AM

Lecture Notes: Chemistry Basics — Electron Shells, Valence, Ionic Bonds, Redox, and Cellular Energy

1. Introduction to Cells

  • Cells are the fundamental structural and functional units of all known organisms.
  • Often referred to as the "building blocks of life."
  • Their study is called cell biology.

2. Basic Characteristics of All Cells

  • Cell Membrane: A selective barrier that encloses the cell's contents and regulates passage of substances.
  • Cytoplasm: The jelly-like substance filling the cell, composed of cytosol (the fluid portion) and organelles.
  • DNA (Deoxyribonucleic Acid): Genetic material that contains instructions for cell function and replication.
  • Ribosomes: Structures responsible for protein synthesis.

3. Types of Cells

3.1. Prokaryotic Cells
  • Definition: Simplest and most ancient type of cell; lack a nucleus and other membrane-bound organelles.
  • Examples: Bacteria and Archaea.
  • Key Features:
    • Genetic material (nucleoid) is located in the cytoplasm.
    • Lack true organelles (e.g., mitochondria, ER, Golgi).
    • Typically much smaller than eukaryotic cells (e.g., 1-10 micrometers, \mu m).
    • Reproduce by binary fission.
    • Often have a cell wall outside the plasma membrane.
    • May have flagella for movement.
3.2. Eukaryotic Cells
  • Definition: More complex cells that possess a true nucleus and other membrane-bound organelles.
  • Examples: Animal cells, plant cells, fungi, and protists.
  • Key Features:
    • Nucleus: Contains the cell's genetic material (DNA) organized into chromosomes.
    • Membrane-bound Organelles: Specialized structures performing specific functions.
    • Mitochondria: "Powerhouses" of the cell; responsible for cellular respiration and ATP production.
    • Endoplasmic Reticulum (ER):
      • Rough ER: Studded with ribosomes; involved in protein synthesis and modification for secretion or insertion into membranes.
      • Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.
    • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
    • Lysosomes (Animal cells): Contain digestive enzymes to break down waste materials and cellular debris.
    • Vacuoles (Plant cells): Large central vacuole stores water, nutrients, and waste products; maintains turgor pressure.
    • Chloroplasts (Plant cells): Sites of photosynthesis.
    • Cell Wall (Plant cells, fungi): Provides structural support and protection outside the cell membrane.
    • Typically larger than prokaryotic cells (e.g., 10-100 \mu m).
    • Reproduce by mitosis and meiosis.