b. Explain how enzymes function as catalysts. SB1. Students will analyze the nature of relationships between structures and functions in living things b. Explain how enzymes function as catalysts.

LEQ1. How do enzymes function as catalysts? Essential Question What is the relationship between structures and functions in living cells? LEQ1. How do enzymes function as catalysts?

WATER/ENZYMES- Vocabulary you should know and understand Catalysts Activation Energy Chemical Reaction Reactants Products Equilibrium Enzyme-Substrate Complex Inhibitor Endergonic Exergonic Reaction Rate Substrate Active Site pH temperature

CHEMICAL REACTIONS The biochemical reactions that occur in living things must occur at certain speeds, or rates, in order for them to be useful. Chemical reactions change substances into different substances by breaking and forming chemical bonds

Bond energy is the amount of energy that is needed to break a bond. Energy is added to break bonds. Energy is released when bonds form. A reaction is at equilibrium when reactants and products form at the same rate. CO2 + H2O H2CO3

Chemical reactions release or absorb energy. Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.

Exothermic reactions release more energy than they absorb. Reactants have higher bond energies than products. Excess energy is released by the reaction.

Endothermic reactions absorb more energy than they release. Reactants have lower bond energies than products. Energy is absorbed by the reaction to make up the difference.

Temperature Concentration pH The rate at which a chemical reaction occurs depends on several factors: Temperature Concentration pH If all of these factors are held constant, the addition of a catalyst can speed up a chemical reaction

ENZYME- Organic catalyst that controls the rate of chemical reactions within the cells. Enzymes = proteins Without enzymes, many of the chemical reactions that occur in living things would not be able to occur or would occur at rates that are too low for the organism to survive.

Reactants and Products Reactants-substances that enter into a chemical reaction Products-substances that are formed in a chemical reaction

Substrates Enzymes provide reactants with a site where they can come together to react. Those reactants that are affected by enzymes in enzyme-catalyzed reactions are called substrates.

Enzymes The surface of an enzyme has a distinct shape that allows it to interact with only certain substances. A single organism may possess thousands of different enzymes. Each one is specific to a certain chemical reaction.

ACTIVE SITE The substrates bind to a part of the enzyme called the ACTIVE SITE. The shape of the substrate and the shape of the active site are opposite, or complementary. The enzyme and substrates fit together much like a lock and key.

ENZYME-SUBSTRATE COMPLEX The enzyme and substrate are held together by intermolecular forces. Together they form the enzyme-substrate complex. This complex stays bound until the reaction is complete. When the reaction is done the, the products are released. The enzyme, which is unchanged, is then free to repeat the process.

CONCEPT CHECK What is the name of the region at which reactants bind to an enzyme during a chemical reaction? Catalyst Product Substrate Active site

If enzymes are not used during a chemical reaction, how do they speed up the rate of the reaction? By providing such a reaction site, enzymes reduce the amount of energy that substrates need to react. In other words, enzymes reduce the ACTIVATION ENERGY

ACTIVATION ENERGY The minimum amount of energy that colliding molecules must possess in order to react.

Temperature Enzymes from different organisms tend to work best at different optimum temperatures. Human optimum temperature = 37 C Plant optimum temperature = 25 C Enzymes are destroyed at temperatures above 50 C

pH The pH of a solution describes how acidic or basic the solution is. Most enzymes function in a very narrow pH range, which varies depending on the enzyme and its job. For most reactions, the optimum pH is close to 7. Low or high pH values tend to inhibit enzyme activity.

Concentration If the number of substrate molecules is greater then the number of enzyme molecules, the reaction rate will rise until the molecules are attached to the substrate. The reaction rate then levels off

CONCEPT CHECK How are enzymes important in the proper functioning of the human body? a. they keep the pH of the body within acceptable levels b. they help essential biochemical reactions occur fast enough to maintain homeostasis c. they enable the body to use energy to produce food d. they provide cells with energy they need to carry out life functions

CONCEPT CHECK How are enzymes able to speed up biochemical reactions? a. they provide energy to the reactants b. they absorb energy from the products c. they lower the activation energy d. they increase the number of available reactant particles

CONCEPT CHECK

CONCEPT CHECK 3. Based on the previous graph, what can you conclude about the relationship between enzyme concentration and reaction rate? a. the reaction rate decreases as the enzyme concentration increases b. the reaction rate increases as the enzyme concentration decreases c. the reaction rate increases as the enzyme concentration increases d. the reaction rate is indirectly proportional to the enzyme concentration