Biology Chapter: Cell Theory and Structure

Cell Theory and Structure

• All living organisms are composed of cells, the fundamental units of structure, function, and organization.
• Differentiation is the specialization of cells from stem cells for specific functions.

Tissues, Organs, and Systems

• Tissues are groups of similar cells performing specific functions (e.g., epithelial, muscle, nervous).
• Organs are collections of tissues performing specific physiological functions (e.g., heart, lungs).
• Organ systems are groups of organs working together (e.g., cardiovascular, respiratory).

Prokaryotic and Eukaryotic Cells

• Prokaryotes (bacteria): Nucleoid, plasmids, 70S ribosomes, capsule, cell wall.
• Eukaryotes (animal): Plasma membrane, cytoplasm, nucleus, endoplasmic reticulum (smooth & rough), Golgi apparatus, vesicles, lysosomes, 80S ribosomes, mitochondria, centriole.
• Eukaryotes (plant): All animal components plus chloroplasts, vacuole, tonoplast, amyloplasts, cell wall, plasmodesmata.

Microscopy and Gram Staining

• Electron micrographs and light microscopes visualize cell organelles.
• Gram staining differentiates bacteria based on cell wall structure.
  • Gram-positive: Thick peptidoglycan layer, sensitive to penicillin.
  • Gram-negative: Thin peptidoglycan layer, outer lipopolysaccharide membrane, less sensitive to penicillin.

Specialized Animal Cells

• Palisade mesophyll cells: Cylindrical shape, chloroplasts for photosynthesis, large vacuole.
• Sperm cells: Nucleus with 23 chromosomes, acrosome, mitochondria, tail.
• Egg cells: Nucleus with 23 chromosomes, large cytoplasm, zona pellucida.
• Root hair cells: Large surface area for absorption, mitochondria, thin walls.
• White blood cells (WBCs):
  • Lymphocytes (T & B cells): Immunological memory, antibody production, destroy infected cells.
  • Neutrophils: Phagocytic, mobile.
• Red blood cells: Biconcave shape for large surface area, no nucleus, flexible for oxygen transport.
• Squamous epithelium: Lines alveoli, thin for rapid diffusion, e.g. in lungs
• Columnar epithelium (with goblet cells): Ciliated, goblet cells secrete mucus; cilia move mucus (trachea).
• Endothelial tissue: Single layer of squamous cells lining blood vessels; reduces friction, regulates blood flow, allows nutrient and waste exchange in capillaries; Damaged endothelium contributes to atherosclerosis.

COPD and Epithelial Tissues

• COPD damage to alveoli reduces surface area and breathing.
• Endothelium is essential for smooth blood flow.

Measuring and Calculating Cell Size

• Use ocular (eyepiece) graticule and stage micrometer to measure cells in micrometers.
• Calculate magnification using the formula: Magnification = Image size / Actual size.

Skeletal Muscle Tissue

• Muscle fibers are multinucleated and striated, composed of repeating sarcomeres.
• Contains Sarcolemma, sarcoplasmic reticulum, mitochondria.
• Sliding filament theory describes muscle contraction, involving actin and myosin filaments sliding past each other.
• Fast-twitch fibers contract quickly but fatigue rapidly, relying on anaerobic metabolism.
• Slow-twitch fibers contract slowly and are fatigue-resistant, utilizing aerobic metabolism.

Myelinated Neurons and Nerve Impulse Conduction

• Myelinated neurons have myelin sheaths speeding up impulse conduction.
• Non-myelinated neurons conduct impulses slower.
• Nerve impulse conduction (action potential) involves resting membrane potential, depolarization, threshold, repolarization, and saltatory conduction (jumping between nodes of Ranvier).

Atherosclerosis

• Atherosclerosis is the build-up of plaques in artery walls.
• White blood cells (foam cells) accumulating, narrowing the lumen (interior space) of arteries.
• Plaque rupture can cause blood clots (thrombus) leading to cardiovascular problems.

Test your knowledge on cell theory, the structure of prokaryotic and eukaryotic cells, and the organization of tissues, organs, and systems. This quiz covers essential concepts about how living organisms are composed of cells and how these cells specialize for various functions. Dive in to learn more about the building blocks of life!