C1.1 - enzymes and metabolism

Question 1

conformation

Answer 1

3D shape

Question 2

allosteric site

Answer 2

a site on the enzyme other than the active site to which the molecule can bind to and modify the activity of the enzyme

Question 3

endorgenic

Answer 3

a reaction that takes in energy

Question 4

exergonic

Answer 4

a reaction that releases energy

Question 5

hydrophobicity

Answer 5

a measure of how hydrophobic or how hydrophilic a molecule is

Question 6

inhibition

Answer 6

reduction in the rate of an enzyme-catalysed reaction

Question 7

enzymes

Answer 7

biological catalysts which increase the rate of reactions by lowering activation energy
- have active sites which bind to specific substrates

Question 8

metabolism

Answer 8

complex network of interdependent and interacting chemical reactions that occur in living organisms

Question 9

what is the role of enzymes in metabolism?

Answer 9

metabolic reactions are controlled by enzymes which each catalyse a specific chemical reaction

Question 10

anabolism

Answer 10

building up
- formation of macromolecules from monomers through condensation

Question 11

catabolism

Answer 11

breaking down
- the breakdown of macromolecules into monomers through hydrolysis

Question 12

what is the structure of enzymes?

Answer 12

globular proteins with a general spherical shape

Question 13

active site

Answer 13

catalytic site onto which the substrate binds
- made up a few amino acids
- has a specific shape, charge and hydrophobicity

Question 14

what is the lock and key theory of enzymes?

Answer 14

substrate binds and fits exactly to the active site which doesn’t change shape to form an enzyme substrate complex
- explains narrow specificity of enzymes
- substrate binding causes weakened substrate bonds which reduce activation energy

Question 15

what are the pros and cons of the lock and key theory?

Answer 15

pro - good analogy for the specificity of enzymes
con - doesn’t account for the significant shape change that occurs when enzymes bind with their substrates

Question 16

what is the induced fit theory of enzymes?

Answer 16

substrate binds to the active site but doesn’t fit exactly, so the active site changes shape slightly to form enzyme-substrate complex
- explains broader specificity
-change in the shape of the substrate weakens the substrate bonds, reducing activation energy

Question 17

what is needed for an enzyme’s active site and a substrate molecule to come together?

Answer 17

movement as collisions allow for binding due to complementary shaped active sites

Question 18

what does binding of a substrate and enzyme occur due to and what does it cause?

Answer 18

occurs due to the attractive chemical properties of the substrate and active site which are in correct orientation
- causes formation of an enzyme-substrate complex in which both slightly change shape, putting strains on chemical bonds of the substrate and weakening them

Question 19

activation energy

Answer 19

minimum amount of energy (kinetic energy or molecular motion) the substrate and enzyme molecules require to successfully collide and start the reaction

Question 20

what happens when the products are formed?

Answer 20

the product is released from the active site, leaving the unchanged enzyme free to combine with other substrate molecules

Question 21

why may enzymes or substrates be immobilized?

Answer 21

increases enzyme activity by making the formation of enzyme-substrate complexes more efficient
- immobilized by being embedded into the membrane

Question 22

denaturation

Answer 22

permanent change in the conformation of the enzyme active site
- reduces the ability to bind with the substrate and catalyse the reaction

Question 23

enzyme specificity

Answer 23

an enzyme’s active site only allows it to bind to specific substrates with a complementary shape to form enzyme-substrate complexes and allow reactions to occur

Question 24

collision theory

Answer 24

considers how factors affect the frequency and success of collisions between two reactants

Question 25

how does enzymes link to collision theory?

Answer 25

enzyme function depends on collisions between the active site and the substrate
- more frequent collisions = faster rate of reaction
- more energy = reaches activation energy

Question 26

what is the effect of temperature on the rate of enzyme activity?

Answer 26

• enzyme activity increases with temperature due to faster molecular motion and more kinetic energy, leading to more collisions
• enzyme reaches highest activity at optimum temperature
• at temperatures above optimum, rate falls as increased vibrations break bonds within the enzyme, so the active site changes

Question 27

what is the effect of pH on the rate of enzyme activity?

Answer 27

• at pH levels below the optimum, ionisation of the amino acid interferes with the ionic bonding and changes the shape of the active site
• enzyme reaches highest activity at optimum pH
• at pH levels above the optimum, ionisation of the amino acid interferes with the ionic bonding and changes the shape of the active site

Question 28

what is the effect of substrate concentration on the rate of enzyme activity?

Answer 28

• enzyme activity increases with substrate concentration due to a greater chance of collisions occurring
• enzyme activity plateaus as enzyme active sites are saturated

Question 29

what are 3 ways enzyme reaction rates can be determined?

Answer 29

• time taken for substrate to be used up
• amount of product formed or substrate used in a set time period
• initial rate of reaction

Question 30

how can you use time taken for substrate to be used up to calculate rates and what are the pros and cons?

Answer 30

• rate is calculated by dividing 1 by the time taken
• accuracy is improved by increasing frequency of samples
  pro - qualitative indicator and data
• end point is subjective, relies on regular sampling and time inefficient

Question 31

how can you use time amount of product formed to calculate rates and what are the pros and cons?

Answer 31

• volume or mass gained or lost in a reaction
  pro - only requires measurements at the start and end of the reaction time
  con - long enough time to measure accurately, but not too long for it to be a limiting factor

Question 32

how can you use initial rate of reaction to calculate rates and what are the pros and cons?

Answer 32

• accuracy can be improved by taking more frequent readings
  pro - initial rates not affected and doesn’t need to reach completion
  con - measurements must be repeated, analysis is a long process, suitable for quantified reactions