8.1 Metabolism

Question 1

What is Metabolism?

Answer 1

Describes the total sum of chemical reactions occurring in a cell

Question 2

What is a Metabolic Pathway?

Answer 2

• split into several steps where each step is controlled by an enzyme
• often arranged into chains (sequential) or cycles (repeating)

Question 3

Describe Enzyme role

Answer 3

catalyze chemical reactions by lowering the activation energy

Question 4

Type of reactions

Answer 4

Exergonic (think exothermic)
- reactants contain more energy than products
- excess energy is released
- catabolic –> usually exergonic

Endergonic (think endothermic)
- reactants contain less energy than products
- energy must be used for reaction to occur
- anabolic –> usually endergonic

Question 5

What is an Enzyme inhibitor?

Answer 5

molecule that binds to enzyme which decreases activity of enzyme

Question 6

Competitive inhibition

Answer 6

inhibitor competes with substrate

Question 7

Non-competitive inihibition

Answer 7

inhibitor and substrate are not in competition

Question 8

How does Competitive inhibition work?

Answer 8

• inhibitor is a similar shape to substrate
• it blocks substrates from binding to enzyme by binding itself to enzyme first
• increasing substrate concentration will minimize effect of inhibition

Question 9

Competitive Inhibition example

Answer 9

Ethanol can be used to treat antifreeze poisoning as it is a competitive inhibitor to prevent the antifreeze from binding to enzymes

Question 10

how does Non-Competitive Inhibition work?

Answer 10

A non-comp inhibitor bind to allosteric site which changes the structure of the enzyme so substrates cannot bind

Question 11

Non-Competitive inhibition example

Answer 11

• Cyanide inhibits electron transport chains
• Protein carriers shuttle electrons in a transport chain to produce ATP
• Cyanide breaks disulfide bonds in protein carrier
• Presents electron shuttling and hence, ATP production
• Without ATP, you die of death

Question 12

Feedback Inhibition

Answer 12

Feedback can negatively control metabolic pathways
- Final product inhibits an enzyme involved in its development
- This ensure tight self-regulation of levels of product

Question 13

Feedback Inhibition Example

Answer 13

• Isoleucine may be synthesized from threonine in plants an bacteria
• pathway involves the intermediate enzyme threonine deaminase
• Isoleucine can non-competitively inhibit this enzyme
• This inhibition ensures isoleucine production does not impact threonine stock

Question 14

Reaction Rates

Answer 14

• measured by amount of product formed or amount of substance consumed
• formula –> rate of reaction/s = 1 / time taken (s)
• inhibitors affect this by limiting the amount of uninhibited enzyme (competitive and non-competitive inhibitors have different effects)

Question 15

Rates of inhibition

Answer 15

Competitive:
- slower rate at low substrate levels
- maximum rate can be achieved at high substrate levels
Non-Competitive:
- slower rate of reaction
- lower maximum reaction rate

Question 16

Rational Drug design

Answer 16

• involves computer modeling in order to develop compounds that are complementary to an enzyme’s active site or allosteric site
• manufactured inhibitors can be used to treat diseases