When asked what is a cell? An individual can actually answer immediately that it is the smallest unit of living thing. It carries the very essence of being a living thing, the DNA and how it works to be a living organism. But what is actually a cell? Although this has been taught many times, it is good to take note of the basic terms and definitions that revolves within the cell and its parts.

In a human body, there are 80 to 100 trillion cells approximately. It exists as an active thing in order to support life of the organism as a whole. Let’s first take note that what will be discussed in the following paragraphs will be parts of a cell in a normal condition. Cancer cells will discuss extensively on a different topic.


In general, protoplasm includes the protein material, carbohydrate material, lipid, nucleic acids and inorganic substances which make a cell to be considered a living entity. Water comprised almost 75% of the protoplasm due to its property to hold things together and make things process properly. In a proper way, the amphipathic property of water contributes a lot to the overall functioning of the cell.

Nine processes in Cell Physiology

  1. Irritability – Cells has the ability to respond to stimulus.
  2. Conductivity – Cells, especially in nerve cells, they have the capacity to transmit information from the outer environment through stimuli and send it to another point.
  3. Contractility – Cells have the ability to change the shape when a stimulus is elicited. Muscle cells are the perfect example.
  4. Absorption – Cells have the capacity to accept materials freely or selectively in order to maintain the proper functioning of each cell.
  5. Metabolism – Cells have the capacity to utilize the materials being taken inside the cell membrane and use it to produce Adenosine Triphosphate (ATP).
  6. Secretion – Some cells may have the capability to release substances which can be protective in nature.
  7. Excretion – Since cells have the capacity to metabolize substances, there are residues from this process in which the excretory system of the cells takes care of.

Parts of the Cell and Its Function – Essence of Cell Physiology

A fundamental knowledge of parts of the cell will enable an individual to deduce cellular abrasions easily and will easily apprehend the impact of each defect on a particular cellular part.

Membranous Organelles Description Function
Cell Membrane It is also called plasmalemma. It has an electron-lucent layer which measures between 3.5 – 4.0 nm.
  1. It permeable to certain substances only.
  2. It involves in cell-to-cell communication.
  3. It can be hormone receptors.
  4. It generates messenger molecules.
Rough endoplasmic reticulum / Granular endoplasmic reticulum Network of continuous irregular channels with surrounding ribosomes. It has cisternae, which are flattened saccules as a result of parallel formation of the membranes.
  1. The place where in secretory proteins are synthesized.
  2. Lysosomal enzymes are synthesized.
Smooth endoplasmic reticulum / Agranular endoplasmic reticulum These are also network of continuous channels with the absence of cisternae. It is found in cells that secrete steroid hormones.
  1. It secretes steroid hormones.
  2. Plays a great role in muscle contraction, as it keeps and release Calcium ions in order to propagate such contraction.
  3. It synthesizes membrane phospolipids, cholesterol, ceramide and glycogen.
Golgi Complex/ Golgi apparatus Several flattened saccules that has the ability to form glycoproteins.
  1. It is primarily the place wherein the packaging and sorting of the glycoproteins and lipoproteins are done in preparation for its delivery to other parts of the cell.
Mitochondria Coined to be the powerhouse of the cell.
  1. Mainly becomes the energy source of the cell.
  2. It also plays a role in formation of steroids.
Lysosomes Though it measures 0.2 to 0.55 micormeters It has more than 50 enzymes within it.
  1. Scavenges the waste materials of the cell.
  2. During the intracellular digestion, those that can be reused for cellular activity may diffuse again into the cytoplasm, while those that are not needed may take the form of residual bodies contained in vacuoles.
Peroxisomes A membrane-bound organelle that is larger than lysosomes. It has nucleoids and 40 other enzymes which are unique only to its structure. It can generate hydrogen peroxide which distinctively inhibits the accumulation of free radicals and its oxidation on the cell.
Cytoskeleton (microtubules, intermediate filaments and microfilaments) It is involved it cell locomotion or structure of the cell which makes it distinct from other cells. Intermediate filaments – provide structure and support on a cell and serves as a joining channel for other cells.

Microtubules – important in cell division and movement of the cell. It takes the form of cilia, flagella and centrioles.

Microfilaments – it has a role in the locomotion of the cell too. However, it has a distinct purpose in enabling certain parts of the cell to contract. Stabilization of the plasmalemma is also in debt for these structures.


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