Cellular Basis of Life

Overview of the Cellular Basis of Life

The cell is the fundamental unit of structure and function in living organisms. All living things are composed of cells, which carry out essential processes for life.

• Cellular Diversity: Cells vary in shape, size, and function, reflecting their specialized roles in the body.

• Cell Components: All cells contain a plasma membrane, cytoplasm, and genetic material (DNA).

• Cell Functions: Cells digest food, excrete waste, and are involved in growth, movement, and metabolism.

Cell Membrane Structure and Function

The plasma membrane is a selectively permeable barrier that surrounds the cell, controlling the movement of substances in and out.

• Structure: Composed mainly of a phospholipid bilayer with embedded proteins.

• Functions: Provides protection, communication, and transport of materials.

• Specializations: May include microvilli (increase surface area) and junctions (tight, gap, desmosomes) for cell-to-cell communication and adhesion.

Cell Physiology

Cell physiology refers to the processes that occur within cells to maintain life.

• Passive Transport: Movement of substances across the membrane without energy input (e.g., diffusion, osmosis, facilitated diffusion).

• Active Transport: Movement of substances against a concentration gradient, requiring energy (ATP).

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Filtration: Movement of water and solutes through a membrane by hydrostatic pressure.

Cell Division and the Cell Cycle

Cell division is essential for growth, repair, and reproduction. The cell cycle consists of interphase (growth and DNA replication) and mitosis (nuclear division).

• Mitosis: Division of the nucleus resulting in two genetically identical daughter cells.

• Meiosis: Specialized cell division producing gametes (sperm and egg) with half the number of chromosomes.

• Control of Cell Division: Regulated by growth factors, cyclins, and checkpoints. Abnormal control can lead to neoplasms (tumors).

Neoplasms and Cell Aging

Neoplasms are abnormal masses of proliferating cells, which may be benign (non-cancerous) or malignant (cancerous). Cell aging involves a decrease in cell function and the ability to divide, leading to tissue atrophy and decreased repair capacity.

• Hypertrophy: Increase in cell size.

• Atrophy: Decrease in cell size or number, often due to lack of use or disease.

Body Tissues

Overview of Body Tissues

Tissues are groups of similar cells that perform a common function. The four basic tissue types are epithelial, connective, muscle, and nervous tissue.

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Functions include protection, absorption, secretion, and filtration.

• Connective Tissue: Supports, protects, and binds other tissues. Includes bone, cartilage, adipose, and blood.

• Muscle Tissue: Responsible for movement. Types include skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Initiates and transmits electrical impulses to coordinate body activities.

Epithelial Tissue

Epithelial tissue forms the covering and lining of body surfaces and cavities, as well as glandular tissue.

• Functions: Protection, absorption, filtration, secretion.

• Characteristics: Cells are closely packed, have a free (apical) surface, and rest on a basement membrane.

• Classification: Based on cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

Connective Tissue

Connective tissue is the most abundant and widely distributed tissue type. It provides support, binds tissues together, and stores energy.

• Components: Cells (e.g., fibroblasts), fibers (collagen, elastic, reticular), and ground substance.

• Types: Loose connective tissue, dense connective tissue, cartilage, bone, blood.

Tishttps://www.pearson.com/channels/anp/flashcardssue Repair

Tissue repair (wound healing) restores tissue integrity after injury. It involves two main processes: regeneration and fibrosis.

• Regeneration: Replacement of destroyed tissue by the same kind of cells.

• Fibrosis: Replacement by dense connective tissue (scar formation).

• Factors Affecting Repair: Type of tissue, severity of injury, and overall health.

Homeostatic Relationships

Skeletal System and Other Body Systems

The skeletal system interacts with other body systems to maintain homeostasis. For example, bones store minerals, protect organs, and provide attachment for muscles.

• Blood Cell Formation: Bones contain marrow that produces blood cells.

• Mineral Storage: Bones store calcium and phosphorus, releasing them as needed.

• Support and Protection: The skeleton supports the body and protects vital organs.

Key Terms and Definitions

• Cell: The basic structural and functional unit of living organisms.

• Plasma Membrane: The outer boundary of the cell, regulating entry and exit of substances.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Neoplasm: An abnormal mass of proliferating cells (tumor).

• Atrophy: Decrease in size or wasting away of a body part or tissue.

• Regeneration: Replacement of destroyed tissue by the same kind of cells.

• Fibrosis: Repair by dense connective tissue (scar tissue).

Sample Table: Comparison of Tissue Types

Key Equations

• Osmosis (Water Potential):

• Where is the water potential, is the solute potential, and is the pressure potential.

Examples and Applications

• Example: When a person suffers a cut, epithelial tissue regenerates to cover the wound, while connective tissue may form a scar if the injury is severe.

• Application: Understanding tissue repair is essential for medical fields such as surgery and physical therapy.

Additional info: Some explanations and definitions were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.