خليه

• Cytology

  The science that studies the cellular organization structurally, functionally and the relation of this organization with metabolic activities, growth, differentiation, evolution, heredity
• Cell theory


  • Scientists first observed living cells under the microscope in 1674 by Robert Hooke
  • Theodor Schwann & Matthias Schleiden concluded all living things are made of cells (1839)
  • Rudolf Virchow formulated the cell theory: 1) all living things are composed of one or more cells, and cell products, 2) a single cell is the smallest unite that exhibits all the characteristic of life, 3) all cells come only from preexisting cell
• Cell

  The basic structural, functional, and biological unit of all known living organisms, consisting of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids
• Types of organisms


  • Unicellular (consisting of a single cell; including bacteria)
  • Multicellular (including plants and animals)
• Animal cells

  • Multicellular, eukaryotic cells
  • Surrounded by plasma membrane
  • Contain nucleus and membrane-bound organelles
  • Various sizes and irregular shapes
  • Most cells range between 1 and 100 micrometers
  • Trillions of cells in the human body
  • Many different types of cells

  
• Parts of the animal cell

  • Cell membrane
  • Cytoplasm
  • Nucleus

  
• Cell membrane


  Forms the outer covering of the cell, and is semi-permeable
• Cytoplasm

  Gel-like matrix where all the other cell organelles are suspended inside the cell
• Nucleus

  Contains the hereditary material DNA and directs the activities of the cell
• Cells are composed of water, inorganic ions, and carbon-containing (organic) molecules
• Water

  The most abundant molecule in cells, accounting for 70% or more of total cell mass
• Carbohydrates

  Compounds containing carbon, hydrogen and oxygen in a 2:1 ratio of hydrogen to oxygen, like in water
• Monosaccharides

  • Glucose
  • Fructose
  • Galactose

  
• Disaccharides

  Two monosaccharides joined by a covalent bond
• Types of disaccharides

  • Sucrose (glucose + fructose)
  • Maltose (two glucose molecules)
  • Lactose (glucose + galactose)

  
• Polysaccharides

  Many monosaccharide molecules joined together with covalent bonds
• Polysaccharides

  • Glycogen
  • Starch
• Glycogen

  A polysaccharide containing many hundreds of monosaccharide subunits, stored in the body for energy in the liver and skeletal muscles

  
• Lipids

  Large molecules that do not dissolve in water, containing carbon, hydrogen and oxygen

  
• Important lipids in the body

  • Fats
  • Phospholipids
  • Steroids

  
• Fats

  • Lipid molecules formed from glycerol and three fatty acids
  • Saturated fats have no double bonds in the fatty acids, are solid at room temperature
  • Unsaturated fats have at least one double bond in the fatty acids, are liquid at room temperature

  
• Phospholipids

  • Similar to fats but with a phosphate group instead of a third fatty acid
  • The phosphate end is hydrophilic ("likes water"), the fatty acid end is hydrophobic ("fears water")
  • Major component of cell membranes

  
• Steroids

  • Complex ring compounds, do not dissolve in water
  • Examples: cholesterol, vitamin D, cortisone, estrogen
• Roles of lipids

  • Provide an important form of energy storage
  • Major components of cell membranes
  • Play roles in cell signaling as steroid hormones and message molecules

  
• Lipid storage disorders

  Inherited metabolic disorders where harmful amounts of lipids accumulate in body cells and tissues due to lack of or malfunctioning enzymes needed to metabolize lipids, leading to cellular and tissue damage
• Proteins

  Very large, complex molecules composed of carbon, hydrogen, oxygen and nitrogen, constructed from amino acid building blocks joined by peptide bonds