Lesson 6.1 Enzyme Structure and Function PDF

**LESSON 6.1** **ENZYME STRUCTURE AND FUNCTION** - Enzymes are essential to the body's normal functions. Many of these end with the suffix -ase. **Examples of Enzymes** ---------------- ----------------------------------------------------------------------- **Enzyme** **Function*...

**LESSON 6.1** **ENZYME STRUCTURE AND FUNCTION** - Enzymes are essential to the body's normal functions. Many of these end with the suffix -ase. **Examples of Enzymes** ---------------- ----------------------------------------------------------------------- **Enzyme** **Function** ***Amylase*** an enzyme found in saliva that helps digest starch ***Trypsin*** an enzyme found in the small intestine that helps break down proteins ***Helicase*** an enzyme that helps in unwinding DNA in the process of replication ***Helicase*** an enzyme that helps in breaking down the sugar lactose ---------------- ----------------------------------------------------------------------- **PROTEIN STRUCTURE** **Primary** - The *primary structure of a protein* **refers to the specific sequence of amino acids in a polypeptide chain.** **Secondary**  The secondary structure ***refers to the protein's folding pattern.*** **Tertiary** The tertiary structure refers to **how the polypeptides form the shape of the molecule.** **Quaternary**  The quaternary structure refers to the **subunits of the protein.** **ENZYME STRUCTURE** Binding site - *[Amino acid]* residues that function **to bind or accommodate the substrate molecule** Catalytic site - *[Amino acid]* residues in the **active site that serve to speed up or catalyze the reactions once binding has occurred** **ENZYME-SUBSTRATE COMPLEXES**  Enzyme-substrate binding **Substrates** - ***molecule that the reactions*** - of which are ***catalyzed by the enzymes.*** - Each enzyme is specific to a substrate. **Products** - ***Once the enzyme and substrate are bound to each other*** and the ***reaction has occurred,*** - a product is then produced by the enzyme. **ENZYME-SUBSTRATE MODELS** ***[Lock-and-Key:]*** - The **specific shape** **between the active site and the substrate** allows only that type of binding to occur between these two molecules. ***[Induced Fit:]*** - ***Interaction is initially weak*** but the ***bond strengthens*** as the active site is modified.  **REMEMBER** - A good indicator for identifying whether a molecule is an enzyme is the **presence of the suffix -ase.** - However, *[not all enzymes end with that suffix]*. - Notable examples are the ***digestive enzymes pepsin, pepsinogen, trypsin, and rennin.*** **FUNCTIONS OF ENZYMES** ***[Functions]*** 1. **C**atalysis of chemical reactions 2. **S**everal functions in the body 3. **F**unctions in cellular processes **Enzymes as Catalysts** - **Catalysis** is the speeding up of reaction rates that are specific to the type of substrate and enzyme involved. Difference in the activation energy between a catalyzed and an uncatalyzed reaction - The ***lowering of the activation energy is possible*** because enzymes modify the reactants into a state known as the **transition state.**  ***Transition states of the reactants*** allow the catalysis of their reactions. **ENZYMES' ROLES IN THE BODY** ---------------------- ----------------------------------------------------------------------------------------------------------- **Function** **Enzymes Involved** **Digestion** Enzymes like amylase, trypsin, pepsin, lactase, and others help in breaking down molecules for digestion. **Cell division** Enzymes like the cyclin-dependent kinases (Cdks) help in modifying proteins for cell division. **Nervous function** Acetylcholinesterase helps in the breakdown of acetylcholine, which is necessary for nerve function. **DNA replication** Many enzymes, like helicase and DNA polymerase, all help cells replicate DNA. ---------------------- ----------------------------------------------------------------------------------------------------------- **Identify the term being described in each of the following statements.** 1. This function of enzymes refers to their ability to speed up chemical reactions. 2. This is the amount of energy needed for a chemical reaction to begin. 3. This is the molecule, the reaction of which is catalyzed by the enzyme. **Refer to the following graph to answer the questions below. Write the number that corresponds to your answer.** 1. Which part of the graph symbolizes the reactants? 2. Which signifies the presence of an enzyme? 3. Which signifies a faster rate of chemical reactions? **SUMMARY** - **Enzymes** are biomolecules that **help in speeding up the chemical reactions** that *occur in cells*. - Cells will require a *large amount of energy to drive chemical reactions* if **enzymes** are not present. - ***Each enzyme has an area known as the [active site]***[,] which is the area that *[recognizes the substrate molecule.]* - For enzymes to perform their specific functions, they usually need to ***bind to a substrate***. - A **substrate** is a molecule, the reactions of which are catalyzed by enzymes. - In the **[lock-and-key model,]** the *specific shape between the active site and the substrate* *allows only that type of binding to occur between the two molecules.* - The **induced-fit model** states that the *interaction between the enzyme's active site and the substrate is initially weak* but leads to the modification of the active site to strengthen the bond between the two molecules.  Enzyme-substrate complex models vary according to whether the active site changes its shape in the presence of substrate molecules.