Chapter 8 Metabolism

Question 1

Metabolism- Catabolism

Answer 1

• breaking down large molecules into smaller molecules
• releasing energy (making ATP)
• Hydrolysis (digestion) reactions

Question 2

Metabolism-Anabolism

Answer 2

• building large molecules from smaller molecules
• requires energy (using ATP)
• Dehydration (condensation) reactions

Question 3

Coupling of Catabolism and. Anabolism

Answer 3

• Catabolic and Anabolic reactions are coupled (connected) by ATP and NADH
• ATP stores energy from the catabolic reactions
• ATP used later in anabolic reactions. •ATP is the cell’s main energy currency

Question 4

Metabolic Pathways

Answer 4

• Series of chemical reactions
• Each step is controlled by an enzyme
• Information to build enzymes is encoded in the cell’s genetic makeup
• Start with substrate, end with product
• Intermediates are short-lived

Question 5

Enzymes: Biological Catalysts

Answer 5

• Catalyst: increases the rate of a reaction
• Enzymes: catalyst made of protein
• Converts substrates (reactants) to products
• Can carry out the reaction repeatedly •Enzyme is not altered as a result of the reaction
• Action of the enzyme is based on shape/structure
• Lower the activation energy of a reaction

Question 6

Activation Energy

Answer 6

• The amount by which the energy of reactants must be raised for reaction to take place
• Energy added at the beginning de-stabilizes the substrates/reactants
• Energy required to form unstable transition state
• Enzymes LOWER the activation energy

Question 7

Apoenzyme

Answer 7

Protein part of the enzyme

Question 8

Cofactors

Answer 8

inorganic part of some enzymes (ions such as calcium, iron or magnesium), can act as electron carriers or participate in ionic bonding
Not all enzymes have cofactors (but if they do, the cofactor is required for the enzyme to function)

Question 9

Coenzymes

Answer 9

organic part of some enzymes (vitamins), act as atom acceptor, sometimes electron carrier (ex: NADH)

Question 10

Holoenzymes

Answer 10

• Holoenzyme is the Apoenzyme + cofactor and/or coenzyme

* Cofactors/coenzymes can be in the active site or away from the active site

Question 11

Active Site

Answer 11

• A region on the enzyme that interacts with the substrate

* Where the reaction occurs

Question 12

Induced fit

Answer 12

• When the substrate arrives to the active site, the enzyme changes shape
• Slight change in shape allows the enzyme to stress bonds, or bring substrates close together, etc.
• Product is formed and released
• Enzyme returns to original conformation

Question 13

Location of Enzyme Action

Answer 13

Endoenzymes: 
stay inside the cell
Exoenzymes: 
•secreted outside of the cell wall
•break down large food molecules or harmful chemicals

Question 14

Regularity of Enzyme Action: Constitutive enzymes

Answer 14

• always produced in equal amounts or at equal rates

* regardless of the amount of substrate

Question 15

Regularity of Enzyme Action: Regulated enzymes

Answer 15

• not constantly present

* production is turned on (induced) or turned off (repressed) in response to changes in the substrate concentration

Question 16

Control of Enzyme Activity

Answer 16

Pathways usually have a point of control - single enzyme affects whole process

Question 17

Types of enzyme control: Competitive Inhibition

Answer 17

•Substrate mimic (inhibitor) binds to active site- fake-out!•Competes for location (active site!)

Question 18

Types of enzyme control: Noncompetitive Inhibition

Answer 18

• Inhibitor doesn’t resemble the substrate
• binds to enzyme at a site different from its active site
• substrate can still bind to the active site, however, the enzyme’s ability to catalyze is significantly slowed down
• no product made while inhibitor is bound

Question 19

Types of enzyme control: Allosteric Control

Answer 19

Allosteric enzymes are: •Large enzymes
•Usually the first reactionin the pathway.

These enzymes are controlled by:
•activators -further in the pathway (B activates E4)
•inhibitors

The activator and inhibitor binding sites are called allosteric (other) sites

Question 20

Types of enzyme control: Feedback Inhibition (example of allosteric inhibition)

Answer 20

• The end-product of the pathway serves as the inhibitor for the allosteric enzyme that catalyzes the reaction at the beginning of the pathway.
• P inactivates E1
• Most efficient stopping point

Question 21

Enzyme Poisons

Answer 21

Permanently inactivate enzymes
•May be competitive or noncompetitive inhibitor that binds irreversibly to the enzyme
•Or may destroy the enzyme chemically

Question 22

Metabolism

Answer 22

All chemical reactions in a living organism

Question 23

Amphibolic pathways

Answer 23

• Metabolic pathways that have both catabolic and anabolic functions
• Can run forwards or backwards
• Link pathways together