Enzymes Flashcards
How do enzymes effect the rate of reaction
Lower activation energy
How do enzymes lower activation energy
Entropy reduction
Desolvation
Induced fit
What is entropy reduction
Enzymes force substrate into correct orientation by binding in the formation they need to be in for the reaction to proceed
What is desolvation
Weak bonds between substrate and enzyme replace most or all H-bonds between substrate and aqueous solution
What is induced fit
Substrate binding causes protein conformational change
What is Michaelis-Menten constant
Km = substrate concentration when reaction is at ½ the maximum velocity (Vmax)
Km is the concentration of a substrate when the reaction is at half of the max velocity
What does Km and Vmax tell us
Km – how specific enzyme is for substrate
Low value = good fit
High value = poor fit i.e. takes a lot of substrate to get to ½ Vmax
Vmax – how fast a reaction is proceeding when enzyme is saturated with substrate
What can affect enzyme reaction
Enzyme concentration - how many enzymes available for substrate binding
Substrate concentration - how much substrate is available to bind to enzymes
Temperature - how close/far from optimum
pH - how close/far from optimum
Inhibitors - alter substrate binding
Describe competitive inhibition
Inhibitir binds to enzyme active site and prevents binding of substrate
Vmax unchanged
Km increases, takes more substrate to overcome inhibition
Describe non-competitive inhibition
Inhibitor binds to secondary site and changes shape of active site
Vmax decreased as many enzymes are not useable
Km remains the same
What is a cofactor
non-protein component needed for reaction e.g. magnesium
What is a coenzyme
Heat-stable substance that can aid enzyme reactions e.g. FAD from riboflavin
What is a isoenzyme
Enzymes that catalyse the same reaction but vary in structure and other biochemical properties
What is a prosthetic group
Non-protein group forming part of or combined with a protein.
What is a spontaneous reaction
Reaction that favors formation of products at conditions under which reaction is occurring
