Overview
This lecture covers the functional anatomy of eukaryotic cells, focusing on organelles, cell structures, and their roles, with comparisons to prokaryotic cells.
Introduction to Eukaryotic Cells
- Eukaryotic cells have membrane-bound organelles and a nucleus containing DNA.
- Cells are diverse in structure and function but share fundamental processes.
- Both animals and plants are made of eukaryotic cells, but with key differences.
Animal vs. Plant Cells
- Animal cells: no cell wall, have lysosomes, centrioles, and sometimes flagella.
- Plant cells: have a cell wall (cellulose), chloroplasts, large central vacuole, and plasmodesmata.
- Lysosomes are unique to animals; central vacuoles and chloroplasts are unique to plants.
Eukaryotic Organelles Overview
- Organelles are membrane-enclosed structures with specialized functions.
- Four main groups: genetic control (nucleus, ribosomes), manufacturing/distribution/breakdown (ER, Golgi, lysosomes, vacuoles), energy processing (mitochondria, chloroplasts), and structural support/movement (cytoskeleton, plasma membrane, cell wall).
Nucleus and Ribosomes
- Nucleus: control center, double membrane, contains DNA and nucleolus.
- Nucleolus: synthesizes ribosomal RNA and assembles ribosome subunits.
- Ribosomes: sites of protein synthesis, can be free (cytoplasm) or bound (ER); eukaryotic ribosomes are 80S, prokaryotic are 70S.
Endomembrane System & Protein Pathway
- Protein synthesis: DNA (nucleus) → transcription → mRNA → ribosome → translation → polypeptide.
- Rough ER: ribosome-bound, folds/processes proteins for secretion or membrane.
- Golgi apparatus: modifies, sorts, and ships proteins.
- Smooth ER: synthesizes lipids, detoxifies drugs/poisons, stores calcium.
Lysosomes and Central Vacuole
- Lysosomes: animal cells' digestive organelles, recycle worn structures, destroy invaders.
- Central vacuole: plant-specific, stores nutrients, pigments, and toxins; maintains cell structure via water uptake.
Mitochondria and Chloroplasts
- Mitochondria: site of cellular respiration, produce ATP, have their own DNA and ribosomes (70S), semi-autonomous.
- Chloroplasts: site of photosynthesis in plants/algae, triple-membrane, also semi-autonomous.
- Endosymbiotic theory: these organelles originated from engulfed prokaryotes.
Cytoskeleton and Cell Motility
- Cytoskeleton provides structural support, maintains shape, and allows movement.
- Microfilaments (actin): cell shape, muscle contraction, movement.
- Intermediate filaments: maintain shape, anchor organelles/nucleus.
- Microtubules: movement of vesicles/chromosomes, structural support, cell motility (cilia/flagella).
Cell Surface and Membranes
- Glycocalyx: polysaccharide outer layer, involved in protection and communication.
- Cell wall: plants/algae (cellulose), fungi (chitin/cellulose); structure differs from bacterial walls.
- Plasma membrane: phospholipid bilayer with embedded proteins and sterols (e.g., cholesterol), selectively permeable.
Key Terms & Definitions
- Organelle — specialized membrane-bound structure within a cell.
- Nucleus — membrane-bound organelle containing genetic material (DNA).
- Ribosome — site of protein synthesis; made of rRNA and protein.
- Endoplasmic Reticulum (ER) — network for protein/lipid synthesis; rough (with ribosomes), smooth (no ribosomes).
- Golgi Apparatus — modifies, sorts, and ships cellular products.
- Lysosome — animal cell organelle digesting macromolecules/waste.
- Central Vacuole — large plant organelle storing water, nutrients, pigments.
- Mitochondria — organelle producing ATP via cellular respiration.
- Chloroplast — plant organelle for photosynthesis.
- Cytoskeleton — network of fibers for structure and movement.
- Glycocalyx — polysaccharide-rich cell exterior for protection/communication.
- Plasma Membrane — lipid bilayer boundary of the cell.
Action Items / Next Steps
- Put the protein production structures (nucleus, ribosome, rough ER, Golgi, vesicle, plasma membrane) in order and describe their functions.
- Prepare answers to questions on alcohol tolerance and cytoskeleton function for class discussion.
- Review summary tables of organelle functions for exam preparation.