control metabolism metabolic reactions can be controlled and sped up by enzymes that lower the...

Control METABOLISMControl METABOLISM

Metabolic reactions can be controlled and Metabolic reactions can be controlled and sped up by enzymes that lower the sped up by enzymes that lower the activation energy needed.activation energy needed.– metabolic reactions would be too slow to metabolic reactions would be too slow to

occur if no enzymes were present!occur if no enzymes were present!

Properties of EnzymesProperties of Enzymes1.1. ProteinsProteins2.2. CatalystsCatalysts3.3. Reusable Reusable 4.4. Substrate Substrate

specificspecific5.5. Sensitive to Sensitive to

temperaturetemperature6.6. Sensitive to Sensitive to

pHpH

Enzymes remain unchanged!Enzymes remain unchanged!

Enzymes are Enzymes are not used upnot used up

Reaction end’s Reaction end’s when there is when there is NO more NO more substrate substrate

Synthesis or Synthesis or Decomposition Decomposition reactionsreactions

Before

After

substrate

enzyme

active site

substrate

Mechanism of enzyme actionMechanism of enzyme action• Each enzyme has an active site• Active site is the place where the substrate

binds with the enzyme

enzyme

Action of enzyme in synthesisAction of enzyme in synthesis

substratesubstrate

enzyme-substrate complex product

enzyme

Action of enzyme in Action of enzyme in decompositiondecomposition

substrate

enzyme-substrate complex

productproduct

Lock and key hypothesisLock and key hypothesis

Enzyme

Substrate

Lock and key hypothesisLock and key hypothesis

SHAPES

DON’T

MATCH

Lock & Key ModelLock & Key Model

One One enzymeenzyme

for every for every substratesubstrate

unique fitunique fit

Enzyme

Substrate

Enzymes are temperature Enzymes are temperature dependent…...dependent…...

0

10

20

30

40

50

60

70

80

90

10 20 37 40

Most work best Most work best at body at body temperaturetemperature

3737ooCC

Denatured at Denatured at high high temperaturestemperaturesInactive at low Inactive at low temperaturetemperature

Temperature oC

Effect of pH on enzyme activityEffect of pH on enzyme activity

Optimum pH : the pH value at which the enzyme has the Optimum pH : the pH value at which the enzyme has the highest activity (fastest rate of reaction)highest activity (fastest rate of reaction)Different enzymes may have different optimum pH’sDifferent enzymes may have different optimum pH’s

pH of substrate higher or lower than optimum pH, it can pH of substrate higher or lower than optimum pH, it can denature the enzyme making it ineffective.denature the enzyme making it ineffective.

Enzyme LabEnzyme LabEnzyme: catalaseEnzyme: catalase

Source: liver, potato, Source: liver, potato, apple etcapple etc

Substrate: HSubstrate: H22OO22

Hydrogen peroxide is Hydrogen peroxide is toxic in cellstoxic in cells

2H2H22OO2 +catalase2 +catalase

22 HH22OO + + O O22

Enzymes end in ‘ase’Enzymes end in ‘ase’

TA TA!TA TA!