Enzymes

Question 1

Are enzymes globular or fibrous?

Answer 1

Globular

Question 2

What two things can enzymes affect in an organism?

Answer 2

Structure
Function

Question 3

What is intracellular enzyme and example?

Answer 3

Works inside cells
Catalase- hydrogen peroxide breakdown catalysed

Question 4

Extra cellular enzymes and example?

Answer 4

Work outside of cells
Amylase- catalyses hydrolysis of starch into maltose

Question 5

What is an enzyme substrate complex?

Answer 5

A substrate bonded to an active site

Question 6

What is an enzyme product complex?

Answer 6

Formed after reaction is catalysed, when product molecule is released from complex

Question 7

Two models for enzyme action and explanation?

Answer 7

Lock and key- active site and substrate complementary in shape
Induced fit- active site undergoes conformational change after substrate binds, completing the fit

Question 8

Two models for enzyme action and explanation?

Answer 8

Lock and key- active site and substrate complementary in shape
Induced fit- active site undergoes conformational change after substrate binds, completing the fit

Question 9

How do enzymes speed up reactions?

Answer 9

By reducing activation energy

Question 10

How does temperature affect rate of reaction at first?

Answer 10

Enzyme and substrate gain kinetic energy
More collisions and more enzyme- substrate complexes form
Rate of reaction increases to optimum temperature

Question 11

How does temperature affect rate of reaction after optimum temperature?

Answer 11

-Molecules in enzyme begin to vibrate more
-Bonds in tertiary structure (ionic/hydrogen) break
-active site changes shape, no longer complementary to substrate
-enzyme denatures

Question 12

What is the temperature coefficient (Q10)?

Answer 12

Unit-less value
Which indicates how much reaction changes if the temperature is increased by 10•C

Question 13

Equation for temperature coefficient?

Answer 13

Q10= R2/R1
R2- rate at higher temp
R1- rate at lower temp

Question 14

How do low pH’s affect rate of reaction?

Answer 14

H+ ions cause hydrogen and ionic bonds in tertiary structure in enzyme to break

Question 15

How do high pH’s affect rate of reaction?

Answer 15

Presence of OH- causes ionic and hydrogen bonds in tertiary structure of enzyme to break

Question 16

What is H+ and OH- ions overall affect on enzymes?

Answer 16

Enzyme may denature, shape of active site changes

Question 17

What does increasing enzyme concentration have on rate of reaction?

Answer 17

More successful collision
More enzymes substrate complexes form
Rate or reaction increase s

Question 18

Why does rate of reaction plateau when enzyme concentration increases?

Answer 18

Amount of substrate is limited, so adding more enzymes has no affect

Question 19

What effect does increasing substrate concentration have on rate of reaction?

Answer 19

More successful collision with active site
Rate increases
More enzyme-substrate complexes form

Question 20

Why does rate of reaction plateau when substrate is increased?

Answer 20

All available active sites are occupied

Question 21

What is Vmax?

Answer 21

Maximum rate of reaction

Question 22

What are inhibitors and what are the two types?

Answer 22

Molecules which bind to enzyme to reduce their activity
Competitive and non competitive inhibitors

Question 23

What do competitive inhibitors do?

Answer 23

Similar shape to substrate
Bind reversible to active site and block it, preventing substrate binding

Question 24

What affect does substrate concentration have on rate of reaction, when competitive inhibitors are involved?

Answer 24

-Increasing substrate concentration, increases rate of reaction
-As substrate concentration increases, there is a higher chance of substrate colliding with active site, instead of inhibitor molecule

Question 25

How do non competitive inhibitors work?

Answer 25

-They bind to allosteric site -This causes active site to change shape, substrate can no longer bind

Question 26

What affect does increasing substrate concentration have on rate of reaction, when non competitive inhibitor is involved?

Answer 26

Little effect, as inhibitor and substrate do not compete Vmax is dependant on inhibitor concentration

Question 27

For each type of inhibition, do the molecules bind reversible or irreversibly?

Answer 27

Both bind irreversibly and reversibly

Question 28

For each type of inhibition, do the molecules bind reversible or irreversibly?

Answer 28

Both bind irreversibly and reversibly

Question 29

What is a metabolic pathway?

Answer 29

Sequence of enzyme controlled reactions, where the product of one reaction, is reactant for next

Question 30

What is end product inhibition?

Answer 30

Final product of metabolic pathway acts as a reversible non competitive inhibitor for first enzyme

Question 31

What is the use of end product inhibition?

Answer 31

Regulates pathway, preventing build up of final product When the levels of product start to fall, the inhibition levels decrease

Question 32

What are co factors and co enzymes?

Answer 32

Non protein molecules, which bind to enzymes, allowing them to function

Question 33

What are inorganic co factors? Example?

Answer 33

Ions which bind to active site alongside substrate They are not involved in reaction Cl- ions are cofactors for amylase

Question 34

What are co enzymes? Example?

Answer 34

-Organic molecules, bind alongside substrate They are involved in the reaction, and are changed by it -NAD removes H from ethanol via ethanol dehydrogenase

Question 35

Where are co enzymes sourced from?

Answer 35

Vitamins e.g. NAD comes from vitamin B3