BSC2010L Final Review: Laboratory Concepts and Techniques in Biology

Syllabus Review and Introductory Material

Course Overview and Lab Safety

• Course Content: Students are responsible for all material covered in the syllabus and introductory PowerPoint, including laboratory procedures and equipment operation.

• Lab Safety: Understand all safety protocols, including proper handling of chemicals, biological materials, and equipment. Always wear appropriate personal protective equipment (PPE) and follow emergency procedures.

Lab 1: Scientific Method and Laboratory Techniques

Scientific Method and Experimental Design

• Scientific Method: A systematic approach to inquiry involving observation, hypothesis formation, experimentation, and conclusion.

• Hypothesis: A testable and falsifiable statement predicting an outcome.

• Variables:

  • Independent Variable: The factor manipulated by the experimenter.

  • Dependent Variable: The factor measured in response to changes in the independent variable.

  • Control: A standard for comparison, not exposed to the experimental treatment.

Laboratory Equipment and Measurements

• Measuring Tools: Know how to use serological pipettes, micropipettes, and graduated cylinders accurately.

• Spectrophotometer: Measures the absorbance of light by a solution at specific wavelengths to determine concentration.

• Absorption Spectrum: A graph showing how a substance absorbs light across different wavelengths; used to identify substances and determine concentrations.

• Standard Curve: A plot of known concentrations versus absorbance; used to determine the concentration of unknown samples.

Example: Standard Curve Equation

$y = mx + b$ Where $y$ is absorbance, $x$ is concentration, $m$ is the slope, and $b$ is the y-intercept.

Lab 2 & 3: Microscope Investigations

Microscopy Basics

• Parts of a Microscope: Know the function of the ocular lens, objective lenses, stage, condenser, diaphragm, coarse and fine focus knobs, and light source.

• Key Terms:

  • Magnification: The degree to which an image is enlarged.

  • Resolution: The ability to distinguish two points as separate.

  • Contrast: The difference in light intensity between the specimen and background.

  • Depth of Field: The thickness of the specimen that is in focus at one time.

  • Index of Refraction: A measure of how light bends as it passes through different media.

• Microscope Techniques: Preparing wet mounts, using immersion oil, and focusing properly.

• Calculations: Total magnification = (ocular lens) × (objective lens).

• Field of View: Estimate cell size using the diameter of the field of view at a given magnification.

• Metric Conversions: 1 meter = 1000 mm = 1,000,000 μm; 1 liter = 1000 ml = 1,000,000 μl.

Cell Types and Organelles

• Prokaryotic vs. Eukaryotic Cells:

  • Prokaryotes: No nucleus, no membrane-bound organelles (e.g., bacteria).

  • Eukaryotes: Nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

• Classification: Identify organisms as prokaryotes/eukaryotes, photosynthetic/non-photosynthetic.

• Cell Size Limitation: Surface area-to-volume ratio limits cell size; larger cells use adaptations (e.g., vacuoles in plants) to survive.

• Endosymbiont Theory: Mitochondria and chloroplasts originated from symbiotic bacteria; evidence includes double membranes and their own DNA.

Lab 4: Diffusion and Osmosis

Principles of Diffusion and Osmosis

• Diffusion: Movement of molecules from high to low concentration (down a concentration gradient) until dynamic equilibrium is reached.

• Temperature: Higher temperatures increase the rate of diffusion.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Tonicity:

  • Hypertonic: Higher solute concentration outside the cell; cell loses water.

  • Hypotonic: Lower solute concentration outside; cell gains water.

  • Isotonic: Equal solute concentrations; no net water movement.

• Effects on Cells:

  • Plant Cells: Turgid in hypotonic, plasmolyzed in hypertonic, flaccid in isotonic solutions.

  • Animal Cells: Lyse in hypotonic, crenate in hypertonic, normal in isotonic solutions.

  • Protists/Bacteria: Use contractile vacuoles or cell walls to manage osmosis.

• Osmometer: Device to measure solute concentration by observing water movement.

• Potato Experiment: Observing mass changes in potatoes placed in solutions of varying solute concentrations demonstrates osmosis.

Lab 5: Cellular Respiration and Fermentation

Metabolic Pathways

• Fermentation: Anaerobic process producing ATP; types include alcohol and lactic acid fermentation.

• Cellular Respiration: Aerobic process converting glucose to ATP, CO2, and H2O.

