8.1 Metabolism

Question 1

Metabolism: Common Patterns

Answer 1

1) most chemical changes happen in a sequence of small steps
2) most metabolic pathways involve a chain of reactions
3) some metabolic pathways form a cycle

Question 2

Transition State

Answer 2

substrates have to pass through transition state before they are converted into products

Question 3

Activation Energy

Answer 3

the energy required to reach the transition state

activation energy is used to break or weaken bonds in the substrates

Question 4

Enzymes

Answer 4

lower the activation energy of the chemical reactions they catalyze
so they speed up reactions
net amount of energy released by the reaction is unchanged by the involvement of the enzyme

Question 5

Enzyme Inhibitors

Answer 5

chemical substances that bind to enzymes and reduce the activity of the enzyme

Question 6

Competitive Inhibitors

Answer 6

interfere with the active site so that the substrate cannot bind

Question 7

Non-Competitive Inhibitors

Answer 7

bind at a location other than the active site (allosteric site)
this results in a change of shape in the enzyme so that it cannot bind to the substrate

Question 8

Example of Competitive Inhibition

Answer 8

enzyme: dihydripteroate synthetase
substrate: para-aminobenzoate
inhibitor: sulfadiazine

Question 9

Example of Non-Competitive Inhibition

Answer 9

enzyme: phosphofructokinase
substrate: fructose-6-phosphate
inhibitor: xylitol-5-phosphate

Question 10

End-product Inhibition

Answer 10

the substance that binds to the allosteric site is the end-product of the pathway
prevents the build-up of intermediate products
if there is an excess of end-product

Question 11

Example of End-Product Inhibition

Answer 11

threonine is converted to isoleucine
when the concentration of isoleucine builds up it binds to the allosteric site if the first enzyme in the chain threonine deaminase