enzymes

Question 1

does the value delta G tell you how fast the reaction will go?

Answer 1

delta G does not tell the speed of the reaction; it only tells how much energy is released or required

Question 2

define activation energy

Answer 2

energy needed to reach transition state

Question 3

define enzyme

Answer 3

catalyst, speeds up reaction without being used

Question 4

do enzymes change activation energy, delta G, or both?

Answer 4

they change activation energy, but not delta G. the enzyme’s active site binds a substrate through multiple weak and temporary interactions that form through spontaneous, exergonic reactions that feed into reducing the activation energy

Question 5

define substrate

Answer 5

reactant of an enzyme

Question 6

define active site

Answer 6

specific region of an enzyme where a substrate binds and catalysis/chemical reaction occurs

Question 7

what is the importance of the weak/temporary bonds that form between the enzyme and substrate in the enzyme-substrate complex?

Answer 7

in the enzyme-substrate complex, the substrate is held in the active site by the weak interactions

Question 8

enzyme regulation can be accomplished by changing the ___ or the ___ of an enzyme. which method is faster?

Answer 8

by changing the amount or the activity of an enzyme. changing the activity is faster

Question 9

difference between reversible and irreversible inhibitors

Answer 9

irreversible inhibitors: (covalent) binds permanently binds to the active site of the enzyme
reversible inhibitors: (ionic) binds temporarily through weak interactions to the active site

Question 10

explain how reversible enzyme inhibitors affect enzyme activity

Answer 10

reversible inhibitors alter the catalytic action of the enzyme and consequently slow down or stop catalysis

Question 11

difference between competitive and non-competitive inhibitors

Answer 11

competitive: similar in shape to substrate, binds to active site and blocks substrate from binding
non-competitive: does not bind to active site, binds to enzyme and causes it to change shape

Question 12

experimental data that graphs reaction time v. substrate concentration

Answer 12

non-competitive inhibitors are not affected by the amount of substrate, while competitive inhibitors decrease in effectivity when substrate concentration is increased

Question 13

explain allosteric regulation of enzymes

Answer 13

allosteric regulation includes non-competitive inhibitiors and allosteric activators; non-covalent attachment which involves attaching a larger regulatory molecule, GTP and ATP. covalent attachment is attaching a phosphate group to the enzyme

Question 14

define feedback inhibition

Answer 14

products of the reaction inhibits the enzyme

Question 15

explain how the following factors affect enzyme activity

• pH
• temperature

Answer 15

pH: all enzymes have an optimum pH

temperature: all enzymes have an optimum temperature
- too high: enzyme denatures
- too low: enzyme becomes too slow

Question 16

what are cofactors

Answer 16

non protein partners:

a. metal ions: electron transfer reactions
b. co-enzymes: larger molecules that bind to an enzyme temporarily
c. prosthetic groups: larger molecules that bind to an enzyme permanently