enzymes

Question 1

what kind of proteins are enzymes?

Answer 1

globular proteins (tertiary structure)

Question 2

what is metabolism?

Answer 2

all enzyme controlled reactions in the body

Question 3

what is anabolism?

Answer 3

synthesis of complex molecules

Question 4

what is catabolism?

Answer 4

the reactions that break down more complex molecules into separate products

Question 5

what are metabolic pathways?

Answer 5

a series of reactions where the product of one enzyme is the substrate of another

Question 6

what is an example of an anabolic reaction?

Answer 6

protein synthesis and photosynthesis

Question 7

what is an example of a catabolic reaction?

Answer 7

digestion and respiration

Question 8

what are the two enzyme-substrate formation theories?

Answer 8

lock and key theory and induced fit theory

Question 9

what is the lock and key theory?

Answer 9

the substrate has a complementary shape to the enzyme’s active site

Question 10

what is the induced fit theory?

Answer 10

the enzymes active site is altered by the binding substrate molecule - active site changes to bind with the substrate

Question 11

what do enzymes do as biological catalysts?

Answer 11

they lower the activation energy needed to start a reaction- chemical reactions speed up

Question 12

what is activation energy?

Answer 12

the minimum energy required that must be put in a chemical system for a reaction to occur

Question 13

what 5 things impact enzyme action?

Answer 13

pH, temperature, enzyme conc., substrate conc., presence of inhibitors

Question 14

what are the two types of inhibitors for enzymes?

Answer 14

competitive and non-competitive inhibitors

Question 15

what are competitive inhibitors?

Answer 15

a molecule that has a similar shape to the substrate and so it also has a complementary shape to the active site - prevents ES complex forming but binding site will eventually become free again

Question 16

what are non competitive inhibitors?

Answer 16

these bind to an allosteric site on the enzyme. this changes the shape of the enzyme, preventing substrate molecules from forming an ES complex

Question 17

what happens to the rate of reaction when the substrate concentration increases?

Answer 17

ROR also increases since there is a greater chance of a successful collision resulting in more ES complexes forming. when all enzyme active sites are occupied, a plateau is reached - max ROR

Question 18

what happens to the rate of reaction when the temperature increases?

Answer 18

both substrate and enzyme gain kinetic energy, so move faster which increases chance of successful collisions. ROR reaches optimum - above this, H bonds break in the tertiary structure due to increased vibrations and enzyme denatures

Question 19

how does the pH level effect the enzyme’s ROR?

Answer 19

when the pH increases/decreases either side of the optimum, the rate of reaction decreases

Question 20

what will happen to the substrate if too many H+ or OH- ions are present?

Answer 20

the substrate can be repelled from the active-site, preventing it from binding

Question 21

what are the use of buffers in enzyme experiments?

Answer 21

ensures that pH is controlled ideally at its optimum, so that it is not limiting the rate of reaction

Question 22

what is a pH buffer for enzymes?

Answer 22

a solution that can resist changes in pH by neutralising acid/alkalis that are added to the solution.

Question 23

what is an immobilised enzyme?

Answer 23

enzymes that are fixed to an inert matrix - does not mix with substrate in solution

Question 24

how are immobilised enzymes achieved?

Answer 24

entrapment (held inside a gel) or micro-encapsulation (trapped inside a micro-capsule)

Question 25

what are 4 advantages to immobilising enzymes?

Answer 25

1. enzyme can be recovered + reused 2. product is not contaminated by enzyme 3. more stable at higher temps. 4. catalyse reactions in a wider range of pH

Question 26

what is a disadvantage of immobilising enzymes?

Answer 26

enzyme may bind with a lower substrate affinity

Question 27

what happens when enzymes are in an inert substance?

Answer 27

reduces ability of polypeptide chain to move, so changes in temperature and pH have less of an effect on the enzyme shape

Question 28

what is an example of an industrial use of immobilised enzymes?

Answer 28

immobilising lactase to produce lactose-free milk

Question 29

how is lactose-free milk produced?

Answer 29

lactase is immobilised in alginate gel beads. milk is passed over the beads and lactase digests the lactose into glucose and galactose. the milk is not contaminated by the enzyme and the beads can be reused

Question 30

what are some examples of immobilised enzymes used in medicine?

Answer 30

biosensors (glucose oxidase) and analytical reagents

Question 31

what are the steps in using a biosensor?

Answer 31

An enzyme electrode is placed on a blood sample. The glucose diffuses up into the immobilised enzyme layer, where O2 is taken up. The rate of O2 uptake is proportional to glucose conc. Glucose conc. is displayed on a digital display

Question 32

How do biosensors work?

Answer 32

work on the principle that enzymes are specific and able to select one type of molecule from a mixture even in very low conc. electrode probe detects changes in substrate or product ect.