Biology Quiz 2 Notes PDF

Biology Quiz 2 Notes ***Enzymes*** **What Are Enzymes?** - **Definition:** Enzymes are proteins that act as biological catalysts, speeding up chemical reactions by lowering the activation energy required for the reaction to proceed. - **Structure:** Enzymes have a tertiary or quatern...

Biology Quiz 2 Notes ***Enzymes*** **What Are Enzymes?** - **Definition:** Enzymes are proteins that act as biological catalysts, speeding up chemical reactions by lowering the activation energy required for the reaction to proceed. - **Structure:** Enzymes have a tertiary or quaternary structure, giving them a specific shape critical for their function. - **Properties:** - Highly specific for their substrates. - Reusable; not consumed in the reaction. - Often named with an \"-ase\" suffix (e.g., lactase, sucrase, catalase). **Key Definitions in Enzymes and Reactions** 1. **Substrate**: - The **reactant molecule** on which an enzyme acts. - It binds to the enzyme's **active site** to undergo a chemical transformation. - **Example**: - In the reaction catalyzed by amylase, **starch** is the substrate. 2. **Product**: - The **molecule(s)** formed after the enzyme catalyzes the reaction. - The substrate is converted into the product through enzymatic action. - **Example**: - Amylase breaks down starch into **maltose** and other sugars (products). 3. **Active Site**: - The specific **region on the enzyme** where the substrate binds. - It has a **specific shape** and chemical properties that match the substrate, allowing the enzyme to function with **high specificity**. - **Function**: - Facilitates the conversion of substrate into product by lowering the **activation energy** required for the reaction. **How Do Enzymes Work?** 1. **Enzyme-Substrate Interaction:** - The enzyme binds to a specific substrate at its **active site** to form an enzyme-substrate complex. 2. **Activation Energy Reduction: Catalysis** - Enzymes weaken substrates\' chemical bonds, reducing the required activation energy and facilitating faster reactions. 3. **Product Formation:** - The enzyme releases the products and returns to its original state, ready for another reaction. **Enzyme Mechanism Explained:** - **Lock-and-Key Model:** Enzymes and substrates fit together precisely, like a lock and key. - **Induced Fit Model:** The enzyme changes shape slightly to accommodate the substrate more snugly, enhancing the reaction\'s efficiency. - Enzyme denaturation refers to the structural alteration of an enzyme, leading to the loss of its biological activity. This occurs when the enzyme\'s three-dimensional shape is disrupted. **Factors Affecting Enzyme Activity** 1. **Environmental Conditions:** - **Temperature:** The optimal temperature for most human enzymes is 37°C (body temperature). High heat denatures enzymes. - Enzyme activity increases with temperature up to an optimal point. - Excessive heat causes denaturation (loss of shape and function). - **pH Levels:** - Most enzymes work best near a neutral pH (6-8). Extreme pH values can denature enzymes. - **Ionic Concentration:** High salt concentrations can disrupt enzyme ionic bonds, affecting their function. 2. **Cofactors and Coenzymes:** - Non-protein molecules that assist enzymes. - Examples: - **Cofactors:** Inorganic ions like zinc or iron. - **Coenzymes:** Organic molecules like vitamins. 3. **Inhibitors:** - **Competitive Inhibitors:** Bind to the active site, blocking the substrate. - **Non-Competitive Inhibitors:** Bind elsewhere, altering the enzyme\'s shape and functionality. **Optimal pH Levels for Common Enzymes** Enzymes have an optimal pH at which they are most active. Deviations can lead to reduced efficiency or denaturation. Here are the best pH levels for some key enzymes: 1. **Amylase** - **Optimal pH:** 6.7-7.0 - **Function:** Breaks down starch into maltose. - **Location:** Saliva and pancreas. 2. **Pepsin** - **Optimal pH:** 1.5-2.0 - **Function:** Break down proteins into peptides. - **Location:** Stomach. 3. **Trypsin** - **Optimal pH:** 7.5-8.0 - **Function:** Break down proteins into smaller peptides. - **Location:** Pancreas and small intestine. 4. **Lipase** - **Optimal pH:** 8.0 - **Function:** Break down fats into glycerol and fatty acids. - **Location:** Pancreas, active in the small intestine. 5. **Lactase** - **Optimal pH:** 6.0 - **Function:** Break down lactose into glucose and galactose. - **Location:** Small intestine. 6. **Catalase** - **Optimal pH:** 7.0 - **Function:** Break down hydrogen peroxide into water and oxygen. - **Location:** Found in most cells, especially liver and plant tissues. **Comparison of Catalase in Animals vs. Plants** - **Similarities:** - Found in peroxisomes. - Breaks down hydrogen peroxide into water and oxygen. - **Differences:** - **Plants:** Involved in managing photorespiration. - **Animals:** Detoxifies hydrogen peroxide in high-energy tissues like the liver. **Important Graphs**  Exploring Enzymes \| Scientific American ***Cellular Respiration*** Cellular respiration is the process by which living cells break down glucose and other molecules to release energy, which is then used to produce ATP---the primary energy currency of cells. This energy enables cellular functions vital for survival, such as growth, repair, and maintaining homeostasis. **Why Do You Need to Breathe?