General Biology: Foundations, Biochemistry, and Cell Structure

Introduction to Biology

Characteristics of Living Things

• Complexity and Organization: Living things are both complex and highly organized.

Levels of Biological Organization

• From least to most complex:

  1. Subatomic

  2. Atomic

  3. Molecular

  4. Organelle

  5. Cellular

  6. Tissue

  7. Organ

  8. Organ System

  9. Organism

  10. Population

  11. Community

  12. Ecosystem

  13. Biosphere

Cells: The Unit of Life

• Cells are the smallest unit of life capable of all life processes.

Energy in Living Systems

• Sun: The primary energy source for most life on Earth.

Domains of Life

• Bacteria

• Archaea

• Eukarya

The Scientific Method

Steps of the Scientific Method

• Observation

• Question

• Hypothesis

• Prediction

• Experiment

• Conclusion

Example: Discovery of Penicillin

• Led to the foundation of antibiotics.

• Helped find treatment for bacterial diseases.

Types of Reasoning

• Inductive Reasoning: Uses specific observations to form general conclusions.

• Deductive Reasoning: Uses generalizations to reach a specific conclusion about an instance.

Basic Chemistry for Biology

Elements in Living Organisms

• Most common elements in humans:

  • Carbon

  • Hydrogen

  • Oxygen

  • Nitrogen

Subatomic Particles

• Proton: Positive charge

• Neutron: Neutral

• Electron: Negative charge

Hydrogen Bonds

• Weak bonds between a slightly positive hydrogen atom and a slightly negative electronegative atom.

Redox Reactions

• Oxidation: Loss of electrons by an atom, ion, or molecule.

• Reduction: Gain of electrons by an atom, ion, or molecule.

• Oxidation and reduction always occur together (redox pair).

Ions and Ionic Bonds

• Ions: Atoms that have gained or lost electrons.

• Cation: Positively charged ion (lost electrons).

• Anion: Negatively charged ion (gained electrons).

• Ionic Bonds: Attraction between oppositely charged ions.

Covalent Bonds

• Formed when atoms share pairs of electrons.

• Can be single, double, or triple bonds depending on the number of shared electron pairs.

Water and Its Properties

• Polarity: Water is a polar molecule with partial positive and negative charges.

• Cohesion: Attraction between water molecules (surface tension).

• Adhesion: Attraction between water and other substances.

pH Scale

• Measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• pH below 7: Acidic (more $H^+$)

• pH above 7: Basic (more $OH^-$)

Biological Macromolecules

Organic Molecules

• Small organic molecules (monomers) join to form polymers via dehydration synthesis.

• Polymers are broken apart by hydrolysis.

Carbohydrates

• Made of C, H, and O.

• Energy source and storage.

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

• Polysaccharides: Starch, glycogen, cellulose, chitin.

Lipids

• Nonpolar molecules, energy storage, insulation.

• Saturated: Single bonds, solid at room temperature.

• Unsaturated: At least one double bond, liquid at room temperature.

• Phospholipids: Major component of cell membranes.

Proteins

• Polymers of amino acids joined by peptide bonds.

• Levels of structure: primary, secondary, tertiary, quaternary.

• Denaturation: Loss of protein structure due to heat, pH, or chemicals.

• Disulfide bridges: Covalent bonds between sulfur atoms of cysteine residues.

Nucleic Acids

• Polymers of nucleotides (phosphate group, sugar, nitrogenous base).

• DNA: Adenine, Cytosine, Guanine, Thymine.

• RNA: Adenine, Cytosine, Guanine, Uracil.

• ATP: Energy currency of the cell.

Cell Structure and Function

Cell Walls

• Present in plants, fungi, and some protists and bacteria.

• Gram staining differentiates bacteria by cell wall structure:

  • Gram-positive: Thick peptidoglycan, stains purple.

  • Gram-negative: Thin peptidoglycan, stains pink.

Cytoskeleton

• Microfilaments: Smallest, actin subunits, 7 nm diameter.

• Intermediate filaments: Twisted protein strands, structural support.

• Microtubules: Largest, tubulin subunits, 25 nm diameter.

Cilia and Flagella

• Cilia: Short, numerous, move fluid past cells.

• Flagella: Longer, fewer, move cells (e.g., sperm).

Nucleus

• Contains genetic material (DNA).

• Components: Nuclear envelope, nucleolus, chromatin, chromosomes.

• Chromatin: DNA and proteins, condenses to form chromosomes during cell division.

Ribosomes

• Sites of protein synthesis (translation of mRNA).

• Can be free in cytoplasm or bound to rough ER.

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes, synthesizes and modifies proteins.

• Smooth ER: Lacks ribosomes, synthesizes lipids, detoxifies chemicals.

Golgi Apparatus

• Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Endomembrane System

• Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, and plasma membrane.

• Coordinates synthesis, modification, and transport of cellular products.

Energy Organelles

• Mitochondria: Site of cellular respiration, produces ATP.

• Chloroplasts: Site of photosynthesis in plants and algae.

Macromolecule	Monomer	Function	Example
Carbohydrate	Monosaccharide	Energy storage, structure	Glucose, starch, cellulose
Lipid	Fatty acid, glycerol	Energy storage, insulation	Triglyceride, phospholipid
Protein	Amino acid	Enzymes, structure, transport	Hemoglobin, keratin
Nucleic Acid	Nucleotide	Genetic information	DNA, RNA

Additional info:

• Some explanations and examples have been expanded for clarity and completeness.

• Table summarizes the four major classes of biological macromolecules.