Enzymes

Question 1

What type of macromolecule are enzymes?

Answer 1

Enzymes are proteins.

Question 2

What is the monomer of enzymes?

Answer 2

Amino acids.

Question 3

How are amino acids linked together in enzymes?

Answer 3

By peptide bonds forming polypeptide chains.

Question 4

How do polypeptide chains become enzymes?

Answer 4

They fold into specific 3D structures.

Question 5

What determines amino acid chemical properties?

Answer 5

Their side chains (R groups).

Question 6

What charges can amino acid side chains have?

Answer 6

Positive, negative, polar, or nonpolar.

Question 7

What is hydrophobicity in amino acids?

Answer 7

Nonpolar side chains are hydrophobic; polar/charged are hydrophilic.

Question 8

How do side chains vary in size/shape?

Answer 8

They influence interactions and protein structure fit.

Question 9

What special roles do functional groups in side chains play?

Answer 9

They can participate in reactions or binding.

Question 10

What determines a protein’s tertiary structure?

Answer 10

Interactions between R groups.

Question 11

Name 4 interactions in tertiary structure.

Answer 11

Hydrophobic interactions, hydrogen bonds, ionic interactions, disulfide bonds.

Question 12

Give an example of hydrogen bonding in proteins.

Answer 12

Serine’s hydroxyl H bonds with threonine’s carbonyl oxygen.

Question 13

What is a disulfide bridge?

Answer 13

A covalent bond between two cysteine sulfur atoms.

Question 14

What must reactants do to react with an enzyme?

Answer 14

Bind to the enzyme’s active site.

Question 15

What is the enzyme-substrate complex?

Answer 15

The binding of substrate to the enzyme’s active site.

Question 16

What happens to the enzyme after a reaction?

Answer 16

It releases products and remains unchanged.

Question 17

Why is metabolism essential?

Answer 17

It provides energy, builds molecules, and maintains homeostasis.

Question 18

What role do enzymes play in metabolism?

Answer 18

They lower activation energy to speed up reactions.

Question 19

Give an example of a metabolic reaction and enzyme.

Answer 19

Glucose to glucose-6-phosphate by hexokinase.

Question 20

What is anabolism?

Answer 20

Synthesis of large molecules from small ones.

Question 21

What is catabolism?

Answer 21

Breakdown of large molecules into smaller ones.

Question 22

Are anabolic reactions endergonic or exergonic?

Answer 22

Endergonic.

Question 23

Are catabolic reactions endergonic or exergonic?

Answer 23

Exergonic.

Question 24

What are the substrates and products in anabolism?

Answer 24

Small molecules → large molecules.

Question 25

What are the substrates and products in catabolism?

Answer 25

Large molecules → small molecules.

Question 26

Is water used or produced in anabolism?

Answer 26

Water is used.

Question 27

Is water used or produced in catabolism?

Answer 27

Water is produced.

Question 28

Name enzymes involved in anabolism.

Answer 28

DNA Polymerase, ATP Synthase, RuBisCO.

Question 29

Name enzymes involved in catabolism.

Answer 29

Amylase, Lipase, Lactase.

Question 30

What shape are enzymes typically?

Answer 30

Globular.

Question 31

What are enzymes made of?

Answer 31

Chains of folded amino acids.

Question 32

What is the active site of an enzyme?

Answer 32

A small region where substrates bind and react.

Question 33

How does the lock-and-key model explain specificity?

Answer 33

Only the correctly shaped substrate fits the active site.

Question 34

What happens when substrate fits the active site?

Answer 34

A reaction is catalyzed, forming products.

Question 35

What happens to the enzyme after the reaction?

Answer 35

It remains unchanged and reusable.

Question 36

What is the induced-fit model?

Answer 36

The enzyme changes shape to better fit the substrate.

Question 37

How does induced fit differ from lock-and-key?

Answer 37

Induced fit allows flexibility; lock-and-key assumes rigid fit.

Question 38

What triggers enzyme conformational change?

Answer 38

Substrate binding.

Question 39

How does induced fit lower activation energy?

Answer 39

It optimally positions molecules and catalytic groups.

Question 40

What is a collision in enzyme catalysis?

Answer 40

A physical interaction between enzyme and substrate.

Question 41

Why don’t all collisions lead to catalysis?

Answer 41

Proper orientation, energy, and lack of steric hindrance are needed.

Question 42

Why is water critical in enzyme reactions?

Answer 42

It serves as solvent, stabilizer, transporter, and reactant in hydrolysis.

Question 43

How does water help with hydrogen bonding?

Answer 43

It stabilizes intermediates and transition states.

Question 44

Why is water’s heat capacity important for enzymes?

Answer 44

It helps maintain stable reaction temperatures.

Question 45

How does water assist with transport in enzyme reactions?

Answer 45

It moves substrates/products to and from the active site.

Question 46

Why do enzymes move slower than substrates?

