bio chapter 4

Question 1

definition of enzymes

Answer 1

proteins that function as biological catalysts that catalyse the rate of chemical reactions and remain unchanged at the end of the reaction

Question 2

definition of catalysts

Answer 2

substances that can speed up a chemical reaction without itself being chemically changed at the end of the reaction

Question 3

what reactions do enzymes catalyse?

Answer 3

1. anabolic reactions
   -> reactions that build up complex substances
2. catabolic reactions
   -> reactions that break down complex substances

Question 4

mode of action of enzyme

Answer 4

1. shape of active site of enzyme is specific and complementary to shape of substrate
2. effective collisions between enzyme’s active site and substrate
3. forms enzyme-substrate complex
4. interactions between enzyme and substrate molecules weaken chemical bonds within substrates, thus lowering activation energy
5. when reaction between enzyme and substrate is completed, products no longer fit into active site of enzymes
6. products are released

Question 5

conditions for effective collisions

Answer 5

1. correct orientation of substrate
   -> so substrate shape can be complementary to enzyme active site
2. sufficient energy for chemical reaction to occur

Question 6

characteristics of an enzymes - speeds up chemical reaction

Answer 6

1. interactions between enzyme and substrate molecules weaken chemical bonds within substrate
2. lowers activation energy needed to start reaction
3. speeds up rate of chemical reaction

Question 7

characteristics of an enzymes - specific in action

Answer 7

1. an enzyme molecule has a specific unique three-dimensional globular shape
2. enzymes have active site
3. only substrates with a shape complementary to enzyme active site can bind with the enzyme and cause a chemical reaction
4. when an enzyme binds to a substrate, it forms an enzyme-substrate complex
5. substrate is converted to products

Question 8

characteristics of an enzymes - required in small quantities and remain chemically unchanged at end of reaction

Answer 8

-> enzyme remains unchanged in reactions they catalyse
-> a small amount of an enzyme can catalyse the reaction for a large amount of substrate

Question 9

characteristics of an enzymes - affected by temperature

Answer 9

-> temperature increases
-> kinetic energy of substrate and enzyme molecules increases
-> rate of effective collision between substrate and enzyme’s active site increases
-> rate of formation of enzyme-substrate complex increases
-> rate of reaction and products formed increases

Question 10

what happens to an enzyme at optimum temperature?

Answer 10

-> rate of enzyme activity is highest at (insert data) at optimum temperature of (insert data)
-> enzyme’s active site is saturated
-> rate of formation of enzyme-substrate complex is highest

Question 11

what happens to an enzyme at low temperature?

Answer 11

-> enzymes at low temperatures have low kinetic energy
-> low frequency of effective collision between substrate and enzyme’s active site
-> enzyme is inactive at low temperatures

Question 12

what happens to an enzyme at high temperature?

Answer 12

-> high temperatures break bonds that keep enzyme protein in its specific shape
-> active site of enzyme loses original shape and is no longer complementary to substrate
-> enzyme is denatured and loses its catalytic function

Question 13

characteristics of an enzymes - affected by pH

Answer 13

-> changes in pH alter bonding pattern of enzyme
-> alters 3D conformation of enzyme’s active site
-> substrate is no longer complementary to active site
-> no enzyme-substrate complex can be formed
-> enzyme is denatured and loses its catalytic function

Question 14

what happens to an enzyme at optimum pH?

Answer 14

-> rate of enzyme activity is highest at (insert data) at optimum pH of (insert data)
-> enzyme’s active site is saturated
-> rate of formation of enzyme-substrate complex is highest