ENZYMES

Enzymes: Temperature, pH, and Specificity Hands-on labs, inc. Version 42-0054-00-01

Review the safety materials and wear goggles when working with chemicals. Read the entire exercise before you begin. Take time to organize the materials you will need and set aside a safe work space in which to complete the exercise.

Experiment Summary:

Students will learn how enzymes act as catalysts to lower the activation energy required for a reaction to proceed in both catabolic and anabolic processes. Students will study competitive inhibition, negative feedback, and enzyme specificity using lactase on various substrates. They will study the effects of temperature and pH on the ability of lactase to break down lactose.

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ExpErimEnt

ObjEctivEs ● To learn how enzymes work

● To understand enzyme specificity

● To relate enzyme activity to temperature, pH, and concentration

● To understand the role of enzymes in digestion of lactose

Time Allocation: 3 hours

Safety: So that you understand the proper procedures to use when handling, pouring, heating, etc. chemicals, if you have not already done so, read the section in the introduction to this Lab Manual titled “Laboratory Equipment and Techniques” before beginning this experiment. Also, always wear goggles when handling chemicals, and also use gloves when directed to do so.

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Experiment EnzymEs TEmpEraTurE pH spEcificiTy

matErials

MATERiAlS FRoM:

lABEl oR BoX/

BAg: QTy iTEM DESCRiPTioN:

Student Provides

10 1

Bathroom or facial tissues Freezer

1 10 Milk, 1 cup Paper, tissue in sheets

1 Oven mitt 1 Scissors 2 Spoons

1 1 1

Sucrose (Table sugar), 2.5 grams Stove and pan for Hot Water Bath Water, distilled (1 liter)

From LabPaq 1 Glucose, 20% solution in pipet 24 Glucose test strips 1 Graduated Cylinder, plastic, 50 mL 2 Lactase pills 1 Pencil, marking

10 Pipet, Empty Long Stem 6 Plastic cup, 9 oz

1

Scale-Digital – iMPoRTANT !!! – If you do not perform the following two steps your scale will not work properly: 1) If present, on the side of the scale underneath the weighing platform, pull out the small plastic strip which is attached to a piece of cardboard that protects the scale during shipping, and 2) Remove the plastic strip between the battery & connectors, or if the batteries are shrink- wrapped, the shrink-wrap must be removed.

1 Test-tube-clamp-holder 1 Test-tube-cleaning-brush 1 Test Tube (3), 13 x 100 mm in Bubble Bag 1 Test-tube-rack -6×13-mm 1 Thermometer-in-cardboard-tube 1 Well-Plate -12 1 Gloves, disposable – pair 1 Rod, Stirring – glass

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Experiment EnzymEs TEmpEraTurE pH spEcificiTy

Enzymes 1 pH 11.5, Buffer- 2 mL in Pipet 1 pH 3.5, Buffer – 2 mL in Pipet 1 pH 5.0, Buffer – 2 mL in Pipet 1 pH 6.8, Buffer – 2 mL in Pipet

Note: The packaging and/or materials in this LabPaq may differ slightly from that which is listed above. For an exact listing of materials, refer to the Contents List form included in the LabPaq.

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Experiment EnzymEs TEmpEraTurE pH spEcificiTy

DiscussiOn anD rEviEw When nutrients are broken down into smaller and simpler molecules, energy is released and these molecules then provide building blocks for the organism. For instance, food consumed is broken down into individual sugar, amino acid, and/or fatty acid components. These components are then recombined with other molecules to make proteins, hormones, or other molecules. The breakdown of large molecules into smaller molecules is called catabolism. The recombining of molecules to synthesize larger molecules is called anabolism.

All of these reactions require the assistance of a type of protein called enzymes. Enzymes are catalysts, chemicals that work in the body by speeding up reaction times. Enzymes work by lowering the amount of energy required to convert molecules from one form to another. The amount of energy required is called activation energy (EA). Enzymes help lower EA, similar to helping another person pull a wagon up a hill: it requires less work when assistance is available. See Figure 1. Enzymes are very specific in that they act by binding to a specific molecule, and alter its shape so that the reaction is more likely to occur. Without enzymes, it would take much longer for chemical reactions to occur. All chemical reactions in biological systems require the presence of enzymes.