• Summary Equations:

Aerobic Respiration: $\mathrm{C_6H_{12}O_6} + 6\mathrm{O_2} \rightarrow 6\mathrm{CO_2} + 6\mathrm{H_2O} + \text{energy (ATP)}$

Alcohol Fermentation: $\mathrm{C_6H_{12}O_6} \rightarrow 2\mathrm{C_2H_5OH} + 2\mathrm{CO_2} + \text{energy (ATP)}$

• Carbohydrates: Monosaccharides (simple sugars), disaccharides (two sugars), polysaccharides (many sugars).

• Measuring Fermentation: Use fermentation tubes to measure CO2 production.

• Redox in Respiration: Glucose is oxidized; oxygen is reduced.

• Measuring Respiration: Methods include respirometers, CO2 sensors, and O2 consumption.

• Factors Affecting Respiration: Temperature, substrate availability, and inhibitors can decrease the rate.

Lab 6: Photosynthesis

Photosynthetic Processes

• Autotrophs vs. Heterotrophs: Autotrophs produce their own food (e.g., plants); heterotrophs consume others for energy.

• Photorespiration: A process where O2 is fixed instead of CO2, reducing photosynthetic efficiency.

• Light Energy: Photosynthetic organisms use pigments (e.g., chlorophyll) to capture light energy for the light-dependent reactions.

• Photosynthetic Anatomy: Key structures include chloroplasts, thylakoids (light reactions), and stroma (Calvin cycle).

• Photosynthesis Equation:

$6\mathrm{CO_2} + 6\mathrm{H_2O} + \text{light energy} \rightarrow \mathrm{C_6H_{12}O_6} + 6\mathrm{O_2}$

• Observed Organisms: S. obliquus and other algae.

• pH Changes: Photosynthesis decreases CO2, raising pH; respiration increases CO2, lowering pH.

• Data Interpretation: Compare algae in light (photosynthesizing) vs. dark (respiring only).

• Carbon Cycle: Photosynthesis removes CO2 from the atmosphere, cycling carbon through ecosystems.

• Comparison Table: Photosynthesis vs. Cellular Respiration

Feature	Photosynthesis	Cellular Respiration
Energy Source	Light	Glucose
Location	Chloroplasts	Mitochondria
Reactants	CO2, H2O	Glucose, O2
Products	Glucose, O2	CO2, H2O
Organisms	Autotrophs	All organisms

Lab 7 & 8: DNA Fingerprinting

DNA Analysis Techniques

• DNA Isolation and Quantification: Extraction and measurement of DNA concentration using spectrophotometry or fluorometry.

• Restriction Enzymes: Proteins that cut DNA at specific sequences, generating fragments of varying lengths.

• Gel Electrophoresis: Technique to separate DNA fragments by size using an electric field in an agarose gel.

• Loading DNA: DNA samples are loaded at the negative (cathode) end; DNA migrates toward the positive (anode) end.

• Fragment Migration: Smaller fragments move faster and farther than larger ones.

• Standard (Marker): DNA ladder with known fragment sizes used to estimate sample fragment sizes.

• Agarose Preparation: % w/v = (grams agarose / volume buffer in mL) × 100; higher % for smaller fragments, lower % for larger fragments.

• Interpreting DNA Fingerprints: Compare band patterns to identify genetic similarities or differences.

Lab 9 & 10: Introduction to Genetics

Cell Division and Genetics

• Onion Root Tip Mitosis: Identify stages: interphase, prophase, prometaphase, metaphase, anaphase, telophase. Estimate phase durations by counting cells in each stage.

• Genotype: Genetic makeup of an organism.

• Phenotype: Observable traits of an organism.

• Prokaryotic vs. Eukaryotic Division: Binary fission vs. mitosis/meiosis.

• P, F1, F2 Generations: Parental, first filial, and second filial generations in genetic crosses.

• Punnett Squares: Used to predict phenotypic ratios for monohybrid (one trait) and dihybrid (two traits) crosses.

• Dominant vs. Recessive Traits: Dominant alleles mask recessive alleles in heterozygotes.

• Homozygous: Two identical alleles; Heterozygous: Two different alleles.

• Yeast Life Cycle: Alternates between haploid and diploid stages via mitosis and meiosis.

• Recombination Frequency: Used to map gene loci; 1% recombination = 1 map unit.

• Sordaria Experiment: Ascospore color arrangements indicate crossing over during meiosis.

• Mitosis vs. Meiosis: Mitosis produces identical cells; meiosis produces genetically diverse gametes.

• Mendelian Laws:

  • Law of Segregation: Alleles separate during gamete formation.

  • Law of Independent Assortment: Genes on different chromosomes assort independently.

Additional info: Where details were not explicit, standard academic explanations and equations were provided for completeness and clarity.