Cell Structure and Function Notes

Overview of Cells

• Cells are the smallest living units of organisms
• Common features of all cells:
  • Cell membrane: Separates inside of cell from environment
  • Cytoplasm: Jelly-like fluid inside the cell
  • DNA: Genetic material of the cell

Categories of Cells

1. Eukaryotic Cells
   • Have organelles (e.g., nucleus, other specialized parts)
   • More complex cells found in plants and animals
2. Prokaryotic Cells
   • Lack a nucleus and membrane-enclosed organelles
   • Genetic material not contained within a nucleus
   • Always unicellular (e.g., bacteria)

Organelles

• Definition: Specialized parts of a cell with unique functions ("little organs")

Nucleus

• Control center of the cell
• Contains DNA (genetic material)
• Chromatin: Tangled form of DNA inside nuclear membrane
• Condenses into chromosomes when cell divides
• Contains nucleolus (where ribosomes are made)

Ribosomes

• Synthesize proteins
• Float freely in cytoplasm or attach to endoplasmic reticulum (ER)

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Has ribosomes attached
  • Smooth ER: No ribosomes
• Membrane-enclosed passageway for transporting materials

Golgi Apparatus

• Receives proteins and customizes them
• Modifications include folding proteins and adding materials (lipids, carbohydrates)

Vacuoles

• Storage structures for different materials
• Central vacuole in plant cells stores water

Lysosomes

• Garbage collectors for damaged cell parts
• Contain enzymes to break down cellular debris

Mitochondria

• Powerhouse of the cell
• Produce ATP through cellular respiration
• More mitochondria in cells requiring more energy

Cytoskeleton

• Maintains cell shape
• Composed of:
  • Microfilaments: Thread-like proteins
  • Microtubules: Thin, hollow tubes

Chloroplasts

• Found in plant cells for photosynthesis
• Contain chlorophyll, a green pigment

Cell Wall

• Found only in plant cells
• Provides shape, support, and protection

Unique Cellular Structures

• Cilia: Microscopic, hair-like projections in some human respiratory cells to trap particles
• Flagella: Tail-like structures in some bacteria for movement; only found in human sperm cells

Summary

• Eukaryotic cells = plant and animal cells (nucleus + organelles)
• Prokaryotic cells = unicellular organisms (no nucleus + organelles)
• All cells have cell membrane, cytoplasm, and genetic material
• Plant cells have chloroplasts; both plant and animal cells have mitochondria.