The Cell

The human body is composed of a large variety of cells, tissues and organs and is originally derived from a single fertilised cell. Most cells have certain features in common.

Once fertilised, an egg cell will develop into an embryo and subsequently into a fully mature body. It intrinsically carries all of the information required to make this complex organism.

When observing a cell under a light microscope, you can observe the outer boundary of the cell membrane, cytoplasm, a gel-like substance inside the cell, the nucleus, the control centre of the cell (often visible as a darker area), organelles, various structures like mitochondria, endoplasmic reticulum and ribosomes, depending on the cell type.

Granules within cells, like those in secretory cells, can become visible using dyes or stains because these substances bind to a specific component of the granules, enhancing contrast under a microscope.

The invention of the electron microscope, first developed in the 1930s and built by Ernst Ruska and Max Knoll in 1931, laid the groundwork for future developments and the widespread use of electronic microscopy in biological research. Electron microscopes can resolve structures down to about one nanometre allowing scientists to observe much smaller components of cells such as organelles (ribosomes and endoplasmic reticulum) and even large molecules. It provides detailed images of cell ultra-structure, revealing intricate details not visible with light microscopes such as the arrangement of proteins and membranes. Scanning electron microscopy (SEM) allows for 3D imaging of surfaces providing spatial context to cellular structures. This technology has led to significant advancement in various fields, including virology (the study of viruses) and the understanding of cellular processes, including the development of new medical therapies.

Within every cell there are tiny organelles in the cytoplasm which carry out all processes of life: growth, respiration, nutrition, digestion, excretion, reproduction and so on. Some cells have become very specialised for the efficient running of the body and others constitute the physical structure of the body.

During early mitotic cell division, cells become allocated different permanent roles and when these cells multiply, they form tissues which are composed of similar cells with a similar function, cooperating at a particular task. Various tissues then become organised to form complex structures like the heart or the liver.

The largest cell organelle, the nucleus is enclosed by a nuclear envelope consisting of 2 membranes perforated with pores. Nuclear pores control the exchange of materials between the nucleus and the cytoplasm. The nucleus contains the coiled-up Chromosome. There are 23 pairs of chromosomes in a human nucleus and these are only visible individually during cell division. The nucleus is the site of storage of Deoxyribonucleic Acid [DNA] on chromosomes. DNA is the molecule of inheritance which controls all the activities of the cell and is well protected from mechanical damage in this location.

There are also nucleoli associated with the nucleus and these manufacture ribosomes which are tiny organelles composed of protein and Ribonucleic acid [RNA], they are vital for the synthesis of proteins. Ribosomes are found in the cytoplasm freely or attached to a system of flattened membrane-bound sacs forming sheets and tubes.

This system is known as endoplasmic reticulum (ER), it is known as rough endoplasmic reticulum with ribosomes attached to it. Smooth ER acts as a system for dispersing and transporting proteins assembled on the ribosomes.

Mitochondria are large cigar-shaped organelles with folded membranes. They are the powerhouse of the cell as they generate ATP [Adenosine triphosphate] by aerobic metabolism. ATP is the universal molecule responsible for supplying energy to all biological processes.

The Golgi apparatus, also known as the Golgi complex or Golgi body, is a vital organelle found in eukaryotic cells. It is made up of a stack of membrane-bound sacs called cisternae. It plays a key role in processing sorting and packaging of proteins and lipids. It could be described as functioning as the cell's post office, processing and sorting proteins and lipids for delivery to their final destinations. Its role in modifying and packaging molecules is essential for maintaining cellular function and overall homeostasis.

Lysosomes are organelles, membranous sacs containing digestive enzymes to facilitate clean-up operation for worn-out cell organelles and other components.

The structure of the plasma membrane surrounding the cell forms a barrier and is essential for maintaining the integrity and functionality of the cell, acting as a gatekeeper that regulates interactions with the external environment, while supporting communication and transport functions.

Cholesterol is a vital component of flexible cell surface membranes, significantly contributing to their flexibility, stability, and function, by regulating fluidity, supporting proteins, and influencing signalling cholesterol. It is essential for the proper functioning of cells and overall cellular health.

We can learn more about the tissues and organs of the amazing human body and understand how too much sugar saturation within the body can prohibit good cell health and even communication.