3.6 & 7.6 Enzymes

IB Biology

Enzyme

Globular protein Made by cells of living organisms

– To help with reactions taking place in cells Catalyst - speed up chemical reactions

enzyme

substrate product

Enzyme Structure

Active site - special region on surface of enzyme where the substrate binds

Other molecules bounce off

Enzyme-Substrate Specificity

Enzymes only work with one specific substrate in one reaction

The shape and chemical properties of the active site and substrate must match

The “Lock and Key” Model

Enzyme is the lock and substrate is the key

Extends the lock and key model to account for the fact that substrates and active sites undergo conformational (shape) changes during binding. This can allow one enzyme to fit a number of substrates.

Catalyzed chemical reaction Substrate binds to enzyme Substrate is converted into products

while bound Products are released Enzyme is unchanged

Animation

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

Activation Energy (Ea)

The energy required to start a reaction Enzymes decrease the Ea so reactions

happen faster

Factors that effect enzyme activity

Can you think of them?

Factors that effect enzyme activity

1. Temperature 2. pH 3. [Enzyme] 4. [Substrate]

* Note: [ ] means concentration

Effect of temperature Increasing temperature increases the

kinetic energy of particles so they move in random motion faster

This increases the chance of collision of a substrate with the active site of the enzyme

Enzyme activity increases

Effect of temperature

Denaturation Increasing temperature causes bonds in

enzyme to vibrate more This increases the chance of bonds

breaking, changing the structure of the active site permanently

Can no longer function as a catalyst

Effect of pH

pH measures acidity or alkalinity– Acidity due to presence of H+ ions

Each enzyme has a pH where is works best (optimal pH)

When [H+] is too high or low, it alters the structure of the enzyme’s active site

Causes denaturation

Effect of pH

Effect of pH

Different enzymes have different optimal pH based on their functions

Effect of [Substrate]

Increasing the amount of substrate in a solution increase the frequency of collisions

Increases enzyme activity When too much substrate present, all

active sites are full and collisions are blocked

Increase in rate of reaction gets smaller

Effect of [Substrate]

Rises less and less steeply but never reaches a maximum

Effect of [Enzyme]

A higher concentration of enzymes means more active sites are present

More collisions occur, and therefore more reactions happen and rate is faster

If all substrate is used up, increasing [enzyme] will not have an effect

Metabolic Pathways are chains and/or cycles of enzyme-catalysed

reactions that create products your body needs.

http://www.wisconline.com/objects/ViewObject.aspx?ID=MBY2604

Biotechnology and enzymes Lactase is an enzyme obtained from

yeast that grows in milk Biotech companies grow yeast, extract

the lactase, purify it and sell it to food manufacturing companies

lactase

Lactose glucose + galactose

Why the need for lactase?

Some people lactose intolerant– Flatulence, bloating, nausea

Glucose and galactose are sweeter than lactose - less sugar added

Lactose gives a gritty texture in ice cream, g&g are more soluble giving smoother ice cream

Faster production of cheese products since bacteria ferment g&g faster than lactose

Lactose-free products

A competitive inhibitor competes with the substrate for the active site. A noncompetitive inhibitor binds to a site other than the active site and changes the shape of the enzyme so it will no longer fit the substrate.

Allosteric enzymes have allosteric sites that bind substances that may inhibit (inhibitors) or stimulate (activators) an enzyme’s activity.

*see allosteric animation

The production of the amino acid isoleucine is regulated by feedback inhibition.

The end product, isoleucine, allosterically inhibits enzyme 1, theorine deaminase.

*see feedback animation

Protein Strength Lab’

HomeworkQ 1-2 pg. 82Critical consideration pg. 78

Design Lab

Design a lab that will investigate the effect of a certain factor on the rate of catalyse activity.