Cellular Organization: Life exhibits a wide variety of levels of organization. For one, the cell is considered the smallest living functional unit of an entity and is always known as the basic unit of life. Despite their minute size, cells are still organized in a precise manner.
Table of Contents
- What is Cellular Organization?
- Functional Components Of The Cell
- Cell Shape And Size
What is Cellular Organization?
By definition, cellular organization is the components that make up the cell and how they are arranged inside it. Each component called an organelle, performs a specific function vital for the cell. This page will explore the basic functional components of the cell and cell shape and its size. Let’s take a closer look.
Functional Components Of The Cell
- The presence of a nucleus is the principal characteristic that distinguishes eukaryotes from prokaryotes. The latter only have a so-called nucleoid wherein the genetic material is embedded.
- In addition to that, the nucleus of eukaryotic organism is surrounded by a nuclear membrane that functions to separate the nucleus from the rest of the organelles in the cytosol.
2. Cell Membrane (also Plasma Membrane)
- As its name suggests, the phospholipid bilayer is composed of two layers of phospholipids, with one layer having hydrophilic heads (water-loving; polar) in its outer side and hydrophobic tails (water-hating; nonpolar) interior side.
- The proteins found in the bilipid layer performs selective transport of molecules and recognition and of cells.
- In eukaryotes, the cytoplasm is consisted of all materials (i.e. organelles) located in within the cell, excluding the nucleus.
- The part of the cytoplasm that does not contain any organelles is referred to as the cytosol.
4. Cell Wall
- While the cell membrane is made up of phospholipids, the cell wall is made up of a sturdier compounds – polysaccharides, usually cellulose (in plants) and peptidoglycan (in bacteria).
- Interestingly, throughout their life cycle, plants develop two types of cell wall: primary and secondary; Primary cell walls are usually thin and stretchable but once the growth ceases, a secondary cell wall is produced. This secondary cell wall is tougher and more rigid due to the added polymer called lignin.
- In animals, the muscle cells contain the most number of mitochondria, which is justifiable because they need much energy for locomotion.
- Interestingly, the mitochondrion (together with the chloroplast) has a distinct genetic material as compared to the nucleus. This phenomenon can be explained by the Endosymbiotic theory that states that the mitochondria and chloroplasts were once unicellular organisms that were engulfed by a larger cell.
- Like mitochondria, chloroplasts are considered to have originated from the engulfment of a cyanobacteria.
7. Rough Endoplasmic Reticulum
- Basically, the rough ER is called as such because of the ribosomes that are attached to it (see smooth ER).
8. Smooth Endoplasmic Reticulum
- Contrary to the rough ER, the smooth ER is called as such because it is associated with slippery fat molecules and there are no attached ribosomes to it.
- Ribosomes are found in both prokaryotic and eukaryotic organisms.
- Inside the cell, the ribosomes are either found to be suspended in the cytoplasm or attached to the rough ER.
10. Golgi Body
- The Golgi body is also responsible for the production of lysosomes.
- The Golgi body was named after the Italian biologist Camillo Golgi.
- Vesicles are formed when a portion of the cell membrane is pinched off.
- Vacuoles are membrane-bound organelles that store food, nutrients, and even non-nourishing chemicals. Aside from that, vesicles can also be temporary storage for waste products.
- In plant cells, vacuoles contribute to the rigidity of the overall structure by storing water in order to create hydro-static pressure.
- Aside from digesting foreign materials and molecules, lysosomes can function to degrade the component of the cell itself.
- Sometimes, lysosomes are considered to be specialized vacuoles whose main function is digestion.
- Centrioles play an important role in the development of spindle fibers during cell division.
Cell Shape And Size
Different cells have different shapes and their unique morphologies are directly related to their function:
- Plant cells, in general, have rectangular, rigid walls, and distinct edges. Such structure is contributed by the presence of cell wall that forces the cell to have a definite shape.
- Unlike plant cells, animal cells tend to have more irregular body shapes due to the absence of cell wall in their overall structure.
- Microorganisms like bacteria have three types of cell shape: oval (cocci), rod-shaped (bacilli), spiral, star-shaped, and rectangular.
- See the differences between plant and animal cells here.
Like shapes, the size of cells is also linked to their functions. Depending on the type of organism, the size of the cell greatly varies.
- In particular, egg cells are the largest cells that an organism has. This is very much related to their function as the development of the zygote after fertilization requires huge amounts of energy. Approximately, the human egg cell measures 0.12 mm in diameter.
- On the other hand, the smallest cell is that of the parasitic bacterium Mycoplasma gallicepticum. This bacterium, which thrives in the bladder, respiratory and reproductive tracts of mammals. This cell has an average diameter of 0.0001 mm.
To perform more efficiently, cells usually undergo a so-called multi-cellular organization where similar cells group together to form tissues. A group of tissues and similar structures which perform similar functions together constitute an organ. A group of organs performing physiological processes form an organ system and organ systems that work together constitute an organism.
Isn’t it amazing how a single cell can be so complex?