Chapter 3

• Cell


  The fundamental unit of any living organism because it exhibits the basic characteristics of life
• Types of cells


  • Eukaryotic
  • Prokaryotic
• Microbes


  • Prokaryotes (bacteria and archaea)
  • Eukaryotes (algae, protozoa, fungi)
  • Non-cellular (viruses, prions, viroids)
• Eukaryotic cells


  • Contain a "true" nucleus
  • Possess a complex system of membranes and membrane-bound organelles
• Prokaryotic cells


  • Do not contain a "true" nucleus
  • Do not possess a complex system of membranes and membrane-bound organelles
• Cell membrane


  Selectively permeable, allowing only certain substances to pass through
• Nucleus


  The "command center" of the eukaryotic cell, containing nucleoplasm, chromosomes, and a nuclear membrane
• Chromosomes


  • Embedded in the nucleoplasm
  • Consist of linear DNA molecules and proteins
  • Genes are located along chromosomes
• Genotype


  An organism's complete collection of genes
• Gene products


  Usually proteins, but some code for ribonucleic acid (RNA)
• Ribosomal ribonucleic acid (rRNA)

  One type of RNA produced by genes
• Transfer ribonucleic acid (tRNA)


  Another type of RNA produced by genes
• Human diploid cells have 46 chromosomes (23 pairs)
• The human genome consists of between 20,000 and 25,000 genes
• Cytoplasm


  A semifluid, gelatinous, nutrient matrix where most metabolic reactions occur
• Endoplasmic reticulum (ER)


  A highly convoluted system of membranes arranged to form a transport network in the cytoplasm
• Rough ER


  Has ribosomes attached to it
• Smooth ER


  Does not have ribosomes attached
• Ribosomes


  Consist of ribosomal RNA and protein, and are the sites of protein synthesis
• Golgi complex


  Also called the Golgi apparatus or Golgi body, it connects or communicates with ER and completes the transformation and packaging of newly synthesized proteins
• Lysosomes


  Membrane-bound vesicles that contain digestive enzymes
• Peroxisomes


  Membrane-bound vesicles where H2O2 is generated and broken down
• Mitochondria


  "Power plants," "powerhouses," or "energy factories" where ATP molecules are produced by cellular respiration
• Plastids


  Membrane-bound structures containing photosynthetic pigments, including chloroplasts
• Cytoskeleton


  A system of fibers (microtubules, microfilaments, and intermediate filaments) throughout the cytoplasm that are essential for various cellular activities
• Cell wall


  An external structure in some eukaryotic cells that provides shape, protection, and rigidity
• Flagella


  Long, thin, whiplike organelles of locomotion found on some eukaryotic cells
• Cilia


  Shorter, thinner, and more numerous than flagella, also used for locomotion in some eukaryotic cells
• Prokaryotic cells are about 10 times smaller than eukaryotic cells
• Prokaryotic cells


  • Reproduce by binary fission
  • Cytoplasm is not filled with internal membranes
  • Surrounded by a cell membrane, cell wall (usually), and sometimes a capsule or slime layer
• Prokaryotic chromosome


  Usually consists of a single, long, supercoiled, circular DNA molecule that serves as the control center of the cell
• Plasmids


  Small, circular molecules of DNA that are not part of the chromosome (extra-chromosomal)
• Cytoplasmic particles


  Mostly ribosomes, some of which occur in clusters
• Bacterial cell wall


  A rigid exterior that defines the shape of bacterial cells, with the main constituent being peptidoglycan
• Gram-positive bacteria


  Have a thick layer of peptidoglycan in their cell walls
• Gram-negative bacteria


  Have a much thinner layer of peptidoglycan in their cell walls
• Mycoplasma


  Do not have a cell wall, and are pleomorphic
• Glycocalyx


  Slimy, gelatinous material produced by the cell membrane and secreted outside the cell wall, including slime layers and capsules
• Bacteria with glycocalyx


  • Pseudomonas spp. (slime layer)
  • Klebsiella pneumoniae, Neisseria meningitidis, Streptococcus pneumoniae (capsule)
• Flagella


  Whiplike appendages composed of threads of protein called flagellin, used for motility