Cell morphology

• Prokaryotes are organisms that do not possess a true nucleus and membrane-bound organelles (e.g., bacteria)
• Eukaryotic organisms are those that possess a true nucleus and membrane-bound organelles. They are usually multicellular organisms and include plants, fungi, parasites, and algae
• Prokaryotic cells:

  • Genetic material not enclosed within a membrane; not associated with histones; usually circular
  • Size smaller (1 - 2 micrometer by 1 - 4 micrometer or less)
  • Cell type mostly unicellular
  • Nucleus no true nucleus and nuclear membrane; nucleoid
  • Cell wall simple
  • Cell division budding or binary fission
  • Cytoskeleton absent
  • Mesosome function as mitochondria and Golgi complex
  • Ribosomes 70S; located in cytoplasm
  • Membrane-bound organelles absent
  • Extrachromosomal plasmid present
  • Duration of cell cycle short (20 - 60mins)
• Eukaryotic cells:

  • Genetic material enclosed within a membrane; associated with histones; usually linear
  • Size greater than 5 micrometer in diameter
  • Cell type mostly multicellular
  • Nucleus with true nucleus enclosed by nuclear membrane
  • Cell wall complex
  • Cell division mitosis
  • Sexual reproduction meiosis
  • Cytoskeleton present
  • Ribosomes 80S; located in membrane such as ER
  • Membrane-bound organelles present
  • Extrachromosomal plasmid absent
  • Duration of cell cycle long (12 - 24 hrs)
• Histones are proteins that DNA wraps around to form chromatin
• Bacteria are prokaryotic cells with majority having an outer covering called the cell wall that is composed of peptidoglycan
• Membrane-bound organelles are present in eukaryotic cells but absent in prokaryotic cells
• Louis Pasteur proved that bacteria could cause a disease
• Viruses are acellular organisms with an outer surface called capsid
• Viruses possess only a single nucleic acid, either DNA or RNA, but never both
• Viruses lack the necessary cellular parts that can allow them to replicate independent of the host cell
• Viruses are obligate intracellular parasites
• Bacteriophages are special types of viruses that primarily infect bacteria
• Bacteriophages play a role in the acquisition of virulence factors of certain bacteria and in the transfer of genetic material from one bacterium to another
• When -ssRNA virus enters the host, it will immediately be translated into protein (True)
• Capsid is a protein (True)
• DNA virus have both + and - ssDNA (False)
• Fungi are eukaryotic cells with an outer surface composed mainly of chitin
• Fungal ribosomes are larger than bacterial ribosomes (80Svedberg unit)
• Fungi possess both DNA and RNA
• Fungi possess a true nucleus that is enclosed by a nuclear membrane and mitochondria that function for ATP production
• Protozoa are eukaryotic cells that have an outer surface called pellicle
• Protozoa are unicellular organisms that usually divide through binary fission
• Algae are eukaryotic organisms whose outer surface consists primarily of cellulose
• Algae do not produce disease in humans
• Algae are important sources of food, iodine, and other minerals
• Algae are composed of roots, stems, and leaves (False)
• Algae use carbon dioxide as an energy source
• Cocci are spherical or round-shaped organisms
• Bacilli are rod-shaped organisms
• Acid-fast cell walls possess an outer layer that is lipid-rich
• Acid-fast cell walls are composed of a large amount of waxes known as myolic acids
• Glycocalyx is the outermost covering of some bacteria
• Cell wall provides rigid support and gives shape to the bacteria
• Teichoic acids function for the attachment of the organism to host cells
• Polysaccharides in gram-positive cell walls include neutral sugars and some acidic sugars
• Outer membrane of gram-negative cell walls is a bi-layered structure with lipopolysaccharides (LPS)
• Lipoprotein anchors the outer membrane to the peptidoglycan layer
• Periplasmic space is a fluid-filled space between the outer membrane and the inner plasma membrane
• The plural form of bacterium is BACTERIA