Why Are Enzymes So Important?
Why are we devoting two whole lecture topic to a enzyme?
Nearly all chemical reactions in biological cells need enzymes to make the reaction occur fast enough to support life.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Image: Jumping rope, Meagan E.
Outline
• Composition, structure and properties of enzyme
• How Enzymes work
• Enzyme activity
• Factors affecting enzyme activity • Regulation of enzyme activities
• Enzymes in clinical diagnosis
1. Definition of enzyme
•Enzymes are biological catalysts.
•A Catalyst is defined as "a substance that increases the rate of a chemical reaction without being itself changed in the process.”
Enzymes as Biological Catalysts
• Enzymes are proteins that increase the rate of reaction by lowering the energy of activation
• They catalyze nearly all the chemical reactions taking place in the cells of the body • Enzymes have unique threedimensional shapes that fit the shapes of reactants
(substrates)
2. Properties of enzymes (important!)
• Catalytic efficiency – high efficiency, 103 to 1017 faster than the corresponding uncatalyzed reactions
• Specificity - high specificity, interacting with one or a few specific substrates and catalyzing only one type of chemical reaction. • Mild reaction conditions37℃, physiological pH, ambient atmospheric pressure 3. Chemical composition of enzymes
(1) Simple protein
(2) Conjugated protein
Holoenzyme= Apoenzyme+
Cofactor
Cofactor
Coenzyme : loosely bound to enzyme
(non-covalently bound).
Prosthetic group : very tightly or even covalently bound to enzyme (covalently bound) 4. Classification of enzymes
(1). By their composition
1). Monomeric enzyme
2). Oligomeric enzyme
3). Multienzyme complex: such as Fatty acid synthase
(2) Nomenclature
• Recommended name
•Enzymes
are usually named according to the reaction they carry out. •To generate the name of an enzyme, the suffix -ase is added to the name of its substrate (e.g., lactase is the enzyme that cleaves lactose) or the type of reaction
(e.g., DNA polymerase forms DNA polymers). •Systematic name (International
5. How enzymes work (important!)
1) Enzymes lower a reaction’s activation energy
– All chemical reactions have an energy barrier, called the activation energy, separating the reactants and the products. – activation energy: amount of energy needed to disrupt stable molecule so that reaction can take place. Enzymes
Lower a
Reaction’s
Activation
Energy
What is the difference between an enzyme and a protein?
Protein Enzymes RNA
•All enzymes are proteins except some
RNAs
2) The active site of the enzyme
• Enzymes bind substrates to their active site and stabilize the transition state of the reaction.
• The active site of the enzyme is the place where the substrate binds and at which catalysis occurs.
• The active site binds the substrate, forming an enzymesubstrate(ES) complex.
Binding site
Active site
Catalytic site
Enzymatic reaction steps
1.
2.
3.
4.
5.
Substrate approaches active site
Enzyme-substrate complex forms
Substrate transformed into products
Products released
Enzyme recycled
6. Enzyme activity
• Enzymes are never expressed in terms of their concentration (as mg or μg etc.), but are expressed only as activities.
• Enzyme activity = moles of substrate converted to product per unit time.
– The rate of appearance of product or the rate of disappearance of substrate
– Test the absorbance: spectrophotometer
7. Factors affecting enzyme activity
•
•
•
•
•
•
Concentration of substrate
Concentration of enzyme
Temperature
pH
Activators
Inhibitors
Enzyme velocity
• Enzyme activity is commonly expressed by the intial rate (V0) of the reaction being catalyzed.
(why?)
• Enzyme activity = moles of substrate converted to product per unit time.