Answer 46

Enzymes are larger, have specificity, regulation, compartmentalization, and depend on substrate concentration.

Question 47

What happens to an enzyme's structure when it is denatured?

Answer 47

The enzyme’s active site changes shape, preventing substrate binding and stopping catalysis.

Question 48

How does denaturation affect enzyme function?

Answer 48

It prevents the enzyme from binding substrates, reducing or stopping the reaction rate.

Question 49

What is the optimum temperature for yeast respiration based on bubble production?

Answer 49

30°C, because that’s when the most gas bubbles are produced.

Question 50

Why does enzyme activity decrease at low temperatures?

Answer 50

Enzyme and substrate particles move more slowly, lowering reaction rates.

Question 51

Why does enzyme activity decrease at high temperatures?

Answer 51

High heat causes enzymes to denature and lose function.

Question 52

What happens if activation energy is not reached in a reaction?

Answer 52

The reaction does not occur or proceeds extremely slowly.

Question 53

What is activation energy?

Answer 53

It is the energy barrier reactants must overcome to form products.

Question 54

How do enzymes affect activation energy?

Answer 54

Enzymes lower the activation energy needed for a reaction to occur.

Question 55

What are intracellular enzyme-catalyzed reactions?

Answer 55

Reactions that occur inside cells and are crucial for energy production and biosynthesis.

Question 56

Give two examples of intracellular enzyme-catalyzed reactions.

Answer 56

Glycolysis and the Krebs cycle.

Question 57

What is the role of enzymes in glycolysis?

Answer 57

Enzymes break down glucose into pyruvate, producing ATP and NADH.

Question 58

Name two enzymes involved in glycolysis.

Answer 58

Hexokinase and phosphofructokinase.

Question 59

Where does the Krebs cycle occur?

Answer 59

In the mitochondria.

Question 60

What does the Krebs cycle produce?

Answer 60

ATP, NADH, FADH₂, and CO₂.

Question 61

Name two enzymes in the Krebs cycle.

Answer 61

Citrate synthase and isocitrate dehydrogenase.

Question 62

Why is heat energy produced in metabolic reactions?

Answer 62

Because energy transfers are inefficient, some energy is lost as heat.

Question 63

What causes heat generation during metabolism?

Answer 63

Energy not converted to ATP is released as heat during reactions like cellular respiration.

Question 64

What is thermogenesis and why is it important?

Answer 64

Internal heat production that maintains body temperature in endothermic animals.

Question 65

What is a cyclical metabolic pathway?

Answer 65

A pathway where the final product regenerates the initial substrate.

Question 66

What is a linear metabolic pathway?

Answer 66

A series of steps where substrates are converted to products without regeneration.

Question 67

Give an example of a cyclical metabolic pathway.

Answer 67

The Krebs cycle.

Question 68

Give an example of a linear metabolic pathway.

Answer 68

Glycolysis.

Question 69

How do cyclical pathways benefit metabolism?

Answer 69

They extract energy gradually and provide biosynthesis intermediates.

Question 70

What is a competitive inhibitor?

Answer 70

A molecule that binds to the enzyme’s active site, blocking the substrate.

Question 71

Who does a competitive inhibitor compete against?

Answer 71

It competes with the substrate for the active site.

Question 72

Is competitive inhibition reversible?

Answer 72

Yes, increasing substrate concentration can outcompete the inhibitor.

Question 73

Why are allosteric inhibitors called non-competitive?

Answer 73

They bind elsewhere on the enzyme, not at the active site.

Question 74

What happens when an allosteric inhibitor binds to an enzyme?

Answer 74

It changes the enzyme's shape, reducing or stopping activity.

Question 75

How do competitive inhibitors reduce enzyme activity?

Answer 75

They block the active site so the substrate can't bind.

Question 76

What is a medical example of a competitive inhibitor?

Answer 76

Statins, which inhibit HMG-CoA reductase to lower cholesterol.

Question 77

What distinguishes competitive from non-competitive inhibition?

Answer 77

Competitive inhibitors bind to the active site; non-competitive bind elsewhere.

Question 78

What is feedback inhibition in metabolism?

Answer 78

When the end product inhibits an earlier enzyme to regulate production.

Question 79

Why is feedback inhibition important?

Answer 79

It prevents overproduction and saves energy and resources.

Question 80

What enzyme starts the isoleucine biosynthesis pathway?

Answer 80

Threonine deaminase.

Question 81

What is mechanism-based inhibition?

Answer 81

Irreversible inhibition where the inhibitor covalently binds to the enzyme.

Question 82

How does mechanism-based inhibition differ from reversible inhibition?

Answer 82

The inhibitor permanently inactivates the enzyme.

Question 83

How does penicillin act as a mechanism-based inhibitor?

Answer 83

It mimics the substrate and forms a covalent bond with transpeptidase.

Question 84

What does penicillin’s binding do to bacteria?

Answer 84

It stops cell wall synthesis, causing cell death.