Enzymes

Question 1

What are enzymes?

Answer 1

-Enzymes are biological catalysts made of globular proteins
-the active site is specific and unique due to the specific folding of the tertiary structure of the protein
-so enzymes can only attach substrates that are complementary to the active site

Question 2

What do enzymes do?

Answer 2

Enzymes catalyse intracellular and extracellular reactions without actually being used up

Question 3

What is an example of an intracellular enzyme and what does it do?

Answer 3

Catalase is an intracellular enzyme found in liver cells and it breaks hydrogen peroxide into oxygen and water

Question 4

What is an example of an extracellular enzyme and what does it do?

Answer 4

Trypsin is an extracellular enzyme found in the small intestine and it hydrolyses proteins

Question 5

What is the activation energy?

Answer 5

The activation energy is the minimum amount of energy required for a reaction to occur

Question 6

What happens when an enzyme attaches to a substrate?

Answer 6

They can lower the activation energy needed for the reaction to occur and therefore speed up the reaction

Question 7

What is the lock and key hypothesis?

Answer 7

Model suggests the enzyme is like a lock and the substrate is like a key that fits into it due to the enzymes specific tertiary structure resulting in a complementarity shape

Question 8

what happens when a substrate attaches and random collisions occur?

Answer 8

Enzyme active site is a fixed shape and due to random collisions the substrate can collide and attach to the enzyme, forming an enzyme substrate complex. The charged groups within the active site can distort the substrate and lower the activation energy

Question 9

What is the induced fit hypothesis?

Answer 9

Enzyme’s active site is induced/slightly changes shape so the substrate can fit. When the enzyme substrate complex occurs, it puts a strain on the bonds and lowers the activation energy

Question 10

What factors affect enzymes

Answer 10

-enzymes are globular proteins.
-Temperature, PH, enzyme concentration and substrate concentration all affect enzyme-controlled reactions

Question 11

How does temperature affect enzyme activity?

Answer 11

-if temperature is too low, there is insufficient kinetic energy for successful collisions
-if the temperature is too high, enzymes denature and the active site changes shape so enzyme-substrate complex cannot form
-high temperatures causes bonds to break and the tertiary structure changes causing a change in the shape of the active site

Question 12

What is the Q10?(the 10 is tiny)

Answer 12

-temperature coefficient is a measure of the rate of change of an enzyme-controlled reaction as a result of increasing the temperature by 10°C
-Q10=R2/R1
R1=rate of reaction at a temperature of X°C
R1=rate of reaction at a temperature(X+10)°C

Question 13

How does the PH affect enzyme activity?

Answer 13

-Too high or too low Ph will interfere with the charges in the amino acids in the active site causing ionic/hydrogen bonds to break
-alters tertiary structure and changes shape of active site and enzyme denatures
-enzymes have different optimal Ph values they work best at

Question 14

How does substrate concentration affect enzyme activity?

Answer 14

-if there is a low concentration of the substrate, reaction will be lower because there are fewer collisions between the enzyme and the substrate
-increasing the substrate concentration increases the rate of the reaction
-at high substrate concentrations, the rate of reaction will plateau because all of enzyme’s active sites are in use(enzymes are saturated)

Question 15

How does enzyme concentration affect the rate of the reaction?

Answer 15

-At low enzyme concentration, there will be a lower rate of reaction
-increasing the enzyme concentration will increase the rate of reaction as enzyme substrate complexes will be more likely to form
-at high enzyme concentration,unless unlimited substrate is added, the rate of reaction plateus as there will be insufficient substrate to bind with the large number of enzymes

Question 16

What are competitive inhibitors?

Answer 16

-same shape as the substrate so they’re also complementary to the enzyme’s active site so they bind to the enzyme’s active site
-prevents substrate from binding and enzyme-inhibitor complexes form instead of an enzyme substrate complex so the rate of reaction is lower
-most competitive inhibitors are reversible(inhibitor can be removed)
-if a high concentration of substrate is added,substrate can knock out the inhibitor and rate of reaction will increase

Question 17

What are non competitive inhibitors?

Answer 17

-they bind to the enzyme away from the active site called the allosteric site
-active site changes and therefore the substrate can no longer bind no matter how much how much substrate is added
-fewer enzyme substrate complexes are formed so rate of reaction is much lower

Question 18

What is the end-product inhibition?

Answer 18

-production of some reactions are reversible inhibitors for the enzymes involved in controlling the reaction
-this enables the reactions to be controlled
-if there is a lot of product present, it will inhibit the enzymes and cause the reaction to slow or stop
-prevents resources from being wasted