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 presentations, including laboratory safety protocols and equipment operation.

• Lab Safety: Understand all safety rules, including proper handling of chemicals, biological materials, and equipment. Always wear appropriate personal protective equipment (PPE) and know 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, data collection, and conclusion.

• Hypothesis: A testable and falsifiable statement that predicts 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 that is 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 Equation: Beer-Lambert Law

• $A = \varepsilon c l$

• Where $A$ = absorbance, $\varepsilon$ = molar absorptivity, $c$ = concentration, $l$ = path length.

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 much light bends as it passes through a medium.

• Microscope Techniques: Preparing wet mounts, using immersion oil for high magnification, and proper focusing.

Calculations and Unit Conversions

• Total Magnification: Multiply ocular lens power by objective lens power.

• Field of View: Diameter decreases as magnification increases; used to estimate cell size.

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

Cell Types and Organelles

• Prokaryotes vs. Eukaryotes:

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

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

• 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 free-living prokaryotes engulfed by ancestral eukaryotic cells. Evidence includes double membranes, their own DNA, and similarities to bacteria.

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.

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

• Effect of Temperature: Higher temperatures increase the rate of diffusion.

Osmotic Environments

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

• Hypotonic: Lower solute concentration outside the cell; water enters the cell.

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

• Effects on Cells:

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

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

  • Adaptations: Contractile vacuoles in protists, cell walls in plants, osmoregulation in bacteria and animals.

Experimental Techniques

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

• Potato Experiment: Observing mass changes in potato slices placed in solutions of varying solute concentrations to determine osmotic behavior.

Lab 5: Cellular Respiration and Fermentation

Overview of Cellular Respiration and Fermentation

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

• Fermentation: Anaerobic process producing ATP and byproducts (e.g., alcohol or lactic acid) from glucose.

• Types of Fermentation: Alcoholic (yeast) and lactic acid (muscle cells, some bacteria).

Key Equations

• Aerobic Respiration:

  • $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \mathrm{ATP}$

• Alcohol Fermentation:

  • $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 \rightarrow 2\mathrm{C}_2\mathrm{H}_5\mathrm{OH} + 2\mathrm{CO}_2 + \mathrm{ATP}$

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides linked (e.g., sucrose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).

Experimental Measurement

• Fermentation Tubes: Used to measure CO2 production during fermentation.

• Cellular Respiration Measurement: Monitored by changes in gas volume, dye reduction, or other indicators.

• Redox Reactions: In respiration, glucose is oxidized and oxygen is reduced.

• Factors Affecting Respiration: Temperature, substrate availability, enzyme inhibitors, and oxygen levels can impact the rate.

Lab 6: Photosynthesis

Photosynthetic Processes

• Autotrophs: Organisms that produce their own food via photosynthesis (e.g., plants, algae).

• Heterotrophs: Organisms that consume other organisms for energy.

• Photorespiration: A process where O2 is consumed and CO2 is released, reducing photosynthetic efficiency.

Photosynthesis Equation

• $6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2$

Photosynthetic Anatomy and Function

• Chloroplasts: Site of photosynthesis; contains thylakoids (light reactions) and stroma (Calvin cycle).

• Observed Organisms: S. obliquus and other algae; be able to identify under the microscope.

• pH Changes: Photosynthesis increases pH (removes CO2), while respiration decreases pH (produces CO2).

• Light vs. Dark Experiments: Compare photosynthetic activity by measuring pH or other indicators in algae exposed to light versus darkness.

Photosynthesis and the Carbon Cycle

• Role in Carbon Cycle: Photosynthesis removes CO2 from the atmosphere, incorporating it into organic molecules.

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
Electron Carrier	NADP+/NADPH	NAD+/NADH

Lab 7 & 8: DNA Fingerprinting

DNA Isolation and Analysis

• DNA Isolation: Extraction of DNA from cells for analysis.

• Quantification: Measuring DNA concentration, often using spectrophotometry.

Restriction Enzymes and Gel Electrophoresis

• 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 Samples: DNA is loaded at the negative (cathode) end; fragments migrate 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 Concentration: Higher % agarose for smaller fragments, lower % for larger fragments.

Preparation and Interpretation

• Preparing Agarose Gel: Calculate mass and volume for any desired % (w/v) and total volume.

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

Lab 9 & 10: Introduction to Genetics

Cell Division and Microscopy

• Onion Root Tip Cells: Identify stages of mitosis: interphase, prophase, prometaphase, metaphase, anaphase, telophase.

• Estimating Phase Lengths: Count cells in each stage to estimate relative duration.

Genetics Terminology

• Genotype: Genetic makeup of an organism.

• Phenotype: Observable traits of an organism.

• Homozygous: Two identical alleles for a gene.

• Heterozygous: Two different alleles for a gene.

Inheritance Patterns

• 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.

Yeast Life Cycle and Genetic Mapping

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

• Recombination Frequency: Used to map gene distances; calculated as:

  • $\text{Recombination Frequency} = \frac{\text{Number of Recombinants}}{\text{Total Offspring}} \times 100\%$

• Map Units: 1% recombination = 1 map unit (centimorgan).

• Sordaria: Arrangement of ascospore colors indicates crossing over during meiosis.

Mitosis vs. Meiosis

• Mitosis: Produces two genetically identical diploid cells.

• Meiosis: Produces four genetically unique haploid cells; includes crossing over and independent assortment.

Mendelian Laws

• Law of Segregation: Each individual has two alleles for each gene, which segregate during gamete formation.

• Law of Independent Assortment: Genes for different traits assort independently during gamete formation.