General Biology: Core Concepts and Principles – Study Guide

General Biology: Core Concepts and Principles

Biological Molecules and Their Functions

Biological molecules are essential for the structure and function of living organisms. They include carbohydrates, lipids, proteins, and nucleic acids, each with unique roles in cellular processes.

• Carbohydrates: Serve as energy sources and structural components. Example: Glucose is a primary energy source.

• Lipids: Include fats, oils, and hormones. They are hydrophobic and function in energy storage, insulation, and cell signaling.

• Proteins: Made of amino acids, they perform structural, enzymatic, and regulatory functions.

• Nucleic Acids: DNA and RNA store and transmit genetic information.

Example: Human sex hormones are classified as lipids because they are derived from fatty acids and are hydrophobic.

Cell Structure and Organelles

Cells are the basic units of life, with specialized structures called organelles that perform distinct functions.

• Nucleus: Contains genetic material (DNA) and controls cellular activities.

• Mitochondria: Site of cellular respiration and energy (ATP) production.

• Chloroplasts: Found in plant cells, responsible for photosynthesis.

• Ribosomes: Synthesize proteins.

• Endoplasmic Reticulum (ER): Synthesizes and transports proteins and lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

Example: Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus and membrane-bound organelles.

Properties of Water and Hydrogen Bonding

Water's unique properties are critical for life, largely due to hydrogen bonding between molecules.

• Cohesion: Water molecules stick together, contributing to surface tension.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes, stabilizing environments.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

Example: The high specific heat and surface tension of water are due to hydrogen bonding.

Atomic Structure and Chemical Bonds

Atoms are the building blocks of matter, consisting of protons, neutrons, and electrons. Chemical bonds form when atoms share or transfer electrons.

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

• Covalent Bonds: Atoms share electrons.

• Ionic Bonds: Atoms transfer electrons, resulting in charged ions.

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and DNA structure.

Equation: $\text{Atomic Mass} = \text{Number of Protons} + \text{Number of Neutrons}$

Example: A neutral atom with atomic number 10 has 10 protons and 10 electrons.

Levels of Biological Organization

Biological systems are organized into hierarchical levels, from molecules to the biosphere.

• Cell: Basic unit of life.

• Tissue: Group of similar cells performing a function.

• Organ: Structure composed of tissues with a specific function.

• Organ System: Group of organs working together.

• Organism: Individual living entity.

• Population: Group of organisms of the same species.

• Community: Different populations living together.

• Ecosystem: Community plus the physical environment.

Example: Tissues are grouped together in functional units called organs.

Scientific Method and Scientific Knowledge

The scientific method is a systematic approach to understanding the natural world through observation, hypothesis formation, experimentation, and analysis.

• Observation: Gathering data about phenomena.

• Hypothesis: Testable explanation for observations.

• Experiment: Testing the hypothesis under controlled conditions.

• Theory: Well-supported explanation based on evidence.

Example: A hypothesis must be testable and falsifiable; a theory is broader and supported by extensive evidence.

Genetics: DNA, RNA, and Protein Synthesis

Genetic information is stored in DNA and used to synthesize proteins through transcription and translation.

• DNA: Double-stranded molecule carrying genetic instructions.

• RNA: Single-stranded molecule involved in protein synthesis.

• Transcription: DNA is copied into RNA.

• Translation: RNA directs the synthesis of proteins.

Example: The correct order of events is: DNA makes RNA, RNA makes protein.

Classification of Life and Domains

Organisms are classified into domains and kingdoms based on cellular structure and genetic relationships.

• Domains: Bacteria, Archaea, Eukarya.

• Eukarya: Includes fungi, plants, animals, and protists.

• Prokaryotes: Bacteria and Archaea, lack a nucleus.

Example: Fungi are classified within the domain Eukarya.

Acids, Bases, and pH

Acids and bases affect the concentration of hydrogen ions in solutions, influencing pH.

• Acid: Substance that increases hydrogen ion concentration.

• Base: Substance that decreases hydrogen ion concentration.

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

Equation: $\text{pH} = -\log_{10}[H^+]$

Example: As an acid is added to water, the pH decreases and the number of hydrogen ions increases. c

Macromolecules: Structure and Function

Macromolecules are large, complex molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.

• Monomers: Building blocks of macromolecules (e.g., amino acids for proteins, nucleotides for nucleic acids).

• Polymers: Chains of monomers linked by covalent bonds.

• Polysaccharides: Carbohydrate polymers such as starch and cellulose.

Example: Proteins are polymers of amino acids joined by peptide bonds.

Cellular Respiration and Photosynthesis

Cells obtain energy through cellular respiration and, in plants, through photosynthesis.

• Cellular Respiration: Process by which cells convert glucose and oxygen into ATP, carbon dioxide, and water.

• Photosynthesis: Plants convert light energy, carbon dioxide, and water into glucose and oxygen.

Equation for Cellular Respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

Equation for Photosynthesis: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Table: Types of Chemical Bonds

Bond Type	Description	Example
Covalent	Atoms share electrons	H2O molecule
Ionic	Atoms transfer electrons	NaCl (table salt)
Hydrogen	Weak attraction between polar molecules	Between water molecules

Additional info:

• Some explanations and examples were expanded for clarity and completeness.

• Tables were inferred and constructed based on standard biology content.