Cell Biology Study Notes 1. Cell Theory Core Principles: ♦ All living organisms are made of one or more cells. ♦ The cell is the smallest unit of life. ♦ All cells arise from pre-existing cells (by division). 2. Types of Cells Prokaryotic Cells:  No nucleus; DNA is in the cytoplasm (nucleoid region).  No membrane-bound organelles.  Example: Bacteria and Archaea. Eukaryotic Cells:  Contains a nucleus where DNA is stored.  Membrane-bound organelles.  Examples: Animal cells, plant cells, fungi, protists. 3. Cell Structure and Organelles Organelle Nucleus Function Controls cell activities; contains DNA. Found in All Mitochondria Chloroplasts Ribosomes Endoplasmic Reticulum (ER) Golgi Apparatus Lysosomes Produces energy (ATP); site of respiration. eukaryotic cells All eukaryotic cells Site of photosynthesis. Plant cells Protein synthesis. All cells Rough ER: Protein processing. Smooth ER: Lipid synthesis. Modifies and packages proteins. All eukaryotic cells All eukaryotic cells Breaks down waste and old cell parts. Animal cells Cell Membrane Controls what enters/exits the cell. Cell Wall Provides structure and support. Cytoplasm Jelly-like fluid where reactions occur. All cells Plant cells, bacteria All cells 4. Cell Membrane Structure Composition: → Phospholipid bilayer with embedded proteins. → Hydrophilic heads face outward; hydrophobic tails face inward. Functions: → Selectively permeable barrier. → Facilitates transport of substances (active and passive). 5. Cell Transport Mechanisms Passive Transport (no energy needed): Diffusion: Movement of molecules from high to low concentration. Osmosis: Diffusion of water across a semi-permeable membrane. Facilitated Diffusion: Uses carrier proteins or channels. Active Transport (energy required):  Moves substances against the concentration gradient.  Example: Sodium-potassium pump. Endocytosis/Exocytosis: Endocytosis: Cell engulfs material into a vesicle. Exocytosis: Cell expels materials via vesicles. 6. Energy Conversion in Cells Mitochondria:  Site of cellular respiration: Converts glucose into ATP.  Process: Glycolysis → Krebs Cycle → Electron Transport Chain. Chloroplasts (Plants):  Site of photosynthesis: Converts light energy into glucose.  Process: Light-dependent reactions → Calvin Cycle. 7. The Cell Cycle Phases: Interphase: Growth and DNA replication (G1, S, G2 phases). Mitosis: Division of the nucleus (PMAT stages: Prophase, Metaphase, Anaphase, Telophase). Cytokinesis: Division of the cytoplasm to form two cells. 8. Specialized Cell Structures Plant Cells:  Have a rigid cell wall (made of cellulose).  Contain chloroplasts for photosynthesis.  Have large central vacuoles for water storage. Animal Cells:  Contain lysosomes for waste breakdown.  Lack chloroplasts and cell walls.  Have small vacuoles compared to plant cells.

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