Macromolecules: Enzymes

Question 1

Enzymes

Answer 1

proteins, biological catalysts, not altered in reactions
most intracellular, can be extracellular
unique 3D structure determines its function/specificity to a reaction

Question 2

Active Site

Answer 2

region on the surface of an enzyme molecule with a shape complementary to a substrate

Question 3

Substrate-Enzyme complex

Answer 3

when substrate & enzyme attached at active site

Question 4

Lock & Key model

Answer 4

substrate + enzyme > substrate-enzyme complex > products + enzyme

Question 5

Induced Fit model

Answer 5

substrate + enzyme > substrate-enzyme complex > product-enzyme complex > products + enzyme

substrate attaches to enzyme at active site, enzyme/active site changes shape slightly to create a better fit & increase ease of chemical reaction

Question 6

Factors affecting Enzyme Activity

Answer 6

• temperature: increasing speeds up the reaction, excessive temps may denature enzymes (breaks H-bonds, active site, shape + function)
• pH: each enzyme has optimum pH, change alters charge on amino acids, affecting force of attraction…shape changes, denatured also
• inhibitors: molecules or chemicals which prevent the substrate from binding to the enzyme
  …competitive = similar shape to substrate, binds to active site & prevents substrate from attaching
  …non-competitive = binds to enzyme not at active site, causes alteration of enzyme shape therefore active site no longer complementary to substrate

Question 7

Activation Energy

Answer 7

= initial input of energy… enzymes increase the rate of reaction by lowering activation energy
enzymes lower activation energy by:
- stressing chemical bonds (induced fit strains)
- correct orientation (induced fit, optimal collision)
- small steps (small energy required)

Question 8

Types of reactions

Answer 8

exergonic: energy produced at the end of reaction eg. glycolysis
endergonic: energy required for reaction to occur eg. protein synthesis, photosynthesis