Enzymes PDF

## Enzymes ### Function of Enzymes - **Enzymes** can break down **substrates.** - **Starch + Water** → **Maltose** - **Maltose + Water** → **Glucose** - **Protein + Water** → **Amino acid** - **Lipids + Water** → **Glycerol + 3 fatty acids** - Enzymes can build up large molecules f...

## Enzymes ### Function of Enzymes - **Enzymes** can break down **substrates.** - **Starch + Water** → **Maltose** - **Maltose + Water** → **Glucose** - **Protein + Water** → **Amino acid** - **Lipids + Water** → **Glycerol + 3 fatty acids** - Enzymes can build up large molecules from smaller ones. - **Glucose + Glucose** → **Maltose** - **Glucose + Glucose + Glucose + Glucose** → **Glycogen** (in animal cells) - **Starch** (in plant cells) ### Role of Enzymes in Chemical Reactions 1. **Enzymes** can **be reused** 2. **Enzymes** **lower the activation energy** ### Effect of Temperature on Enzyme Activity * **Describe:** * Enzyme activity (rate of reaction) increases until it reaches the optimal temperature * Beyond the optimal temperature, enzyme activity decreases and eventually reaches zero * **Explain:** * **a.** At low temperatures, the molecules have low kinetic energy and collide less frequently, resulting in slower reactions. * **b.** As the temperature increases, the kinetic energy of the molecules increases, resulting in more frequent collisions and faster reactions. * **c.** At the optimal temperature, the enzyme reaches its peak activity. * **d.** At temperatures above the optimal, the enzyme begins to denature, losing its shape and function. This is due to the breaking of the weak bonds that hold the enzyme together. ### Denaturation - Enzymes lose the shape of their active site. - Substrates cannot fit and bind to the active site. - Enzymes cannot perform their function. ### Effect of pH on Enzyme Activity - **pH** is a measure of the concentration of hydrogen ions (H+) in a solution. - **Acidic pH:** pH lower then 7. - **Alkaline pH:** pH higher than 7. - **Neutral pH:** pH of 7 - **Each** enzyme works best at a **specific pH**. ### Effect of pH on Enzyme Activity - Enzyme activity is highest at the optimal pH, where the active site of the enzyme has the correct shape for the substrate to bind. - As the pH moves away from the optimal, the enzyme activity decreases due to changes in the shape of the active site. - At extreme pH values, the enzyme can become denatured, losing its function completely. ### Examples of Enzyme Activity at Different pH - **Pepsin** (enzyme in stomach) works best at an acidic pH (pH 1.5). - **Amylase** (enzyme in saliva) works best at a neutral pH (pH 7). - **Lipase** (enzyme in small intestine) works best at an alkaline pH (pH 8). ### The Role of Enzymes in Seed Germination - **Seed germination** is the process by which a seed develops into a new plant. - **Dry broad bean:** - **Testa:** The outer covering of the seed, which is impermeable to water. - **Micropyle:** A small pore in the testa through which water enters the seed. - **Cotyledon:** The first leaves of the plant, which store food reserves. - **Starch, protein, lipid, and enzymes** are stored in the cotyledons. - **Plumule:** The shoot tip of the plant - **Radicle:** The root tip of the plant #### Steps of Seed Germination 1. **Absorption of water:** - Water enters the seed through the micropyle and activates the enzymes. 2. **Amylase breaks down starch to Maltose:** - This is a **hydrolysis** reaction, where water molecules are used to break down the starch molecule into smaller maltose molecules. 3. **Maltose is converted to glucose:** - The maltose molecules are then converted to glucose molecules through another hydrolysis reaction. 4. **Glucose diffuses into the cells of the embryo:** - The glucose provides the energy needed for the embryo to grow. 5. **Respiration and energy release:** - The embryo uses the glucose as fuel for respiration, which releases energy for growth and development. 6. **Phloem transports small water-soluble molecules such as glucose and amino acids from the source (cotyledon) to sink (cells of the embryo)** - The phloem is a type of vascular tissue in plants that transports food and nutrients. ### Protease breaks down protein to amino acid, to be used by the embryo cells in growth. ### Investigations 1. **Starch + drops of iodine solution (yellow) → color becomes blue-black** - Iodine solution is a reagent that turns blue-black in the presence of starch. 2. **Effect of Amylase on Starch:** - **Procedure:** - Prepare a solution of amylase in a buffer solution (to maintain a constant pH). - Add a few drops of iodine solution to a few test tubes. - Add a measured amount of starch solution to each test tube. - Add a few drops of the amylase solution to one of the test tubes. - Leave the test tubes at room temperature. - Observe the color change in the test tubes at different times. - **Results:** - The test tube containing amylase will show a gradual change in color from blue-black to light blue, and eventually to a yellow-brown color. - The test tube without amylase will remain blue-black. - **Analysis:** - The amylase breaks down the starch into smaller sugar molecules, which do not react with iodine solution. - The change in color indicates the breakdown of starch by amylase. ### Effect of Catalase on H₂O₂ - **Procedure:** - Place a potato disc in a test tube containing hydrogen peroxide (H₂O₂). - Observe the formation of bubbles. - **Results:** - Bubbles of oxygen gas (O₂) are produced. - The disc floats to the surface due to the production of oxygen gas. - **Analysis:** - **Catalase** is an enzyme that catalyzes the decomposition of hydrogen peroxide into water and oxygen. - The faster the bubbles form, the more active the catalase. - Hydrogen peroxide (H₂O₂) is a toxic byproduct of cellular metabolism, so it is important to break it down.