Cell Organelles – Meaning, List, Functions, and FAQs

What are Cell Organelles?

Cell organelles are small structures inside cells that have specific functions. Some organelles, like the nucleus, are large and easy to see with a microscope. Others, like the mitochondria, are much smaller. Each organelle has a specific job to do in order to keep the cell alive and functioning.

Cell Organelles Definition

Cell organelles are the specialized parts of a cell that carry out specific functions. The most common organelles are the nucleus, mitochondria, and ribosomes.

Cell organelles/structures can be divided into three types

prokaryotic, eukaryotic, and organelle.

• Prokaryotic cells are the simplest type of cell and lack a true nucleus. They are found in bacteria and other single-celled organisms.
• Eukaryotic cells are more complex and have a true nucleus as well as other membrane-bound organelles. They are found in all other forms of life, from plants to animals.
• Organelle cells are specialized eukaryotic cells that carry out specific functions. For example, liver cells are specialized to carry out the function of the liver, and muscle cells are specialized to carry out the function of muscles.

List of Cell organelles and their function

• Cell organelles are tiny, specialized parts of cells that carry out specific functions. The main cell organelles are the nucleus, the mitochondria, the endoplasmic reticulum, the Golgi apparatus, the lysosomes, and the plasma membrane.
• The nucleus is the largest and most prominent organelle in the cell. It is responsible for controlling the cell’s activities, including its DNA replication and protein synthesis. The mitochondria are the energy-producing organelles in the cell. They generate energy by breaking down glucose and other nutrients. The endoplasmic reticulum is a network of membranous tubes and sacs that manufactures and transports proteins and other molecules. The Golgi apparatus processes and packages proteins and other molecules for transport within and outside of the cell. The lysosomes are sacs of enzymes that digest unwanted materials and recycle cellular components. The plasma membrane is the thin, flexible layer that surrounds the cell and controls the passage of molecules in and out of the cell.

List of Cell Organelles and their Functions

• Cellular organelles are microscopic structures that make up the cells of plants and animals. Each type of organelle has a specific function within the cell.
• The nucleus is the largest organelle in the cell. It is surrounded by a nuclear membrane and contains the cell’s genetic material, or DNA. The DNA is organized into chromosomes, which are responsible for the inheritance of genetic traits.
• The cytoplasm is the gel-like substance that fills the cell. It is composed of water, proteins, and other molecules. The cytoplasm contains the organelles of the cell, including the nucleus, mitochondria, and ribosomes.
• The mitochondria are the powerhouses of the cell. They are responsible for the production of energy in the form of ATP.
• The ribosomes are the factories of the cell. They are responsible for the synthesis of proteins.
• The endoplasmic reticulum is a network of interconnected tubes that surrounds the nucleus. It is responsible for the synthesis and modification of proteins.
• The Golgi apparatus is a network of flattened sacs and tubes. It is responsible for the packaging and transport of proteins and other molecules.
• The lysosomes are sac-like structures that contain digestive enzymes. They are responsible for the breakdown of proteins, carbohydrates, and lipids.
• The cell membrane is a thin layer of lipid and protein that surrounds the cytoplasm

Plasma Membrane

• The plasma membrane is a thin, semipermeable membrane that surrounds the cells of living organisms. It is composed of a lipid bilayer with embedded proteins.
• The plasma membrane is responsible for regulating the movement of molecules in and out of the cell.

Cytoplasm

• Cytoplasm is the jelly-like substance that fills the cells of plants and animals. It contains the cell’s genetic material (DNA) and many of the cell’s organelles, such as the mitochondria.
• The cytoplasm of a cell is a thick, viscous fluid that contains the cell’s genetic material (DNA) and many of the cell’s organelles, such as the mitochondria. The cytoplasm surrounds the cell’s nucleus, which contains the cell’s genetic information. The cytoplasm also contains other organelles, such as the golgi apparatus and the endoplasmic reticulum. The cytoplasm is important for the cell’s metabolism and for the transport of materials in and out of the cell.

Nucleus

A nucleus is a dense, central region of an atom that contains the atom’s protons and neutrons. The number of protons in a nucleus determines an atom’s atomic number and the type of element it is.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a membranous network of tubes and sacs that extends throughout the cytoplasm of the cell. It is responsible for the synthesis and transport of proteins and other molecules. The ER is also involved in the folding of newly-synthesized proteins and in the modification of proteins with lipid molecules.

