Introduction
Cells are the basic building blocks of living organisms. They vary greatly in size, shape, and structure and perform a wide array of activities that are essential to life. All cells are derived from other cells through the process of cell division, which involves the multiplication of specialized contents within an organism’s body.
There are two main types of cells: prokaryotic and eukaryotic. Prokaryotes lack a nucleus and membrane-bound organelles; these are single-celled organisms that include bacteria, archaea, and some protozoans. On the other hand, eukaryotes contain both a nucleus and membrane-bound organelles such as mitochondria; they can be either single-celled (e.g., yeast) or multicellular (e.g., plants and animals).
This article will explore the different types of cells in greater detail to help you understand how they differ from one another:
Prokaryotic Cells
Prokaryotic cells are the most basic cells found in nature, and they are found in both plants and animals. They are much simpler than eukaryotic cells, and they typically lack a nucleus and any internal organelles. Prokaryotic cells have very small structures and are important components of many biological processes.
In this section, we will discuss prokaryotic cells in more detail.
Bacterial Cells
Bacterial cells are prokaryotic cells, meaning they lack a nucleus and membrane-bound organelles like other kinds of eukaryotic cells. They have a cell wall outside the cell membrane that provides shape and strength. Bacteria typically range in size between 0.1-10 μm, with most being around 1 μm long. Shapes of bacteria depend on their species but may include rods, spiral helixes, balls or cocci as well as more complex shapes.
Unlike eukaryotes, bacterial cells replicate by binary fission rather than mitosis. During this type of replication all the DNA is duplicated and then the cell splits to create two new identical daughter cells with all of the original genetic information intact. This process can happen rapidly for some types of bacteria, allowing them to multiply quickly within the body or in an environment to create infection or illness.
Bacterial cells also contain several cellular components essential for their survival that are not found in eukaryotes including:
- Ribosomes (for protein production)
- Pili (to help attach to other surfaces)
- Flagella (for motion)
- Fimbria (to generate inflow of nutrients).
Additionally, these organisms possess an energy generating system that allows them utilize organic compounds as energy sources using a process called respiration rather than photosynthesis like plants do. Finally, bacteria possess different types of capsule layers which help them adhere better to certain surfaces, further aiding colonization and infection capabilities.
Archaea Cells
Archaea cells are single-celled prokaryotes that inhabit a variety of extreme environments. They can be found in places where most other living things cannot survive, including hydrothermal vents, deserts, and saline lakes. Archaea cells receive their energy from metabolism rather than photosynthesis and tend to look different from both bacteria and eukaryotic organisms. They often appear larger and somewhat more complex than bacteria with an extra layer of cell membrane and a distinctive outer covering known as a glycocalyx.
Archaea possess traits typically found in both prokaryotes and eukaryotes, making them something of a mysterious mixture between the two organism types. Unlike bacteria or other prokaryotes that have a circular DNA genome or loop, archaea species are distinct in that they contain linear chromosomes inside a nucleoid region within the bowels of their cell. While many archaea species exist as singular cells, some form colonies that are often encased in protective sheaths called tubules or capsular sheaths.
Eukaryotic Cells
Eukaryotic cells are present in all eukaryotic organisms, from the tiniest single-celled organisms to complex multi-cellular organisms like humans. These cells are characterized by their membrane-bound organelles which are specialized for specific functions.
In this heading, we’ll discuss some of the key features of eukaryotic cells and their importance in the functioning of the organisms:
Animal Cells
Animal cells are eukaryotic cells forming the basic structure of multicellular organisms classified under Animalia. Animal cells, unlike Prokaryotic cells, are more structured and contain cellular components, each specialized for specific functions. These components are collectively called the organelles.
Major differences between plant and animal cells include the presence of cell walls, vacuoles and plastids in plant cells, which animal cells do not possess.
The basic structure of animal cells consists of a plasma membrane that encloses various organelles. A prominent internal organelle is the endoplasmic reticulum (ER), which helps maintain homeostasis within the cell by regulating protein synthesis and aiding in lipid storage and metabolism. Another important organelle is the Golgi body which carries out two vital functions – storage and transport (secretion) of secretory products. Other prominent features include mitochondria, ribosomes, lysosomes and cilia/ flagella.
In addition to these components, there are also proteins present on both sides of the cell membrane that form part of its external structure known as cytoskeletons; their major function is to provide support to maintain their shape as well as their motility by providing locomotion during cell movement or formation of filopodia during endocytosis or phagocytosis activities to engulf foreign objects entering inside them. These proteins also aid in anchoring external secretory vesicles carrying extracellular signals from outside environment into different parts inside a cell or even connecting with other closely located neighbor cells during growth or differentiation activities giving rise to various structures like nervous system, muscles etc outside it’s perimeter.
