10/21/2015 CHAPTER 5 ENZYMES

10/21/2015 ENZYMES All organisms require energy to perform life functions. All organisms require energy to perform life functions. Growth, development, reproduction, etc. Growth, development, reproduction, etc. Energy needed for living things is derived from nutrients. Energy needed for living things is derived from nutrients. Broken down in biochemical reactions Broken down in biochemical reactions To break down nutrients, an initial amount of energy must be supplied to start the reactions. To break down nutrients, an initial amount of energy must be supplied to start the reactions. This energy is known as activation energy. This energy is known as activation energy. To sustain life, biochemical reactions must occur at very rapid rates. To sustain life, biochemical reactions must occur at very rapid rates. Reactions rates can be accelerated with increased temperature, pressure, or the use of a catalyst. Reactions rates can be accelerated with increased temperature, pressure, or the use of a catalyst.

10/21/2015 ENZYMES A catalyst is a molecule that speeds up a reaction. A catalyst is a molecule that speeds up a reaction. Lowers the activation energy Lowers the activation energy Living things cannot have too much increase in temperature or pressure to accelerate a reaction, so a catalyst must be used. Living things cannot have too much increase in temperature or pressure to accelerate a reaction, so a catalyst must be used. Enzymes are biological catalysts that accelerate chemical reactions in living cells at normal body temperature. Enzymes are biological catalysts that accelerate chemical reactions in living cells at normal body temperature.

10/21/2015 ENZYMES

ENZYMES As with any catalyst, enzymes speed up a reaction but are not used up in the reaction. As with any catalyst, enzymes speed up a reaction but are not used up in the reaction. The instructions for producing enzymes are found on the DNA of the organism. The instructions for producing enzymes are found on the DNA of the organism. Each organism produces thousands of specific enzymes that the cell needs. Each organism produces thousands of specific enzymes that the cell needs. Each enzyme is very specific on the reaction that it catalyzes. Each enzyme is very specific on the reaction that it catalyzes.

10/21/2015 ENZYMES Each enzyme has a specific 3-D shape. Each enzyme has a specific 3-D shape. This shape allows the enzyme to attach specifically to a substrate that matches. This shape allows the enzyme to attach specifically to a substrate that matches. Like a puzzle or lock and key Like a puzzle or lock and key The substrate (or reactant) is the molecule to which the enzyme binds. The substrate (or reactant) is the molecule to which the enzyme binds. When attached, an enzyme-substrate complex is formed and the reaction proceeds. When attached, an enzyme-substrate complex is formed and the reaction proceeds.

10/21/2015 ENZYMES

ENZYMES Enzymes have an active site, which is the area where the enzyme binds to the substrate. Enzymes have an active site, which is the area where the enzyme binds to the substrate. Because enzymes are specific, they are named based on the name of the substrate. Because enzymes are specific, they are named based on the name of the substrate. The first part is the name of the molecule to which it can become attached. The first part is the name of the molecule to which it can become attached. The second part may indicate the type of reaction it facilitates. The second part may indicate the type of reaction it facilitates.

10/21/2015 ENZYMES The third part of the enzyme is “–ase,” the ending that tells you it is an enzyme. The third part of the enzyme is “–ase,” the ending that tells you it is an enzyme. Lactase (enzyme) acts on lactose (carbohydrate) Lactase (enzyme) acts on lactose (carbohydrate) Alcohol dehydrogenase acts on alcohol, removing a hydrogen ion Alcohol dehydrogenase acts on alcohol, removing a hydrogen ion DNA polymerase attaches to a DNA molecule and is responsible in increasing its length through polymerization reaction DNA polymerase attaches to a DNA molecule and is responsible in increasing its length through polymerization reaction Some enzymes have kept their old names, e.g., pepsin and trypsin. Some enzymes have kept their old names, e.g., pepsin and trypsin.

10/21/2015 ENZYMES Some enzymes need other molecules to function well. Some enzymes need other molecules to function well. Called cofactors Called cofactors Cofactors temporarily attach to enzymes and speed up the reaction. Cofactors temporarily attach to enzymes and speed up the reaction. If the cofactor is not a protein but another organic molecule, it is called a coenzyme. If the cofactor is not a protein but another organic molecule, it is called a coenzyme. Many coenzymes are made from minerals (zinc, magnesium, or iron) vitamins, and nucleotides. Many coenzymes are made from minerals (zinc, magnesium, or iron) vitamins, and nucleotides. Can be used for many different enzymes. Can be used for many different enzymes.

10/21/2015 ENZYMES Enzymes are very specific and extremely efficient. Enzymes are very specific and extremely efficient. A single enzyme can accelerate a reaction 10 thousand trillion (1016) times faster per minute than the reaction would occur without the enzyme. A single enzyme can accelerate a reaction 10 thousand trillion (1016) times faster per minute than the reaction would occur without the enzyme. Temperature has two effects on enzyme action: Temperature has two effects on enzyme action: Can cause the molecules to move faster Can cause the molecules to move faster Can change the shape of an enzyme Can change the shape of an enzyme Enzymes can be denatured by high temperatures. Enzymes can be denatured by high temperatures. Enzymes work best at their optimum temperature. Enzymes work best at their optimum temperature. Usually around normal body temperature Usually around normal body temperature

10/21/2015 OPTIMUM TEMPERATURE

10/21/2015 ENZYMES An enzyme that is denatured has lost its ability to function properly. An enzyme that is denatured has lost its ability to function properly. Like cooking an egg Like cooking an egg pH changes can also denature an enzyme and impair its function. pH changes can also denature an enzyme and impair its function. Each enzyme has an optimum pH at which it works best, but most enzymes work best around pH 7. Each enzyme has an optimum pH at which it works best, but most enzymes work best around pH 7. There are control processes in each cell to make sure all metabolic reactions occur in the proper sequence. There are control processes in each cell to make sure all metabolic reactions occur in the proper sequence.

10/21/2015 OPTIMUM pH

10/21/2015 REGULATION The number and kind of enzymes produced are regulated by the cell’s genes. The number and kind of enzymes produced are regulated by the cell’s genes. Enzymes are regulated by negative-feedback inhibition, which works by inhibiting the enzyme from performing at its best. Enzymes are regulated by negative-feedback inhibition, which works by inhibiting the enzyme from performing at its best. Inhibitors can also influence the activity of an enzyme by attaching themselves to an enzyme and interfering with the formation of enzyme- substrate complex. Inhibitors can also influence the activity of an enzyme by attaching themselves to an enzyme and interfering with the formation of enzyme- substrate complex. Competitive inhibitors are molecules that bind to the active site of an enzyme and make it unavailable to bind to the substrate. Competitive inhibitors are molecules that bind to the active site of an enzyme and make it unavailable to bind to the substrate. Is used to control bacterial growth Is used to control bacterial growth

10/21/2015 CHAPTER 5 ENZYMES

10/21/2015