IndietroCell Structure, Membrane Transport, and Tissue Types: Study Notes for Anatomy & Physiology
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Cells
Cell Structure
Cells are the basic structural and functional units of all living organisms. Understanding cell structure is fundamental to the study of anatomy and physiology.
Cell Membrane: The outer boundary of the cell, controlling the movement of substances in and out.
Cytoplasm: The jelly-like substance within the cell, containing organelles and cytosol.
Nucleus: The control center of the cell, containing genetic material (DNA).
Organelles and Their Functions
Organelles are specialized structures within cells that perform distinct processes.
Mitochondria: Produce energy (ATP) through cellular respiration.
Endoplasmic Reticulum (ER): Synthesizes proteins (rough ER) and lipids (smooth ER).
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris.
Ribosomes: Sites of protein synthesis.
Example: Muscle cells contain many mitochondria to meet high energy demands.
Membrane Transport
Overview
Membrane transport refers to the movement of substances across the cell membrane. Some substances pass easily, while others require assistance or energy.
Small, nonpolar molecules (e.g., oxygen, carbon dioxide) pass easily through the membrane.
Large or charged molecules (e.g., glucose, ions) require transport proteins or energy.
Diffusion vs. Osmosis
Both are passive transport processes, but they differ in what is being moved.
Diffusion: Movement of molecules from an area of higher concentration to lower concentration.
Osmosis: Movement of water molecules across a selectively permeable membrane from high to low concentration.
Active Transport
Active transport requires energy (ATP) to move substances against their concentration gradient.
Example: Sodium-potassium pump actively exchanges Na+ and K+ ions across the cell membrane.
Equation for Active Transport (Sodium–Potassium Pump):
Facilitated Diffusion
Facilitated diffusion is a type of passive transport where molecules move across the membrane via specific transport proteins.
Example: Glucose enters cells through GLUT transporters.
Osmosis and Types of Solutions
Osmosis is influenced by the type of solution surrounding the cell.
Type of Solution | Description | Effect on Cell |
|---|---|---|
Hypertonic | Higher solute concentration outside the cell | Cell loses water and shrinks (crenation) |
Hypotonic | Lower solute concentration outside the cell | Cell gains water and swells (lysis) |
Isotonic | Equal solute concentration inside and outside | No net water movement; cell remains the same size |
Example: Red blood cells in a hypotonic solution swell and may burst.
Tissues
Types of Tissues
Tissues are groups of similar cells that perform specific functions. There are four main types in the human body.
Epithelial Tissue: Covers body surfaces and lines cavities; involved in protection, absorption, and secretion.
Connective Tissue: Supports, binds, and protects organs; includes bone, blood, and adipose tissue.
Muscle Tissue: Responsible for movement; includes skeletal, cardiac, and smooth muscle.
Nervous Tissue: Conducts electrical impulses; found in the brain, spinal cord, and nerves.
Example: Muscle tissue enables movement of limbs and internal organs.
