General Biology Exam 1 Study Guide: Chemistry of Life, Water, and Biological Molecules

General Information & Scientific Method

Introduction to Scientific Inquiry

The scientific method is a systematic approach used in biology to investigate natural phenomena. It involves observation, hypothesis formation, experimentation, and analysis.

• Observation: Gathering information about a phenomenon.

• Hypothesis: A testable statement or prediction.

• Experiment: A controlled procedure to test the hypothesis.

• Independent Variable: The factor that is changed in an experiment.

• Dependent Variable: The factor that is measured.

• Control Group: The group that does not receive the experimental treatment.

• Data Analysis: Using graphs and statistics to interpret results.

Example: Testing the effect of sunlight on plant growth by varying light exposure and measuring height.

Basic Chemistry

Atoms, Elements, and Bonds

Understanding the chemical basis of life is essential in biology. Atoms are the basic units of matter, composed of protons, neutrons, and electrons.

• Element: A pure substance consisting of one type of atom (e.g., Carbon, Oxygen).

• Compound: A substance formed from two or more elements chemically bonded.

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

• Isotope: Atoms of the same element with different numbers of neutrons.

Chemical Bonds:

• Covalent Bond: Atoms share electrons.

• Ionic Bond: Atoms transfer electrons, forming charged ions.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen in water).

Example: Water molecules are held together by hydrogen bonds, giving water its unique properties.

Properties of Water

Water's Unique Characteristics

Water is vital for life due to its chemical and physical properties.

• Cohesion and Adhesion: Water molecules stick to each other and to other surfaces.

• Thermal Regulation: Water absorbs and releases heat slowly, stabilizing temperatures.

• Expansion Upon Freezing: Ice is less dense than liquid water, allowing it to float.

• Universal Solvent: Water dissolves many substances due to its polarity.

Property	Biological Importance
Cohesion	Transport of water in plants
Adhesion	Water movement in capillaries
High Specific Heat	Temperature stability in organisms
Solvent	Dissolves nutrients and gases

Acids and Bases:

• Acid: Substance that increases hydrogen ion concentration ($[H^+]$).

• Base: Substance that decreases hydrogen ion concentration.

• pH Scale: Measures acidity or alkalinity (0-14).

• Buffer: Substance that minimizes changes in pH.

Example: Blood contains buffers to maintain a stable pH.

Carbon Chemistry & Organic Molecules

Organic Molecules and Functional Groups

Carbon forms the backbone of biological molecules due to its ability to form four covalent bonds.

• Hydrocarbons: Compounds of hydrogen and carbon.

• Isomers: Molecules with the same formula but different structures.

• Functional Groups: Specific groups of atoms that confer properties to molecules:

  • Hydroxyl (-OH)

  • Carbonyl (C=O)

  • Carboxyl (-COOH)

  • Amino (-NH2)

  • Methyl (-CH3)

  • Phosphate (-PO4)

Example: Amino acids contain both amino and carboxyl groups.

Biological Macromolecules

Polymers and Monomers

Biological macromolecules are large molecules made from smaller units called monomers.

• Polymer: Long chain of monomers.

• Dehydration Synthesis: Reaction that joins monomers by removing water.

• Hydrolysis: Reaction that breaks polymers by adding water.

Carbohydrates

Carbohydrates are energy sources and structural components.

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

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

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

Type	Function
Starch	Energy storage in plants
Glycogen	Energy storage in animals
Cellulose	Structural support in plants

Glycosidic Linkage: Covalent bond joining carbohydrate monomers.

Lipids

Lipids are hydrophobic molecules used for energy storage and cell membranes.

• Fats: Composed of glycerol and fatty acids.

• Saturated Fats: No double bonds, solid at room temperature.

• Unsaturated Fats: One or more double bonds, liquid at room temperature.

• Phospholipids: Major component of cell membranes; amphipathic (hydrophilic head, hydrophobic tail).

• Steroids: Lipids with four fused rings (e.g., cholesterol).

Proteins

Proteins are polymers of amino acids and perform diverse functions.

• Amino Acids: Building blocks of proteins; 20 types with different side chains.

• Peptide Bond: Covalent bond between amino acids.

• Protein Structure:

  • Primary: Sequence of amino acids

  • Secondary: Alpha helix and beta sheet

  • Tertiary: 3D folding

  • Quaternary: Multiple polypeptides

Example: Hemoglobin is a protein with quaternary structure.

Nucleic Acids

Nucleic acids store and transmit genetic information.

• DNA (Deoxyribonucleic Acid): Double helix, stores genetic code.

• RNA (Ribonucleic Acid): Single-stranded, involved in protein synthesis.

• Nucleotide: Monomer of nucleic acids, composed of a sugar, phosphate group, and nitrogenous base.

• Phosphodiester Bond: Covalent bond joining nucleotides.

Component	Function
Sugar	Forms backbone
Phosphate	Links sugars
Nitrogenous Base	Encodes genetic information

Additional info:

• Practice questions and answer key included in the file reinforce understanding of hydrogen bonds, water properties, pH buffers, and macromolecule functions.

• Structural formula of adrenaline is provided for functional group identification.