Enzymes speed up biochemical reactions Graph features an exergonic reaction

Enzymes Catalyst  lowers the activation energy needed to start a chemical reaction; thus speeding up the rate of a reaction. Enzymes Proteins Biological catalysts Have ideal conditions Are not used up during a reaction (can be used again and again)

Enzymes lower activation energy Graph features an endergonic reaction Activation energy - the minimum amount of energy required for reactants to form products in a chemical reaction.

Enzyme-Substrate Binding Lock & Key Model

Enzyme-Substrate Binding- Induced Fit

Enzyme names often describe what they do Enzyme names often describe what they do. For example, lactase speeds up the breakdown of lactose, a product found in milk products. This illustrates an important point… Click cow Click cow for 1 min video clip Most enzymes are SPECIFIC to one reaction! (meaning they can only catalyze a single reaction)

Factors that affect enzymes Increase reaction rate Increasing amount of enzyme Increasing amount of substrate Decrease reaction rate Altering environmental conditions beyond ideal range (pH, temperature, salinity) Inhibitors- can be competitive or non-competitive

How Does pH Affect an Enzyme? Catalase is an enzyme that helps decompose the toxic hydrogen peroxide that is produced during normal cell activities. The products of this reaction are water and oxygen gas. The pressure of the oxygen gas in a closed container increases as oxygen is produced. Any increase in the rate of the reaction will cause an increase in the pressure of the oxygen. The purple line on the graph represents the normal rate of the reaction in a water solution of hydrogen peroxide and catalase. The red line represents the rate of reaction when an acid is added to the solution. The blue line represents the rate of reaction when a base is added to the solution.

How Does pH Affect an Enzyme? Applying Concepts What variable is plotted on the x-axis? What variable is plotted on the y-axis? Interpreting Graphics How did the rate of reaction change over time in the control reaction? Inferring Suggest an explanation for the change in the control reaction at about 40 seconds. Drawing Conclusions What effect do acids and bases have on the enzyme catalase? Drawing Conclusions Would it be valid to conclude that if a base were added, the rate of the reaction would slow down? Explain. Going Further Predict what would happen if vinegar were added to a water solution of hydrogen peroxide and catalase.

Enzyme Denaturation Environmental conditions affect the way proteins fold If conditions aren’t ideal, the enzyme’s shape can change Active site might not match substrate anymore Enzyme can’t function Enzyme has been denatured

How Competition Affects Enzyme Activity Substrate molecules typically bind to the active site of enzymes, but what if the active site changes shape or is blocked? In many cases, the inhibitor is the product of the reaction that the enzyme catalyzes.

Many Factors Affect Enzyme Activity

Many Factors Affect Enzyme Activity In a process called negative feedback, the product of a reaction slows the production of more product.

Many Factors Affect Enzyme Activity In the opposite process, called positive feedback, the product of a reaction stimulates its own production. Positive feedback Enzyme 4’s product stimulates action of enzyme 1