** Breathing supplies the oxygen necessary for aerobic cellular respiration. Without oxygen: - The electron transport chain (ETC) cannot function, halting ATP production. - Cells must resort to fermentation, which provides significantly less energy (only 2 ATP per glucose molecule). Breathing also removes carbon dioxide, a waste product of respiration, preventing it from accumulating to toxic levels. **Types of Respiration:** - **Aerobic Respiration:** Requires oxygen and produces a high yield of ATP. - **Anaerobic Respiration (Fermentation):** Occurs without oxygen, yielding less ATP and producing by-products like lactic acid or ethanol. **General Overview of Cellular Respiration** The overall reaction for aerobic respiration is: C6​H12​O6​+6O2​→6CO2​+6H2​O+Energy (36-38 ATP) Inputs and Outputs: - **Reactants:** Glucose and oxygen. - **Products:** Carbon dioxide, water, and ATP (energy). Why is ATP Important? - ATP powers various cellular processes such as active transport (e.g., pumping ions like Na⁺ and K⁺ across membranes), muscle contraction, and biosynthesis of molecules. - ATP acts like a rechargeable battery: when cells use energy, ATP is converted to ADP, which is then recharged back to ATP during cellular respiration. **Stages of Cellular Respiration in Detail** 1. **Glycolysis: The First Stage** - **Definition:** Glycolysis is the first step in breaking down glucose (a 6-carbon sugar) into two molecules of pyruvate (3-carbons each). - **Location:** Occurs in the cytoplasm. - **Details of Phases:** 1. **Energy Investment Phase:** - Two ATP molecules are used to phosphorylate glucose, making it more reactive. - Glucose is split into two 3-carbon molecules, glyceraldehyde-3-phosphate (G3P). 2. **Energy Payoff Phase:** - Each G3P is oxidized, transferring electrons to NAD⁺, forming 2 NADH. - Four ATP molecules are produced through substrate-level phosphorylation. - Two pyruvate molecules and two water molecules are the final products. - **Net Yield:** 1. **ATP:** 2 (4 produced - 2 consumed). 2. **NADH:** 2. 3. **Pyruvate:** 2. 2. **Pyruvate Oxidation (Link Reaction)** - **Definition:** Converts pyruvate into acetyl-CoA, preparing it for the citric acid cycle. - **Location:** Mitochondrial matrix. - **Steps:** 1. Pyruvate (3 carbons) is decarboxylated, releasing one molecule of CO₂. 2. The remaining 2-carbon fragment is oxidized, reducing NAD⁺ to NADH. 3. The oxidized fragment binds to coenzyme A, forming acetyl-CoA. - **Products per pyruvate:** 1. 1 NADH. 2. 1 CO₂. 3. 1 Acetyl-CoA. 3. **Citric Acid Cycle (Krebs Cycle)** - **Definition:** A cyclic series of reactions that further breaks down acetyl-CoA to generate electron carriers and ATP. - **Location:** Mitochondrial matrix. - **Key Steps:** 1. Acetyl-CoA (2-carbons) combines with oxaloacetate (4-carbons) to form citrate (6-carbons). 2. Citrate undergoes a series of transformations, releasing two CO₂ molecules and regenerating oxaloacetate. 3. Along the way, electrons are transferred to NAD⁺ and FAD, forming NADH and FADH₂. 4. One ATP (or GTP) is generated directly per cycle. - **Yield per acetyl-CoA:** 1. 3 NADH. 2. 1 FADH₂. 3. 1 ATP. 4. 2 CO₂. 4. **Electron Transport Chain (ETC) and Oxidative Phosphorylation** - **Definition:** A series of protein complexes in the inner mitochondrial membrane that use electrons from NADH and FADH₂ to produce ATP. - **Process:** 1. NADH and FADH₂ donate electrons to the ETC. 2. Electrons move through the complexes, releasing energy at each step. 3. This energy pumps H⁺ ions into the intermembrane space, creating a proton gradient. 4. H⁺ ions flow back into the matrix through ATP synthase, driving the production of ATP. 5. Oxygen is the final electron acceptor, combining with electrons and H⁺ to form water. - **Yield:** Approximately 28-32 ATP. **Fermentation: Anaerobic Pathway** - When oxygen is unavailable, cells switch to fermentation. - **Types:** 1. **Lactic Acid Fermentation:** Pyruvate is reduced to lactic acid (common in muscle cells). 2. **Alcoholic Fermentation:** Pyruvate is converted to ethanol and CO₂ (used by yeast). - **Net Yield:** 2 ATP per glucose (from glycolysis only). **Redox Reactions** - Cellular respiration involves oxidation-reduction (redox) reactions. - **Oxidation:** Loss of electrons (e.g., glucose is oxidized to CO₂). - **Reduction:** Gain of electrons (e.g., O₂ is reduced to H₂O). - **Electron Carriers:** - **NAD⁺ → NADH** and **FAD → FADH₂** transport high-energy electrons to the ETC. **ATP Yield Summary**  **Connection to the Ecosystem** - **Photosynthesis and Cellular Respiration Cycle:** - Plants convert sunlight into glucose via photosynthesis. - Animals and plants break down glucose during cellular respiration, releasing CO₂ and H₂O. - These products are used by plants for photosynthesis, completing the cycle. **Important Graphs** A diagram of a cell Description automatically generated  A diagram of a reaction Description automatically generated