Essential Cellular Organelles and Their Functions

Plasma Membrane

A lipid bilayer containing various types of proteins. It controls the passage of substances between the inside and outside of the cell and isolates it from the environment.

Cell Wall

A rigid layer consisting of cellulose and other sugars, exclusive to plant cells. It provides support, confers protection, and gives shape to the cells.

Chromosomes

Composed of DNA and proteins. When a cell is at rest, they appear as a mass called chromatin while maintaining their individuality. The number of chromosomes is characteristic of each species and is best observed during cell division. DNA acts as the carrier of genetic information and controls cellular activities.

Nucleolus

A mass of RNA, proteins, and a small proportion of DNA. There may be one or several. They assist the cell in the manufacture of proteins and originate ribosomes.

Nuclear Membrane

Composed of two membranes and crossed by a large number of pores. It regulates the passage of substances between the nucleus and the cytoplasm.

Endoplasmic Reticulum

A network of tanks and tubes connected to the cell membrane and nuclear envelope.

• Rough ER: Contains ribosomes and stores/secretes proteins.
• Smooth ER: Lacks ribosomes and produces/secretes fats.

Golgi Apparatus

A set of sacs from which small vesicles emerge. It completes the manufacture of compounds from the ER and segregates them to other areas of the cell or abroad.

Ribosomes

Granules composed of RNA and proteins. They are responsible for protein synthesis.

Lysosomes

Vesicles consisting of a membrane that originate in the Golgi apparatus and contain enzymes. They digest food within cells. Their enzymes can destroy the cell itself, so the inner membrane has a protective coating.

Vacuoles

Large vesicles. In plant cells, they can occupy 90% of the cellular volume. Some have digestive, transport, or backup storage functions.

Mitochondria

Bounded by two membranes, with the internal one forming folds called cristae. The internal space, called the matrix, contains many enzymes. These are the power plants of eukaryotic cells, forming ATP through the oxidation of organic compounds.

Chloroplasts

Delimited by two membranes and containing chlorophyll. Unique to plants and some unicellular organisms, they are the site of photosynthesis, where solar energy is converted into useful energy for the cell.

Centrioles

Tubes made of protein located in a perpendicular arrangement. Exclusive to animal cells and some unicellular organisms, they assist in the formation of the spindle during cell division.

Microtubules

Protein filaments that form the basis of the cellular cytoskeleton and support cellular movements.