chapter 3

Cards (18)

  • Cell
    The basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed
  • Cell
    • A single cell is often a complete organism in itself, such as a bacterium or yeast
    • Cells acquire specialized functions as they mature
    • Cells cooperate with other specialized cells and become the building blocks of large multicellular organisms, such as humans and other animals
  • Cells are much larger than atoms, but still very small
  • The smallest known cells are a group of tiny bacteria called mycoplasmas; some of these single-celled organisms are spheres as small as 0.2 μm in diameter (1μm = about 0.000039 inch), with a total mass of 10−14 gram—equal to that of 8,000,000,000 hydrogen atoms
  • Cells of humans typically have a mass 400,000 times larger than the mass of a single mycoplasma bacterium, but even human cells are only about 20 μm across
  • It would require a sheet of about 10,000 human cells to cover the head of a pin, and each human organism is composed of more than 30,000,000,000,000 cells
  • Cytoplasm
    Surrounds the cell's specialized structures, or organelles
  • Ribosomes
    • Sites of protein synthesis, found free in the cytoplasm or attached to the endoplasmic reticulum, through which materials are transported throughout the cell
  • Mitochondria
    • Release energy needed by the cell
  • Golgi complex
    • Stacks of flattened sacs that process and package materials to be released from the cell in secretory vesicles
  • Lysosomes
    • Contain digestive enzymes
  • Peroxisomes
    • Contain enzymes that detoxify dangerous substances
  • Centrosome
    • Contains the centrioles, which play a role in cell division
  • Microvilli
    • Fingerlike extensions found on certain cells
  • Cilia
    • Hairlike structures that extend from the surface of many cells, can create movement of surrounding fluid
  • Nuclear envelope
    • A double membrane surrounding the nucleus, contains pores that control the movement of substances into and out of the nucleoplasm
  • Chromatin
    • A combination of DNA and proteins that coil into chromosomes, makes up much of the nucleoplasm
  • Nucleolus
    • The dense site of ribosome production