Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Chemical Reactions and
Enzymes
Review
• Living organisms are composed of organic molecules: carbohydrates, lipids, proteins and nucleic acids
• Cellular processes are based on numerous chemical reactions
Chemical Reactions
Chemical Reactions
• During a chemical reaction, one set of chemical is transformed (or changed) into another set of chemicals
Write down the following chemical equation:
CO2 + H2O H2CO3
• In this reaction, carbon dioxide and water react to form carbonic acid
Reactants and Products
• The compounds that enter into a chemical reaction are called the reactants
• The compounds that are produced by a chemical reaction are called the products
Metabolism• The entirety of the chemical reactions
that occur within the cells of a living organism is called metabolism
Metabolic Reactions• Metabolic reactions are grouped into
two general categories: anabolic and catabolic reactions
• During anabolic reactions, simpler substances are combined to form complex molecules
• Energy is absorbed during the reaction• Examples of anabolic reactions include:
protein synthesis and photosynthesis
Anabolic Reactions
• During catabolic reactions, complex molecules are broken down into simpler substances
• Energy is released during the reaction• Examples of catabolic reactions
include: cellular respiration and food digestion
Catabolic Reactions
• Many times, the energy released during a catabolic reaction is used to build molecules during an anabolic reaction
• Metabolic reactions are catalyzed by enzymes
Metabolic Reactions Continued
Enzymes
Enzymes
• Without enzymes, cellular chemical reactions would occur to slowly to sustain the life of the organism
• Most enzymes are found in the cytoplasm of cells, some are found within individual organelles
Enzymes
• Enzymes are proteins that act as organic catalysts to speed up chemical reactions within cells
• As a catalyst, enzymes lower the amount of activation energy required to initiate a chemical reaction
Activation Energy
• Activation energy is the minimum quantity of energy which the reactants must possess in order to undergo a specified reaction
Enzyme-Substrate Complex
• During a chemical reaction, an enzyme binds to a substrate
• The substrate is the reactant that the enzyme will act upon
Enzyme Specificity
• Each enzyme only recognizes a specific substrate and therefore will only catalyze one type of chemical reaction
• For example, the enzyme maltase will only bind to maltose sugar
Enzyme Binding Site
• Only a small part of the enzyme actually binds to the substrate
• This site is called the active site
Lock and Key Model of Enzyme Action
• The enzyme and substrate have complementary shapes
Lock and Key Model of Enzyme Action
Enzyme-Substrate Example
Enzyme Examples
Carbonic anhydrase
Luciferase
Lipase
Helicase
Enzyme Characteristics
Globular Proteins
• Enzymes are globular proteins that act as biological catalysts
• Functional in its tertiary form
Unchanged By Chemical Reactions
• Enzymes do not become “part” of the reaction (unchanged with the exception of the “induced fit theory”)
• Only facilitate the reaction
Enzyme Specificity
• Enzymes are highly specific for their substrate
• Molecular recognition system based on complementary structures (shapes)
Factors That Affect Enzyme
Function
Enzyme Concentration
• An increase in enzyme concentration will increase the rate of the reaction, as long as substrates are available
Substrate Concentration
• An increase in substrateconcentration will increase the rate of the reaction, as long as sufficient enzyme is available
Temperature
• Each enzyme has an optimal temperature for maximum activity
• Temperatures higher than optimal cause enzymes to denature
• Temperatures that are lower than optimal will interfere with enzyme substrate collisions
pH
• Enzymes have optimal pH levels for maximum activity
• Changes in pH may also denature enzymes
• Most enzymes work optimally in neutral conditions, some prefer acidic or alkaline conditions
Enzymes and pH
• Pepsin is an enzyme that functions in the stomach
• Chemotrypsin functions in the small intestine
Activators
• Activators are molecules that bind to enzymes and increase enzyme activity
• Examples of activators include cofactors (inorganic) and coenzymes (organic)
Inhibitors
• Inhibitors are molecules that decrease enzyme activity
• Examples of inhibitors are competitiveand noncompetitive inhibitors (allosteric)
Competitive Inhibitors
• Competitive inhibitors block the substrate from entering the active site on the enzyme
Noncompetitive Inhibitors
• Noncompetitive inhibitors bind to another area on the enzyme and distort the shape of the enzyme, altering the enzyme active site