Eukaryotic cells have several types of organelles working inside them.
In this lesson, we will examine the various types of membrane-bound organelles and their functions.
Membrane-Bound Organelles in Eukaryotic Cells
Eukaryotic cells contain many membrane-bound organelles. An organelle is an organized and specialized structure within a living cell. The organelles include the nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuoles, lysosomes, mitochondria, and, in plants, chloroplasts.The nucleus is often referred to as the control center of the eukaryotic cell. This is because it contains the information needed to make proteins. Every part of the cell needs proteins to do its job, so by containing the blueprint to make proteins, the nucleus controls the activities of the other organelles.
Ribosomes are cellular organelles that assemble enzymes and other proteins according to the directions found in the DNA code. Structurally, ribosomes consist of two major subunits. The smaller subunit reads mRNA, and the larger subunit assembles amino acids into a peptide chain that will be folded into a protein.The endoplasmic reticulum is the site of cellular chemical reactions. It is composed of a series of highly-folded membranes.
The endoplasmic reticulum basically functions as a large workspace within the cell. It is folded in this manner to save space. The folds in the endoplasmic reticulum are like the folds of an accordion; if it were not folded, it would take up a tremendous amount of space, but the folds allow a lot of surface area for cellular reactions to fit into a small space. If ribosomes are attached to the endoplasmic reticulum, it is referred to as rough endoplasmic reticulum.The Golgi apparatus is a flattened system of tubular membranes that modifies proteins to perform certain functions. Proteins are transferred to the Golgi apparatus after being assembled in the ribosomes. After the proteins receive any needed modifications, they are sorted in the Golgi and sent to their appropriate destination.
In this way, the Golgi serves as a sort of post office for proteins.Vacuoles are essentially sacs surrounded by a membrane. They are used by cells as temporary storage sites. They often store food, enzymes, and other materials needed by the cell, and some vacuoles store waste products.Have you ever been asked to take out the trash? If so, you know what it feels like for lysosomes. These organelles contain digestive enzymes that are used to break down excess or worn out organelles, food particles, viruses, and bacteria. If they get too full, lysosomes can fuse with vacuoles and dispense their enzymes into the vacuoles.
All of the processes that occur within a cell – including protein production, modification, transportation, and digestion – require energy. The two organelles that provide energy are known as the mitochondria and chloroplasts.Plants must capture energy from light to turn it into food. The organelles that capture the light and produce food are known as chloroplasts.
Chloroplasts consist of a double membrane. Inside the inner membrane are stacks of sacks known as grana. Inside the inner membrane, sunlight is processed and used to make food for the plants.The energy generated by the chloroplasts is stored until it is broken down and released by organelles known as mitochondria.
Mitochondria are found in both plant and animal cells and are used to transform energy. A mitochondrion has an outer membrane and a highly folded inner membrane. These folds of the inner membrane provide a greater surface area for the various chemical reactions to take place.
As you can see, eukaryotic cells are like little factories. Each cell has a specific job to do and utilizes its organelles to do the work. It is easy to think of the nucleus as the manager, the ribosomes and endoplasmic reticulum as the assembly line, the Golgi as the mailroom, the vacuoles as storage containers, and the lysosomes as a cleanup crew. All of these parts of the cellular factory are powered by materials generated in the mitochondria and chloroplasts.
After you’ve completed this lesson, you’ll have the ability to:
- Define organelle
- Describe the function of the nucleus, ribosomes, endoplasmic reticulum, the Golgi apparatus, vacuoles, and lysosomes
- Explain what mitochondria and chloroplasts do