Cell Structure, Tissues, and Human Biology Fundamentals
Cellular Components and Their Functions
Organelles
Endoplasmic Reticulum: Membrane system forming a complex network of tubules and sacs throughout the cytoplasm. Two types exist: smooth and rough.
Mitochondria: Elongated organelles with a double membrane. Their primary function is to generate energy for the cell.
Vacuoles: Membranous vesicles responsible for storing various substances.
Lysosomes: Membranous vesicles containing digestive enzymes.
Golgi Apparatus: Membranous organelle composed of grouped vesicles and flattened sacs.
Ribosomes: Small, non-membranous organelles made of RNA and proteins.
Cytoskeleton: A network of protein filaments that maintains the cell’s shape.
Tissues
Epithelial Tissue
Composed of one or more layers of closely packed cells. There are two main types:
- Epithelium Tissue: Covers the body’s external surface (skin) and lines cavities and tracts, such as the digestive and respiratory systems.
- Glandular Epithelium: Groups of cells that form glands, producing and releasing substances (e.g., pancreas, salivary glands).
Muscle Tissue
Composed of specialized elongated cells called muscle fibers, which contract to produce movement. There are three types:
- Skeletal or Striated Muscle Tissue: Forms the muscles of the locomotor system. Contracts voluntarily.
- Cardiac Muscle or Myocardium: Found in the heart. Contracts involuntarily.
- Smooth Muscle: Found in the walls of some organs (e.g., stomach, uterus). Contracts involuntarily.
Cell Differentiation
The process by which cells specialize during embryonic development, involving changes at different levels:
- Cell Shape: Related to the function performed. Can be spherical, polyhedral, prismatic, elongated, or starry.
- Function: Cells are programmed to perform specific functions.
- Activity of Cytoplasmic Organelles: The number and activity of organelles depend on the cell’s function.
Cell Transport Mechanisms
Diffusion: The free passage of small molecules, such as oxygen and carbon dioxide, from an area of higher concentration to an area of lower concentration.
Osmosis: A special type of diffusion involving the passage of water from a more diluted to a more concentrated medium. Tonicity measures the concentration of a solution.
Active Transport: Requires energy (ATP) to transport substances from an area of lower concentration to an area of higher concentration.
Cell Structure and Theory
The cell was first observed in 1665 by Robert Hooke, who examined cork oak under a microscope.
Schleiden and Schwann formulated the Cell Theory, which states:
- All living things are composed of cells.
- Cells are the basic units of structure and function in living things.
- All cells are produced from pre-existing cells.
Human Biology Fundamentals
Definition of a Human Being
Human beings are living organisms (belonging to the animal kingdom) with eukaryotic cells and heterotrophic nutrition.
Like all living things, humans are made of cells and perform three vital functions: nutrition, interaction, and reproduction.
Levels of Organization
Subatomic → Atomic → Molecular → Cellular (Organelles) → Cellular Level
Proton, Neutron, Electron → Atoms → Molecules (Complex Biological Functions) → (Vital Functions)
Macromolecules
Biomolecules → Multicellular Level (Tissues, Organs, Systems)
Ecosystem Level → Community Level → Population Level
Eukaryotic Cell Structure
Eukaryotic cells have three basic structures:
- Membrane: A thin layer that separates the cell from the external environment.
- Cytoplasm: The interior of the cell, composed of liquid (water) and organelles.
- Nucleus: Contains the genetic material (DNA) to control vital functions.