AP Biology - Unit 3

Enzymes

substances that speed up the chemical reactions that occur in all living things without changing

All enzymes…

are catalysts

Catalyst

substance that speeds up chemical reactions without being changed or used up

Enzymes speed reactions by…

lowering the activation energy in the reaction

Substrate

what an enzyme acts upon

Lock and Key model

the perfect fit between an enzyme’s active site and an enzyme’s substrate

Induced Fit

the changing of an enzyme’s active site shape to match with its substrate

Denaturation of Enzymes

the change in an enzyme’s environment(pH,temp,salinity) that changes the enzyme’s shape, reducing its ability to catalyze reactions

Products

substances that result from a reaction

Catalyst in living systems…

are enzymes which are proteins and RNA

Activation Energy

the initial energy required to get a chemical reaction started

Active Site

specific area on an enzyme where the enzyme binds with its substrate

Enzyme-substrate complex

forms through ionic and hydrogen bonds when an enzyme binds with its substrate at the active site

Exergonic Reaction

releases energy(Ex: cellular respiration)

Endergonic Reaction

absorbs energy(Ex: photosynthesis)

Anabolism

endergonic, combining two substances into a molecule

Catabolism

exergonic, breaking down a molecule into substances

Entropy

the measure of disorder

Competitive Inhibition

an inhibitor molecule and a substrate compete for access to an enzyme’s active site, can be overcome by increasing substrate concentration

Non-competitive Inhibition

an inhibitor molecule binds with the allosteric site of an enzyme and takes away the ability of the enzyme to bind with its substrate

Metabolic Pathway

a series of enzyme-catalyzed reactions in which the product of one reaction becomes the substrate for the next reaction

Feedback Inhibition

the product of a metabolic pathway binds with the allosteric site of the first enzyme, causing the active site of that enzyme to no longer be able to bind with its substrate

Allosteric Site

site on an enzyme that when binded with a molecule, will change the enzyme’s active site

Allosteric Inhibitor

molecule that binds with the allosteric site and takes away an enzyme’s active site ability to bind with its substrate

Allosteric Activator

molecule that binds with the allosteric site and gives an enzyme’s active site the ability to bind with its substrate

What are enzymes considered when their active site is engaged?

enzymes are considered saturated

Optimum

the peak of reaction rate or fastest reactions for enzymes under certain conditions like enzyme/substrate concentration, temperature, pH, and salinity

Changes in pH of Enzyme

Increasing pH from Optimum: decreased enzyme activity and eventual denaturation

Decreasing pH from Optimum: decreased enzyme activity and eventual denaturation

Changes in Temp of Enzyme

Increasing Temp from Optimum: increased enzyme activity until denatured

Decreasing Temp from Optimum: slowed enzyme activity(cold temps slow down molecules)

Irreversible Inhibition

an inhibitor molecule permanently binds with the enzyme competitively(at active site) or non-competitively(at allosteric site)