Enzymes in Physiology

Question 1

Why are enzymes important for pharmacy?

Answer 1

Involved in biochemical reactions
Reactions needed for survival
* component of pharmaceutical management of disease in patients
Used diagnostically
Used therapeutically

Question 2

What are functions of enzymes?

Answer 2

Weaken bonds in reactions
May provide nucleophiles
Biological catalyst
Active site
Provide suitable environment 
Position reactants correctly 
May provide acid/base catalyst

Question 3

What does enzymes NOT change?

Answer 3

Eqm position

Question 4

What is an active site?

Answer 4

Region within enzyme that fits the shape of substrate molecules

Question 5

What happens when enzyme and substrate bind?

Answer 5

Amino acid side chains align to bind to substrate through H-bonding
Products released (no longer fit active site)

Question 6

Describe lock + key model

Answer 6

Rigid active site
Fit between active site + substrate = exact
Enzyme-substrate complex formed
Product different shape to substrate
Enzyme free to bind to another substrate when product released

Question 7

Describe induced fit

Answer 7

Active site flexible + can change
Shape of enzyme, active site + substrate adjust to fit
Changed environment = improved catalysis
Greater range of substrate specificity

Question 8

What is optimum pH?

Answer 8

7.4

Question 9

What happens to enzyme activity at high/low pH?

Answer 9

Activity lost

= tertiary structure changes

Question 10

What are exceptions to optimum pH?

Answer 10

Pepsin
Urease
Sucrase
Amylase
Trypsin
Arginase

Question 11

What is pepsin pH?

Answer 11

2

Question 12

What is urease pH?

Answer 12

5

Question 13

What is sucrase pH?

Answer 13

6.2

Question 14

What is amylase pH?

Answer 14

7

Question 15

What is trypsin pH?

Answer 15

8

Question 16

What is arginase pH?

Answer 16

9.7

Question 17

What does changing pH alter?

Answer 17

Ionisation state of amino acid side chains

Question 18

What is optimum temp?

Answer 18

37 degrees

Question 19

Why is little activity at low temp?

Answer 19

Little KE

Question 20

Why is little activity at high temp?

Answer 20

Denaturation

Question 21

What are cofactors?

Answer 21

Bind to enzyme to maintain correct configuration of active site
Metal ions or other inorganic factors

Question 22

Describe coenzyme

Answer 22

Required by some enzymes
Most carry e-
Many have modified vitamins in structure

Question 23

What is a coenzyme?

Answer 23

An organic molecule bound to enzyme by weak interactions/H bonds

Question 24

What do oxidoreductases do?

Answer 24

Catalyse transfer of e- from donors to acceptors

Question 25

What is an example of an oxidoreductase?

Answer 25

Dehydrogenase accept + donate e- as hydride ions

Question 26

What do transferases do?

Answer 26

Catalyse transfer of specific functional groups between molecules

Question 27

What is an example of a transferase?

Answer 27

Glycosyltransferase transfers carbohydrate residues

Question 28

What do hydrolases do?

Answer 28

Catalyse cleavage of bonds by addition of H2O molecules

Question 29

What is an example of hydrolase?

Answer 29

Lipases hydrolyse ester bonds

Question 30

What do lyases do?

Answer 30

Catalyse addition of H2O, NH3 or CO2 double bonds or remove them to create double bonds Cleave bonds by means other than hydrolysis or oxidation

Question 31

What is an example of lyase?

Answer 31

Decarboxylase remove CO2

Question 32

What do isomerases do?

Answer 32

Catalyse interconversion of isomeric forms of a molecule by transferring groups within the same molecule

Question 33

What is an example of isomerase?

Answer 33

Conversion of Cis + Trans isomers | Conversion of D + L isomers

Question 34

What do ligases do?

Answer 34

Catalyse synthesis of new covalent bonds using ATP

Question 35

What is an example of a ligase?

Answer 35

Synthetases

Question 36

What can enzymes catalyse?

Answer 36

Single substrate Group of substrates Particular type of bond

Question 37

What is an absolute enzyme catalysis ?

Answer 37

Catalyses one type of reaction for a single substrate

Question 38

What is a group enzyme catalysis?

Answer 38

Catalyses one type of reaction for similar substrates

Question 39

What is a linkage group catalysis?

Answer 39

Catalyses one type of reaction for specific type of bond

Question 40

What does active site conformation drive?

Answer 40

Selectivity

Question 41

What does chymotrypsin prefer?

Answer 41

Aromatic side chains adjacent to scissile bond

Question 42

What does trypsin prefer?

Answer 42

Positively charged side chains that can interact with ASP189

Question 43

What does elastase prefer?

Answer 43

Small uncharged side chains, as pocket blocked

Question 44

What are isoenzymes?

Answer 44

Different forms of an enzyme catalysing same reaction in different tissues

Question 45

What are the difference between isoenzymes?

Answer 45

Slight variations in sequences of subunits in quaternary structure Can have different attributes + optimal conditions

Question 46

Describe allosteric regulation of enzyme action | non-competitive inhibition

Answer 46

Effector molecules change activity of enzyme by binding to 2nd site

Question 47

What is positive allosterification?

Answer 47

Speed up enzyme activity

Question 48

What is negative allosterification?

Answer 48

Slow enzyme action

Question 49

What is feedback inhibition?

Answer 49

Product late in series of enzyme-catalysed reactions serves as an inhibitor for previous allosteric enzyme earlier in series