Cell Biology Essentials: Components, Differentiation, and Tissue Types
Cell Components
Membrane
A thin layer that separates the cell from the external environment. It allows the entrance of nutrients and the exit of waste products.
Cytoplasm
The cell’s interior where organelles can be found.
Nucleus
Contains genetic material that holds the information to control vital functions such as nutrition, reproduction, and interaction.
Endoplasmic Reticulum (ER)
A membranous system formed by a complex set of tubules and sacs. Two types:
Rough Endoplasmic Reticulum (RER)
Has ribosomes. It synthesizes proteins.
Smooth Endoplasmic Reticulum (SER)
Does not contain ribosomes.
Mitochondria
Made of a double membrane. Its main function is to obtain energy and perform cellular respiration.
Vacuoles
Membranous vesicles that store different substances.
Lysosomes
Membranous vesicles that perform the digestion of molecules.
Golgi Apparatus
A membranous organelle formed by a group of vesicles and flattened sacs. Its main function is to process proteins from the ER.
Ribosomes
Do not have a membrane. They appear scattered throughout the cytoplasm or attached to the RER.
Cytoskeleton
A set of protein filaments. They help maintain the cell’s shape.
Cell Differentiation
The process used by cells to specialize. It involves changes at different levels:
Cell Shape
The shape is related to different specific functions. Most cells have a spherical shape.
Function
Some cells are programmed to perform certain functions.
Activity of Cytoplasmic Organelles
Cell specialization also requires changes at the cytoplasmic level, affecting the number and activity of the organelles.
Types of Tissues
A tissue is a cluster of cells with the same morphology and function. A basic classification includes epithelial, connective, muscular, and nervous tissues.
Epithelial Tissue
Covers the surface of the body, lining internal cavities and enveloping different organs.
Epithelium Tissue
Lines the surface of the body, including the skin and hollow cavities that communicate with the exterior. Examples: respiratory tract (mucosa) and the digestive tract.
Glandular Epithelium
Produces and releases substances. Example: salivary glands.
Connective Tissues
They have three functions: support, unify, and connect systems. There are two types: non-specialized (connective tissue proper) and specialized (adipose, cartilaginous, bone).
Connective Tissue Proper
Located in the deepest layer of our skin. It constitutes the stuffing between organs.
Adipose Tissue
Composed of cells that accumulate fats. Their main function is to accumulate energy.
Cartilaginous Tissue
Is firm and elastic, and its main function is to protect joints from bones.
Bone Tissue
Is a rigid tissue, due to the great amount of minerals that are deposited in the matrix.
Muscle Tissue
Composed of special types of elongated cells called muscle fibers. They are able to contract and facilitate movement. There are two types:
Striated Muscle Tissue
Contracts voluntarily, allowing movement of the skeleton.
Smooth Muscle Tissue
Contracts involuntarily, facilitating organ movements.
Nervous Tissue
Composed of special cells called neurons, which transmit nerve impulses. The nervous system coordinates the organism.