A LOOK AT THE CELLS (2)

• Cell


  The basic unit of living matter in the human body, varying from simple squamous epithelial cells to highly specialized neurons
• Cell structure


  • Generally, the simpler the cell, the greater its power to regenerate
  • The more specialized the cell, the weaker its regenerative power
  • Cells with greater regenerative power have shorter life spans than those with less regenerative power
• Components of cells


  • Protoplasm
  • Plasma membrane
  • Nucleus
• Protoplasm


  The viscous, translucent, watery material that is the primary component of plant and animal cells, containing water, inorganic ions, and organic compounds
• Electrolytes


  The inorganic ions within protoplasm that regulate acid-base balance and control the amount of intracellular water
• Nucleoplasm


  The protoplasm of the cell's nucleus that plays a part in reproduction
• Cytoplasm


  The protoplasm of the cell body that surrounds the nucleus, converting raw materials to energy and being the site of most synthesizing activities
• Components of cytoplasm


  • Cytosol
  • Organelles
  • Inclusions
• Cytosol


  The viscous, semitransparent fluid that is 70% to 90% water and contains proteins, salts, and sugars
• Organelles and their functions

  • Mitochondria (provide ATP energy)
  • Ribosomes (sites of protein synthesis)
  • Endoplasmic reticulum (transports and processes molecules)
  • Golgi complex (processes and packages proteins)
  • Lysosomes (contain digestive enzymes)
  • Peroxisomes (contain oxidases)
  • Cytoskeletal elements (provide structural support)
• Inclusions


  Nonfunctioning units in the cytoplasm that are commonly temporary, such as the pigment melanin and the stored nutrient glycogen
• Plasma membrane


  The gatekeeper of the cell, serving as the cell's external boundary and a semipermeable membrane that only allows certain molecules in and out
• Nucleus


  The cell's mission control, playing a role in cell growth, metabolism, and reproduction, and containing chromosomes that control cellular activity and direct protein synthesis
• DNA


  Carries genetic information and provides the blueprint for protein synthesis
• RNA


  Transfers genetic information from DNA to the ribosomes, where protein synthesis occurs
• Types of RNA


  • Ribosomal RNA (used to make ribosomes)
  • Messenger RNA (directs arrangement of amino acids to make proteins)
  • Transfer RNA (transfers genetic code for production of specific amino acids)
• components and structures of cells

  A) Cytoplasm

  B) cell membrane

  C) mitochondrion

  D) centriole

  E) endoplasmic reticulum

  F) ribosomes

  G) golgi complex

  H) microvilli

  I) Nucleus

  J) nucleolus

  K) ribonucleic acid

  L) chromatin

  M) lysosome

  
• nucleotide


  basic structural unit of DNA
• four different DNA bases

  adenine (A)

  guanine (G)

  thymine (T)

  cytosine (C)
• double-ring compounds classified as purines

  adenine and guanine
• single-ring compounds classified as pyrimidines

  thymine and cytosine