Overview
This lecture covers the structure and function of animal cells and their organelles, movement across the plasma membrane, and the stages of the cell cycle including mitosis and meiosis.
Introduction to Cells
- Cells are the smallest basic units of life responsible for all life processes.
- Cellular organization: cells → tissues → organs → systems → organism.
- The number of cells varies among different organisms and individuals.
- Robert Hooke discovered cells in 1665 using a compound microscope.
Types of Cells: Prokaryotes vs. Eukaryotes
- Prokaryotes lack a nucleus (genetic material in a nucleoid), are single-celled, reproduce via binary fission, examples: bacteria and cyanobacteria.
- Eukaryotes have a true nucleus, contain organelles, can be multicellular (animals, plants, fungi, protozoans), reproduce via mitosis and meiosis.
Cellular Functions
- Metabolism: all chemical reactions for energy production.
- Synthesis: production of proteins, nucleic acids, lipids.
- Communication: cells send and receive chemical/electrical signals.
- Reproduction: cells contain genetic information for inheritance.
Cell Organelles & Their Functions
- Nucleus: stores DNA, site of RNA synthesis.
- Rough ER: synthesizes proteins, studded with ribosomes.
- Smooth ER: synthesizes lipids, detoxifies, stores calcium.
- Ribosomes: protein synthesis.
- Golgi apparatus: modifies, sorts, and packages proteins.
- Secretory vesicles: transport substances out (exocytosis).
- Lysosomes: digest materials.
- Mitochondria: site of ATP synthesis (powerhouse).
- Centrioles: help in chromosome movement during division.
- Microtubules/microvilli/cilia/flagella: structure, absorption, movement.
Plasma Membrane Structure & Function
- Consists of a phospholipid bilayer with embedded proteins and cholesterol.
- Selectively permeable: controls entry/exit of substances.
- Components include integral/peripheral proteins, glycoproteins, glycolipids (glycocalyx).
- Functions: boundary, cell recognition, ion regulation (PISO: Potassium In, Sodium Out).
Movement Across the Plasma Membrane
- Passive transport: no energy required (diffusion, osmosis, facilitated diffusion).
- Active transport: energy required (primary: antiport, sodium-potassium pump; secondary: symport).
- Vesicular transport: endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis.
Solution & Tonicity
- Diffusion: solutes move from high to low concentration.
- Osmosis: water moves from low to high solute concentration.
- Tonicity: isotonic (equal), hypertonic (shrink/crenation), hypotonic (swell/burst).
Cell Cycle and Division
- Cell Cycle Phases: G1 (growth), S (DNA synthesis), G2 (preparation), M (mitosis).
- Mitosis Steps: prophase (chromatin condenses, spindle forms), metaphase (chromosomes align), anaphase (chromatids separate), telophase (nuclei reform), cytokinesis (cytoplasm divides).
- Meiosis: occurs in sex cells (gametes).
Cellular Disorders
- Atrophy: decrease in cell size.
- Hypertrophy: increase in cell size.
- Hyperplasia: increase in cell number.
- Metaplasia: change in cell type.
- Neoplasia: abnormal cell structure.
- Hypoxia: decreased oxygen to cells, leads to ischemia.
Key Terms & Definitions
- Prokaryote — cell without nucleus or organelles.
- Eukaryote — cell with true nucleus and organelles.
- Organelle — specialized cell structure with specific function.
- Plasma membrane — double-layered boundary of the cell.
- Diffusion — movement of solutes from high to low concentration.
- Osmosis — movement of water through a semipermeable membrane.
- Mitosis — cell division producing two identical cells.
- Cytokinesis — division of cytoplasm into two cells.
Action Items / Next Steps
- Review diagrams of animal and plant cell organelles.
- Memorize stages of the cell cycle and mitosis.
- Complete assigned exercises on membrane transport.