8.1 Enzymes HL

Question 1

metabolic chain reaction pathways vs. cyclical reaction pathways [CONTRAST]

Answer 1

• most metabolic pathways involve a chain of reactions
• some metabolic pathways form a cycle instead and in this type of pathway, end product of one reaction is the reactant that starts the rest of the pathway

Question 2

activation energy

Answer 2

• energy necessary for reaciton to occur as it is used to weaken/break bonds in substrate

Question 3

how enzymes lower activation energy

Answer 3

• the binding of substrate to active site of enzyme lowers the overall energy level of transition state & reduces the activation energy

Question 4

enzyme inhibitor

Answer 4

• chemical substances that bind to enzymes & reduce the activity of enzyme

Question 5

competitive vs. non-competitive enzyme inhibition [CONTRAST]

Answer 5

• competitive inhibitors: interfere w/ active site -> substrate can’t bind to active site
• non-competitive inhibitors: bind at a location other than active site (allosteric sites) -> substrate can’t bind to active site / reaction is slowed

Question 6

example of competitive enzyme inhibitor

Answer 6

• sulfadiazine: blocks para-aminobenzoate from binding to dihydropteroate synthetase

Question 7

example of non-competitive inhibitor

Answer 7

• xylitol-5-phosphate: blocks fructose-6-phosphate from binding to phosphofructokinase

Question 8

allosteric regulation of enzyme activity

Answer 8

• regulation of enzyme by binding effector molecule at a site other than active site

Question 9

mechanism of end-product inhibition

Answer 9

enzyme that is regulated catalyzes one of the first reactions in metabolic pathway & substance that binds to allosteric site is the end product of the pathway
- end product acts as inhibitor

Question 10

benefit of end-product inhibition

Answer 10

• economical way to control metabolic pathways:
• allows concentration of the end product to be controlled
• increase in concentration of product causes reaction to eventually slow down and stop because reactions often reach equilibrium position instead of going to completion -> this reverberates back through metabolic pathway when end product accumulates w/ all intermediates accumulating
  
  • end-product inhibition prevents this build-up of intermediate products

Question 11

end-product inhibition of metabolic pathway that converts threonine to isoleucine

Answer 11

• through a series of 5 reactions, amino acid threonine is converted to isoleucine
• as concentration of isoleucine builds up, it binds to allosteric site of first enzyme in the chain, threonine deaminase <- isoleucine acts as non-competitive inhibitor

Question 12

consequence of increase in isoleucine concentration

Answer 12

conc of isoleucine increases -> isoleucine binds to allosteric site of first enzyme in chain, threonine deaminase (isoleucine acts as non-competitive inhibitor)

Question 13

reasons for development of new anti-malarial drugs

Answer 13

• increasing resistance of Plasmodium falciparum (pathogen that causes malaria) to anti-malarial drugs such as chloroquine
• dependence of all new drug combinations on narrow range of medicines
• increasing global efforts to eradicate malaria

Question 14

use of databases in identification of potential new anti-malarial drugs

Answer 14

Plasmodium falciparum strain 3D7: variety of the malarial parasite for which the genome has been sequenced

Question 15

why the rate of reaction with increasing substrate concentration is lower with a non-competitive inhibitor compared to a competitive inhibitor

Answer 15

• competitive inhibitor: concentration of substrate begins to exceed the amount of inhibitor -> maximum rate of uninhibited enzyme can be achieved BUT takes much higher concentration of substrate to achieve this maximum rate
• non-competitive inhibitor: enzyme doesn’t react the same maximum rate bc binding of non-competitive inhibitor prevents some enzymes from being able to react regardless of substrate concentration -> enzymes that don’t bind to inhibitors follow same pattern as normal enzyme -> takes approximately same conc of enzyme to reach maximum rate, but max rate is lower than uninhibited enzyme

Question 16

two methods for determining the rate of enzyme controlled reactions

Answer 16

1) measuring the rate of disappearance of substrate
2) measuring the rate of appearance of product

Question 17

unit for enzyme reaction rate

Answer 17

amount of reaction per unit time
e.g. %/s

Question 18

uses and benefits of bioinformatics technique of chemogenomics in development of new pharmaceutical drugs

Answer 18

• bioinformatics: approach whereby multiple research groups can add information to a database enabling other groups to query the database
• chemogenomics: one promising bioinformatics technique that has facilitated research into metabolic pathways
• scientists look to develop new drugs and test massive libraries of chemicals on a range of organisms to find which ones are effective on particular parts of different metabolic pathways
• there’s often a huge database and metabolic pathways they affect