Cell Structure

• Cells


  The smallest living units of an organism
• Things all cells have in common

  • Cell membrane
  • Cytoplasm
  • DNA
• Eukaryotic cells

  • Have organelles, including nucleus
  • More advanced complex cells, such as those found in plants and animals
• Prokaryotic cells


  • Don't have a nucleus or membrane-enclosed organelles
  • Have genetic material not contained within a nucleus
  • Always one-celled or unicellular organisms, such as bacteria
• Organelles


  Specialized parts of a cell that have unique jobs to perform
• Nucleus


  • Control center of the cell
  • Contains DNA or genetic material
  • DNA dictates what the cell is going to do and how it's going to do it
  • Contains a nucleolus where ribosomes are made
• Chromatin


  • Tangled, spread-out form of DNA found inside the nuclear membrane
• Chromosomes


  • DNA condenses into these structures when a cell is ready to divide
• Ribosomes


  • Synthesize or make proteins
  • May wander freely within the cytoplasm or attach to the endoplasmic reticulum
• Endoplasmic reticulum (ER)


  • Membrane-enclosed passageway for transporting materials, such as the proteins synthesized by ribosomes
  • Two types: rough ER has ribosomes attached, smooth ER doesn't
• Golgi apparatus


  • Receives proteins and other materials from the endoplasmic reticulum
  • Customizes proteins into usable forms by folding them or adding other materials like lipids or carbohydrates
• Vacuoles


  • Sac-like structures that store different materials, like water in plant cells
• Lysosomes


  • Garbage collectors that take in and break down damaged or worn-out cell parts
• Mitochondria


  • Powerhouse for both animal and plant cells
  • During cellular respiration, make ATP molecules that provide energy for the cell's activities
  • Cells that need more energy have more mitochondria
• Cytoskeleton

  • Maintains the cell's shape
  • Includes microfilaments and microtubules
• Chloroplasts


  • Where photosynthesis happens in photoautotrophic organisms like plants
  • Contains chlorophyll, giving it a green color
• Cell wall


  • Found outside the cell membrane in plant cells, shapes, supports, and protects the plant cell
  • Animal cells never have a cell wall
• Other unique cell structures

  • Cilia in human respiratory tract cells
  • Flagella in some bacteria and human sperm cells
• Eukaryotic cells are plant and animal cells with a nucleus and membrane-enclosed organelles
• Prokaryotic cells are unicellular organisms without a nucleus or membrane-enclosed organelles