1.4- enzymes

Question 1

what is an enzyme?

Answer 1

-a biological catalyst , which control rate of reactions that take place in individual cells or entire organisms

Question 2

what is a catalyst?

Answer 2

-a substance that changes the rate of a reaction without changing the substances produced
-catalysts are unaffected at the end of the reaction and can be used again

Question 3

what are the 2 factors which can affect enzymes

Answer 3

pH and temperature

Question 4

why do enzymes each have a specific shape

Answer 4

-because of the protein structure
-this means they show specificity

Question 5

2 main types of reactions

Answer 5

1.catabolic
2.anabolic

Question 6

what is a catabolic reaction

Answer 6

-breaking substances down within a cell

Question 7

what is an anabolic reaction

Answer 7

-reaction that builds up (synthesises) new molecules in a cell

Question 8

what is activation energy

Answer 8

-amount of energy substrates need to overcome before they will convert to products
-a barrier

Question 9

what do enzymes have to do with activation energy

Answer 9

-enzymes are catalysts as they lower the activation energy needed to drive a reaction

Question 10

what is metabolism

Answer 10

• the sum of the anabolic and catabolic processes in a cell

Question 11

intracellular vs extracellular enzymes

Answer 11

intra- enzymes that catalyse reactions within the cell
extra- enzymes that catalyse reactions outside of the cell in which they were made

Question 12

how does temp effect enzyme activity

Answer 12

-low temp= enzymes have too little kinetic energy and move slowly, few successful collisions so low reaction rate

optimum temp= low of KE, lots of successful collisions, high reaction rate

high temp=heat breaks bonds, changing tertiary structure, active site denatured and substrate does not fit, no successful collisions so low reaction rate

Question 13

temp coefficient

Answer 13

• between 0-40 degrees, rate of reaction doubles for every 10 degrees temp rise
  -in humans, it stops completely at 60 degrees

Question 14

how pH affects enzyme activity

Answer 14

low pH= acidity breaks bonds, maintaining tertiary structure of enzyme, active site denatured, no successful collisions so low reaction rate

optimum pH= many collisions means high reaction rate

high pH= alkalinity breaks bonds maintaining tertiary structure, denatured, no successful collisions

Question 15

how substrate conc affects enzyme activity

Answer 15

low substrate conc= limits chance of successful collisions, low rate of reaction

high substrate conc= more molecules increases chance of successful collisions, high rate of reaction

Question 16

what is a substrate

Answer 16

• a reactant which gets altered in a reaction catalysed by the enzyme

Question 17

what is an IV

Answer 17

• the variable that you change t see what effect it has (cause)

Question 18

what is a DV

Answer 18

-the variable you measure, as a result of the change in the IV (effect)

Question 19

what is a control variable

Answer 19

-kept he same
-effects the outcome of the investiagtion

Question 20

enzyme core prac- what is happening?

Answer 20

-milk protein (casein) is broken down by protease enzymes such as trypsin
-opaque colour of milk replaced by a clear solution
-light passes more easily through this solution, so reaction measured using calorimeter

Question 21

enzyme core prac- method

Answer 21

1. plan dilutions of 1% trypsin solution with distilled water, producing 10cm3 of each conc
   2.place 2cm3 of tryspin solution and 2cm3 of d water in cuvette, use as reference to set absorbance to 0
   3.measure 2cm3 of milk suspension in second cuvette
   4.add 2cm3 t solution in milk cuvette, mix and place in calorimeter, start timer
   5.measure absorbance immediately then at 15 sec intervals for 5 mins or until little change
   6.rinse cuvette and repeat for all concs

Question 22

enzyme core prac- dilutions

Answer 22

0.8%= 8ml t, 2ml water
0.6%= 6ml t, 4ml water
0.4%= 4ml t, 6ml water
0.2%= 2ml t, 8ml water

Question 23

calculating rate from a graph

Answer 23

1. draw a tangent to curve
   2.draw vertical line and horizontal line to form right angle triangle with tangent
   3.read off change in amount of product
   4.read off change in time
   5.calculate gradient, step3 divided by step4

Question 24

what is an enzyme inhibitor

Answer 24

-any substance which stops enzymes from working

Question 25

2 main types of inhibition

Answer 25

-reversible
-irreversible

Question 26

2 main forms of reversible inhibition

Answer 26

1. competitive
2. non competitive

Question 27

reversible inhibition- competitive

Answer 27

-similar shape to substrate
-competes with the substrate to bind to the active site of the enzyme
-inhibition can be reduced by increasing conc of substrate (if amount of inhibitor is fixed)

Question 28

reversible inhibition- non competitive

Answer 28

-bind to enzyme (not active site) and change its shape
-substrate no longer fits
-so inhibitor does not compete for the active site
-level of inhibition controlled by conc of inhibitor only

Question 29

irreversible inhibition

Answer 29

-inhibior combines with the enzyme by permanent covelant bonds to one of the groups needed for catalysis to occur
-it changes the shape of the molecule that cannot be reversed
-tends to be slower but effects are more devastating
-e.g. nerve gases such as arsenic