Cells and Tissues Powerpoint

• Cells


  The structural units of all living things
• The human body has 50 to 100 trillion cells
• Cell Theory


  • A cell is the basic structural and functional unit of living organisms
  • The activity of an organism depends on the collective activities of its cells
  • According to the principle of complementarity, the biochemical activities of cells are dictated by their structure (anatomy) which determines their function (physiology)
  • Continuity of life has a cellular basis
• Elements most cells are composed of

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
• Cells are about 60% water
• Main regions or parts of a cell

  • Plasma membrane
  • Nucleus
  • Cytoplasm
• Plasma membrane


  • Transparent barrier for cell contents
  • Contains cell contents
  • Separates cell contents from surrounding environment
• Fluid mosaic model


  • Constructed of two layers of phospholipids arranged "tail to tail"
  • Cholesterol and proteins scattered among the phospholipids
  • Sugar groups may be attached to the phospholipids, forming glycolipids
• Phospholipid arrangement in the plasma membrane

  • Hydrophilic ("water loving") polar "heads" are oriented on the inner and outer surfaces of the membrane
  • Hydrophobic ("water fearing") nonpolar "tails" form the center (interior) of the membrane
  • This interior makes the plasma membrane relatively impermeable to most water-soluble molecules
• Role of proteins in the plasma membrane

  Responsible for specialized membrane functions: Enzymes, Receptors for hormones or other chemical messengers, Transport as channels or carriers
• Role of sugars in the plasma membrane

  • Glycoproteins are branched sugars attached to proteins that abut the extracellular space
  • Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell's surface
• Main types of cell junctions

  • Tight junctions
  • Desmosomes
  • Gap junctions (communicating junctions)
• Tight junctions


  Impermeable junctions that bind cells together into leakproof sheets, with plasma membranes fusing like a zipper to prevent substances from passing through extracellular space between cells
• Desmosomes


  Anchoring junctions, like rivets, that prevent cells from being pulled apart as a result of mechanical stress, created by buttonlike thickenings of adjacent plasma membranes
• Gap junctions (communicating junctions)


  Allow communication between cells, with hollow cylinders of proteins (connexons) spanning the width of the abutting membranes to allow molecules to travel directly from one cell to the next through these channels
• Nucleus


  Control center of the cell, containing genetic material known as DNA which is needed for building proteins and cell reproduction, with three regions: Nuclear envelope (membrane), Nucleolus, Chromatin
• Nuclear envelope (membrane)


  Consists of a double membrane that bounds the nucleus, contains nuclear pores that allow for exchange of material with the rest of the cell, and encloses the jellylike fluid called the nucleoplasm
• Nucleolus


  Sites of ribosome assembly, with ribosomes migrating into the cytoplasm through nuclear pores to serve as the site of protein synthesis
• Chromatin


  Composed of DNA wound around histones (proteins), scattered throughout the nucleus and present when the cell is not dividing, condensing to form dense, rodlike bodies called chromosomes when the cell divides
• Cytoplasm


  The cellular material outside the nucleus and inside the plasma membrane, which is the site of most cellular activities and includes cytosol, inclusions, and organelles
• Three major components of the cytoplasm

  • Cytosol: Fluid that suspends other elements and contains nutrients and electrolytes
  • Inclusions: Chemical substances, such as stored nutrients or cell products, that float in the cytosol
  • Organelles: Metabolic machinery of the cell that perform functions for the cell, many of which are membrane-bound, allowing for compartmentalization of their functions
• Mitochondria


  "Powerhouses" of the cell, with a mitochondrial wall consisting of a double membrane with cristae on the inner membrane, carrying out reactions in which oxygen is used to break down food into ATP molecules
• Ribosomes


  Made of protein and ribosomal RNA, sites of protein synthesis in the cell, found at two locations: free in the cytoplasm and attached to the rough endoplasmic reticulum
• Endoplasmic reticulum (ER)


  Fluid-filled tunnels (or canals) that carry substances within the cell, continuous with the nuclear membrane, with two types: Rough ER and Smooth ER
• Rough endoplasmic reticulum


  Studded with ribosomes, synthesizes proteins, with transport vesicles moving proteins within the cell, abundant in cells that make and export proteins
• Smooth endoplasmic reticulum


  Lacks ribosomes, functions in lipid metabolism and detoxification of drugs and pesticides
• Golgi apparatus


  Appears as a stack of flattened membranes associated with tiny vesicles, modifies and packages proteins arriving from the rough ER via transport vesicles, producing different types of packages: secretory vesicles, in-house proteins and lipids, and lysosomes
• Lysosomes


  Membranous "bags" that contain digestive enzymes, which can digest worn-out or nonusable cell structures, and house phagocytes that dispose of bacteria and cell debris
• Peroxisomes


  Membranous sacs of oxidase enzymes that detoxify harmful substances such as alcohol and formaldehyde, break down free radicals, and replicate by pinching in half or budding from the ER
• Cytoskeleton


  Network of protein structures that extend throughout the cytoplasm, providing the cell with an internal framework that determines cell shape, supports organelles, and provides the machinery for intracellular transport, consisting of three different types of elements: Microfilaments, Intermediate filaments, and Microtubules
• Centrioles


  Rod-shaped bodies made of nine triplets of microtubules that generate microtubules and direct the formation of mitotic spindle during cell division
• Cell extensions


  Surface extensions found in some cells, including cilia that move materials across the cell surface, flagella that propel the cell, and microvilli that increase surface area for absorption
• Cell types that vary in size, shape, and function

  • Fibroblast
  • Erythrocyte (red blood cell)
  • Epithelial cell
  • Skeletal muscle and smooth muscle cells
  • Fat cells
  • White blood cells, such as the macrophage
  • Nerve cell (neuron)
  • Oocyte (female)
  • Sperm (male)
• Cell physiology


  Cells have the ability to metabolize, digest food, dispose of wastes, reproduce, grow, move, and respond to a stimulus
• Solution


  Homogeneous mixture of two or more components, with the solvent being the dissolving medium present in the larger quantity (the body's main solvent is water) and the solutes being the components in smaller quantities within the solution
• Intracellular fluid


  Nucleoplasm and cytosol, a solution containing gases, nutrients, and salts dissolved in water
• Extracellular fluid (interstitial fluid)


  Fluid on the exterior of the cell, containing thousands of ingredients such as nutrients, hormones, neurotransmitters, salts, and waste products
• Plasma membrane


  A selectively permeable barrier, where some materials can pass through while others are excluded
• Two basic methods of transport

  • Passive processes: substances are transported across the membrane without any input from the cell
  • Active processes: the cell provides the metabolic energy (ATP) to drive the transport process
• Diffusion


  Molecule movement is from high concentration to low concentration, down a concentration gradient, with particle distribution tending to be even within a solution due to kinetic energy (energy of motion) causing random molecular movement, where size of the molecule and temperature affect the speed of diffusion