Lab Exam 1 Study Guide PDF

Lab Exam 1 Study Guide Lab #1: Experimental Design, Lab Fundamentals, and Diffusion Hypothesis: A testable statement predicting the outcome of an experiment. Dependent Variable: The outcome being measured, affected by changes in the independent variable. Independent Variable: T...

Lab Exam 1 Study Guide Lab #1: Experimental Design, Lab Fundamentals, and Diffusion Hypothesis: A testable statement predicting the outcome of an experiment. Dependent Variable: The outcome being measured, affected by changes in the independent variable. Independent Variable: The variable manipulated by the researcher to observe its effect on the dependent variable. Random Errors: Unpredictable variations in measurements (e.g., environmental changes). Systematic Errors: Consistent, repeatable errors (e.g., calibration issues). Metric Conversions: 1 milliliter (mL) = 1000 microliters (μL); 1 liter (L) = 1000 milliliters (mL). Micropipette Use: Set volume, use appropriate tip, avoid air bubbles, dispense smoothly. Volume Inaccuracy Factors: User error, wrong tip, bubbles in the tip. Rate of Diffusion: Affected by temperature, molecule size, and concentration gradient. ○ Higher temp → Diff Increases ○ Bigger Molecule size → Diff Decreases ○ A steeper concentration gradient (large difference in concentration between two areas) increases the rate of diffusion Lab #2: Microscopy Microscope Parts: Eyepiece, objective lenses, stage, coarse/fine focus knobs. Microscope Types: Light microscopes use light; electron microscopes use electrons. Total Magnification: Magnification of eyepiece x magnification of objective lens. ○ Objective lens = 10 Field of View: Area visible through the microscope; decreases as magnification increases. Magnification vs. Resolution: Magnification enlarges, resolution clarifies. Cell Staining: Enhances contrast to view transparent structures. ○ When you dye them Lab #3: Biological Molecules Monomers vs. Polymers: Monomers are single units; polymers are chains of monomers. Categories of Biological Molecules: Carbohydrates, proteins, lipids, nucleic acids. Dehydration Reaction: Joins monomers by removing water. Amino/Carboxyl Groups: Structural components of amino acids. Protein Structures: ○ Primary: Amino acid sequence.  ○ Secondary: Alpha helices or beta sheets. ○ Tertiary: 3D folding. ○ Quaternary: Multiple polypeptides. Triglycerides vs. Monoglycerides: Three vs. one fatty acid chain. DNA Structure: Double helix; bases pair as A-T and G-C. Purines/Pyrimidines: Purines = Adenine, Guanine; Pyrimidines = Thymine, Cytosine. Indicators: ○ Benedict's Test (for reducing sugars): Purpose: Detects the presence of reducing sugars, like glucose and fructose. Procedure: A sample is mixed with Benedict's reagent and heated. Positive Result: If reducing sugars are present, the solution changes color from blue to green, yellow, orange, or brick-red, depending on the amount of sugar. Negative Result: The solution remains blue. ○ Biuret Test (for proteins): Purpose: Identifies the presence of peptide bonds, which are indicative of proteins. Procedure: Biuret reagent (a blue solution) is added to the sample. Positive Result: The solution turns violet or black when proteins are present. Negative Result: The solution remains blue. ○ Iodine Test (for starch) (carbohydrate) Purpose: Detects the presence of starch (a polysaccharide). Procedure: Iodine solution (brownish-yellow) is added to the sample. Positive Result: The solution turns a dark blue or black color if starch is present. Negative Result: The solution remains yellowish-brown.  ○ Sudan IV Test (for lipids): Purpose: Detects lipids (fats and oils). Procedure: Sudan IV, a fat-soluble dye, is added to the sample. Positive Result: Lipids absorb the dye and appear as red-stained oil droplets. Top layer: red-orange Bottom: white Negative Result: No red-staining, and the solution remains uncolored or uniformly pink. One layer Ninhydrin Test (for amino acids): Purpose: Detects free amino acids, which are the building blocks of proteins. Lab #4: Enzyme Kinetics Spectrophotometer: Measures absorbance to determine concentration. ○ Absorbance vs. Concentration: Higher absorbance = higher concentration. Enzyme: A biological catalyst that speeds up chemical reactions in cells without being consumed in the process. Enzymes are usually proteins. Substrate: The specific molecule that an enzyme acts upon in a reaction. Enzyme-Substrate Complex: A temporary molecule formed when the enzyme binds to its substrate at the enzyme's active site. Active Site: The region on the enzyme where the substrate binds. The shape and chemical environment of the active site allow the enzyme to interact with its substrate. Activation Energy: The minimum amount of energy required to initiate a chemical reaction. How Enzymes Work: Enzymes facilitate reactions by lowering the activation energy, making it easier for reactions to occur. By lowering the activation energy, enzymes allow reactions to proceed faster than they would without a catalyst. Factors Affecting the Rate of a Reaction: Several factors can influence the rate at which enzymes catalyze reactions: 1. Substrate Concentration: Increasing substrate concentration increases the reaction rate until the enzyme becomes saturated. Once all active sites are occupied, increasing substrate levels won’t speed up the reaction further.  2. Enzyme Concentration: More enzyme molecules increase the rate of the reaction, provided there is enough substrate available. 3. Temperature: Reaction rates typically increase with temperature, but high temperatures can denature the enzyme (change its structure), reducing activity. 4. pH: Each enzyme has an optimal pH at which it works best. Deviation from this pH can alter the enzyme’s shape and function. Enzyme Kinetics: ○ Vmax: Maximum reaction rate. ○ Km: Substrate concentration at half Vmax. pH and Temperature: Affect enzyme activity by altering shape or stability. Michaelis-Menten Kinetics: Describes the rate of enzyme-catalyzed reactions. Vmax: The maximum velocity or rate of the reaction when the enzyme is fully saturated with substrate. At this point, increasing substrate concentration won’t increase the reaction rate. Km (Michaelis constant): The substrate concentration at which the reaction rate is half of Vmax. It represents the enzyme’s affinity for the substrate: Lab #5: Chemotaxis and Bioconvection Chemotaxis: Movement of organisms (e.g., Tetrahymena) toward or away from chemicals. cellobiase is an enzyme that catalyzes the breakdown of cellobiose, a disaccharide, into two glucose molecules. - In the detection system, a substrate analog (usually a synthetic molecule resembling cellobiose) is used, which releases a colored product upon enzymatic cleavage. How it works: 1. Cellobiase reacts with the substrate analog, breaking it down. 2. A colored product is released, which can be measured using a spectrophotometer to quantify enzyme activity. 3. Absorbance is directly proportional to the amount of product formed and thus reflects the enzyme’s activity. Analyzing a hypothetical experiment: If you have varying enzyme concentrations or different conditions (e.g., pH, temperature), you can measure the absorbance at different time points to determine how these factors affect cellobiase activity. Higher absorbance indicates more product formation, suggesting higher enzyme activity. Chemorepellents vs. Chemoattractants: Substances that repel or attract organisms. Pattern Formation: Due to gradients or environmental factors. C1V1 = C2V2: Concentration and volume equation used in dilutions. Lab #6: Osmosis and Phagocytosis Osmosis: Movement of water across a semipermeable membrane from low to high solute concentration. Tonicity: ○ Hypertonic: More solute outside the cell, water leaves the cell. ○ Hypotonic: Less solute outside, water enters the cell. ○ Isotonic: Equal solute, no net water movement. Cell Membrane: Composed of a phospholipid bilayer; hydrophilic heads, hydrophobic tails. Phagocytosis: Cell "eating"; lysosomes digest engulfed particles.