an extensive network of flattened membrane sacs that manufactures proteins. These proteins are transferred to the Golgi apparatus, from which they will be exported from the cell. There are two types of endoplasmic reticulum: rough and smooth. Rough endoplasmic reticulum is studded by ribosomes covering its exterior. These ribosomes make the rough endoplasmic reticulum a prime location for protein synthesis. The smooth endoplasmic reticulum moves the proteins around the cell and then packages them into small containers called vesicles that travel to the Golgi apparatus. The smooth endoplasmic reticulum also functions in the synthesis of fats and lipids.
Golgi apparatus:
a complex of membrane-bound sacs that package proteins for export from the cell. Proteins enter the Golgi complex from the endoplasmic reticulum and proceed through the stacks, where they are modified and stored before secretion. When proteins are ready for export, pieces of the Golgi membrane bud off, forming vesicles that send them to the cell membrane.
Lysosomes:
small membrane-bound packages of acidic enzymes that digest compounds and worn-out cellular components that the cell no longer needs.
| Cell Organelles |
| Organelle |
Function |
Found in which Type of Cell |
| Cytoplasm |
Home for the organelles |
Prokaryotes and eukaryotes |
| Cytoskeleton |
Maintains cell shape, moves organelles, moves cell |
Eukaryotes |
| Nucleus |
Contains the genetic material |
Eukaryotes |
| Mitochondria |
Produce energy for the cell |
Eukaryotes |
| Ribosomes |
Synthesize proteins |
Prokaryotes and eukaryotes |
| Endoplasmic Reticulum |
Manufactures and transports proteins, manufactures fats |
Eukaryotes |
| Golgi Complex |
Packages proteins for secretion |
Eukaryotes |
| Lysosomes |
Digest wastes |
Eukaryotes |
| Chloroplasts |
Make food |
Plant eukaryotes |
| Vacuoles |
Storage |
Plant eukaryotes (contractile vacuoles are found in some animal cells) |
| Cell Wall |
Stability and protection |
Plant eukaryotes; some prokaryotes have a cell wall made of peptidoglycan |
Plant Cell Organelles
The organelles described above are found in both animal and plant eukaryotic cells. But plants have additional organelles—chloroplasts, vacuoles, and cell walls—that support their unique life cycles.
Chloroplasts:
Animal cells break down the food that they ingest to produce energy. Plants do not need to ingest food; they manufacture their own from sunlight, using the process of photosynthesis (covered in the chapter on Plant Structure and Function). Chloroplasts are the organelles in which photosynthesis takes place. They are large oval-shaped structures containing a green pigment called chlorophyll that absorbs sunlight. Chloroplasts, like mitochondria, are built from two membranes: an external membrane forming the boundary of the organelle and a stacked inner membrane within the organelle.
