Anatomy of the Human Cell

Written By: Alicia Roice

Image by Technology Networks via https://www.technologynetworks.com/cell-science/news/human-body-mostly-composed-of-just-five-major-groups-of-cell-338321

Cells are the basic building blocks of human life. They’re what help us carry out our day-to-day activities, makeup tissues and organs, provide body structure, convert nutrients into energy, and execute other specialized functions. They also carry genetic material in the form of DNA or deoxyribonucleic acid.

Cells consist of many different parts with specialized functions, called organelles. Each of these organelles plays a role in maintaining the cell’s shape and other cellular activities. This article will be discussing the anatomy of a human cell.

ORGANELLES AND THEIR FUNCTIONS:

Picture from Body Structure and Functions, 13th Edition, Chapter 4

This is a list of some of the most important organelles in a human cell, as well as their functions:

• Cell membrane: The cell membrane, or plasma membrane, surrounds the cell, separating the cell from its external environment, protecting it from invaders, and regulating the passage of materials into and out of the cell. This makes it semipermeable — though it is able to let some materials in, it ejects other materials out. The membrane is a phospholipid bilayer, and it allows water to pass through by the process of diffusion (materials moving from areas of higher to lower concentration). Embedded proteins in the phospholipid bilayer permit molecules and ions to pass through.
• Nucleus: The nucleus is the “brain” of the cell, as it directs all cellular activities and facilitates cell division. It also contains DNA, or deoxyribonucleic acid, the genetic material of the cell, which holds all of the material that makes us who we are in terms of genetic traits and characteristics. The nucleus is surrounded by a membrane called the nuclear envelope, and it protects the DNA and holds the nucleus away from the rest of the cell.
• Nucleolus: Each nucleus contains one or more nucleoli. The nucleolus is a small round body that consists of ribosomes. The nucleolus aids in protein synthesis.
• Ribosomes: Ribosomes are found in the nucleolus, the endoplasmic reticulums, and are scattered throughout the cell. They are made up of ribonucleic acid and protein. Ribosomes move from the nucleus through pores in the nucleus into the cytoplasm to assist in protein synthesis by processing the nucleus’ directions for making proteins.
• Cytoplasm: The cytoplasm is a jelly-like fluid that contains cytosol. It fills the space between the plasma membrane and the nucleus and holds the organelles. The cytoplasm is also where chemical reactions of the cell take place, such as protein synthesis and cellular respiration.
• Centrosome and centrioles: Centrosomes and centrioles play an important role in cell division, as the centrosomes manufacture spindle fibers used during the metaphase stage of mitosis. A centrosome consists of two centrioles, which, in turn, are also involved in developing spindle fibers.
• Endoplasmic reticulum: The endoplasmic reticulum acts as a transportation channel, transporting materials out of the cell. It can also accumulate essential proteins and store them, acting as a storage area. There are two types of endoplasmic reticulum: rough and smooth. Rough ER contains ribosomes on the outside and plays a crucial role in synthesizing proteins. Smooth ER does not have ribosomes on its outer surface, but it plays a role in the production of cholesterol, metabolism, and detoxifying the body of harmful drugs.
• Mitochondria: The mitochondria are responsible for converting energy that comes from the food we eat into ATP, the form of energy that the cell uses. It contains its own DNA, called mitochondrial DNA, so it can make copies of itself apart from the cell.
• Golgi apparatus: The Golgi apparatus is responsible for synthesizing carbohydrates and combining them with protein molecules as they pass through. It also stores and packages secretions so that they can be transported from the cell by the endoplasmic reticulum.
• Lysosomes and peroxisomes: Both of these organelles are responsible for recycling worn-out cell components, digesting foreign invaders, and cleansing the cell of toxic substances.
• Cytoskeleton: The cytoskeleton makes up the structure of the cell, and it gives it its shape. It consists of long fibers that intertwine to support the cell, and it also plays a role in cell division and movement. It also directs organelle and substance movement within the cell.
• Pinocytic Vesicles: In order to obtain large molecules such as proteins or lipids for food, the cell will use pinocytic vesicles. These are formed when the cell membrane folds inward, creating a pocket, which then closes and pinches away from the cell membrane and forms a vacuole in the cytoplasm from which it can obtain the food. This process is called pinocytosis, or “cell drinking.”
• Cilia and flagella: Both of these are used for transportation. The cilia are short, hairlike protrusions, while the flagella have a singular, tail-like protrusion. Both of these are composed of fibrils that vibrate to produce movement.

Sources

“What Is a Cell? — Genetics Home Reference — NIH.” U.S. National Library of Medicine, National Institutes of Health, ghr.nlm.nih.gov/primer/basics/cell.

Body Structures and Functions Updated 13th Edition. www.amazon.com/Structures-Functions-Updated-Softcover-Version/dp/1337907545.