General Biology Lab Study Guide: Measurements, Acids & Bases, Molecules, and Microscopy

1. Laboratory Practices

1.1 Keeping a Lab Notebook

Maintaining a detailed and organized lab notebook is essential for recording experimental procedures, observations, and results. Accurate record-keeping ensures reproducibility and scientific integrity.

• Purpose: To document all aspects of laboratory work for future reference and validation.

• Best Practices: Record dates, experiment titles, objectives, methods, data, and conclusions. Use ink and do not erase entries; instead, cross out errors with a single line.

• Legal and Academic Importance: Lab notebooks can serve as legal documents and are often required for academic assessment.

2. Measurements and Units

2.1 Metric Prefixes and Unit Conversions

Understanding metric prefixes and unit conversions is fundamental in biology for accurate measurement and data analysis.

• Common Prefixes: micro- (10-6), nano- (10-9), milli- (10-3), centi- (10-2), kilo- (103), etc.

• Unit Conversion: To convert between units, multiply or divide by the appropriate power of ten.

• Example: 1 millimeter (mm) = 0.001 meters (m).

• Know Terms: Be familiar with all measurement terms and their abbreviations.

Note: No questions about chi-squared calculations will be included.

3. Acids and Bases

3.1 pH and the pH Scale

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or basicity.

• pH Definition: pH = -log10[H+]

• Scale: Ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.

• Example: A solution with [H+] = 1 x 10-7 M has a pH of 7.

3.2 Acids and Bases in the Lab

• Common Reagents: Hydrochloric acid (HCl) and sodium hydroxide (NaOH) are often used to adjust pH in experiments.

• Application: These are typically added in controlled amounts using dropper bottles.

3.3 Variables in Experiments

• Dependent Variable: The variable measured in an experiment (e.g., pH).

• Independent Variable: The variable manipulated by the experimenter (e.g., number of drops added).

3.4 Buffer Range and pH Shifts

• Buffer Range: The range of pH over which a buffer can effectively neutralize added acids or bases.

• Experimental Analysis: By adding acid and measuring pH shifts, you can determine which solution is a better buffer (less pH change indicates a better buffer).

3.5 Hydrogen Ion Concentration and pH

• Relationship: Each decrease of 1 pH unit increases [H+] by 10 times.

• Example: A solution with pH 1 has 1000 times more H+ than a solution with pH 4.

Formula:

$[H^+] = 10^{-pH}$

4. Biological Molecules

4.1 Recognizing and Naming Molecules

Understanding the structure and function of biological molecules is central to biology. You should be able to recognize and name key molecules from diagrams or models.

• Common Molecules: Water (H2O), oxygen (O2), carbon dioxide (CO2), maltose, glycerol, fatty acids, triglycerides, cholesterol, amino acids, peptides, ATP.

• Ball-and-Stick Models: These models represent atoms as balls and bonds as sticks, helping visualize molecular structure.

4.2 Functional Groups

• Methyl (-CH3): Nonpolar, hydrophobic group.

• Hydroxyl (-OH): Polar, found in alcohols.

• Amino (-NH2): Basic, found in amino acids.

• Carboxyl (-COOH): Acidic, found in amino acids and fatty acids.

4.3 Peptide Bonds and Polypeptides

• Peptide Bond: A covalent bond formed between the amino group of one amino acid and the carboxyl group of another.

• Counting Peptide Bonds: A polypeptide with n amino acids has n-1 peptide bonds.

• Example: 29 amino acids = 28 peptide bonds.

4.4 Water Release During Synthesis

• Dehydration Synthesis: Formation of peptide bonds or triglycerides releases water molecules.

• Example: Building a tripeptide (3 amino acids) releases 2 water molecules.

• Triglyceride Formation: Glycerol + 3 fatty acids → triglyceride + 3 H2O.

4.5 Key Biological Molecules to Recognize

• Water (H2O)

• Oxygen (O2)

• Carbon Dioxide (CO2)

• Maltose (disaccharide)

• Glycerol

• Saturated Fatty Acid

• Monounsaturated Fatty Acid

• Triglyceride

• Steroid (cholesterol)

• Amino Acids (glycine and alanine)

• Dipeptide, Tripeptide

• ATP (adenosine triphosphate)

5. Microscopy

5.1 Parts and Functions of the Microscope

Microscopes are essential tools in biology for observing cells and microorganisms. Knowing the parts and their functions is crucial for proper use.

• Eyepiece (Ocular Lens): The lens you look through, usually 10x magnification.

• Objective Lenses: Provide various magnification levels (e.g., 4x, 10x, 40x, 100x).

• Stage: Platform where the slide is placed.

• Coarse and Fine Focus: Used to bring the specimen into clear view.

• Light Source: Illuminates the specimen.

• Condenser and Diaphragm: Focus and adjust the amount of light.

5.2 Identifying Organisms

• Common Specimens: Be able to identify flea, tick, and mite under the microscope based on their morphology.

Additional info: For all molecule recognition, students should be familiar with both 2D structural formulas and 3D ball-and-stick models. For microscopy, practice identifying key features of arthropods (flea, tick, mite) using reference images.