Enzymes

Question 1

Chemical agents that speed up chemical reactions without being consumed

Answer 1

Catalysts

Question 2

Chemical agents that speed up chemical reactions without being consumed (Catalysts in biomolecules)

Answer 2

Enzymes

Question 3

Chemical reaction involves

Answer 3

breaking or forming a bond

Question 4

Changing one molecule into another generally involves

Answer 4

contorting the starting molecule into a highly unstable state before the reaction can proceeed

Question 5

To reach the contorted state, molecules need to absorb

Answer 5

Energy — Activation Energy (supplied with thermal energy)

Question 6

What does the energy do?

Answer 6

The energy accelerates the reactant molecules and collides more often causing the breakage of a bond.

Question 7

When molecules absorb enough energy,

Answer 7

the reactant molecule goes into an unstable condition called a transition state

Question 8

What comes after the transition state?

Answer 8

Atoms settle into more stable bonding arrangement as energy is released into their surroundings. Molecules return to the stable shape and lower energy.

Question 9

[ToF] Can too much heat kill the cell?

Answer 9

Ye

Question 10

How does an enzyme catalyze a reaction?

Answer 10

by lowering the Energy Activation barrier, enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures.

Question 11

The reactant an enzyme acts on

Answer 11

Substrate

Question 12

Forms after enzymes bind to its substrate

Answer 12

Enzyme-substrate Complex

Question 13

Summary of catalytic action of enzymes

Answer 13

Enzyme + Substrate <-> Enzyme-substrate complex <-> Enzyme + products

Question 14

Typically a pocket or groove on the surface of the enzyme where catalysis occurs

Answer 14

Active site

Question 15

Formed by only a few amino acids, with the rest of the protein molecule providing a framework that determines the shape of the active site

Answer 15

Active site

Question 16

[ToF] Enzymes are stiff structures locked into a given shape

Answer 16

False

Question 17

The tightening
of the binding after initial contact; the shape change that makes the active site fit even more snugly around the substrate

Answer 17

Induced fit

Question 18

Process of catalysis

Answer 18

1. Substrate enters the active site, enzyme changes shape to fit it
2. Substrates are held in the active site by weak interactions (hydrogen bonds/ionic bonds)
3. Active site lowers activation energy and speeds up the reaction
4. Substrates are converted into products (wahhaha binubugbog)
5. Products are released
6. Active sites are available for more molecules

Question 19

Components of an enzyme

Answer 19

Cofactor (co-enzyme, metal ions, prosthetic groups), Apoenzymes, Holoenzymes

Question 20

Nonproteins that help mediate enzymatic reactions. They serve as nucleophiles, mediate covalent catalysis, form electrostatic interactions with the substrate, and stabilize the transition state.

Answer 20

Cofactors

Question 21

Bind to the enzyme and remove electrons/protons/chemical groups from the substrate

Answer 21

Cofactors

Question 22

Loosely-bound organic cofactors that may assume the role of hydrogen acceptors [Nicotinamide adenine dinucleotide (NAD), Adensonine Triphosphate (ATP)]

Answer 22

Co-enzyme

Question 23

Tightly-bound inorganic/organic cofactors (Heme, biotin, flavin, iron sulphides, copper, and ubiquinone)

Answer 23

Prosthetic groups

Question 24

Inorganic such as the metal atoms zinc, iron, and copper in ionic form

Answer 24

Metal ions

Question 25

No associated cofactors

Answer 25

Apoenzymes

Question 26

Complete enzymes

Answer 26

Holoenzymes

Question 27

Model that suggests that enzymes are rigid (cannot change) [maling model lmfaoo]

Answer 27

Lock and key model

Question 28

Suggests that enzymes are flexible, and can change to accommodate substrates

Answer 28

Induced fit model

Question 29

Characteristics of Enzymes

Answer 29

• Specific
• Reusable (into the same chemical reactions)
• Flexible

Question 30

Limit catalysts/enzymes and prevent them from doing their jobs

Answer 30

Inhibitors

Question 31

In which an inhibitor competes with substrate for binding to an active site. When it occupies said active site, it forms an enzyme-inhibitor complex and the enzyme cannot react until the inhibitor dissociates.

Answer 31

Competitive Inhibition

Question 32

They have a structure similar to the substrate, but they are unreactive.

Answer 32

Competitive Inhibitors

Question 33

Example of competitive inhibitor

Answer 33

Statins - a class of drugs that reduces cholesterol levels. They are inhibitors of the enzyme HMG-CoA
reductase. HMG-CoA reductase is the enzyme that synthesizes cholesterol from lipids

Question 34

In which an inhibitor binds to an enzyme at a location other than the active site. In some cases, these inhibitors physically block the normal active site or change the shape of the enzyme molecule entirely, deforming the active site. Involves negative feedback.

Answer 34

Noncompetitive inhibition

Question 35

In which inhibitors bind only to the substrate-enzyme complex. Common in reactions involving two or more substrates or products. Products leave the active site less easily, slowing the reaction

Answer 35

Uncompetitive Inhibition

Question 36

Factors affecting enzyme activity

Answer 36

Temperature, pH, substrate concentration, enzyme concentration

Question 37

Relationship between Enzyme Activity and Temperature

Answer 37

The higher the temperature, the faster the reaction (substrates and active sites collide more frequently)

Question 38

Relationship between Enzyme Activity and pH

Answer 38

The optimal pH value for enzymes is between pH 6-8.

Exceptions include pepsin that works at a low pH, and trypsin in more alkaline parts of the intestine that are more denatured.

Question 39

Relationship between Enzyme Activity and Substrate Concentration

Answer 39

Increasing substrate concentration also increases the rate of reaction until all enzymes have bound

Question 40

Relationship between Enzyme Activity and Enzyme Concentration

Answer 40

Increasing enzyme concentration will speed up the reaction as long as there is substrate available to bind to. Once all of the substrate is bound, the reaction will no longer speed up because additional enzymes will have nothing to bind to.