Enzyme properties, kinetics and regulation Flashcards Preview

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Flashcards in Enzyme properties, kinetics and regulation Deck (63)
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1

Definition of an enzyme

Biological catalyst, increase R of R without altering final equilibrium between reactants and products, v efficient

2

Definition of cofactors

Inorganic elements, often transition metals as oxidation state can change

3

Definition of coenzymes

Not enzymes or inorganic ions but are still vital to enzyme function

4

Definition of isoenzymes

Different protein structures but catalyst same reaction

5

Definition of enzyme kinetics

The study of the rate of an enzyme catalyses reaction and how that rate varies with different substrate concs, amount of inhibitors, metal ions and cofactors, pH

6

Definition Kcat

Turnover number is equivalent to no of substrate molecules => product in a given unit of time on a single enzyme molecule when enzyme is saturated (s-1)

7

Definition of competitive inhibitors

Block enzyme AS, does not actually bind

8

Definition of non competitive inhibitors

Interfere in some other way, can be reversible or irreversible
Doesn't actually change shape of AS, changes bonds within AS

9

Process of enzyme catalysis

S complementary to AS
Greater affinity between S and AS to form ESC
Catalysis
Lower affinity between S and AS in EPC
Product released from AS

10

Consequences of enzyme specificity in a compartment

Results in complex coordinated metabolic pathways

11

Classification of the enzymes based on catalytic reaction

Further divided into groups according to substrate/source
With 4 digits

12

Classification on enzymes

Oxidoreductase,
Transferase,
Hydrolase,
Lyase,
Isomerase,
Ligase,

13

Oxidoreductase

Oxidation or reduction

14

Transferase

Transfer functional groups from donor to acceptor

15

Hydrolase

Hydrolysis w H2O

16

Lyase

Groups to C=C, cleavage of C-C, C-O, C-N

17

Isomerase

Isomerisations in same molecule

18

Ligase

Form C-C/C-N w ATP cleavage

19

Naming of enzymes

Substrate reaction type + are
No at front=class

20

Enzyme structure

Proteins, 1+ polypeptide chains w 3D structures
Stabilized by weak HB, ionic bonds, hydrophobic interactions, easy to break
Sensitive to environmental changes, can denature
AS has functional groups that stabilize transition state of reaction
Bonds maintain 3D structures of AS

21

Lock and key model assumptions

Assumes enzyme and AS is rigid

22

Modifies lock and key model assumptions

AS does not have to be completely complementary to S
As S moves into AS, S distorted so it is complementary
Increase in energy level of S, decrease in free energy of product

23

Induced fit model

Shape of AS and S changes, less competition from other molecules
As will only bind to specific functional groups

24

Catalytic triad in chymotrypsin by hydrolysis

Enzyme creates nucleophile from serine side chain
Nucleophile attacks substrate
Covalent intermediate is formed with second product bonded to serine and first product released
Enzyme creates a nucleophile from water molecule
Nucleophile attacks covalent intermediate, breaking covalent bond to serine
Second product is released

25

Effects of temperature on enzyme reactions

Increased temp, increased KE, increased collision theory
Increased optimum, AS denatures, no further reactions can take place

26

Effect of pH on enzymes reactions

Optimum pH can cary depending on the physiological compartment it works in

27

Common enzyme cofactors

Cu2+
Fe2+/3+
K+
Mg2+
Ni2+
Se
Zn2+

28

Enzyme coenzymes

NaD+ => NADH + H+
FAD => FADH2
ATP => ADP + Pi

29

What makes isoenzymes different to normal enzymes

Different genetic code, catalyses same reaction with different protein structures
Often found in different cellular compartments or different amounts in different tissues
Have distinct biochemical roles

30

Rate of reaction equation

change in product/change in time = rate (v)