General Biology Study Guide: Scientific Process, Bonds, Macromolecules, and Nucleic Acids

The Scientific Process

Deductive vs. Inductive Reasoning

The scientific process relies on logical reasoning to draw conclusions from observations and experiments.

• Deductive reasoning: Starts with a general principle or theory and predicts specific results. (e.g., If all cells come from pre-existing cells, then observing cell division supports this theory.)

• Inductive reasoning: Begins with specific observations and develops general principles. (e.g., Observing that all examined organisms are made of cells leads to the cell theory.)

• Both types of reasoning are used together in scientific investigations.

Key Scientific Terms

• Observation: Gathering information using the senses or instruments.

• Fact: An observation that has been repeatedly confirmed.

• Hypothesis: A testable explanation for an observation or question.

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

• Prediction: A statement about what will happen under specific conditions, based on a hypothesis.

Variables in Experiments

• Independent variable: The factor that is changed or controlled by the experimenter.

• Dependent variable: The factor that is measured or observed in response to changes in the independent variable.

• Example: In testing the effect of sunlight on plant growth, sunlight is the independent variable, and plant growth is the dependent variable.

Data Interpretation

• Be able to interpret graphs, tables, and experimental results.

• Understand what the data shows, what variables were tested, and what conclusions can be drawn.

Bonds

Types of Bonds

Bonds are forces that hold atoms together in molecules and compounds. They determine the structure and properties of substances.

• Covalent bonds: Atoms share electron pairs. Strong and common in biological molecules (e.g., H2O, CH4).

• Ionic bonds: Electrons are transferred from one atom to another, creating charged ions that attract each other (e.g., NaCl).

• Hydrogen bonds: Weak attractions between a hydrogen atom covalently bonded to an electronegative atom (like O or N) and another electronegative atom. Important in water and DNA structure.

Bond Strengths and Biological Importance

• Covalent bonds are strong and stable, forming the backbone of most biological molecules.

• Hydrogen bonds are weaker but crucial for the structure of proteins and nucleic acids.

• Ionic bonds are important in cell signaling and maintaining cell structure.

Macromolecules

Macromolecules are large, complex molecules essential for life. The four main types are proteins, carbohydrates, lipids, and nucleic acids.

Polymers and Monomers

• Monomers: Small, repeating units that join to form polymers.

• Polymers: Large molecules made by linking monomers together.

• Dehydration reaction: Monomers are joined by removing a water molecule.

• Hydrolysis: Polymers are broken down into monomers by adding water.

Types of Macromolecules

• Proteins

  • Monomer: Amino acids

  • Structure: Primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple polypeptides)

  • Function: Enzymes, structural support, transport, signaling

  • Bonding: Peptide bonds link amino acids

• Carbohydrates

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

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

  • Function: Energy storage, structural support

• Lipids

  • Not true polymers, but grouped due to hydrophobic properties

  • Types: Fats (triglycerides), phospholipids, steroids

  • Function: Energy storage, membrane structure, signaling

• Nucleic Acids

  • Monomer: Nucleotides (phosphate group, sugar, base)

  • Polymer: DNA, RNA

  • Function: Store and transmit genetic information

Table: Comparison of Macromolecules

Macromolecule	Monomer	Bond Type	Main Functions
Proteins	Amino acids	Peptide bonds	Enzymes, structure, transport
Carbohydrates	Monosaccharides	Glycosidic bonds	Energy, structure
Lipids	Glycerol, fatty acids	Ester bonds	Energy, membranes, signaling
Nucleic Acids	Nucleotides	Phosphodiester bonds	Genetic information

Nucleic Acids

Structure and Components

• Nucleotide: Consists of a phosphate group, a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.

• Phosphate group, sugar, base: The backbone of nucleic acids is formed by alternating sugars and phosphates.

DNA vs. RNA

• DNA: Double-stranded, deoxyribose sugar, bases A, T, C, G

• RNA: Single-stranded, ribose sugar, bases A, U, C, G

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

Base Pairing Rules

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

• Purines: Adenine (A), Guanine (G)

• Complementary base pairing: A pairs with T (or U in RNA), C pairs with G

• Hydrogen bonds hold the base pairs together: A-T (2 bonds), C-G (3 bonds)

Structure of DNA

• Double helix: Two strands run in opposite directions (antiparallel)

• Hydrogen bonds between complementary bases

• 5' and 3' ends: Directionality is important for replication and transcription

Denaturation and Renaturation

• Denaturation: Separation of DNA strands due to heat or chemicals

• Renaturation: Rejoining of DNA strands under suitable conditions

Table: Comparison of DNA and RNA

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

Example: Writing a Complementary DNA Sequence

• Given a DNA strand 5'-ATCG-3', the complementary strand is 3'-TAGC-5'.

Additional info: This guide is based on lecture outlines and is suitable for exam preparation in a General Biology course. It covers foundational concepts in scientific reasoning, molecular biology, and biochemistry.