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 hill.com/sites/ /student_view 0/chapter2/animation__how_enzymes_ work.html hill.com/sites/ /student_view 0/chapter2/animation__how_enzymes_ work.html

Activation Energy (E a ) The energy required to start a reaction Enzymes decrease the E a 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

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.

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’ Homework Q 1-2 pg. 82 Critical consideration pg. 78

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