Comprehensive Review Topics for General Biology

Comprehensive Review Topics in General Biology

Introduction to Biological Molecules and Central Dogma

Understanding the structure and function of biological macromolecules is fundamental to biology. The central dogma describes the flow of genetic information from DNA to RNA to protein.

• Monomers and Polymers: Monomers are small molecules that can join together to form polymers. Examples include nucleotides (form nucleic acids), amino acids (form proteins), and monosaccharides (form polysaccharides).

• Central Dogma of Molecular Biology: Genetic information flows from DNA → RNA → Protein.

• Relationship between DNA, RNA, and Proteins: DNA is transcribed into RNA, which is then translated into proteins. Proteins perform most cellular functions.

• Examples: Enzymes are proteins that catalyze biochemical reactions; hemoglobin is a protein that transports oxygen.

Genetic Variation and Evolution

Genetic variation is the raw material for evolution, which is the change in allele frequencies in a population over time.

• Evolution: The process by which populations change over generations due to genetic variation and natural selection.

• Fitness: An organism's ability to survive and reproduce in its environment.

• Mutation: A change in DNA sequence that can introduce new genetic variation.

• Phenotype: The observable traits of an organism, influenced by genotype and environment.

• Example: Antibiotic resistance in bacteria is an example of evolution by natural selection.

Cell Structure and Function

Cells are the basic units of life, with prokaryotic and eukaryotic cells differing in structure and complexity.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria, archaea).

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

• Cell Membranes: Composed of a phospholipid bilayer with embedded proteins; regulate the movement of substances in and out of the cell.

• Phospholipid Bilayer: Provides a semi-permeable barrier; hydrophilic heads face outward, hydrophobic tails face inward.

• Example: Mitochondria are organelles in eukaryotic cells responsible for energy production.

Macromolecules: Structure and Function

Biological macromolecules include carbohydrates, proteins, nucleic acids, and lipids, each with specific functions.

• Carbohydrates: Provide energy and structural support (e.g., glucose, glycogen, cellulose).

• Proteins: Serve as enzymes, structural components, and signaling molecules.

• Nucleic Acids: Store and transmit genetic information (DNA and RNA).

• Lipids: Form membranes, store energy, and act as signaling molecules.

• Example: Glycogen is a polysaccharide used for energy storage in animals.

Energy and Metabolism

Cells obtain and use energy through metabolic pathways, including glycolysis, pyruvate oxidation, and the citric acid cycle.

• Glycolysis: The breakdown of glucose to pyruvate, producing ATP and NADH.

• Pyruvate Oxidation: Converts pyruvate to acetyl-CoA, releasing CO2 and generating NADH.

• Citric Acid Cycle (Krebs Cycle): Completes the oxidation of glucose, producing ATP, NADH, and FADH2.

• Electron Transport Chain (ETC): Uses electrons from NADH and FADH2 to generate a proton gradient for ATP synthesis.

• Substrate-level vs. Oxidative Phosphorylation: Substrate-level phosphorylation generates ATP directly in metabolic reactions; oxidative phosphorylation uses the ETC and chemiosmosis.

• Example: Muscle cells use glycolysis for rapid ATP production during intense exercise.

Genetic Information and Cell Division

Cells replicate their genetic material and divide to produce new cells, ensuring genetic continuity and variation.

• DNA Synthesis: The process of copying DNA before cell division.

• Prokaryotic Cell Division: Binary fission produces two genetically identical cells.

• Genetic Variation in Prokaryotes: Achieved through conjugation, transformation, transduction, and vesiculation.

• Eukaryotic Cell Division: Includes mitosis (produces identical cells) and meiosis (produces gametes with genetic variation).

• Types of Cells: Zygotic, sporic, and gametic cells are involved in sexual reproduction and life cycles.

• Example: Meiosis increases genetic diversity in sexually reproducing organisms.

Summary Table: Key Biological Molecules and Their Functions

Macromolecule	Monomer	Main Function	Example
Carbohydrate	Monosaccharide	Energy storage, structure	Glucose, cellulose
Protein	Amino acid	Catalysis, structure, signaling	Enzymes, hemoglobin
Nucleic Acid	Nucleotide	Genetic information storage and transfer	DNA, RNA
Fatty acid, glycerol	Membranes, energy storage, signaling	Phospholipids, triglycerides

Additional info:

• Allosteric and active sites refer to regions on enzymes where substrates or regulators bind, affecting enzyme activity.

• Structure determines function: The three-dimensional shape of a molecule (especially proteins) is critical for its function.