enzymes 2.10, 2.11, 2.12, 2.13 & 2.14B

Question 1

what are enzymes?

Answer 1

biological catalysts

Question 2

what controls the chemical reactions in cells?

Answer 2

the group of proteins called enzymes

Question 3

what is a catalyst?

Answer 3

a chemical that increases the rate of reaction without being used up in the reaction
increase rate of reaction by providing an alternate pathway with lower activation energy

Question 4

how do enzymes work?

Answer 4

have: enzyme, substrate, active site

• substrate and enzyme collide
  -substrate binds to active site of enzyme
• enzyme-substrate complex
• after reaction the products do not fit active site shape (no longer complementary)

Question 5

what affects the rate of enzyme?

Answer 5

temperature

adding more substrate or enzyme

Question 6

how does high temperature increase rate of reaction (enzymes)?

Answer 6

as temp increases the enzyme and substrate have more kinetic energy, faster and there are more successful collisions

this occurs until the optimum temperature is reached

Question 7

what can cause an enzyme denaturing?

Answer 7

high temperatures
changes of pH

active site so no longer complementary to substrate
substrate cannot bind to the active site

Question 8

what does rate mean?

Answer 8

how many events happen in a given amount of time

Question 9

how does pH affect rate of reaction?

Answer 9

pH inside cells is 7 (neutral) - most cells work best at this pH

if pH changes it can affect shape of enzyme, active site changes shape and no longer complementary to substrate, enzyme denatured.

Question 10

practical: investigate how enzyme activity can be affected by changes in temperature.

Answer 10

investigate effect of amylase and how it digests starch

mix 10cm^3 of 10% starch suspension
5cm^3 of amylase in a boiling tube and heat in a water bath

every minute take a drop of the mixture and add a drop of iodine solution in spotting tile

when digestion is complete and no starch is present, iodine will stay orange (rather than turning black/blue)

repeat using different temperatures

Question 11

practical: investigate how enzyme activity can be affected by changes in pH

Answer 11

potato contains enzyme catalase (which breaks down into hydrogen peroxide) forming water and oxygen

add 10 potato disks (1cm thick, cut with cork corker)
add to 20cm^3 of catalase
measure volume of gas produced in 5 minutes

pH altered by adding different volumes of a weak alkali (sodium carbonate) or weak acid (ethanoic acid)

use universal indicator paper to determine pH of solution