General Biology Study Guide: Introduction to Life, Chemistry of Life, Macromolecules, and Cell Structure

Chapter 1: Introduction to Life on Earth

Key Characteristics of Life

Biology is the scientific study of living organisms and their life processes. All living things share certain characteristics that distinguish them from non-living matter.

• Order: Living things exhibit complex but ordered organization.

• Regulation (Homeostasis): Organisms maintain a stable internal environment.

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Energy Processing: Living things acquire and use energy to maintain life and fuel activities.

• Response to Stimuli: Organisms respond to environmental changes.

• Reproduction: Organisms reproduce their own kind, either sexually or asexually.

• Evolutionary Adaptation: Populations evolve over generations through natural selection.

Example: Humans maintain a constant body temperature (homeostasis) and respond to cold by shivering.

Levels of Biological Organization

Life is organized in a hierarchy from smallest to largest:

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Domains of Life and Classification

All living organisms are classified into three domains:

• Bacteria

• Archaea

• Eukarya

Binomial Nomenclature: The two-part scientific naming system for species (e.g., Homo sapiens).

Scientific Method and Theories

• Hypothesis: An educated guess based on prior knowledge and observation.

• Scientific Theory: A well-supported explanation of natural events based on many observations and experiments.

Chapter 2: Atoms, Molecules, and Life

Atomic Structure and Chemical Bonds

All matter is composed of atoms, which consist of protons, neutrons, and electrons.

• Protons and neutrons are found in the nucleus; electrons orbit the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., carbon-12, carbon-13, carbon-14).

• Ionic Bonds: Formed when electrons are transferred between atoms (e.g., NaCl).

• Covalent Bonds: Formed when atoms share electrons (e.g., H2O).

• Hydrogen Bonds: Weak bonds between polar molecules, important in biological molecules.

Properties of Water

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

• Ice Floats: Ice is less dense than liquid water, allowing aquatic life to survive under ice.

• pH: Measures the concentration of hydrogen ions ($pH = -\log[H^+]$).

  • Acidic: pH < 7

  • Neutral: pH = 7

  • Basic: pH > 7

• Buffers: Substances that resist changes in pH by accepting or donating H+ ions.

Chapter 3: Organic Molecules and Macromolecules

Macromolecules: Types and Functions

Organic molecules are carbon-based and form the basis of life. The four major classes of macromolecules are:

• Carbohydrates: Energy storage and structural support.

• Lipids: Energy storage, insulation, and membrane structure.

• Proteins: Enzymes, structural components, transport, and signaling.

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

Monomers and Polymers

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

• Polymers: Long chains of monomers (e.g., proteins, polysaccharides, nucleic acids).

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Proteins: Structure and Function

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Regular folding (alpha helices, beta sheets) stabilized by hydrogen bonds.

• Tertiary Structure: 3D shape formed by interactions among R groups.

• Quaternary Structure: Association of multiple polypeptide chains.

Peptide Bonds: Link amino acids in proteins.

ATP: The main energy carrier molecule in cells.

Comparison of Saturated and Unsaturated Fats

Saturated Fats	Unsaturated Fats
No double bonds between carbons; usually solid at room temperature; most animal fats	One or more double bonds; usually liquid at room temperature; most plant oils

Chapter 4: Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

Prokaryotes	Eukaryotes
No nucleus or nuclear envelope DNA in a "nucleoid region"	Nucleus with nuclear envelope DNA within the nucleus

Cell Organelles and Their Functions

• Nucleus: Contains genetic material (DNA).

• Ribosomes: Site of protein synthesis.

• Mitochondria: "Powerhouse" of the cell; produces ATP from organic molecules.

• Chloroplasts: Site of photosynthesis in plants and algae.

• Endoplasmic Reticulum (ER): Rough ER synthesizes proteins; smooth ER synthesizes lipids.

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

• Lysosomes: Contain digestive enzymes to break down waste.

• Vacuoles: Storage and structural support in plant cells.

• Cytoskeleton: Network of protein fibers for cell shape, movement, and division.

Endomembrane System

• Nuclear envelope

• Endoplasmic reticulum (rough and smooth)

• Golgi apparatus

• Lysosomes

• Vacuoles

Pathway of Protein Secretion

1. Protein synthesized by ribosome on rough ER

2. Transported to Golgi apparatus in vesicle

3. Modified and packaged in Golgi

4. Transported to cell membrane for secretion

Compartmentalization in Eukaryotic Cells

Compartmentalization increases efficiency and specialization by creating separate, membrane-bound organelles that house specific functions, preventing interference between different biochemical pathways.

Example: Mitochondria and chloroplasts both have their own DNA and ribosomes, reflecting their evolutionary origins and specialized functions.