Cytoplasm

ancreatic cancer cells, SEM
Pancreatic cancer cells. Coloured scanning electron micrograph (SEM) of pancreatic cancer cells. The cells are joined by a cytoplasmic bridge. The irregular shape of the cells, the cellular projections and blebs (nodules) are typical of cancer cells. Pancreatic cancer often causes no symptoms until it is well established and untreatable. Science Photo Library - STEVE GSCHMEISSNER/ Brand X Pictures/ Getty Images

Definition: The cytoplasm consists of all of the contents outside of the nucleus and enclosed within the cell membrane of a cell. It is clear in color and has a gel-like appearance. The cytoplasm is composed mainly of water and also contains enzymes, salts, organelles, and various organic molecules.

Cytoplasm Function

The cytoplasm functions to support and suspend organelles and cellular molecules. Many cellular processes also occur in the cytoplasm.

Some of these processes include protein synthesis, the first stage of cellular respiration known as glycolysis, mitosis, and meiosis. In addition, the cytoplasm helps to move materials, such as hormones, around the cell and also dissolves cellular waste.

Cytoplasm Components

In prokaryotic cells (such as bacteria) that do not have a membrane-bound nucleus, the cytoplasm consists of all of the contents of the cell inside the plasma membrane. In euckaryotic cells, (such as plant and animal cells) the cytoplasm consists of three main components. They are the cytosol, organelles, and various particles and granules called cytoplasmic inclusions.

Cytosol

The cytosol is the semi-fluid component or liquid medium of a cell's cytoplasm. It is located outside of the nucleus and within the cell membrane.

Organelles

Organelles are tiny cellular structures that perform specific functions within a cell. Examples of organelles include: mitochondria, ribosomes, nucleus, lysosomes, chloroplasts, endoplasmic reticulum, and Golgi apparatus.

Also located within the cytoplasm is the cytoskeleton, a network of fibers that help the cell maintain its shape and provide support for organelles.

Cytoplasmic Inclusions

Cytoplasmic inclusions are particles that are temporarily suspended in the cytoplasm. Inclusions consist of macromolecules and granules.

Three types of inclusions found in the cytoplasm are secretory inclusions, nutritive inclusions, and pigment granules. Examples of secretory inclusions are proteins, enzymes, and acids. Glycogen (glucose storage molecule) and lipids are examples of nutritive inclusions. Melanin found in skin cells is an example of a pigment granule inclusion.

Cytoplasmic Divisions

The cytoplasm can be divided into two primary parts: the endoplasm (endo-,-plasm) and ectoplasm (ecto-,-plasm). The endoplasm is the central area of the cytoplasm that contains the organelles. The ectoplasm is the more gel-like peripheral portion of the cytoplasm of a cell.

Cell Membrane

The cell membrane or plasma membrane is the structure that keeps cytoplasm from spilling out of a cell. This membrane is composed of phospholipids, which form a lipid bilayer that separates the contents of a cell from the extracellular fluid. The lipid bilayer is semi-permeable, meaning that only certain molecules are able to diffuse across the membrane to enter or exit the cell. Extracellular fluid, proteins, lipids, and other molecules may be added to a cell's cytoplasm by endocytosis. In this process, molecules and extracellular fluid are internalized as the membrane turns inward forming a vesicle.

The vesicle encloses the fluid and molecules and buds off from the cell membrane forming an endosome. The endosome moves within the cell to deliver its contents to their appropriate destinations. Substances are removed from the cytoplasm by exocytosis. In this process, vesicles budding from Golgi bodies fuse with the cell membrane expelling their contents from the cell. The cell membrane also provides structural support for a cell by serving as a stable platform for the attachment of the cytoskeleton and cell wall (in plants).

Sources:

  • cytoplasmic inclusions. (n.d.) Saunders Comprehensive Veterinary Dictionary, 3 ed.. (2007). Retrieved January 25 2016 from http://medical-dictionary.thefreedictionary.com/cytoplasmic+inclusions
  • ectoplasm. (n.d.) Collins Dictionary of Biology, 3rd ed.. (2005). Retrieved January 25 2016 from http://medical-dictionary.thefreedictionary.com/ectoplasm
  • endoplasm. (n.d.) Collins Dictionary of Biology, 3rd ed.. (2005). Retrieved January 25 2016 from http://medical-dictionary.thefreedictionary.com/endoplasm
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Bailey, Regina. "Cytoplasm." ThoughtCo, Feb. 24, 2017, thoughtco.com/cytoplasm-defined-373301. Bailey, Regina. (2017, February 24). Cytoplasm. Retrieved from https://www.thoughtco.com/cytoplasm-defined-373301 Bailey, Regina. "Cytoplasm." ThoughtCo. https://www.thoughtco.com/cytoplasm-defined-373301 (accessed December 18, 2017).