enzymes

Question 1

active site

Answer 1

-a depression on the surface of an enzyme where substrates enter and bind to
- a specific 3D conformation and distribution of electrical charge where only substrates of complementary shape and charge will fit into

Question 2

enzymes reduce activation energy by

Answer 2

• holding the substrates close together at the correct angle and orientation at the active site for successful interaction and collision
• straining the chemical bonds within the substrates until they break

Question 3

enzymes are highly specific

Answer 3

• only substrates of complementary shape will enter and bind to an active site with specific 3D conformation - spatial fit
• enzyme and substrate must be chemically compatible - chemical fit

Question 4

induced fit hypothesis

Answer 4

• initial shape of the active site of the enzyme may not be exactly complementary to that of the substrate
• the substrate enters and binds to the active site, it induces a conformational change in the shape of the enzyme such that the substrate can fit more snugly into the active site

Question 5

temperature

Answer 5

-at very low temperatures near 0°C, enzyme activity is very low. the enzyme is said to be inactivated as it possesses minimal kinetic energy for collision with substrate to form e-s complexes
- as temperature increases, before optimum temperature is reached, the rate of reaction increases. the increase in heat increases the kinetic energy of the substrate and enzyme, hence increasing molecular. frequency of successful collisions between enzyme and substrate increases, increasing the rate of formation of e-s complex, increasing rate of formation of products.
- at optimum temperature, maximum rate of reaction occurs. there is highest frequency of effective collisions
- as temperature increases beyond the optimum temperature, the rate of reaction decreases despite molecules have increased kinetic energy. heat has disrupted the hydrogen bonds and hydrophobic interactions within the secondary and tertiary structures of enzymes, resulting in a loss of specific 3D conformation of enzyme and its active site of the enzyme to form e-s complex

Question 6

pH

Answer 6

-at optimum pH, maximum rate of reaction occurs, as bonds maintaining the secondary and tertiary structures of the enzyme are intact, enabling highest frequency of successful collisions between substrate and enzyme. this increases the rate of formation of e-s complexes, increasing formation of products
- at other than optimum pH, the rate of reaction decreases. the change in pH alters the ionic charge of the acidic (coo-) and basic (nh3+) R groups on the amino acids at the active site of the enzyme. the ionic bonds and hydrogen bonds that help to maintain the specific 3D conformation of the active site. the enzyme is denatured. substrate can no longer bind to active site of enzyme, rate of formation of e-s complexes decreases.

Question 7

enzyme concentration

Answer 7

at low enzyme concentration, the rate of reaction is low. as enzyme concentration increases, rate of reaction increases linearly. as enzyme concentrations increases, more active sites are now available for successful collisions with substrate. increase in frequency of effective collisions between enzyme and substrate, increasing rate of formation of products. enzyme concentration limiting factor.
at very high enzyme concentrations, as enzyme concentration increases, the rate of reaction remains constant. substrate concentration is the limiting factor

Question 8

substrate concentration

Answer 8

at low substrate conc, rate of rxn increases with substrate conc as many enzyme molecules have unoccupied active sites. substrate conc limiting factor.
-as substrate conc increases, rate of rxn increases linearly. more substrates avail for successful collisions. increase in frequency of successful collisions between enzyme and substrate, increasing formation of e-s complexes, increasing rate of formation of products
- at very high substrate conc, as substrate conc increases, the rate of reaction remains constant. all available enzyme active sites are saturated with substrates. enzyme conc limiting factor.