Difference Between Organ and Organelle

Main Difference – Organ vs Organelle

Organ and organelle are two structural units, which are specialized to perform a unique function in the body of animals. The main difference between organ and organelle is that organ is a large part of an organism, composed of tissues which perform similar functions whereas organelle is a specialized structure found inside cells, which carries out a specific life process. Organelles form cells. Cells form tissues, and tissues form organs. Organelles occur in all eukaryotes. They are microscopic. But, organs are macroscopic and only found in animals and plants. Mitochondria, chloroplast, Golgi apparatus, endoplasmic reticulum, and the nucleus are organelles. Kidney, heart, liver, lungs, and brain are the organs in humans. Flower, seeds, and spores are the reproductive organs in angiosperms.

Key Areas Covered

1. What is an Organ 
      – Definition, Composition, Role, Examples
2. What is an Organelle
      – Definition, Composition, Role, Examples
3. What is the difference between Organ and Organelle
      – Comparison of Key Differences

Key Terms: Human organs, Organs, Organelles, Organ systems, Organelles of eukaryotes, Organelles of prokaryotes, Primary organs in plants

What is an Organ

An organ is a group of tissues which are adapted to perform a specific function in an organism’s body. The cells in organs are highly specialized to perform necessary actions at a specific time. A human body consists of 78 organs. Five organs among them, brain, heart, lungs, kidneys, and liver, are vital for the survival. The brain is the control center of the body, which coordinates other organs of the body through the nervous system. It is responsible for thoughts, feelings, general perception, and memory storage. The heart pumps blood throughout the body. The lungs oxygenate the blood, which is circulated throughout the body, and remove carbon dioxide from the blood. The kidneys remove metabolic wastes as well as the excess fluid from the circulating blood. The liver is the main storage of food. Chemicals like drugs and toxins are detoxified by the liver.

Figure 1: Internal organs in human

Organs are grouped into organ systems in higher animals. Usually, ten organ systems occur in higher animals as skeletal, muscular, nervous, respiratory, digestive, integumentary, circulatory, excretory, reproductive and endocrine. These systems are also found in lower organisms with less complexity. Stem, root, and leaves are the primary organs in plants, whereas flowers, seeds, and spores are the reproductive structures. The cone is the reproductive structures of conifers. Organs are responsible for the basic life-sustaining functions in organisms.

What is an Organelle

An organelle is the functional analogue of an organ in single-cell organisms like bacteria. It is a tiny cellular structure, performing a specific function in the body. Organelles are embedded in the cytoplasm. In eukaryotes, organelles are enclosed by a membrane. Eukaryotic cells contain organelles like cell wall, cell membrane, nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, ribosomes, lysosomes, peroxisomes, vacuole, centrioles, cilia, and flagella. The nucleus contains the hereditary information, which controls the growth, development, and reproduction of the cell. The cellular site of energy production is the mitochondria, where the respiration occurs in the cell. The chloroplast is a plastid, found only in photosynthesizing organisms. The endoplasmic reticulum is responsible for protein synthesis, maturation, and transport. Cell wall and cell membrane serve as a protective barrier to the cell, defining the boundaries of the cell.

Prokaryotes do not have membrane-enclosed organelles like nucleus, mitochondria, and chloroplasts. The prokaryotic genetic material is concentrated into a region called nucleoid in the cytoplasm. But, prokaryotes contain cell membrane, cell wall, cytoplasm, ribosomes, and flagella in their cells. Organelles in animal cells are shown in figure 2.

Figure 2: Organelles in an Animal Cell

Difference Between Organ and Organelle

Definition

Organ: An organ is a part of the body, which performs a specific function.

Organelle: An organelle is a part of the cell, which performs a specific function.

Composition

Organ: Organs are composed of organ systems.

Organelle: Organelles are composed of a single cell.

Life Processes

Organ: Organs perform life processes in the body.

Organelle: Organelles perform processes in the cell.

Size

Organ: Organ is a macroscopic structure.

Organelle: Organelle is a microscopic structure.

Examples

Organ: Kidney, heart, lungs, liver, stem, root, and leaves are organs.

Organelle: Nucleus, mitochondria, chloroplasts, endoplasmic reticulum, and Golgi apparatus are organelles.

Conclusion

Organ and organelle are two structural units, which are specialized to perform a unique function. Organs are found in higher organisms like plants and animals. The organelle is the functional analogue of organs in a single-cell like bacteria. Hence, organs are macroscopic and organelles are microscopic. The main difference between organ and organelle is in their organization.

Reference:

1. “Organ.” Encyclopædia Britannica. N.p., 31 Jan. 2017. Web. Available here. 03 June 2017. 
2. “The Human Body: Anatomy, Facts & Functions.” LiveScience. Purch, 10 Mar. 2016. Web. Available here. 03 June 2017.
3. Bailey, Regina. “Why Organelles Are Important to Cells.” ThoughtCo. N.p., n.d. Web. Available here. 03 June 2017. 

Image Courtesy:

1.”Internal organs”By Mikael Häggström (2014). “Medical gallery of Mikael Häggström 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. (Public Domain) via Commons Wikimedia
2. “Cell-organelles-labeled” By Koswac –  (CC BY-SA 4.0) via Commons Wikimedia