Cell Biology

Cell biology or cytology is a branch of biology that deals with studies related to the structure and function of a cell-based on the concept that the cell is the fundamental unit of life.

• A detailed study of the cellular structure and function provides a basis for studies related to tissues, organs, and the body.
• The number of cells in an organism might differ as some organisms have a single cell while others are made up of billions of cells.
• In the case of single-celled organisms, the singular cell is studied, whereas, for multicellular organisms, individual cells of different tissues are studied.
• Initially, only the outer structure of a cell was studied due to the lack of complex microscopic processes.
• Over the years, however, advancements in other areas have made it possible to study the internal cellular components of a cell.
• Apart from the cell structure and function, cell biology also deals with cell communication and signaling.
• Cell biology also involves the studying of the cell cycle and cell division, which provides insight into the cellular composition of an organism.
• Cell biology is also linked with other studies like genetics, molecular biology, cytochemistry, and biochemistry.
• Cells are distinguished as prokaryotic and eukaryotic cells based on the complexity of the cell.
• Cell biology enables studying the biochemical mechanisms involved in cell metabolism and different forms of cellular energy.
• Focusing on the structural and functional aspects of a single cell allows a detailed understanding of the body overall.
• It is also easier to perform research on a single cell as it can be modified and observed efficiently.
• Techniques in cell biology have advanced over the years with new and improved imaging techniques to observe smaller cellular organelles.
• Cell biology, together with systemic biology, helps in the answering of complex questions like the relationship between cellular networks, the evolutionary relationship between genomes, and the complexity of the biomolecular composition of different living organisms.

Definition of animal cell

An animal cell is a eukaryotic cell that lacks a cell wall, and it is enclosed by the plasma membrane. The cell organelles are enclosed by the plasma membrane including the cell nucleus. Unlike the animal cell lacking the cell wall, plant cells have a cell wall.

Animals are a large group of diverse living organisms that make up three-quarters of all species on earth. With their ability to move, respond to stimuli, respond to environmental changes, and adapt to different modes of feeding defense mechanisms and reproduction, all these mechanisms are enhanced by their constituent elements in the body. However, animals cannot manufacture their own food like plants and hence they depend on plants in one way or another.

All living things are made up of cells that make up their body structure. Some of these living things are single-celled (unicellular) and other organisms are made up of more than one cell (Multicellular).

A cell is the smallest (microscopic) structural-functional unit of life of an organism. The cells that constitute an animal are called Animal cells and those that constitute plants are known as plant cells.

Most cells are covered by a protective membrane known as the cell wall which gives the cells their shape and rigidity.

Since animal cells lack a rigid cell wall it allows them to develop a great diversity of cell types, tissues, and organs. The nerves and muscles are made up of specialized cells that plant cells cannot evolve to form, hence giving these nerve and muscle cells have the ability to move.

Animal cell size and shape

Animal cells come in all kinds of shapes and sizes, with their size ranging from a few millimeters to micrometers. The largest animal cell is the ostrich egg which has a 5-inch diameter, weighing about 1.2-1.4 kg and the smallest animal cells are neurons of about 100 microns in diameter.

Animal cells are smaller than the plant cells and they are generally irregular in shape taking various forms of shapes, due to lack of the cell wall. Some cells are round, oval, flattened or rod-shaped, spherical, concave, rectangular. This is due to the lack of a cell wall. Note: most of the cells are microscopic hence they can only be seen under a microscope in order to study their anatomy.

But animal cells share other cellular organelles with plant cells as both have evolved from eukaryotic cells.

As noted earlier, animal cells are eukaryotic cells with a membrane-bound nucleus. therefore they have their genetic material in the form of DNA enclosed in the nucleus. They also have several structural organelles within the plasma membrane which perform various specific functions for proper cell function and generally to maintain the body normal mechanisms.

List of Animal cell organelles

Plasma membrane (Cell membrane)

Nucleus

Cytoplasm

Mitochondria

Ribosomes

Endoplasmic Reticulum (ER)

Golgi apparatus (Golgi bodies/Golgi complex)

Lysosomes

Cytoskeleton

Microtubules

Centrioles

Peroxisomes

Cilia and Flagella

Endosome

Vacuoles

Microvilli