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Flashcards in 2.09 Enzymes Deck (62)
1

specialized protein catalysts that accelerate chemical reactions, used in biochemical reactions and pathways

Enzymes

2

Mechanism of enzymes wherein there is conformational change when the substrate binds to the enzyme's active site

Induced fit (Daniel Koshland)

3

The molecule acted upon by the enzyme to form a product

Substrate

4

Enzymes that require a metal in their composition

Metalloenzymes

5

Parts of a holoenzyme

Protein part
Cofactor (Non-protein part)

6

Examples of Cofactors

Coenzymes
Prosthetic groups
Metal Ions

7

Classes of Coenzymes

Activation Transfer Coenzymes
Oxidation Reduction Coenzymes

8

What to look for in enzyme cofactors

Coenzyme
Enzyme
Chemical groups transferred
Vitamin Precursor

9

The enzyme that catalyzes the rate-limiting or committed step of a metabolic pathway

Regulatory enzyme

10

Intracellular locations of some important biochemical pathways

Mitochondria
Cytosol
Nucleus
Lysosome

11

Different structural forms of an enzyme which catalyze the same chemical reactions

Isoenzyme

12

Enzymes that act on the same substrate and produce the same products but exhibit differing degrees of efficiency

Isoenzyme

13

Six major classes of enzymes

Oxidoreductases
Transferases
Hydrolases
Lyases
Lysases
Isomerases
Ligases

14

Part of the enzyme which contains amino acid side chains that participate in substrate binding and catalysis

Active site

15

Enzyme that transfer of electron and hydrogen atoms from donors

Oxidoreductases

16

Enzyme that transfers functional groups from donors to acceptors

Transferases

17

Enzyme that csatalyze cleavage of chemical bonds by addition of H2O, producing 2 products

Hydrolases

18

Enzyme that cleaves C-C, C-O, and C-N bonds by means other than hydrolysis or oxidation

Lyases

19

Enzyme that catalyzes a psychologically important reaction that favors the formation of a C-C bond

Synthase

20

Type of lyases that adds H2O to a substrate

Hydratase

21

Transfer of functional groups or double bonds within the same molecule

Isomerases

22

Enzyme that catalyzes the joining of substrates in the presence of ATP

Ligases

23

Characteristics of enzymes

Not changed in the reaction
Do not change or alter the equilibrium of the reaction
Increase reaction rates by decreasing activation energy
Highly specific
Mostly proteins in nature

24

Significance of the Km

1) Substrate concentration at which half the active sites of the enzyme are filled up
2) Inverse measure of the affinity of the substrate for the enzyme

25

Reversible inhibitions of enzymatic reactions

Competitive
Non competitive
Uncompetitive

26

Type of inhibition wherein the inhibitor binds specifically at the active or catalytic site, where it competes with the substrate for binding

Competitive inhibition

27

Type of inhibition wherein the inhibitor binds a substance other than at the active or catalytic site

Non competitive

28

Type of inhibition wherein the inhibitor binds only to ES complexes at locations other than the catalytic site, modifying enzyme structure, making the inhibitor binding site available

Uncompetitive inhibition

29

Type of inhibition wherein the inhibition is reversed by increasing substrate concentration

Competitive inhibition

30

Type of inhibitor
Vmx: decrease proportionately to inhibitor concentration
Km: unchange

Non competitive inhibitor

31

Type of inhibitor
Vmax: decrease
Km: decrease

Uncompetitive inhibitor

32

Type of inhibitor
Vmax: unchange
Km: increase

Competitive inhibitor

33

Enzymes following Michaelis-Menten kinetics show (linear/hyperbolic/sigmoid) curve.

Hyperbolic

34

Allosteric enzymes exhibit (linear/hyperbolic/sigmoid) curve

Sigmoid

35

Methods of regulating enzyme activity

Feedback inhibition
Allosteric (non-covalent) modification
Covalent modification
Zymogen activation
Induction or repression of enzyme synthesis

36

Binding of modulator to allosteric site, which causes a conformational change in the regulatory enzyme, alters the activity of the enzyme

Allosteric modification

37

(Low/High) Activity
Dephosphorylating Acetyl Coa Carboxylase

High

38

(Low/High) Activity
Phosphorylating Glycogen synthase

Low

39

(Low/High) Activity
Phosphorylating Pyruvate dehydrogenase

Low

40

(Low/High) Activity
Dephosphorylating HMG CoA reductase

High

41

(Low/High) Activity
Phosphorylating Glycogen phosphorylase

High

42

(Low/High) Activity
Dephosphorylating Citrate lyase

Low

43

(Low/High) Activity
Dephosphorylating Phosphorylase b kinase

Low

44

(Low/High) Activity
Phosphorylating HMG CoA reductase kinase

High

45

(Low/High) Activity
Dephosphorylating HMG CoA reductase kinase

Low

46

(Low/High) Activity
Phosphorylating Phosphorylase b kinase

High

47

(Low/High) Activity
Phosphorylating Citrate lyase

High

48

(Low/High) Activity
Dephosphorylating glycogen phosphorylase

Low

49

(Low/High) Activity
Phosphorylasing HMG CoA reductase

Low

50

(Low/High) Activity
Dephosphorylating pyruvate dehydrogenase

High

51

(Low/High) Activity
Dephosphorylating glycogen synthase

High

52

(Low/High) Activity
Phosphorylating Acetyl CoA carboxylase

Low

53

Factors affecting enzyme activity

Temperature
pH
Substrate concentration
Co-factors

54

As the temperature increases (until the optimum temperature is reached), the reaction velocity or the enzyme activity (increases/decreases)

Increases

55

Beyond the optimum temperature, the reaction velocity/enzyme activity (increases/decreases) as the temperature increases

Decreases

56

Increasing the pH value will (increase/decrease) the reaction rate

Increase
But, beyond the optimum pH, the reaction rate will decrease

57

Cofactors (chlorides, bromides, iodides) ___ the rate of enzyme-catalyzed reactions

Increase

58

As the substrate concentration increases, the reaction velocity (increases/decreases)

Increases
Up to a certain point

59

Substate concentration at which half of the active sites of the enzyme are filled up

Km

60

The lower the Km, the ___ is the affinity

Higher

61

The higher the Km, the ___ is the affinity

Lower

62

Models of enzyme-substrate complex

Lock and Key Model
Induced Fit Model