MICROPARA 3

• Cell


  Fundamental unit of any living organism
• Cell


  • Exhibits the basic characteristics of life
  • Obtains food (nutrients) from the environment to produce energy for metabolism and other activities
  • Can respond to stimuli in its environment such as light, heat, cold, and the presence of chemicals
  • Can mutate (change genetically) as a result of changes in its genetic material – the deoxyribonucleic acid (DNA) that makes up the genes of its chromosomes
• Metabolism


  All of the chemical reactions that occur within a cell; because of its metabolism, a cell can grow and reproduce
• Prokaryotes


  Less complex cells, which include Bacteria and Archaea, that do not have the complex system of membranes and organelles
• Eukaryotes


  More complex cells that contain a true nucleus and many membrane-bound organelles
• Eukaryotes


  • Algae, protozoa, fungi, plants, animals, and humans
• Viruses


  Composed of only a few genes protected by a protein coat, and may contain one or a few enzymes; depend on the energy and metabolic machinery of a host cell to reproduce; are not composed of cells
• Viroids


  Infectious agents that consist only of naked RHA without any protective layer such as a protein coat; infect plants and are replicated at the expense of the host cell; have small single-stranded circles of RNA that are only 250-400 bases long
• Prions


  Types of proteins that can cause disease in animals and humans by triggering normally healthy proteins in the brain to fold abnormally; are simply proteins devoid of any genetic material
• Cell membrane


  Mosaic composed of large proteins and phospholipids; regulates the passage of nutrients, waste products, and secretions into and out of the cell; is selectively permeable
• Nucleus


  Controls the functions of the entire cell and can be thought of as the "command center" of the cell; has three components: nucleoplasm, chromosomes, & a nuclear membrane
• Nucleoplasm


  Gelatinous matrix or base material of the nucleus
• Chromosomes


  Embedded or suspended in the nucleoplasm; consist of linear DNA molecules and proteins; genes are located along the DNA molecules
• Nuclear membrane


  Contains holes (nuclear pores) through which large molecules can enter and exit the nucleus
• Genotype (genome)


  Organism's complete collection of genes
• Cytoplasm


  Semifluid, gelatinous, nutrient matrix; where most of the cell's metabolic reactions occur
• Cytoplasmic organelles


  Endoplasmic reticulum, ribosomes, Golgi complexes, mitochondria, centrioles, microtubules, lysosomes, and other membrane-bound vacuoles
• Endoplasmic reticulum (ER)


  Highly convoluted system of membranes that are interconnected and arranged to form a transport network of tubules and flattened sacs within the cytoplasm; rough ER functions in protein folding, sorting, and transporting the proteins outside the cell; smooth ER is responsible for the synthesis of essential lipids and the production and secretion of steroid hormones
• Ribosome


  Eukaryotic ribosomes are 18 to 22 nm in diameter, consist mainly of rRNA and protein, and play an important part in the synthesis of proteins; clusters of ribosomes (called polyribosomes or polysomes) are held together by a molecule of mRNA; each eukaryotic ribosome is composed of two subunits – a large subunit (the 60S subunit) and a small subunit (the 40S subunit) that are produced in the nucleolus; the subunits are then transported to the cytoplasm where they remain separate until they join together with an mRNA molecule to initiate protein synthesis
• Golgi complex


  Connects or communicates with the ER; stack of flattened, membranous sacs that completes the transformation of newly synthesized proteins into mature, functional ones and packages them into small, membrane-enclosed vesicles for storage within the cell or export outside the cell
• Lysosome


  Small (about 1-μm diameter) vesicles that originate at the Golgi complex; contain lysozyme and other digestive enzymes that break down foreign material taken into the cell by phagocytosis and aid in breaking down worn out parts of the cell
• Peroxisome


  Membrane-bound vesicles in which hydrogen peroxide is both generated and broken down; contain the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide into water and oxygen
• Mitochondria


  Powerhouses of the eukaryotic cell because this is where most of the ATP molecules are formed by cellular respiration; energy necessary for cellular function is provided by the formation of high-energy phosphate molecules such as adenosine triphosphate (ATP)
• Plastids


  Membrane-bound structures containing various photosynthetic pigments; chloroplasts, one type of plastid, contain green, photosynthetic pigment called chlorophyll
• Photosynthesis


  Process by which light energy is used to convert carbon dioxide and water into carbohydrates and oxygen; conversion of light energy into chemical energy
• Cytoskeleton


  System of fibers present throughout the cytoplasm; three types of cytoskeletal fibers are microtubules, microfilaments (actin filaments), and intermediate filaments; serve to strengthen, support, and stiffen the cell, and give the cell its shape
• Cell wall


  Eukaryotic cell walls are much simpler in structure than prokaryotic cell walls and may contain cellulose, pectin, lignin, chitin, and some mineral salts
• Flagella


  Relatively long, thin structures that allow some eukaryotic cells to be motile; referred to as organelles of locomotion (cell movement)
• Cilia


  Shorter (more hair-like), thinner, and more numerous than flagella; can be found on some species of protozoa and certain types of cells in our bodies
• Prokaryotic cell


  About 10 times smaller than eukaryotic cells; reproduction is by binary fission, the simple division of one cell into two cells after DNA replication and the formation of a separating membrane and cell wall; embedded within the cytoplasm are a chromosome, ribosomes, and other cytoplasmic particles
• Prokaryotic chromosome


  Usually consists of a single, long, supercoiled circular DNA molecule which serves as the control center of the bacterial cell; is capable of duplicating itself, guiding cell division, & directing cellular activities; the DNA-occupied space within a bacterial cell is referred to as the bacterial nucleoid
• Plasmid


  Small, circular molecules of double-stranded DNA that are not part of the chromosome; may contain anywhere from fewer than 10 genes to several hundred genes
• Bacterial cell wall


  Main constituent is a complex macromolecular polymer known as peptidoglycan (murein) consisting of many polysaccharide chains linked together by small peptide chains; Gram-positive bacteria have a thick layer of peptidoglycan combined with teichoic acid & lipoteichoic acid molecules, while Gram-negative bacteria have a much thinner layer of peptidoglycan
• Bacterial nucleoid


  The DNA-occupied space within a bacterial cell
• Plasmids


  Small, circular molecules of double-stranded DNA that are not part of the chromosome
• Plasmids may contain anywhere from fewer than 10 genes to several hundred genes
• Peptidoglycan (murein)


  The main constituent of most bacterial cell walls, a complex macromolecular polymer consisting of many polysaccharide chains linked together by small peptide chains
• Gram-positive bacteria cell walls

  • Thick layer of peptidoglycan combined with teichoic acid & lipoteichoic acid molecules
• Gram-positive bacteria


  • Staphylococci, streptococci, pneumococci, Bacillus anthracis, Corynebacterium diptheriae
• Gram-negative bacteria cell walls


  • Much thinner layer of peptidoglycan, covered with a complex layer of lipid macromolecules