Overview
This lecture introduces cell structure, compares prokaryotic and eukaryotic cells, and describes major organelles and their functions in plant and animal cells.
Basic Cell Structure
- Cells are the smallest living units in organisms.
- All cells have a cell membrane, cytoplasm (jelly-like fluid), and DNA (genetic material).
Types of Cells
- Eukaryotic cells have a nucleus and membrane-bound organelles; found in plants and animals.
- Prokaryotic cells lack a nucleus and membrane-bound organelles; always unicellular, such as bacteria.
Organelles and Their Functions
- Organelles ("little organs") are specialized structures within cells.
- The nucleus contains DNA and controls cell activities; also has a nucleolus for making ribosomes.
- Chromatin is the loose form of DNA; DNA condenses into chromosomes before cell division.
- Ribosomes make proteins and can be free in cytoplasm or attached to rough ER.
- Endoplasmic reticulum (ER) transports materials; rough ER has ribosomes, smooth ER does not.
- The Golgi apparatus modifies and customizes proteins, adding materials like lipids or carbohydrates.
- Vacuoles store materials; central vacuole in plant cells stores water.
- Lysosomes (found in animal cells) break down worn-out cell parts using enzymes.
- Mitochondria perform cellular respiration and produce ATP (energy); found in both plant and animal cells.
- Chloroplasts (in plant cells only) conduct photosynthesis and contain green chlorophyll pigment.
- Plant cells have a rigid cell wall for structure and protection; animal cells do not.
Cell Movement and Support Structures
- The cytoskeleton maintains cell shape, made of microfilaments (protein threads) and microtubules (hollow tubes).
- Cilia are hair-like projections on some human cells (e.g., respiratory tract) that move substances.
- Flagella (whip-like tails) enable movement in some bacteria and human sperm cells.
Key Terms & Definitions
- Cell membrane — barrier separating the cell from its environment.
- Cytoplasm — jelly-like fluid filling the cell.
- DNA — molecule containing cell's genetic instructions.
- Eukaryotic — cells with a nucleus and organelles.
- Prokaryotic — cells without a nucleus or membrane-bound organelles.
- Organelle — specialized cell structure with a specific function.
- Nucleus — organelle holding DNA and controlling cell activity.
- Ribosome — structure that synthesizes proteins.
- Endoplasmic reticulum (ER) — transport network for materials.
- Golgi apparatus — organelle that modifies and packages proteins.
- Vacuole — storage sac within a cell.
- Lysosome — organelle that digests cell waste.
- Mitochondria — energy-producing organelle.
- Chloroplast — organelle for photosynthesis in plant cells.
- Cell wall — rigid layer outside plant cell membranes.
- Cytoskeleton — structural support network in a cell.
- Cilia — hair-like structures for movement or filtering.
- Flagellum — tail-like structure for movement.
Action Items / Next Steps
- Review and memorize the functions of each main organelle.
- Compare and contrast prokaryotic and eukaryotic cells for class discussion.