Enzymes Flashcards
What are the three ways that enzymes can reduce activation energy?
Entropy reduction, Desolvation, Induced fit
What is entropy reduction?
Enzyme positions substrate so it’s in the correct orientation to fit - reducing entropy
What is desolvation?
Water surrounding the enzyme and substrate make it energetically favourable for the substrate to enter the enzyme, pushing water away
What is induced fit?
Enzyme having a conformational change to fit the substrate better after its bound
What does the Michaeles-menten plot tell us?
The amount/conc. of substrate and the rate of reaction
What does Km tell us on the Michaeles-menten plot?
Km = substrate conc. at 1/2Vmax
What does Vmax tell us?
The maximum velocity of the equation once all the enzymes have been used up - plateaux
What does the change in Km tell us?
Low Km tells us that the reaction doesn’t require a lot of substrate - faster reaction. High Km tells us the reaction requires a lot of substrate - slower reaction.
What does change in Vmax tell us?
Higher Vmax - faster enzyme. Lower Vmax - slower enzyme
What are 5 factors that effect enzyme inhibition?
Temp, pH, Enzyme conc. Substrate conc. and inhibition
What are the 2 types of enzyme inhibition?
Competitive and non-competitive
What happens during competitive inhibition? (Vmax and Km)
Inhibitor binds directly to the active site, blocking a substrate from binding. Vmax stays the same but Km decreases
What happens during non-competitive inhibition? (Vmax and Km)
Inhibitor binds to alternative site on enzyme, changing the shape of the active site. Vmax decreases as not enough enzyme, but Km stays the same (as Vmax decreases in inhibited reaction)
Why do we measure enzymes?
Many reasons including detecting diseases and deficiencies
What 8 factors affect enzyme activity?
Age, race, gender, time of day, disease, genetics, pregnancy, drugs
Give some examples of when enzymes would be released
Hypoxia, cellular damage, physical damage
What is an enzyme assay?
A laboratory technique used to measure enzyme activity. It must be optimised to the specific requirements of the enzyme we are measuring
How do we analyse enzymes in a lab?
We look at plasma/ serum samples. We measure the rate of an enzyme-substrate reaction
What is an issue with enzyme measurement in labs?
Enzymes each have a specific optimum requirements, incl. pH and temp.
What are isoenzymes?
Enzymes which have the same exact function but differ in structure
Why does Phenylketonurea occur in humans?
Inability to break down amino acid phenylananine (using phenylalanine hydroxylase enzyme)
What does reaching Vmax imply?
substrate occupies all available active sites of the enzyme
What does denaturation refer to?
Weak bonds (hydrogen bonds) that maintain the secondary, tertiary and quaternary structures are lost but the covalent links between amino acids is retained.
What does isomerase do?
Transfers groups within a molecule, forming an isomer
