Overview
This lecture covers key organelles unique to eukaryotic cells, focusing on their structures, functions, and differences between plant and animal cells.
Endoplasmic Reticulum (ER)
- The ER is a continuous network of membranes connected to the nuclear envelope.
- Rough ER has ribosomes attached and is a site of protein synthesis and modification.
- Smooth ER lacks ribosomes, synthesizes lipids and carbohydrates, produces some hormones, detoxifies substances, and stores calcium ions.
- The structure of ER can shift between rough and smooth based on cell needs.
Golgi Apparatus
- The Golgi apparatus is a stack of individual, unconnected membrane sacs.
- Functions to sort, package, tag, and distribute proteins and lipids received from the ER.
- Described as the "UPS" of the cell due to its role in distribution.
Vesicles and Vacuoles
- Vesicles are small membrane sacs for transport within the cell, such as moving proteins from ER to Golgi or to the plasma membrane.
- Vacuoles are mainly for storage; the central vacuole in plant cells stores water and maintains cell structure.
Lysosomes and Peroxisomes
- Both are small, enzyme-filled membrane sacs for breaking down molecules.
- Lysosomes (animal cells) contain acid hydrolases to digest old organelles and foreign material.
- Peroxisomes (plant and animal cells) detoxify substances and break down fatty and amino acids.
- Plant cells use vacuoles for lysosome-like functions.
Endomembrane System
- Includes the nuclear envelope, ER, Golgi, vesicles, lysosomes, and plasma membrane.
- Coordinates protein and lipid synthesis, modification, sorting, and distribution using interconnected membranes.
Cytoskeleton
- Comprised of protein fibers: microtubules, microfilaments (actin filaments), and intermediate filaments.
- Microtubules are hollow protein tubes acting as "train tracks" for organelle and vesicle movement; form spindle fibers for chromosome separation.
- Microfilaments are thin actin strands involved in cell movement, muscle contraction, and cytokinesis.
- Intermediate filaments provide cell shape, strength, and structural integrity; types vary by tissue.
- The cytoskeleton maintains cell shape, enables movement, and organizes organelles.
Centrioles and Centrosomes
- Centrioles are microtubule structures found only in animal cells, always in pairs.
- Located in the centrosome, they organize spindle fibers for chromosome separation during cell division.
Key Terms & Definitions
- Endoplasmic Reticulum (ER) — Network of membranes for synthesis and modification of molecules.
- Golgi Apparatus — Stacked membrane sacs that sort and distribute cellular products.
- Vesicle — Membrane sac for transport within cells.
- Vacuole — Membrane sac for storage, especially prominent in plant cells.
- Lysosome — Enzyme-filled sac in animal cells for digesting materials.
- Peroxisome — Membrane sac with enzymes for detoxification and breakdown of fatty acids.
- Cytoskeleton — Network of protein fibers providing shape and movement.
- Microtubule — Hollow protein tube for intracellular transport and cell division.
- Microfilament — Thin, actin-based strand for movement and structure.
- Intermediate Filament — Multiple protein strands twisted for strength and structure.
- Centriole — Microtubule-based structure in animal cells aiding cell division.
- Centrosome — Region containing centrioles, organizing spindle fibers.
Action Items / Next Steps
- Review diagrams of organelles, especially the ER and Golgi.
- Watch recommended YouTube videos on cytoplasmic streaming and the endomembrane system.
- Prepare for upcoming topics on cell wall, chloroplasts, mitochondria, endosymbiosis, flagella, cilia, fimbriae, and pili.