Chapter 3: Section D: Enzymes and Chemical Energy

Question 1

Metabolism

Answer 1

all the chemical reactions that occur within out cells

Question 2

Anabolism

Answer 2

synthesis of organic molecules (together)

Question 3

Catabolism

Answer 3

breakdown of organic molecules (apart)

Question 4

Chemical reactions

Answer 4

• reactants react with each other chemically to form a product
• glucose + fructose (reactants) sucrose (product)
• chemical reactions either use energy (transfer it to molecules ) or release energy as heat (energy measured in kilocalories)
• chemical reactions are reversible

Question 5

Exergonic reactions

Answer 5

• the reactants contain more energy than the products
• releases energy
• once begun, occur spontaneously
• ATP –> ADP+Pi+energy

Question 6

Endergonic reactions

Answer 6

• the products contain more energy than the reactants
• use energy
• will only occur if energy is added
• ADP+Pi+energy –> ATP

Question 7

Irreversible reactions

Answer 7

• use large amount of energy because almost all reactant molecules have become product

Question 8

Four factors that affect reaction rates

Answer 8

• reactant concentrations (higher concentrations: faster reaction rates)
• activation energy (higher activation energy: slower reaction rate)
• temperature (higher temperature: faster reaction rate)
• catalyst (presence of catalyst: faster reaction rate)

Question 9

Law of mass action

Answer 9

• an increase in the concentration of the reactants (or decrease in product concentration) will increase the rate of the forward reaction, increasing product formation and v.v.

Question 10

Activation Energy

Answer 10

• once an exergonic reaction begins, it proceeds spontaneously but because existing chemical bonds need to be destabilized to get the reactions started, a small amount of energy must be added to start the reaction = activation energy
• activation energy is like a ball rolling down a hill, takes a push to get started (Energy) but then rolls freely

Question 11

Enzyme

Answer 11

• biological catalyst
• molecule that lowers the activation energy of a chemical reaction and speeds up the rate at which chemical reactions occur
• the enzyme is not used up in the reaction

Question 12

substrates

Answer 12

• reactants in an enzymatic reaction (E+S–> ES–> E+P)
• enzyme-substrate complex forms when the substrate binds to the active site on the enzyme
• shape of active site is specific for a given substrate
• induced fit vs. lock&key model

Question 13

Induced Fit substrate

Answer 13

• somewhat fits into ligand, however once it is close, then it is molded into the binding site

Question 14

Lock&Key Model

Answer 14

• fits binding site for a very specific shape

Question 15

Cofactors

Answer 15

• non-protein molecules that are required by an enzyme for it to function
• metal ions & coenzymes

Question 16

Metal enzymes

Answer 16

copper, zinc, iron

Question 17

coenzymes

Answer 17

nonprotein organic molecules (derived from vitamins)

Question 18

regulation of enzyme-mediated reactoins

Answer 18

• affect rate or effectiveness
  1) substrate concentration
  2) enzyme concentration
  3) pH of environment
  4) temperature
  5) regulation of enzyme activity

Question 19

Allosteric modulation

Answer 19

• activation or inhibition or change in affinity
• modulator molecule binds to regulatory site on enzyme that changes shape of active site
• increase affinity –> increase reaction rate, however max rate doesn’t change
• any enzyme can have variety of allosteric and/or covalent modulation sites

Question 20

noncompetitve inhibition

Answer 20

• inhibitor binds to an allosteric (regulatory) site or causes covalent modulation on the enzyme –> shape change, preventing substrate binding

Question 21

competitve inhibition

Answer 21

• inhibitor has a shape similar to the substrate; binds to active site and enzyme activity ends

Question 22

feedback inhibition/end-product inhibition

Answer 22

• the product of an enzyme-catalyzed metabolic reaction or pathway inhibits enzyme activity
• regulates amount of product produced by inhibiting itself when has enough product (self-regulating process)

Question 23

metabolic pathways

Answer 23

• series of linked reactions that result in a desired product
• each step is controlled by a specific enzyme
• A–E1–> B–E2–> C–E3–> D
• takes to get from A to D many enzymes (E1, E2, E3)