Proteins as Catalysts

Question 1

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

Answer 1

Enzymes

Question 2

What is the effect of enzymes on the activation energy?

Answer 2

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

Question 3

Enzymes are ___ by the reaction

Answer 3

recycled

Question 4

Most enzymes are___

Answer 4

proteins

Question 5

Some enzymes are ___

Answer 5

RNA or ribosymes

Question 6

Some enzymes work as a ___

Answer 6

complex of many enzymes

Question 7

What are ribozymes?

Answer 7

RNA with enzymatic abilities

Question 8

Assists in synthesizing proteins

Answer 8

Ribosomal RNA

Question 9

Keeps reactants of the same pathway close together and accessible.

Answer 9

Pyruvate dehydrogenase Complex

Question 10

What are the advantages of multienzymes complexes?

Answer 10

• 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

Question 11

Enzyme interacts with__

Answer 11

substrate (they bind to it)

Question 12

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

Answer 12

Substrate

Question 13

Catalyze only one particular reaction

Answer 13

Absolute specificity

Question 14

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

Answer 14

OK

Question 15

The enzyme SUCRASE splits _____ into ____ and ___

Answer 15

splits sucrose into fructose and glucose

Question 16

Enzymes are indicated by the suffix ____

Answer 16

–ASE (protein enzyme mostly)

Question 17

The prefix SUCR- indicates what?

Answer 17

It indicates the substrate acted on by the enzyme

Question 18

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

Answer 18

Active site

Question 19

Active site on enzyme binds on ____

Answer 19

Specific substrates

Question 20

Formula for enzyme activity

Answer 20

E + S ES complex —-> E + P

E: enzyme, S: substrate, P: product

Question 21

Binding substrate causes the enzyme to ____

Answer 21

Change shape, producing a better induced fit between the molecules

Question 22

Induced Fit Model ways (3)

Answer 22

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

Question 23

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

Answer 23

OK

Question 24

Moving potential energy around during metabolism is done by _____

Answer 24

moving electrons (requires electron carriers)

Question 25

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

Answer 25

cofactors (they are reusable, like enzymes) i.e. ZN(+), Fe(+)

Question 26

Usually metal ions (inorganic)

Answer 26

Cofactors

Question 27

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

Answer 27

Coenzymes

Question 28

Cytoplasmic and mitochondrial coenzymes : _______ and _____

Answer 28

FAD and NAD(+)

Question 29

Chloroplast coenzyme: ____

Answer 29

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

Question 30

An enzyme without a coenzyme does not work. Why?

Answer 30

Coenzyme is the activator

Question 31

NAD(+) and FAD used in production of __

Answer 31

ATP

Question 32

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

Answer 32

pH temperature salt regulatory molecules (inhibition)

Question 33

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

Answer 33

Denaturation of Protein

Question 34

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

Answer 34

If the change is extreme

Question 35

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

Answer 35

Mild change

Question 36

Enzyme activity may be affected by ___(2 factors)

Answer 36

1. Concentration factors 2. Efficiency factors due shape of enzyme Environmental conditions can affect enzyme activity

Question 37

Concentration factors

Answer 37

Substrate | Enzyme

Question 38

Enzyme shape can be affected by (3)

Answer 38

pH Temperature Salt

Question 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

Answer 39

OK

Question 40

pH can disrupt ionic bonds

Answer 40

okidou

Question 41

Dependent on the type of enzyme.

Answer 41

Optimum levels

Question 42

Function at an optimum pH and temperature

Answer 42

Enzymes

Question 43

Used to control the amount of product

Answer 43

Regulation of metabolism

Question 44

Helps maintain homeostasis

Answer 44

Regulation of metabolism

Question 45

Controls pathways by slowing down production of END-PRODUCT

Answer 45

Inhibitor (they block or slow down the enzyme activity)

Question 46

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

Answer 46

End-product inhibition

Question 47

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

Answer 47

Principle of feedback inhibition

Question 48

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

Answer 48

Principle of feedback inhibition

Question 49

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

Answer 49

Principle of feedback inhibition

Question 50

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

Answer 50

Principle of feedback inhibition

Question 51

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

Answer 51

Principle of feedback inhibition

Question 52

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

Answer 52

negative feedback control

Question 53

Compete with the substrate for binding to the same active site

Answer 53

competitive inhibitors

Question 54

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

Answer 54

noncompetitive inhibitors

Question 55

Interferes with active sites of enzyme so substrate cannot bind

Answer 55

Competitive inhibition

Question 56

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

Answer 56

Noncompetitive inhibition

Question 57

Possess an allosteric site different from the active site

Answer 57

Allosteric enzymes

Question 58

Can be inactivated or activated by the molecule binding

Answer 58

Allosteric enzymes

Question 59

Bind to the allosteric site to inactivate the enzyme

Answer 59

Allosteric inhibitors

Question 60

Bind to the allosteric site to activate the enzyme

Answer 60

Allosteric activators

Question 61

Important in cell signalling

Answer 61

Allosteric activation

Question 62

Controls many pathways

Answer 62

Allosteric inhibition

Question 63

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

Answer 63

Affinity = Km

Question 64

A function of concentration and reaction rate

Answer 64

Affinity = Km

Question 65

The lower the [substrate]

Answer 65

the higher the affinity for the enzyme

Question 66

Due to low number of substrate encountering active site of enzymes

Answer 66

Initial reaction rates are slow

Question 67

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

Answer 67

the affinity is high.

Question 68

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

Answer 68

Maximum velocity (Vmax)

Question 69

Concentration of substrate at ½ Vmax

Answer 69

Km

Question 70

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

Answer 70

Effect of noncompetitive inhibition on Km

Question 71

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

Answer 71

Effect of competitive inhibition on Km