All cells, whether prokaryotic or eukaryotic, share fundamental parts and functions that are essential for life. These include a plasma membrane, cytoplasm, DNA, and ribosomes.
Common Parts of a Cell
-
Plasma Membrane: This outer boundary acts as a selective barrier, regulating the passage of substances in and out of the cell. It's composed primarily of a phospholipid bilayer with embedded proteins. Its main function is to provide a barrier between the inside and outside of the cell and to regulate transport of materials.
-
Cytoplasm: The cytoplasm is the gel-like substance within the cell membrane, excluding the nucleus in eukaryotic cells. It consists of cytosol (fluid) and organelles. It provides a medium for chemical reactions and supports organelles.
-
DNA (Deoxyribonucleic Acid): DNA carries the genetic instructions for the cell's functions and development. In prokaryotes, DNA is usually a single circular chromosome located in the nucleoid region. In eukaryotes, DNA is organized into multiple linear chromosomes within the nucleus. The primary function is to store and transmit genetic information.
-
Ribosomes: These are responsible for protein synthesis. They read the mRNA (messenger RNA) instructions from the DNA and assemble amino acids into proteins. Ribosomes are found in both prokaryotic and eukaryotic cells, either free in the cytoplasm or bound to the endoplasmic reticulum. Their main function is to synthesize proteins.
Common Functions of a Cell
-
Metabolism: All cells carry out metabolic processes, which are the sum of all chemical reactions that occur within the cell. These reactions provide energy and building blocks for the cell.
-
Growth and Reproduction: Cells grow by increasing in size and mass. Cells reproduce to create new cells, either through binary fission (in prokaryotes) or mitosis and meiosis (in eukaryotes).
-
Response to Stimuli: Cells can respond to changes in their environment, such as changes in temperature, pH, or the presence of chemicals. This responsiveness allows cells to maintain homeostasis.
-
Homeostasis: Cells maintain a stable internal environment despite external changes. This involves regulating temperature, pH, ion concentrations, and other factors.
-
Protein Synthesis: Using the genetic information encoded in DNA, cells synthesize proteins, which carry out a vast array of functions, from catalyzing reactions to providing structural support. Ribosomes are the primary site of protein synthesis.
Examples of Organelle Functions (Eukaryotic Cells)
While not all cells have organelles, eukaryotic cells do. These membrane-bound structures perform specific tasks within the cell.
| Organelle | Function |
|---|---|
| Nucleus | DNA storage, control center of the cell |
| Mitochondrion | Energy production (ATP synthesis) |
| Endoplasmic Reticulum (ER) | Lipid and protein synthesis; detoxification (Smooth ER); protein folding and modification (Rough ER) |
| Golgi Apparatus | Modifies, sorts, and packages proteins and lipids for transport |