Plant Cells
Plant cells are unique and distinct from other eukaryotic cells like animal cells. The most distinguish feature is that plant cells have a thick outer wall, known as the cell wall. This wall is composed of cellulose, which provides the cell with structural integrity and shape. It also serves to regulate the flow of water and solutes into and out of the cell.
Additionally, plant cells contain chloroplasts which are specialized organelles containing chlorophyll that allow for photosynthesis; a process used for energy production by plants. Furthermore, plant cells contain plastids called leucoplasts that perform functions such as oil production or storage, while chromoplasts can produce pigments in different colors in fruits or flowers.
The cytoplasm contains various structures such as vacuoles, endoplasmic reticulum, mitochondria and ribosomes just like any eukaryotic cell. However condensation granules could be found in greater number to limit the movement of cytoplasm within a cell due to its thick cell walls which means they remain embedded inside them there entire life cycle.
The nucleus on the other hand contains several nucleoli embedded into it that are responsible for protein synthesis within the cell by functioning as sites of assembly for ribosomes thus facilitating protein syntheisis throughout different subcellular areas depending upon the requirement unlike what animal cells possess where these processes take place only in cytoplasmic membrane.
Fungal Cells
Fungal cells are unique eukaryotic cells which are present in all forms of life, from single-celled microorganisms to complex multicellular organisms. Fungal cells typically have a cell wall composed of chitin, which is a polysaccharide consisting of N-acetylglucosamine. These walls protect fungi from the environment and provide stability. Fungal cells also contain other cellular components such as cytoplasm, nucleus, mitochondria, vacuoles, and in some cases even flagella.
Fungi can form hyphae to connect with other fungal and host tissues for nutrition exchange. In these hyphae structures known as plasmogamy and then karyogamy happens inside their cells when two haploid nuclei from different parent mycelia fuse to create a single diploid nucleus. This process often creates asexual and sexual reproductive strategies within the fungal species. Additionally some fungi may also produce spores during sexual reproduction which can be dispersed through air or water currents and then germinate at another location where they will begin new colonies.
The importance of fungal cells is linked to the important roles they have in the food chain processes like decomposition of organic material like leaves or dead animals in forests ecosystems; as well personal relationships with humans due to the study of medicinal agents derived from them or industrial uses such as enzymes production used in bread baking and bioethanol production processes among many others examples.
Algal Cells
Eukaryotic cells, found in single-celled and multi-celled organisms, include a variety of cell types. Algal cells are eukaryotic cells that can contain one or more chloroplasts. Chloroplasts are the organelles within the cell which capture sunlight energy and use this energy to produce food from carbon dioxide, water and minerals through a process known as photosynthesis.
Photosynthesizing algal cells can be found in both saltwater and freshwater ecosystems from coastlines to ponds and lakes. There are both unicellular (one-celled) algal species such as Euglena and diatoms, and multicellular species such as seaweeds which may grow up to several meters in length. Algal cells may be autotrophic or heterotrophic; the former make their own food while the latter feed on other organisms.
The walls of algal cells helps give structure to their bodies; these providing protection from environmental stressors that occur in aquatic environments such as extremes temperatures or varying salinity levels. Additionally, many algal species have specialized structures called flagella that help them move around in their environment. These unicellular algae can reproduce asexually by dividing themselves in half when conditions are favorable for growth; others may reproduce sexually within larger populations through meiosis or through sexual fusion of two compatible gametes (individually anisogamous).
Conclusion
All living things – from plants and animals to fungi and bacteria – are made up of cells. The study of cells is a branch of biology called cellular biology.
There are thousands of different types of cells, each specialized to carry out specific functions in an organism. Cells are broadly divided into two categories based on their structure and function: prokaryotic cells (bacteria) and eukaryotic cells (plants, animals, algae, fungi).
- Prokaryotic cells are simple, small structures without membrane-bound organelles; most often found in the single-celled organisms like bacteria.
- Eukaryotic cells contain several membrane-bound organelles that contain their own set of genetic instructions within them, providing more complexity than prokaryotic cells. Examples include plant and animal cells with complex organelles like the nucleus, mitochondria and chloroplasts.
No matter what type of cell it is, each one contains genetic material in some form which tells the cell how to make proteins for it to function correctly within an organism. Without this vital genetic information from DNA or RNA codes stored in these cellular structures, organisms would not survive or grow as they do today.
