Living organisms are made up of basic microscopic units called cells. Cells are prokaryotic and eukaryotic cells, wherein the latter is more complex and contains nuclear material. Plants and animals are made of cells and though most of the cell organelles are the same, they do have their differences. This article provides information about the different cell organelles present in the animal cell, diagram and functions. The labeled animal cell diagram will help understand the parts of the animal cell.
Cell membrane or plasma membrane is a membrane common to both plant and animal cells. As observed in the labeled animal cell diagram, the cell membrane forms the confining factor of the cell, that is it envelopes the cell constituents together and gives the cell its shape, form and existence. Cell membrane is made up of lipids and proteins and forms a barrier between the extracellular liquid bathing all cells on the exterior and the cell organelles floating in the cell’s cytoplasm. This membrane is semi-permeable, thus, it allows only selected substances to pass through it into the cell’s interior.
Cytoplasm or Cytosol is nothing but the jellylike substance filling the cell. To be more precise, it is that fluid material present outside the nucleus and within the cell membrane, into which various cell organelles are scattered. The jelly like substance is made of dissolved nutrients and helps different material move throughout the cell by a process called cytoplasmic streaming. Cytoplasm comprises of a network of cytoplasmic filaments, that are responsible for the shape of the cell. Moreover, they also help the cell move. Read more on structure and functions of cytoplasm.
The cell nucleus is the trademark of any eukaryotic cell. Plant and animal cells are eukaryotic cells, which means they possess a true nucleus. The cell nucleus is a spherical shaped body encompassing a nucleolus, chromosomes with DNA and some other organelles with the help of a nuclear membrane. This nucleus consists of highly specialized cell organelles that take care of storing the cell’s hereditary material (DNA) and also co-ordination of different cell activities like protein synthesis, cell division, growth, etc. Read more on cell nucleus: structure and functions.
Mitochondria (singular – mitochodrion) are double membrane bound cells, scattered in the cell’s cytoplasm. The double membrane comprises one outer smooth membrane and one inner convoluted membrane, forming loops called cristae. Both these membranes together form the outer double membrane and keep the fluid filled matrix within the mitochondria from mingling with the cytoplasm of the cell. Mitochondria is popularly called ‘power house of the cell’ as it furnishes the cell with all the energy required (ATP) for locomotion, cell division, production of secretory products, etc. The number of mitochondria present in cells may vary depending on the cell’s activity. Read more on mitochondrial DNA.
Centrioles are self-replicating, cylindrical bodies comprised of 9 triplet bundles of microtubules, which means each bundle has 3 microtubules and there are such 9 bundles. Centrioles are present only in animal cells and each animal cell contains two centrioles arranged perpendicular to each other. Their main function is assisting in the organization of cell division process. When animal cells divide, they centrosome of the cell divides into two and the centriole replicates. Thus, the new centrosome halves have a pair of centrioles each and form new independent daughter cells.
Endoplasmic Reticulum (ER)
ER is a vast network of membranous tubules and sacs called cisternae in the cell’s cytoplasm. There exists two types of ER: Rough ER and Smooth ER. Rough ER features several ribosomes attached to its surface, thereby conducing to its rough appearance. The function of rough ER is protein synthesis and transport of nutrients. The smooth ER unlike the rough one does not have ribosomes attached to their surface, thereby giving them the smooth appearance. Its function is lipid synthesis, carbohydrate metabolism and detoxification of poisons and other harmful substances.
Also known as golgi complex, these are piles of flattened sacs layered one above the other. One can observe the golgi apparatus in the labeled animal cell parts diagram. The golgi apparatus is situated near the cell nucleus and besides the stacked sacs, it also contains large number of vesicles. The main function of this golgi complex to receive proteins synthesized in the ER and transformed it into more complex proteins. The vesicles in the apparatus are used to send molecules to the cellular membrane, from where excretion takes place.
Lysosomes are produced by the Golgi apparatus and appear like small spherical bodies featuring a single membrane confining it. Their prime function is breaking down of cellular waste substances from the cell into simplified substances. The simplified versions are then transferred to the cytoplasm of the animal cell for building new cell materials. Lysosomes are able to do this with the help of over three dozen types of hydrolytic enzymes like lipases, nucleases, proteases, polysaccharidases, etc. Thus, lysosomes are responsible for digestion of nutrients in animal cells.
Ribosomes are small, spherical organelles comprising 65% ribosomal RNA and 35% ribosomal proteins. These organelles are sites of protein assemblage and are responsible for protein synthesis. They occur scattered in the cytoplasm and are also found adhering to the surface of ER. Animal cells contain ribosomes with four strands of RNA.
Vacuoles are fluid-filled cavities encompassed by a membrane present within the cell itself. These vacuoles act as storage areas for the cells and play significant roles in release of cellular waste substances and intracellular digestion. Vacuoles present in animal cells are small as compared to plant cell vacuole.
As you read the information on each organelle, refer to the labeled animal cell diagram for better clarity. To check if you have understood the cell parts, draw a blank animal cell diagram and try to fill in the different parts without referring to the labeled animal cell diagram. This will help you understand how much you have comprehended. Read more on similarities between prokaryotic and eukaryotic cells.