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Flashcards in Proteins as Catalysts Deck (71):
1

They allow reactions in living cells to use less energy to start a reaction

Enzymes

2

What is the effect of enzymes on the activation energy?

It lowers the activation energy required for a reaction to occur.

3

Enzymes are ___ by the reaction

recycled

4

Most enzymes are___

proteins

5

Some enzymes are ___

RNA or ribosymes

6

Some enzymes work as a ___

complex of many enzymes

7

What are ribozymes?

RNA with enzymatic abilities

8

Assists in synthesizing proteins

Ribosomal RNA

9

Keeps reactants of the same pathway close together and accessible.

Pyruvate dehydrogenase Complex

10

What are the advantages of multienzymes complexes?

- Product of one reaction can be directly delivered to the next enzyme
-Possibility of unwanted side reactions is eliminated
-All of the reactions can be controlled as a unit

11

Enzyme interacts with__

substrate (they bind to it)

12

Molecule that will undergo a reaction either to make or break a bond

Substrate

13

Catalyze only one particular reaction

Absolute specificity

14

Other enzymes will be specific for a particular type of chemical bond or functional group.

OK

15

The enzyme SUCRASE splits _____ into ____ and ___

splits sucrose into fructose and glucose

16

Enzymes are indicated by the suffix ____

–ASE (protein enzyme mostly)

17

The prefix SUCR- indicates what?

It indicates the substrate acted on by the enzyme

18

Region of the enzyme that binds the substrate and causes the change

Active site

19

Active site on enzyme binds on ____

Specific substrates

20

Formula for enzyme activity

E + S ES complex ----> E + P

E: enzyme, S: substrate, P: product

21

Binding substrate causes the enzyme to ____

Change shape, producing a better induced fit between the molecules

22

Induced Fit Model ways (3)

-Substrate squeezes into active site
-Active site changes shape slightly
-Exerts force on substrate

23

The binding of the substrate and enzyme places stress on the glucose-fructose bond and the bond breaks

OK

24

Moving potential energy around during metabolism is done by _____

moving electrons (requires electron carriers)

25

To help carry electrons or small chemical groups, some enzymes require additional molecules called _______

cofactors (they are reusable, like enzymes)

i.e. ZN(+), Fe(+)

26

Usually metal ions (inorganic)

Cofactors

27

Non-protein molecules (organic), often used to carry electrons in RedOx reactions

Coenzymes

28

Cytoplasmic and mitochondrial coenzymes : _______ and _____

FAD and NAD(+)

29

Chloroplast coenzyme: ____

NADP(+) (used in plants during carbon fixation in photosynthesis)

30

An enzyme without a coenzyme does not work. Why?

Coenzyme is the activator

31

NAD(+) and FAD used in production of __

ATP

32

Give the 4 factors that can change an enzyme's 3D shape.

pH
temperature
salt
regulatory molecules (inhibition)

33

When environmental conditions exceed the limitations of a protein the secondary, tertiary and quaternary bonds are overcome (broken), it is called _____

Denaturation of Protein

34

Denaturation results from degradation of these bonds
The protein (enzyme) will no longer function
Damage is permanent (irreversible)

If the change is extreme

35

What in conditions may only temporarily alter protein (reversible) but will affect the time it takes to convert substrate to product?

Mild change

36

Enzyme activity may be affected by ___(2 factors)

1. Concentration factors
2. Efficiency factors due shape of enzyme

Environmental conditions can affect enzyme activity

37

Concentration factors

Substrate
Enzyme

38

Enzyme shape can be affected by (3)

pH
Temperature
Salt

39

The activity of an enzyme may be increased with increasing T, up to an optimum T due to motion of molecules. However, temperatures too far above T optimum can denature the enzyme, destroying its function

OK

40

pH can disrupt ionic bonds

okidou

41

Dependent on the type of enzyme.

Optimum levels

42

Function at an optimum pH and temperature

Enzymes

43

Used to control the amount of product

Regulation of metabolism

44

Helps maintain homeostasis

Regulation of metabolism

45

Controls pathways by slowing down production of END-PRODUCT

Inhibitor (they block or slow down the enzyme activity)

46

End-product resembles closely an earlier substrate in the pathway and can bind to the final enzyme in the pathway

End-product inhibition

47

When the pathways product is temporarily not needed by the cell, it begins to accumulate

Principle of feedback inhibition

48

Higher concentration of product accumulates thus end-product begins to out-compete with the initial substrate concentration.

Principle of feedback inhibition

49

Since end-product resembles the initial substrate, product will bind reversibly to the initial enzyme

Principle of feedback inhibition

50

The normal substrate can no longer bind to this inhibited enzyme, as long as the inhibitor stays bound to the enzyme

Principle of feedback inhibition

51

Pathway is blocked until the product is used by the cell, thus decreasing its concentration

Principle of feedback inhibition

52

the end-product and initial substrate have a similar structure thus both recognize the enzyme (E1)

negative feedback control

53

Compete with the substrate for binding to the same active site

competitive inhibitors

54

bind to the allosteric site (site other than the enzyme’s active site)

noncompetitive inhibitors

55

Interferes with active sites of enzyme so substrate cannot bind

Competitive inhibition

56

Changes shape of enzyme so the active site does not bind the enzyme as well

Noncompetitive inhibition

57

Possess an allosteric site different from the active site

Allosteric enzymes

58

Can be inactivated or activated by the molecule binding

Allosteric enzymes

59

Bind to the allosteric site to inactivate the enzyme

Allosteric inhibitors

60

Bind to the allosteric site to activate the enzyme

Allosteric activators

61

Important in cell signalling

Allosteric activation

62

Controls many pathways

Allosteric inhibition

63

Measures how much the substrate and enzyme like each other and meet to convert substrate to product

Affinity = Km

64

A function of concentration and reaction rate

Affinity = Km

65

The lower the [substrate]

the higher the affinity for the enzyme

66

Due to low number of substrate encountering active site of enzymes

Initial reaction rates are slow

67

If a substrate has a high attraction to the active site then________

the affinity is high.

68

Represents the maximum rate the enzyme is capable of working to convert substrate to product, and represents enzyme saturation

Maximum velocity (Vmax)

69

Concentration of substrate at ½ Vmax

Km

70

Km (affinity) does not change, but max velocity is decreased.

Effect of noncompetitive inhibition on Km

71

Result is the Km (affinity) changes, but max velocity is the same.

Effect of competitive inhibition on Km