Biology

• Hyperbaric oxygen therapy


  Increases the partial pressure of oxygen in the patient's tissues, used to treat infections with obligate anaerobic bacteria
• Connective Tissue Cells

  • They account for most cells in muscles, bones, and tendons
  • They secrete substances to form the extracellular matrix
  • In organs, they tend to form the stroma and provide support for epithelial cells
• Types of nucleic acid that could form the genome of a virus

  • Single-stranded RNA
  • Double-stranded DNA
  • Single-stranded DNA
• The theory of spontaneous generation states that living organisms can arise from nonliving material. In 1859, Pasteur demonstrated that no organisms emerged from sterilized growth media, weakening the theory of spontaneous generation and supporting the tenet of cell theory that cells arise only from preexisting cells.
• Mitochondrial DNA


  It is circular and self-replicating
• Smooth endoplasmic reticulum


  Its functions include lipid synthesis, poison detoxification, and transport of proteins, but not protein synthesis
• Nucleolus


  Its main function is ribosomal RNA synthesis
• A difference that would NOT allow one to distinguish a prokaryotic and a eukaryotic cell is the presence of a membrane on the outside surface of the cell
• Tubulin


  It is found in cilia, flagella, and centrioles, but not in microfilaments
• Herpes simplex virus (HSV)


  It adds its genetic information to the genetic information of the host cell when it remains dormant in the nervous system
• Mechanisms that can account for a bacterium's ability to increase its genetic variability and adapt to resist different antibiotics


  • Binary fission
  • Conjugation
  • Transduction
• Conjugation is not likely to account for a penicillin-resistant bacterial cell exhibiting other phenotypic changes like secretion of a novel protein, as the rest of the colony did not become resistant
• Alzheimer's disease


  The mechanism of disease is most similar to prions, where a protein (amyloid precursor protein) is cleaved to form a protein (β-amyloid) that has a β-pleated sheet structure and precipitates to form plaques
• Viral particle


  After infecting a cell, it must transport itself to the nucleus in order to produce viral proteins, and its genomic content is likely double-stranded DNA
• Eukaryotic cells


  Cells that contain a true nucleus enclosed in a membrane
• Eukaryotic cells


  • Can be unicellular or multicellular
  • Contain membrane-bound organelles
• Prokaryotic cells


  Cells that do not contain a true nucleus
• Major organelles in eukaryotic cells

  • Nucleus
  • Mitochondria
  • Lysosomes
  • Endoplasmic reticulum
  • Golgi apparatus
• Nuclear membrane/envelope


  Double membrane that maintains a nuclear environment separate from the cytoplasm
• Nuclear pores


  Allow selective two-way exchange of material between the cytoplasm and the nucleus
• Mitochondria


  • Contain two membranes: an outer membrane and an inner membrane with cristae
  • Provide energy for the cell through oxidative phosphorylation
• Lysosomes


  Membrane-bound structures containing hydrolytic enzymes that can break down cellular waste and materials
• Endoplasmic reticulum (ER)


  • A series of interconnected membranes continuous with the nuclear envelope
  • Rough ER has ribosomes for protein synthesis, smooth ER lacks ribosomes and is used for lipid synthesis and detoxification
• Golgi apparatus


  • Consists of stacked membrane-bound sacs
  • Modifies and sorts cellular products for delivery to specific locations
• Mitochondria are semi-autonomous and contain some of their own genes
• Mitochondria and lysosomes can trigger apoptosis (programmed cell death) by releasing their contents
• Smooth endoplasmic reticulum (SER)

  Lacks ribosomes and is utilized primarily for lipid synthesis (such as the phospholipids in the cell membrane) and the detoxification of certain drugs and poisons. The SER also transports proteins from the RER to the Golgi apparatus.
• Golgi apparatus


  Consists of stacked membrane-bound sacs. Materials from the ER are transferred to the Golgi apparatus in vesicles. Once inside the Golgi apparatus, these cellular products may be modified by the addition of groups like carbohydrates, phosphates, and sulfates. The Golgi apparatus may also modify cellular products through the introduction of signal sequences, which direct the delivery of the product to a specific cellular location. After modification and sorting in the Golgi apparatus, cellular products are repackaged in vesicles, which are then directed to the correct cellular location. If the product is destined for secretion, the secretory vesicle merges with the cell membrane and its contents are released via exocytosis.
• Peroxisomes


  Contain hydrogen peroxide. One of the primary functions of peroxisomes is the breakdown of very long chain fatty acids via β-oxidation. Peroxisomes participate in the synthesis of phospholipids and contain some of the enzymes involved in the pentose phosphate pathway.
• Cytoskeleton


  Provides structure to the cell and helps it to maintain its shape. In addition, the cytoskeleton provides a conduit for the transport of materials around the cell. There are three components of the cytoskeleton: microfilaments, microtubules, and intermediate filaments.
• Microfilaments


  Made up of solid polymerized rods of actin. The actin filaments are organized into bundles and networks and are resistant to both compression and fracture, providing protection for the cell. Actin filaments can also use ATP to generate force for movement by interacting with myosin, such as in muscle contraction.
• Microfilaments


  Play a role in cytokinesis, or the division of materials between daughter cells. During mitosis, the cleavage furrow is formed from microfilaments, which organize as a ring at the site of division between the two new daughter cells. As the actin filaments within this ring contract, the ring becomes smaller, eventually pinching off the connection between the two daughter cells.
• Microtubules


  Hollow polymers of tubulin proteins. Microtubules radiate throughout the cell, providing the primary pathways along which motor proteins like kinesin and dynein carry vesicles.
• Cilia and flagella structure

  Composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center, known as a 9 + 2 structure. This is seen only in eukaryotic organelles of motility. Bacterial flagella have a different structure with a different chemical composition.
• Centrioles


  Found in the centrosome. They are the organizing centers for microtubules and are structured as nine triplets of microtubules with a hollow center. During mitosis, the centrioles migrate to opposite poles of the dividing cell and organize the mitotic spindle. The microtubules emanating from the centrioles attach to the chromosomes via complexes called kinetochores and exert force on the sister chromatids, pulling them apart.
• Intermediate filaments


  A diverse group of filamentous proteins, which includes keratin, desmin, vimentin, and lamins. Many intermediate filaments are involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton. Intermediate filaments are able to withstand a tremendous amount of tension, increasing the structural rigidity of the cell. In addition, intermediate filaments help anchor other organelles, including the nucleus. The identity of the intermediate filament proteins within a cell is specific to the cell and tissue type.
• Tissue formation


  One of the unique characteristics of eukaryotic cells is the formation of tissues with division of labor, as different cells in a tissue may carry out different functions. There are four tissue types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
• Epithelial tissue


  Covers the body and lines its cavities, providing a means for protection against pathogen invasion and desiccation. In certain organs, epithelial cells are involved in absorption, secretion, and sensation. Epithelial cells are tightly joined to each other and to an underlying layer of connective tissue known as the basement membrane. Epithelial cells are highly diverse and serve numerous functions depending on the identity of the organ in which they are found.
• Epithelial cell polarization


  One side faces a lumen (the hollow inside of an organ or tube) or the outside world, while the other side interacts with underlying blood vessels and structural cells.
• Epithelial tissue classification


  • Simple epithelia (one layer of cells)
  • Stratified epithelia (multiple layers)
  • Pseudostratified epithelia (appear to have multiple layers but are one layer)