Cells are the basic structural and functional units of life.
They can be classified into two main types: prokaryotic cells (found in bacteria and archaea) and eukaryotic cells (found in plants, animals, fungi, and protists).
Both cell types share some basic structures and functions, but eukaryotic cells are generally larger and more complex than prokaryotic cells.
Structure of Cell
Here are the main structures (organelles) and functions of a typical eukaryotic cell:
1. Cell membrane (plasma membrane):
A selectively permeable barrier that surrounds the cell, controlling the passage of substances in and out of the cell.
It is composed of a phospholipid bilayer with embedded proteins.
Function:
Controls the movement of substances in and out of the cell, maintaining a balance of ions, nutrients, and waste products.
It also mediates cell-to-cell communication and recognition.
2. Cytoplasm:
The gel-like substance within the cell membrane that contains organelles, enzymes, and other molecules required for the cell's functions.
It is the site of many cellular processes.
Function:
Provides a medium for cellular processes to occur, suspending organelles and facilitating the transport of molecules throughout the cell.
3. Nucleus:
The control center of the cell, which contains the cell's DNA, organized into chromosomes.
The nucleus is surrounded by a double-layered nuclear membrane and contains a nucleolus, which is involved in ribosome synthesis.
Function:
Contains genetic information (DNA) and regulates gene expression, controlling the synthesis of proteins required for cellular function, growth, and reproduction.
It also houses the nucleolus, which produces ribosomes.
4. Endoplasmic reticulum (ER):
A network of membranous tubules and sacs that play a crucial role in protein and lipid synthesis.
The ER can be classified into two types:
Smooth ER (involved in lipid synthesis and detoxification)
Rough ER (studded with ribosomes and involved in protein synthesis).
Function:
Involved in protein synthesis (rough ER) and lipid synthesis (smooth ER).
The rough ER is studded with ribosomes and produces proteins destined for secretion or incorporation into the cell membrane.
The smooth ER produces lipids and detoxifies harmful substances.
5. Ribosomes:
Small structures made of protein and RNA that are responsible for protein synthesis.
They can be found free-floating in the cytoplasm or attached to the rough ER.
Function:
Small structures made of protein and RNA responsible for protein synthesis.
They can be found free-floating in the cytoplasm or attached to the rough ER.
6. Golgi apparatus:
A series of flattened, membrane-bound sacs that modify, package, and sort proteins and lipids for transport to their final destinations within or outside the cell.
Function:
Modifies, packages, and sorts of proteins and lipids for transport to their final destinations within or outside the cell.
7. Mitochondria:
The powerhouse of the cell, responsible for producing ATP (adenosine triphosphate), the cell's primary energy source, through cellular respiration.
Mitochondria have their own DNA and are believed to have originated from an endosymbiotic relationship with bacteria.
Function:
Produce ATP (adenosine triphosphate), the cell's primary energy source, through cellular respiration.
8. Lysosomes:
Small, membrane-bound organelles containing hydrolytic enzymes that break down waste materials, cellular debris, and foreign substances.
Function:
Contain hydrolytic enzymes that break down waste materials, cellular debris, and foreign substances.
9. Peroxisomes:
Organelles that contain enzymes involved in various metabolic reactions, including the breakdown of fatty acids and the detoxification of harmful substances.
Function:
Contain enzymes involved in various metabolic reactions, including the breakdown of fatty acids and the detoxification of harmful substances.
10. Cytoskeleton:
A network of protein filaments that provides structural support, maintains cell shape, and aids in cell movement and division.
The cytoskeleton consists of microtubules, microfilaments, and intermediate filaments.
Function:
A network of protein filaments that provide structural support, maintain cell shape, and aid in cell movement and division.
The cytoskeleton consists of microtubules, microfilaments, and intermediate filaments.