Cytoplasm

Cytoplasm of eukaryotic cells

The cytoplasm of a eukaryotic cell is defined as the component of the cell internal to the cell/plasma membrane and external to the nuclear membrane. The cytoplasm of both plant and animal eukaryotic cells are composed of numerous membrane- and non-membrane bound organelles suspended in cytosol. 

Take a closer look at the structures of a eukaryotic cell with the study unit below.

Forming a major component of the cytoplasm of eukaryotic cells is the endoplasmic reticulum which can be divided into smooth and rough components. The endoplasmic reticulum is a system of interconnected membrane lined channels which function in lipid and protein synthesis. The rough and smooth endoplasmic reticulum surrounds the nuclear membrane of the eukaryotic cells, suspended within cytosol. 

Another important organelle of the cytoplasm of the eukaryotic cell is the Golgi apparatus. The Golgi apparatus lies adjacent to the nucleus and centriole, suspended in cytosol and functions to modify, sort and pack proteins in preparation for their transport to cellular destinations. 

Dispersed throughout the cytosol of eukaryotic cells are small sacs of digestive enzymes known as the lysosomes and peroxisomes which function in intracellular digestion. Located freely within the cytoplasm are numerous non-membrane bound organelles known as ribosomes. Ribosomes function to produce proteins within the cell. 

Giving the cytoplasm its shape and structure is the cytoskeleton which is composed of a dynamic network of protein filaments embedded throughout the cytoplasm. 

Animal vs plant cell

While the cytoplasm of all eukaryotic cells maintain many similarities there are some major differences between the cytoplasm of animal and plant eukaryotic cells. 

Unique to animal eukaryotic cells are the paired centrioles. Centrioles are barrel-shaped non-membrane bound organelles which function to organize the cytoskeleton of the animal cytoplasm and also help to determine the location of other organelles of the cytoplasm. 

Contributing further to the structure and stability of the plant cell is a rigid cell wall. The cell wall gives the plant eukaryotic cell its rigidity and maintains the shape of the cytoplasm. 

Also, unique to the cytoplasm of a plant cell are chloroplasts which function as the site of photosynthesis. Forming the bulk of the cytoplasm of a plant cell is the permanent vacuole which aids in maintaining water balance. The cytoplasm of animal cells may also contain vacuoles but they are much smaller in comparison and are only present temporarily. 

Cytoplasm of prokaryotic cells

As prokaryotic cells do not contain a nuclear membrane or nucleus, the cytoplasm of a prokaryote encompasses the total structure of a cell internal to the plasma membrane. Similar to the eukaryotic cell, prokaryotic cells are filled with cytosol. However, unlike the eukaryotic cell, prokaryotic cells do not contain membrane bound organelles. 

Located within the cytoplasm of a prokaryotic cell is a single loop of DNA known as a nucleoid. The nucleoid is not membrane bound and suspends freely within the cytosol. Accompanying the nucleoid material of the prokaryotic cell is a small ring of extrachromosomal DNA known as plasmid. 

Within the cytosol of both eukaryotic and prokaryotic cells are ribosomes. Ribosomes are non-membrane bound organelles which function in the synthesis of proteins. Ribosomes of prokaryotic cells are typically smaller when compared to eukaryotic cells.