Chapter 3: Cells and Tissues

Cards (77)

  • Structural Levels of Organization
    - describe the biological arrangement of human organism
  • cells are the structural units of all living things, from one-celled organisms such as amoe- bas to complex multicellular organisms such as humans, dogs, and trees.
  • The human body contains 50 to 100 trillion of these tiny building blocks.
  • For cells, “headquarters,” or the control center, is the nucleus.
  • nucle = kernel
  • Genetic material, or deoxyribonucleic acid (DNA), is a blueprint that contains all the instructions needed for building the whole body
  • The nuclear boundary is a double membrane barrier called the nuclear envelope.
  • At various points, the two layers of the nuclear envelope fuse, generating openings called nuclear pores
  • nuclear membrane encloses a jellylike fluid called nucleoplasm
  • Nucleolus is an area within the nucleus where ribosomes are manufactured.
  • When a cell is not dividing, its DNA is carefully wound around proteins called histones to form a loose network of “beads on a string” called chromatin
  • chromatin threads coil and condense to form dense, rodlike bodies called chromosomes
  • chromo = colored, soma = body
  • plasma membrane is a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment
  • Fluid Mosaic Model - The model that describes the structure of the plasma membrane.
  • “sugar-proteins” are called glycoproteins
  • the cell surface is a fuzzy, sticky, sugar-rich area called the glycocalyx
  • Tight junctions
    - impermeable junctions that encircle the cells and bind them together into leakproof sheets.
  • Desmosomes
    - are anchoring junctions scattered like rivets along the sides of adjacent cells.
  • Gap Junction
    - function mainly to allow communication between two neighboring cells
  • connexons - hollow cylinders composed of proteins that connects two cells
  • Cytoplasm - the cellular material outside the nucleus and inside the plasma membrane; the site of most cellular activities
  • Cytosol - semitransparent fluid that suspends the other elements
  • Inclusions - chemical substances that may or may not be present, depending on the specific cell type.
  • Organelles - specialized cellular compartments that are the metabolic machinery of the cell.
  • Mitochondria - usually depicted as tiny, lozenge-like or sausage-shaped organelles
  • Ribosomes - are tiny, bilobed, dark bodies made of proteins and one vari- ety of RNA called ribosomal RNA
  • Endoplasmic Reticulum - a system of fluid-filled tunnels (or canals) that coil and twist through the cytoplasm
  • Endoplasmic Reticulum - a mini circulatory system for the cell because it provides a network of channels for carrying substances
  • Rough ER
    - synthesizes proteins and secretes it
  • Smooth ER - functions in lipid metabolism (cholesterol and fat synthesis and breakdown) and detoxification of drugs and pesticides.
  • Golgi Apparatus - appears as a stack of flattened membranous sacs that are associated with swarms of tiny vesicles
  • Lysosomes - membranous “bags” containing powerful digestive enzymes. Because lysosomal enzymes are capable of digesting worn-out or nonusable cell structures and most foreign substances that enter the cell,
  • Peroxisomes - membranous sacs containing powerful oxidase enzymes that use molecular oxygen (O2) to detoxify a number of harmful or poisonous substances
  • Free radicals - highly reactive chemicals with unpaired elec- trons that can damage the structure of proteins and nucleic acids.
  • peroxisomes = peroxide bodies
  • catalase - converts excess hydrogen peroxide to water
  • Cytoplasm - elaborate network of protein structures extends throughout the cytoplasm
  • Microfilaments - involved in cell motility and in producing changes in cell shape
  • Intermediate filament - the strong, stable, ropelike structure; provide internal guy wires to resist pulling forces on the cell