Overview
This lecture reviews the structures and functions of different types of cells, focusing on comparing prokaryotic and eukaryotic cells and identifying key organelles and their functions.
Types of Cells
- Prokaryotic cells are bacterial cells; eukaryotic cells include plant and animal cells.
- Prokaryotic cells lack a nucleus; their DNA is free-floating.
- Eukaryotic cells have a nucleus containing genetic material.
- Prokaryotic cells are simpler and smaller (1–10 µm) than eukaryotic cells (10–100 µm).
- 1 millimeter (mm) equals 1,000 micrometers (µm).
Animal Cell Structure
- Contains a nucleus (controls the cell and stores genetic material).
- Has mitochondria (site of respiration), cytoplasm (site of chemical reactions), and a cell membrane (controls entry/exit).
- Animal cells do NOT have a cell wall.
Plant Cell Structure
- Shares nucleus, mitochondria, cytoplasm, and cell membrane with animal cells.
- Additional structures: vacuole (supports the cell), chloroplasts (photosynthesis), and a cell wall (made of cellulose).
Prokaryotic (Bacterial) Cell Structure
- Core structures: genetic material (circular DNA), cytoplasm, cell membrane, and cell wall (made of peptidoglycan).
- Optional features: flagella (movement), plasmids (extra DNA), pili (attachment/transfer), and slime capsule (protection).
- Prokaryotic cells are unicellular and the smallest living things.
- Common bacteria: Streptomyces, Streptococcus, and E. coli.
Subcellular Structures & Their Functions
- Nucleus: controls cell, contains DNA (only in eukaryotes).
- Cytoplasm: site of chemical reactions (in all cells).
- Cell membrane: controls movement in/out and has receptor molecules (in all cells).
- Mitochondria: site of respiration (only in eukaryotes).
- Cell wall: supports the cell; made of cellulose in plants, peptidoglycan in prokaryotes (not in animals).
- Chloroplasts: contain chlorophyll for photosynthesis (only in plants).
- Vacuole: contains cell sap, supports plant cells (only in plants).
- Free genetic material: circular DNA in cytoplasm (only in prokaryotes).
- Flagella: movement (only in prokaryotes).
- Pili: attachment and gene transfer (only in prokaryotes).
- Slime capsule: protection and adhesion (only in prokaryotes).
- Plasmids: extra DNA, often with useful genes like antibiotic resistance (only in prokaryotes).
Key Terms & Definitions
- Prokaryotic cell — single-celled organism without a nucleus (e.g., bacteria).
- Eukaryotic cell — cell with a nucleus (e.g., plant and animal cells).
- Cytoplasm — jelly-like substance where chemical reactions occur.
- Cell membrane — selectively permeable barrier controlling entry/exit.
- Nucleus — organelle containing genetic material, controls cell.
- Mitochondria — site of cellular respiration, produces energy.
- Cell wall — rigid structure for support (cellulose in plants, peptidoglycan in bacteria).
- Chloroplast — organelle for photosynthesis, contains chlorophyll.
- Vacuole — sac containing cell sap, provides support in plant cells.
- Flagella — tail-like structure for movement in bacteria.
- Plasmid — small DNA loop with extra genes in bacteria.
- Pili — hairlike structures for attachment and DNA transfer in bacteria.
- Slime capsule — protective outer layer in some bacteria.
Action Items / Next Steps
- Practice labeling diagrams of animal, plant, and bacterial cells.
- Memorize functions and locations of key organelles.
- Review and spell key terms accurately (especially "peptidoglycan").
- Learn examples of common bacteria (Streptomyces, Streptococcus, E. coli).