Metabolic reactions and Enzymes.

Lecture 13

Chemical reactions

occur when atoms have sufficient energy to combine or change bonding partners

Catabolic reaction

complex molecules broken down into simple molecules

Anabolic reaction

simple molecules form more complex molecules

ATP transfers energy

via its phosphate groups

Exergonic reactions

release energy.

Endergonic

require or consume energy

Exergonic reaction

-releases energy

-cell respiration

-catabolism

Endergonic reaction

-requires energy

-active transport

-cell movements

-anabolism

ATP hydrolysis is coupled to

endergonic reactions

Enzymes act as coupling agents to

to couple endergonic reactions with exergonic reactions

Reactants are stable but require an input of what to destabilize them

energy (activation energy)

Enzymes participate in chemical reactions

1. Substrates enter active site.

2. Substrates are held in active site by weak interactions.

3. The active site lowers EA

4. Substrates are converted to products.

5. Products are released.

6. Active site is available for new substrates.

Allosteric regulation:

Regulatory molecule changes the shape of an enzyme.

the active site becomes available to the substrates when a regulatory molecule binds to a different site on the enzyme

can active or inhibit enzyme activity

Competitive inhibitors

-block substrate binding

-the active site becomes unavailable to the substrates when a regulatory molecule binds to a different site on the enzyme