Overview
This lecture covers the structure and function of cells and tissues, including their components, processes, and roles in the organization of the human body.
Organization of the Body
- Levels of organization: atom → cell → tissue → organ → system → organism.
- The cell is the fundamental unit of all living things.
Structure and Components of the Cell
- Major cell parts include the cell membrane, nucleus, chromosomes, genes, DNA, cytoplasm, mitochondria, endoplasmic reticulum (ER), and Golgi apparatus.
- The cell membrane is a double layer of phospholipids with embedded proteins, controlling movement of substances in/out.
- The nucleus is the control center with a double membrane and contains chromatin (loosely coiled DNA).
- Chromatin condenses into chromosomes (23 pairs in humans except sex cells).
- Genes are DNA segments that code for proteins; the complete set is the human genome.
- Karyotype is a photo of someone's chromosomes to detect abnormalities.
- The nucleolus produces ribosomes for protein synthesis.
- The ER consists of rough (with ribosomes, makes proteins) and smooth (synthesizes lipids, detoxifies drugs).
- Golgi apparatus processes and packages proteins; makes lysosomes for digestion.
- Mitochondria perform cellular respiration, supplying ATP energy and regulating cell death (apoptosis).
- Cytoskeleton gives structural support and enables cell movement/division.
- Cilia and flagella aid movement (e.g., sperm uses flagellum).
Cell Transport and Communication
- Plasma membrane is selectively permeable.
- Passive processes: diffusion (movement from high to low concentration), osmosis (water diffusion), and filtration (by pressure).
- Active transport moves substances against the gradient, requiring ATP (e.g., sodium-potassium pump).
- Phagocytosis (cell eating) and pinocytosis (cell drinking) are forms of active transport.
- Cells communicate via chemical signals, receptors, signal transduction, and responses to maintain homeostasis.
Cell Division
- Before division, chromosomes duplicate; mitosis creates two identical cells.
- Stages of mitosis: prophase, metaphase, anaphase, telophase.
- Interphase is the period between mitoses.
Tissues: Types and Functions
- Tissues are groups of similar cells with a common function.
- Epithelial tissue protects, covers, lines body surfaces, and forms glands (exocrine with ducts, endocrine without ducts/hormones).
- Connective tissue supports, joins, and protects, and includes loose, adipose (fat), cartilage, bone, and blood.
- Muscle tissue contracts for movement; types are skeletal (voluntary, striated), cardiac (involuntary, striated, intercalated discs), and smooth (involuntary).
- Nervous tissue transmits information; consists of neurons (conduct impulses) and glial cells (support neurons).
Membranes
- Membranes cover or line body surfaces.
- Epithelial membranes: mucous (open to outside) and serous (closed cavities—parietal vs. visceral).
- Connective tissue membranes include synovial (lines joints), periosteum (covers bone), and perichondrium (covers cartilage).
Key Terms & Definitions
- Cell membrane — Outer plasma membrane controlling entry/exit of substances.
- Nucleus — Control center containing DNA.
- Chromosomes — Structures carrying genetic information (DNA).
- Gene — Segment of DNA coding for a protein.
- Karyotype — Chromosome photo arranged by size/number.
- Mitochondria — Organelles producing ATP energy.
- Cytoskeleton — Protein filaments supporting cell shape and movement.
- Diffusion — Movement of molecules from high to low concentration.
- Osmosis — Diffusion of water through a membrane.
- Active transport — Energy-requiring movement against concentration gradient.
- Tissue — Group of similar cells with a common function.
- Epithelial tissue — Covers and lines surfaces, forms glands.
- Connective tissue — Supports and connects other tissues.
- Muscle tissue — Contracts to produce movement.
- Nervous tissue — Transmits electrical signals.
Action Items / Next Steps
- Learn and review the stages of the cell cycle and mitosis.
- Study major tissue types and their functions.
- Re-watch the lecture video for reinforcement.