An Overview Of Cells And Organelles

Cells, the basic building blocks of organisms. Because they are so small, we can’t see them with our naked eyes. However, these small units contain even smaller things that are important for our daily life - organelles. What are cells? What are organelles and what do they do? Read this article to find out!

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Cells

There are four concepts of the cell theory:

1. A cell is the basic structural and functional unit of living organisms.

2. The activity of an organism depends on the collective activities of its cells.

3. According to the principle of complementary, the biochemical activities of cells are dictated by the relative number of their specific subcellular structure.

4. Continuity of life has a cellular basis.

Cells are significant because our daily movement, performance of vital life functions, growth, repair, and reproduce all depend on them.

In general, a cell has three main regions or parts, that is, the nucleus, cytoplasm and plasma membrane.

Nucleus

The nucleus is the control center of the cell. It contains genetic material known as deoxyribonucleic acid, or DNA. DNA is needed for building proteins and necessary for cell reproduction.

Plasma Membrane

The plasma membrane is the transparent barrier for cell contents, and it also contains cell contents. Primarily, the plasma membrane has four functions:

1. Physical barrier: separating the external and internal world of the ell.

2. Regulate entry

3. Responsiveness and communication (ability to send and receive messages)

4. Structure and stability

We call the plasma membrane’s structure a fluid mosaic model, which is constructed of phospholipids, cholesterol, proteins, and sugars.

Phospholipid arrangement, or the phospholipid bilayer, is semipermeable, which means it only lets in and out certain molecules, and the others are blocked. The important characteristic is that the polar “heads” of the lipids are hydrophilic, or “water loving”. They are oriented on the inner and outer surfaces of the membrane. And the nonpolar “tails” of the lipid, are “water hating”, or hydrophobic, and are located in the center of the membrane. This important structure makes the plasma membrane impermeable to most water-soluble molecules.

Proteins in the plasma membrane are responsible for specialized functions. Proteins can be enzymes, receptors, or channels or carriers that transport molecules or particles.

Sugars, typically glycoproteins that are attached to proteins that abut the extracellular space. Additionally, Glycocalyx, the fuzzy, sticky, sugar-rich surface, provides another layer of protection to the cell.

Cytoplasm

Cytoplasm, the material outside of the nucleus and inside the plasma membrane, is the site of most cellular activities, and houses the organelles.

Organelles are metabolic machinery of the cell, and they are like the “little organs” that perform functions for the cell.

• Mitochondria, known as the “powerhouses” of the cell. Mitochondrial wall consists of a double membrane with cristae on the inner membrane, and provides cellular energy.

• Ribosomes, made of protein and ribosomal RNA, are the sites of protein synthesis, a process where proteins are made. Ribosomes can be found at two locations, in the cytoplasm and as part of the rough endoplasmic reticulum (rough ER).

• Endoplasmic reticulum (ER), Including rough ER and smooth ER. Rough ER is covered with ribosomes, and synthesizes proteins. It is also responsible for the transportation of proteins. Smooth ER related to lipid metabolism, and detoxifies drugs and pesticides.

• Golgi apparatus, appears as a stack of flattened membranes, modifies and packages proteins arriving from the rough ER via transport vesicles.

• Lysosomes, the membranous “bags” packaged by the Golgi apparatus. It contains enzymes produced by ribosomes.

By reading and learning the functions of the organelles, it is not hard to discover that the interaction and communication between them are extremely important for the regular performances of actions. These organelles make up our cells, and cells make up us!

It is amazing how our body contains these cells and systems that work like elaborate machineries, so it becomes important for us to cherish life, keep health, and love ourselves!

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Written by: Benetta Wang