Enzymes They be proteins.

What should I Be able to do after reading about enzymes? Understand these concepts: Enzymes have an active site to which specific substrates bind. Enzyme catalysis involves molecular motion & the collision of substrates with the active site. Temp, pH & substrate concentration affect the rate of activity of enzymes. Enzymes can be denatured. Immobilized enzymes are widely used in industry. Explore the Nature of Science: Experimental design: accurate quantitative measurements in enzyme experiments require replicates to ensure reliability. Further your understanding by studying this example: Methods of production of lactose-free milk and its advantages. Apply your understanding by performing this Skill: Design of experiments in to test the effect of temperature, pH & substrate concentration on the activity of enzymes. Experimental investigation of a factor affecting enzyme activity. (Practical 3)

Understanding: Enzymes have an active site to which specific substrates bind. Globular proteins Biological catalysts = made by cells AND speed up chem rxns without being altered themselves Found in all cells Specific = only catalyze one kind of rxn SUBSTRATES: Converted into products by enzymes Usually smaller than the enzymes they bind to substrate enzyme product

How enzymes speed up rxns: Active site = specific region on the surface of enzyme to which substrate binds Active site only binds to one specific substrate because the shape and chemical properties of both match up Substrates converted into products while bound to active site of enzyme Enzyme can be re-used after products released from active site

Understanding: Enzyme catalysis involves molecular motion and the collision of substrates with the active site. Enzyme activity = catalysis of a rxn by enzyme 3 stages: Substrate(s) binds to active site of enzyme. Substrates converted (change) to products. Products separate from active site, leaving it open for new substrates. Collision = coming together of substrate and active site Occur because of random movements of substrate and enzyme, which are both In constant motion because most substrates are dissolved in liquid water around the enzyme. Liquids are in continual motion.

Two models to explain enzyme activity: Lock and Key (1890) and Induced Fit (1959)

Understanding: Temp, pH & substrate concentration affect the rate of activity of enzymes. Temperature and enzyme activity: Increase in temp causes increase in enzyme activity – due to molecules moving faster at higher temps, which increases chances for random collisions Too much heat decreases enzyme activity – due to increasing chances of bonds breaking in enzyme because of vibrations, which causes denaturation

pH and enzyme activity: Slight pH increases or decreases from the optimum reduces enzyme activity – due to slightly altering shape of active site so sometimes substrate doesn’t fit Extreme pH increases or decreases from the optimum will denature enzyme

Different enzymes have diff pH optimums! Biological laundry detergent contains a protease made by B. licheniformis, which has pH optimum of 9-10.

Substrate concentration & enzyme activity:

Understanding: enzymes can be denatured. Denaturation = permanently changing shape of active site so that substrates can no longer bind or rxn does not occur Can cause dissolved enzymes to come out of solution and form a precipitate Caused by 2 conditions: 1) heat 2) Extreme pH (away from the optimum)

On individual whiteboards: Draw the graphs for the effects of temp, pH, and substrate concentration on enzyme activity!

Nature of Science: Experimental design: accurate quantitative measurements in enzyme experiments require replicates to ensure reliability Basics to remember when designing your own experiment (IA): Measure quantitative and qualitative data Record accurate measurements using accurate units & uncertainties Provide for repeats, then compare the repeats to assess reliability of data 5X5 Experimental Design is BEST!! (5 forms of independent variable with 5 repeats of an experiment)

Understanding: immobilized enzymes are widely used in industry Remember the falsification of the vitalism theory? Artificial synthesis of urea in a lab, instead of kidneys synthesizing it (1828, Wohler) Now we have more support: conversion of sugar to alcohol using only yeast extract without any cells (1897, Buchner bros) Create immobilized enzymes 3 ways: (Immobilized = can’t move) Attach enzymes to glass surface Trap enzymes in gel Bond enzymes together (aggregates) Advantages of immobilizing enzymes for the industries that use them: Easy separation of enzyme and products at ideal time Easy reusing of enzyme Increases stability of enzyme to temp and pH changes Faster rxn rates, since substrates can be exposed to higher enzyme concentrations

WHY are all of these advantages for companies?

What kind of industries use immobilized enzymes? Biotechnology Food & nutrition Medical Biosensors (pregnancy tests; blood sugar tests) Environmental Agriculture Energy

Application: methods of production of lactose-free milk and its advantages Lactose = sugar in milk Lactose = disaccharide: _________ + _________ ? Enzyme that breaks down lactose = ___________ ? Lactase obtained from K lactis, yeast in milk Reasons lactase used by food manufacturers: For lactose-intolerant ppl (they lack enzyme to break lactose down) If product needs to be sweet (milk shake, fruit yogurt), glucose and galactose are sweeter than lactose, so less sugar added Smoother texture for ice cream if use glucose and galactose Faster production of yogurt and cottage cheese if use glucose and galactose

Lactase Products