Overview
This lecture covered the historical development of cell theory, its main postulates, and the structure and function of major cell organelles, with interactive review activities.
Cell Discovery Timeline & Historical Milestones
- 1590s: Zacharias Jansen invented the microscope.
- 1665: Robert Hooke observed and named "cells" while examining cork under the microscope.
- 1674: Anton van Leeuwenhoek, "Father of Microbiology," discovered "animalcules" (microorganisms) in pond water.
- 1838: Matthias Schleiden stated that plants are made up of cells.
- 1839: Theodor Schwann concluded that animals are also made of cells.
- 1855: Rudolf Virchow proposed that cells come from pre-existing cells through cell division.
Cell Theory and Its Postulates
- Cell theory was first proposed in the mid-19th century.
- First postulate: All living things are made up of cells.
- Second postulate: The cell is the basic unit of structure and function in organisms.
- Third postulate: All cells arise from pre-existing cells.
- Modern cell theory adds:
- Cells carry genetic material passed on during cell division.
- All cells of the same species have similar structure and composition.
- Energy flow and biochemical processes occur within cells.
Major Organelles and Their Functions
- Cell membrane: Semi-permeable barrier that regulates material in/out of the cell; found in both plant and animal cells.
- Cell wall: Rigid layer providing support found only in plant cells.
- Nucleus: Contains genetic material (DNA) and controls cell activities; has a nucleolus inside for ribosome assembly.
- Ribosomes: Sites of protein synthesis; can be free or attached to rough endoplasmic reticulum (ER).
- Mitochondria: Powerhouse of the cell, producing energy (ATP); present in both cell types and contains its own DNA.
- Endoplasmic reticulum (ER):
- Rough ER (with ribosomes) modifies proteins.
- Smooth ER (no ribosomes) synthesizes lipids, detoxifies, and stores calcium.
- Golgi apparatus: Sorts, tags, and packages proteins/lipids for delivery.
- Lysosome: Contains digestive enzymes for breakdown of waste; found mainly in animal cells.
- Chloroplast: Site of photosynthesis; contains chlorophyll; found only in plant cells.
- Vacuole: Stores water, nutrients, and waste; large and central in plant cells.
- Cytoskeleton: Framework providing cell shape, structure, and mobility; helps in cell division.
Key Terms & Definitions
- Cell — Basic structural and functional unit of life.
- Organelle — Specialized structure within a cell performing a specific function.
- Semi-permeability — Property allowing selective substances to cross the membrane.
- ATP (Adenosine Triphosphate) — Main energy-carrying molecule in cells.
- Apoptosis — Programmed cell death, often involving lysosomes.
Action Items / Next Steps
- Prepare a cell model project using creative or recycled materials.
- Review organelles and their functions for quizzes and future discussions.
- Submit photos of cell models to your tutors for a chance to be featured as student of the week.