Cell Structure & Function Overview

Universal Features of All Cells

• Cell membrane: boundary between cytoplasm and exterior
• Cytoplasm: jelly-like fluid where reactions occur
• DNA: genetic material governing cell function

Two Major Cell Types

• Eukaryotic
  • Nucleus and membrane-bound organelles
  • Found in plants, animals, fungi, protists
• Prokaryotic
  • No nucleus; DNA free in cytoplasm
  • No membrane-bound organelles
  • Always unicellular (e.g., bacteria)

Key Organelles (Eukaryotic)

• Nucleus
  • Stores DNA (chromatin ➝ chromosomes during division)
  • Nucleolus forms ribosomes
• Ribosomes: protein synthesis; free or attached to rough ER
• Endoplasmic reticulum (ER)
  • Rough ER: protein processing (ribosomes attached)
  • Smooth ER: lipid synthesis, detoxification
• Golgi apparatus: modifies, folds, and packages proteins/lipids into vesicles
• Vacuoles: storage (water, nutrients, waste)
• Lysosomes (animal): enzyme-filled sacs for digestion/recycling
• Mitochondria: cellular respiration ➝ ATP production; more numerous in high-energy cells
• Cytoskeleton: microfilaments + microtubules for shape, transport, movement

Plant-Specific Components

• Chloroplasts: photosynthesis; contain chlorophyll (green pigment)
• Large central vacuole: water storage, turgor pressure
• Cell wall (cellulose): rigid support and protection (absent in animals)

Specialized Surface Structures

• Cilia: short, numerous projections; move fluids/particles (e.g., human airways)
• Flagellum: long tail-like appendage for locomotion (bacteria; human sperm)

High-Yield Reminders

• Eukaryotes = nucleus + organelles; prokaryotes = none
• Both plant and animal cells contain mitochondria; only plants have chloroplasts
• Organelle = “little organ” performing a specific cellular job