Mitochondria

• Mitochondria are organelles found in the cytoplasm of eukaryotic cells. These organelles are responsible for the generation of ATP, the energy currency of the cell.
• Mitochondria are oval-shaped organelles that are typically about 1-2 micrometers in diameter. They have a double membrane, with the outer membrane being highly permeable and the inner membrane being much less permeable. The inner membrane is folded into cristae, which increases the surface area available for the generation of ATP.
• Mitochondria contain their own DNA, which is separate from the DNA found in the nucleus. This mitochondrial DNA encodes for proteins that are necessary for the generation of ATP.

Plastids

• Plastids are organelles in plants that are unique in that they are able to change their shape and size. Plastids are responsible for photosynthesis, which is the process that produces glucose from sunlight. There are three types of plastids: chloroplasts, chromoplasts, and leucoplasts.
• Chloroplasts are the most important type of plastid and are responsible for the majority of photosynthesis. Chromoplasts are responsible for the color of fruits and vegetables, and leucoplasts are responsible for the storage of starch and other nutrients.

Ribosomes

• Ribosomes are small, round, and dense organelles that are found in the cytoplasm of all cells. They are responsible for the synthesis of proteins from mRNA transcripts. Each ribosome is composed of two subunits, a small subunit and a large subunit. The small subunit is composed of a protein called ribosomal RNA (rRNA) and a few small proteins. The large subunit is composed of a protein called large ribosomal RNA (lrRNA) and a few small proteins.
• Ribosomes play a crucial role in the synthesis of proteins. Proteins are synthesized when an mRNA transcript is read by a ribosome. The ribosome uses the information in the mRNA to assemble the protein. The ribosome contains a special region called the Shine-Dalgarno sequence. This sequence is complementary to the sequence on the mRNA that codes for the protein. When the ribosome binds to the mRNA, the Shine-Dalgarno sequence and the coding sequence on the mRNA are in close proximity. This allows the ribosome to read the mRNA and assemble the protein.

Golgi Apparatus

The Golgi apparatus is a cellular organelle that is found in the cytoplasm of eukaryotic cells. It is responsible for the processing and packaging of proteins and lipids that are destined for transport within the cell or for secretion from the cell. The Golgi apparatus is named after its discoverer, Camillo Golgi.

Microbodies

• Microbodies are small, round or oval, and are found in the cytoplasm of cells. There are several different types of microbodies, including lysosomes, peroxisomes, and ribosomes.
• Lysosomes are sac-like organelles that contain digestive enzymes. These enzymes break down proteins, carbohydrates, and lipids into small molecules that can be used by the cell.
• Peroxisomes are organelles that contain enzymes that break down hydrogen peroxide into water and oxygen. Hydrogen peroxide is a toxic by-product of cellular metabolism that can damage cells if it is not broken down.
• Ribosomes are organelles that are responsible for protein synthesis.

Cytoskeleton

The cytoskeleton is a network of proteins that forms a scaffold inside cells. It helps to organize the cell’s components and to control their movement. The cytoskeleton is made up of three types of protein filaments: microfilaments, intermediate filaments, and microtubules.

Cilia and Flagella

Cilia and flagella are small, hair-like organelles that project from the surface of cells. Cilia are shorter and more numerous than flagella. Cilia are used for locomotion, while flagella are used for propulsion.

Centrosome and Centrioles

A centrosome is a small, organelle found in the center of animal cells. It is responsible for organizing the cell’s microtubules. Microtubules are long, thin tubes that help the cell move and divide.

Centrioles are small, cylindrical structures found in the centrosome. They help organize the cell’s microtubules.

Vacuoles

A vacuole is a membrane-bound organelle that is present in all plant and animal cells. Vacuoles are filled with a water-soluble substance called the vacuole sap.

Organelles of the Endomembrane System

Endoplasmic Reticulum

• The endoplasmic reticulum is a network of membranous tubes and sacs that forms a continuous internal surface around the cytoplasm of a eukaryotic cell. It is involved in a variety of cellular activities, including protein synthesis, lipid synthesis, and transport.
• The endoplasmic reticulum consists of two main types of membranes: the smooth endoplasmic reticulum and the rough endoplasmic reticulum.
• The smooth endoplasmic reticulum is a continuous, sheet-like membrane that is studded with small, round sacs called sacculi. The sacculi are the sites of lipid synthesis.
• The rough endoplasmic reticulum is a network of branching tubes that are studded with ribosomes. The ribosomes are the sites of protein synthesis.

Golgi Apparatus

• The Golgi apparatus is a stack of membranous sacs and tubes that forms a complex system of internal surfaces in the cytoplasm of a eukaryotic cell. It is involved in a variety of cellular activities, including protein transport, lipid transport, and carbohydrate metabolism.
• The Golgi apparatus consists of a series of flattened sacs and tubes called cisternae. The cisternae are connected to each other by small bridges of membrane.