

  At saturation, all enzyme is bound to substrate, and it is working at maximum rate.
• What are prosthetic groups, inorganic cofactors, and coenzymes?

  Prosthetic groups are non-amino acid groups bound to enzymes, inorganic cofactors are ions permanently bound to enzymes, and coenzymes are small carbon-containing molecules not permanently bound.
• What is irreversible inhibition in enzyme activity?

  Irreversible inhibition occurs when an inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme.
• What is reversible inhibition in enzyme activity?

  Reversible inhibition occurs when an inhibitor bonds noncovalently to the active site and prevents substrate from binding.
• What are competitive inhibitors?

  Competitive inhibitors compete with the natural substrate for binding sites, and the degree of inhibition depends on concentrations of substrate and inhibitor.
• What are uncompetitive inhibitors?

  Uncompetitive inhibitors bind to the enzyme-substrate complex, preventing the release of products.