Identify the major eukaryotic organelles and describe the specific job each one performs.
A eukaryotic cell is less like a single room and more like a small, organized factory city, where each organelle handles one job. The nucleus is the control center, holding the cell's DNA and containing a nucleolus that assembles ribosomes. Ribosomes -- found floating free in the cytoplasm or attached to the endoplasmic reticulum -- build proteins by translating genetic instructions (Unit 7 covers exactly how). The endoplasmic reticulum comes in two forms: rough ER, studded with ribosomes, builds and modifies proteins destined for secretion or other organelles; smooth ER lacks ribosomes and instead builds lipids and helps detoxify certain chemicals. The Golgi apparatus receives, further modifies, sorts, and ships proteins and lipids in membrane-bound sacs called vesicles, much like a post office packaging and routing shipments to their correct destination.
Mitochondria are the cell's power plants, running cellular respiration to convert food energy into a usable form (Unit 4) -- notably, mitochondria carry their own small loop of DNA, one of the strongest pieces of evidence for the endosymbiotic theory, which holds that mitochondria descend from free-living bacteria engulfed by an ancestral cell roughly two billion years ago. Lysosomes contain digestive enzymes that break down worn-out organelles, waste, and engulfed particles, mainly in animal cells. Vacuoles store water, nutrients, and waste; plant cells typically have one large central vacuole that also provides structural rigidity by pressing outward against the cell wall. Chloroplasts, found only in plants and algae, capture light energy to build sugar through photosynthesis (Unit 4) and, like mitochondria, carry their own DNA and are also explained by endosymbiotic theory. Finally, the cytoskeleton, a internal scaffolding of protein fibers, gives the cell shape and enables movement of organelles and, in some cells, the whole cell itself; and a rigid cell wall, present in plants, fungi, and bacteria but never in animal cells, provides structural support and protection outside the cell membrane.
Mastery looks like: They can name each major organelle and correctly describe its specific function without confusing organelles that sound similar.
Common stumbles: Mixing up rough ER and smooth ER's functions; forgetting that mitochondria appear in both plant and animal cells, while chloroplasts appear only in plants and algae.