General Biology Study Notes: Foundations, Macromolecules, and Nucleic Acids

The Scientific Process

Deductive vs. Inductive Reasoning

The scientific process relies on both deductive and inductive reasoning to form hypotheses and interpret data. Understanding the distinction between these reasoning types is essential for scientific inquiry.

• Deductive reasoning: Starts with a general principle or theory and applies it to specific cases to predict outcomes.

• Inductive reasoning: Involves making generalizations based on specific observations or experimental results.

• Interaction: Both reasoning types are used together to develop and test scientific theories.

Key Scientific Terms

• Observation: Gathering information through senses or instruments.

• Fact: An objective and verifiable observation.

• Hypothesis: A testable statement explaining observations.

• Theory: A well-substantiated explanation of some aspect of the natural world.

• Prediction: A statement about what will happen under specific conditions.

Variables in Experiments

• Dependent variable: The variable being tested and measured.

• Independent variable: The variable that is changed or controlled.

• Application: Identify variables in graphs and tables, and interpret experimental results.

Case Study Analysis

• Understand the experimental design, results, and interpretation.

• Be able to explain what was tested, findings, and their significance.

Bonds

Types of Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules. Understanding the types of bonds is crucial for explaining molecular structure and function.

• Covalent bonds: Atoms share electron pairs. Example: H2O (water).

• Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N). Example: Between water molecules.

• Noncovalent bonds: Include hydrogen bonds and other interactions like ionic and van der Waals forces.

Bond Construction and Diagrams

• Be able to identify and draw covalent and hydrogen bonds in molecular diagrams.

Strengths and Weaknesses of Bonds

• Covalent bonds: Strong, stable, form the backbone of biological molecules.

• Hydrogen bonds: Weaker, but important for structure and function (e.g., DNA base pairing).

• Application: Bonds are used for cellular processes such as energy storage, molecular recognition, and structural integrity.

Macromolecules

Polymers and Monomers

Macromolecules are large molecules composed of smaller units called monomers. The formation and breakdown of polymers involve specific chemical reactions.

• Polymer: A large molecule made of repeating monomer units.

• Monomer: A small molecule that can join with others to form a polymer.

• Dehydration reaction: Monomers are joined by removing water ($A + B \rightarrow AB + H_2O$).

• Hydrolysis: Polymers are broken down by adding water ($AB + H_2O \rightarrow A + B$).

• Water loss/gain: Water is lost during polymerization and gained during hydrolysis.

Types of Macromolecules

• Proteins:

  • Composed of amino acids (monomers).

  • Structure: Linear chains that fold into specific shapes.

  • Function: Enzymes, structural support, transport, signaling.

  • Structure-function relationship: The sequence and shape of a protein determine its function.

• Carbohydrates:

  • Monomers: Monosaccharides (e.g., glucose).

  • Polymers: Disaccharides, oligosaccharides, polysaccharides (e.g., starch, glycogen, cellulose).

  • Function: Energy storage, structural support.

  • Comparison: Ability to compare/contrast structures and functions.

• Lipids:

  • Types: Fats, phospholipids, steroids.

  • Function: Energy storage, membrane structure, signaling.

  • Structure: Hydrophobic molecules, not true polymers.

  • Examples: Triglycerides, cholesterol.

Table: Comparison of Macromolecules

Macromolecule	Monomer	Polymer	Main Function
Proteins	Amino acids	Polypeptides	Enzymes, structure, transport
Carbohydrates	Monosaccharides	Polysaccharides	Energy, structure
Lipids	Fatty acids, glycerol	Triglycerides, phospholipids	Energy, membranes, signaling
Nucleic acids	Nucleotides	DNA, RNA	Genetic information

Nucleic Acids

Structure and Components

Nucleic acids are polymers that store and transmit genetic information. The two main types are DNA and RNA.

• Phosphate group, sugar, base: Each nucleotide consists of these three components.

• DNA vs. RNA: DNA contains deoxyribose sugar; RNA contains ribose sugar.

• Base pairing: Purines (adenine, guanine) pair with pyrimidines (thymine, cytosine, uracil).

• Complementarity: Specific base pairing (A-T, G-C in DNA; A-U, G-C in RNA).

Overall Structure of DNA

• Double helix: Two strands twisted around each other.

• Hydrogen bonds: Hold complementary bases together.

• Antiparallel: Strands run in opposite directions (5' to 3' and 3' to 5').

• Writing sequences: Be able to write complementary DNA or RNA sequences.

RNA vs. DNA

• Uses: DNA stores genetic information; RNA is involved in protein synthesis and regulation.

• Structure: DNA is double-stranded; RNA is usually single-stranded.

• Bases: DNA uses thymine; RNA uses uracil.

Table: Comparison of DNA and RNA

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Strands	Double	Single
Bases	A, T, G, C	A, U, G, C
Function	Genetic storage	Protein synthesis, regulation

Levels of Protein Structure

• Primary structure: Sequence of amino acids.

• Secondary structure: Local folding (alpha helices, beta sheets).

• Tertiary structure: Overall 3D shape.

• Quaternary structure: Multiple polypeptide chains.

• Bonding: Types of bonds include peptide, hydrogen, ionic, and disulfide bonds.

• Denaturation/renaturation: Loss and recovery of structure due to environmental changes.

Base Pairing Rules

• Purines: Adenine (A), Guanine (G).

• Pyrimidines: Cytosine (C), Thymine (T), Uracil (U).

• Pairing: A-T (DNA), A-U (RNA), G-C (both).

Example: Writing a Complementary DNA Sequence

• Given: 5'-ATGC-3'

• Complementary: 3'-TACG-5'

Additional info: Some context and explanations have been expanded for clarity and completeness, including definitions, examples, and tables for comparison.