Copy button on the panel above to save your report) Activity: Name: Instructor: Date: Enzyme Activity Pam Campbell Id 0002337 Dr. Murphy Nmezi August 9, 2011 Predictions 1. Sucrase will have the greatest activity at pH 6 2. Sucrase will have the greatest activity at 40 °C (104 °F) 3. Sucrase activity increases with increasing sucrose concentration until a plateau is reached. Materials and Methods Effect of pH on Enzyme Activity. 1. Dependent Variable. amount of product (glucose and…
ENZYME ACTIVITY BACKGROUND Enzymes are the catalysts of biological systems. They speed up chemical reactions in biological systems by lowering the activation energy, the energy needed for molecules to begin reacting with each other. Enzymes do this by forming an enzyme-substrate complex that reduces energy required for the specific reaction to occur. Enzymes have specific shapes and structures that determine their functions. The enzyme’s active site is very selective, allowing only certain substances…
The Effect of Temperature on Enzyme Activity – Stage 2 Biology Nick Greco Abstract: The hypothesis of the experiment was 'raising the temperature of the hydrogen peroxide solution will increase the rate of reaction until it reaches its optimum temperature at which point the rate of reaction will begin to decrease.' This theory was tested by changing the temperature of hydrogen peroxide and recording the time it took for a yeast-covered filter-paper disc to reach the top. It was concluded that…
temperature has on the rate of enzyme activity. The way we figured this out was by taking four different temperatures and testing the difference absorbance levels they produced every 20 seconds for about 2 minutes straight using a spectrophotometer. The important part of this experiment was the temperature the enzyme concentration was made at. What we got from the experiment was at lower temperature we got very low numbers for the absorbance, which gave us a lower rate for the enzyme reaction to complete,…
Concentration On The Activity Of The Enzyme Catalase A Level Biology Project Aims This is an experiment to examine how the concentration of the substrate hydrogen peroxide affects the rate of reaction of the enzyme catalase. Background Information Enzymes such as Catalase are protein molecules which are found in living cells. They are used to speed up specific reactions in the cells. They are all very specific as each enzyme just performs one particular reaction. Catalase is an enzyme found in food…
Enzyme Activity II: The Breakdown of Starch Due to Amylase Enzyme Ceara Sibley Central Michigan University Biology Lab 110 3:00-5:50 October 6, 2014 Introduction The ultimate goal of this experiment is to determine how much starch a particular amount of amylase enzyme is able to convert into sugar in the span of one minute. Certain variables can change the amount of sugar converted, such as the pH or temperature of the given solution. Enzymes, natural catalyst…
Background Information Part 1 In the first part of the enzyme lab, we mixed a substrate and an indicator with an enzyme. There was also a neutral buffer in each of the chemical mixtures. The neutral buffer regulated the pH to around 7. We got a color palette and once we mixed each together, we observed and saw a change in the color of the substance. The darker and more brown the substance got, the more oxygen produced by the reaction. Our results showed that amount of oxygen produced increased…
Bio 132-Spring 2015 Pre-Lab (see attached copies of worksheets.) Questions from pages 29-39 What is an enzyme? An enzyme is a catalyst that works by speeding up the process of digestion. It is a substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction. How does an increase in temperature affect kinetic energy and enzyme activity? 1. An increase in temperature will lead to more energetic collisions. When molecules collide, kinetic energy…
concentration in peroxidase activity. Peroxidase is an enzyme that converts toxic hydrogen peroxide (H2O2) into water and another harmless compound. In this experiment we use, turnips and horseradish roots which are rich in the peroxidase to study the activity of this enzyme. The activity of peroxidase with change in temperature was highest at 320 Celsius and lowest at 40C. The activity of peroxidase was highest at a pH of 7, while it was lowest at pH of 9.Peroxidase activity was very low and constant…
Enzymes By Jadaida Glover Jadaida glover 1. What are enzymes? 1. What are enzymes made of? Like all other proteins, enzymes are made of amino acids. Each enzyme is made of between a hundred and upwards of a million amino acids placed like pearls on a string. Each amino acid is bonded to the next by chemical bonds . 2. How are enzymes made? Enzymes are made by stringing together between 100 and 1,000 amino acids in a very specific and unique order…