Enzymes and Catalysis

Question 1

What are proteins?

Answer 1

• Polymers
• Linked together by peptide bonds
• Arranged in 3D structural hierarchy

Question 2

Tertiary structure

Answer 2

single polypeptide chain

Question 3

quaternary structure

Answer 3

multiple polypeptide chains

Question 4

made up of monomers:

Answer 4

acid amino
= determines 3D structure - depends on sequence of a.a

Question 5

Enzymes

Answer 5

Biological catalysts that speed up enzymatic/ chemical reactions

Question 6

which organisms are enzymes present?

Answer 6

Present in EVERY chemical reaction in EVERY organism

Question 7

What are proteins made out of?

Answer 7

Proteins
(except for catalytic RNA’s - ribozymes)

Question 8

Single enzymes

Answer 8

single polypeptide chain

Question 9

Allosteric and multifunctional enzymes

Answer 9

complex - more of subunits / multiple polypeptide chains

Question 10

What determines on how good catalytic activity?

Answer 10

the native folding of protein

Question 11

What are the properties of enzymes?

Answer 11

• specific for substrates
• catalytic power = fast
• Efficient. not altered after reaction (stays the same shape and size)
• can be regulated

Question 12

What is substrate specificity?

Answer 12

• Ability of the enzyme to specifically recognise the proper substate (reactant)
• Molecular recognition mechanism - based on structural complementary
• substrate bind to specific region of enzyme - ACTIVE SITE

Question 13

1st step of enzymatic catalysis

Answer 13

substrate-complex (E-S)

Question 14

Lock and key model

Answer 14

Enzyme fits PERFECTLY into substrate

Question 15

Induced fit

Answer 15

• Substrate is NOT exactly complementary to active site SFTR binding
• Conformational change occurs to allow better fit between active fit and substrate (hand in glove)

Question 16

What is the active site? Where?

Answer 16

• 3D pocket where substrate binds to
• Small region of enzyme (10-20%)

Question 17

What is the enzyme COMPOSED of?

Answer 17

1. SUBSTRATE BINDING SITE
2. CATALYTIC SITE

Question 18

SUBSTRATE BINDING SITE

Answer 18

• A.a side chains interact with substrate
• Interactions that orientate the substate within the active site

Question 19

CATALYTIC SITE

Answer 19

• A.a that performs or catalyses the reaction
• The correct folding of enzyme is required
  S-E binding alters the structure of the substrate to promote the formation of the transition state

Question 20

Catalytic power..

Answer 20

Increase the rate of chemical reaction

Question 21

How many times can rate of reaction increase with the presence of enzyme?

Answer 21

range: 10^6&raquo_space; 10^17

Question 22

For start of reaction - energy is required. What’s this called?

Answer 22

Activation energy

Question 23

Define activation energy

Answer 23

the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction

Question 24

Lower the activation energy…

Answer 24

faster the rate of reaction

Question 25

Does enzyme have an affect on the equilibrium of reactions?

Answer 25

No - no affect

Question 26

Efficiency and reusability?

Answer 26

- unaffected by reaction which they catalyse - can be reused -active in LOW concentrations

Question 27

Conditions that affect enzyme functions:

Answer 27

1. Temp 2. Ionic condition 3. pH 4. Substate concentration 5. Presence of inhibitors

Question 28

Temp and enzymatic activity

Answer 28

- ^ temp = higher the rate of reaction - Usually 37C in humans (some archae - extremophiles its higher)

Question 29

Denturation

Answer 29

Loss of native folding in protein - active side no longer matches the substrate = loss of catalytic activity

Question 30

pH and enzymatic activity

Answer 30

- most active optimum pH

Question 31

Optimum pH in the body

Answer 31

- Small intensine enzymes : 7.5 - Stomach enzymes : 1.5 - Digestive lysosomal enzymes : 4-5

Question 32

when is structure disturbed by pH

Answer 32

in very low or very high pH as tertiary structure is disturbed

Question 33

Constant concentration of enzyme + increase in substrate

Answer 33

Concentration will cause increase in enzyme activity up to the point where enzyme is SATURATED with the substrate WILL NOT change rate of reaction!!!

Question 34

Saturated meaning:

Answer 34

enzymes has reached their maximum activity (steady rate) and Maximum rate of reaction (Vmax)

Question 35

Reaction rate

Answer 35

ONLY measures on how rapidly the enzyme can process the substrate

Question 36

What is kinetics

Answer 36

the study of reaction rates

Question 37

Km

Answer 37

concentration of substrate at which reaction rate is half-maximal

Question 38

Higher Km

Answer 38

-weaker binding

Question 39

Lower Km

Answer 39

-stronger binding

Question 40

Competitive inhibitors

Answer 40

Competing with substrate by binding at active side and blocking it (effect can be reversible or irreversible (covalent bonds)

Question 41

Non-competitive inhibitors

Answer 41

Bind into allosteric site on enzyme (NOT active site) -Cause conformational change in enzyme and block of the catalytic activity / active site changes in shape -Effect is reversible (usually)

Question 42

Enzyme cofactors

Answer 42

additional components - provide active site REACTIVE GROUPS *they are NOT substrates*

Question 43

Coenzymes

Answer 43

- Temporarily/ weakly bound to the enzyme - Altered during course of reaction and dissociate from the active site

Question 44

Examples of coenzymes:

Answer 44

1. NAD+ 2. NADP+

Question 45

Protheic groups

Answer 45

-Tightly bound to enzyme = covalent bond - must be regenerated each catalytic cycle

Question 46

examples of prothetic groups

Answer 46

- HAEM (in haemoglobin) for oxygen REDOX reactions - FAD in REDOX reactions - VITAMIN B7 or Biotin = carboxylse enzymes

Question 47

HOLOENZYME

Answer 47

Complete catalytically-active enzyme together with its cofactor

Question 48

APONZYME (not active)

Answer 48

Protein part of enzyme on its own without its cofactor

Question 49

7 major groups of the international Union of Biochemistry

Answer 49

1. Oxidoreductases 2. Transferases 3. Hydrolases 4. Lyases 5. Isomerase 6. Ligases 7. Translocases

Question 50

ENZYME Class 1 Oxidoreductases

Answer 50

Catalyse REDOX reactions

Question 51

ENZYME Class 2 Transferases

Answer 51

Catalyse functional group transfer reactions

Question 52

ENZYME Class 3 Hydrolases

Answer 52

Catalyse hydrolasis reactions (transfer functional groups to water by breaking down of a bond)

Question 53

ENZYME Class 4 Lyases

Answer 53

- Catalyse the cleavage of C-C, C-O, C-N or other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds - They catalyse the breaking of a chemical bond between two parts of a molecule (other than hydrolytic or oxidative bond breaking)

Question 54

ENZYME Class 5 Isomerases

Answer 54

Catalyse transfer of groups within molecules to yield isomeric forms

Question 55

ENZYME Class 6 Ligases

Answer 55

- The joining ligation of two large molecules by forming a new chemical bond with the release energy

Question 56

ENZYME Class 7 translocases

Answer 56

- Movement of molecules or ions across membranes or their separation within membranes