2.5. Enzymes

Question 1

enzyme

Answer 1

globular protein that increases rate of biochemical reaction by lowering activation E threshold

Question 2

substrate

Answer 2

substance on which enzyme act

Question 3

active site

Answer 3

region on surface of enzyme which binds to substrate molecule

Question 4

relationship between substrate & active site

Answer 4

• substrate must fit into active site of enzyme before catalysis can occur
• only properly shaped molecules can serve as substrates for given enzyme -> shape of substrate is specific to the enzyme

Question 5

induced-fit model

Answer 5

• maintains that enzymes are rather flexible structures -> active site is reshaped by its interactions w/ the substrate until the time the substrate is completely bound to it
• explains how enzymes may exhibit broad specificity

Question 6

role of random collisions in binding of substrates with active site

Answer 6

• random collisions allow susbtrate to bind with enzyme active site
• substances can only bind to active site if it’s really close to it -> random collision needs to be successful for substrate to end up in active site & for reaction to start

Question 7

effect of temperature on enzyme activity rate

Answer 7

• reaction rate increases as temp increases to an optimal level then abruptly declines as temp increases further
• most enzymes rapidly become denatured at higher temps

Question 8

effect of pH on enzyme activity rate

Answer 8

• extremely high/low pH values -> complete loss of activity for most enzymes
• factor in chemical stability of enzyme structure
• enzyme activity increases around an optimum pH
• when pH moves out of optimum range, enzyme activity decreases bc pH alters charges, thus affecting shape of enzyme and denaturing it

Question 9

effect of substrate concentration on enzyme activity rate

Answer 9

• one single enzyme has maximum number of substrate molecules it can combine with per minute
• at low conc of substrate: steep increase in reaction rate as substrate conc increases
  
  • bc active site is empty & waiting for substrate to bind most of the time
  • reaction rate is limited by conc of substrate that’s available
• as substrate conc increases: enzyme becomes saturated w/ substrate
  
  • when active site is empty, more substrate is available to bind & undergo reaction
  • rate of reaction depends on activity of enzyme & adding more substrate won’t affect reaction rate to any significant effect

Question 10

denaturation

Answer 10

• at high temp & extreme pH, bonds btwn amino acids in enzyme changes, changing shape
• bc shape of active site is altered, enzyme no longer can bind its substrate & enzyme function is lost

Question 11

enzyme use in industry

Answer 11

• food production
• food processing & preservation
• washing powder
• leather industry
• medical applications

Question 12

immobilized enzyme

Answer 12

• enzyme attached to inert, insoluble material
• widely used in industry for enzyme catalysed reactions bc it lets enzymes be held in place throughout reaction so that they can be easily separated from products & reused

Question 13

source of the lactase enzyme used in food processing

Answer 13

obtain from yeast
- yeast is cultured then lactase is extracted & purified

Question 14

reaction catalysed by lactase

Answer 14

converts disaccharide sugar in milk, lactose, into two monosaccharides, galactose and glucose

lactose —lactase—> glucose+galactose

Question 15

4 reasons for using lactase in food processing

Answer 15

• to form lactose-free milk for ppl who are lactose intolerant
• to make milk sweeter so that no additional sweetener is needed
• to prevent crystallization of the milk when making ice cream
• to reduce production time of cheese/yogurt

Question 16

3 techniques for measuring enzyme activity

Answer 16

• enzyme reaction rate
• amount of product
• amount of substrate