Eukaryotic Cells Have Organelles

Nucleus

Animals, plants, fungi, and protozoans are eukaryotes. They are made up of eukaryotic cells, which contain many organelles, as shown here in an animal and a plant cell. Organelles are the membrane-bound compartments of eukaryotic cells that carry out specific functions.

The defining feature of eukaryotic cells is an organelle called the nucleus. The nucleus contains the cells DNA, the stored genetic instructions of each cell, and for this reason is the control center of the cell. Important reactions for interpreting the genetic instructions occur in the nucleus.

Endoplasmic Reticulum and Golgi Apparatus

The endoplasmic reticulum (ER) is an extensive, membranous intracellular "plumbing" system that is critical for the production of new proteins.

The "rough ER" has a rough appearance because it is studded with ribosomes. Ribosomes are protein-making machines, and they pass newly made proteins into the interior of the ER.

In addition to having ribosomes on the endoplasmic reticulum, eukaryotic cells also have ribosomes in the cytoplasm.

The rough ER is contiguous with the "smooth ER," which lacks ribosomes on its surface. The smooth ER is the site of lipid production.

The Golgi apparatus is a series of flattened membrane compartments whose purpose is to process and package proteins produced in the rough endoplasmic reticulum.

Transport vesicles deliver proteins from the rough endoplasmic reticulum, where the proteins were made, to the Golgi apparatus. As the proteins make their way through the Golgi apparatus they are processed. Proteins are then packaged into transport vesicles, which deliver the proteins to their final destination.

Mitochondria and Chloroplasts

Mitochondria are found in almost all eukaryotes, including plants and animals. Mitochondria carry out critical steps in the extraction of energy from food, converting it into a more usable form of energy. Mitochondria are the cell's "power plants."

An organelle called a chloroplast is found in the cells of plants and algae, but not in animal cells. Chloroplasts are the sites of photosynthesis, the process by which light energy is captured and converted into chemical energy. Chloroplasts allow plants to create the food that all animals depend on for survival.

Lysosomes

Lysosomes are the cell's "recycling centers." Full of digestive enzymes, lysosomes break down food and a variety of other particles taken in by the cell. The subunits from the particles can be used to build new cellular structures.

Lysosomes can also break down and recycle materials from inside the cell, such as worn-out cell parts or molecules.

Cell Membranes, Walls, and the Cytoskeleton

Plant and animal cells have at their periphery a cell membrane made up of a phospholipid bilayer. Plant cells have an added layer outside the cell membrane, called the cellulose cell wall, which provides strength and protection.

In a fully hydrated plant, a large water vacuole dominates the plant cell. The vacuole and the cell wall together keep the plant cell rigid, helping the plant stand upright.

Both plants and animals have a cytoskeleton, which is a network of protein fibers that carry out a variety of functions, including cell support and the movement of structures within cells. The cytoskeleton also provides animal cells with cell movement.

Activity 1

The organelles of a eukaryotic cell have specific functions. Drag the correct functions to the organelles shown.

Activity 2

Plant and animal cells have a number of structures in common, but plant cells also contain their own unique structures. For each of the organelles listed, choose whether the structure is found in just animal cells (A), just plant cells (P), or both (B). Click A, P, or B for each label.