LESSON 3 BIO

• The cell is the basic structural and functional unit of living organisms
• The cell theory states that all biological organisms are composed of cells, cells are the unit of life, and all life come from preexisting life
• Modern cell theory


  DNA is passed between cells during cell division, cells of all organisms within a similar species are mostly the same structurally and chemically, and energy flow occurs within cells

  
• Types of organisms based on cell count

  • Unicellular
  • Multicellular
• Unicellular organisms


  Organisms made up of a single cell that carries out all functions needed by the organism
• Unicellular organisms

  • Bacterium, amoeba, yeast
• Multicellular organisms


  Organisms made up of multiple cells that perform different functions for survival
• Multicellular organisms


  • Plants, animals, insects
• In humans, cells differentiate early in development to become nerve cells, skin cells, muscle cells, blood cells, and other types of cells
• Cell size


  Most cells are microscopic, some may be macroscopic, measured in micrometers
• Cell sizes


  • Ostrich egg (18 cm), Mycoplasma (0.1 micrometer), Sperm cell (smallest), Ovum (largest), Nerve cell (longest)
• Cell shape


  Depends on the functions they serve, some can change shape, most have a fixed shape
• Cell shapes

  • Amoeba, human red blood cells, nerve cells, muscle cells, white blood cells
• Factors affecting cell shape variations

  • Elasticity/rigidity of membrane, surface tension, viscosity of cytoplasm, pressure from neighboring cells, functional adaptation
• Microscopes were invented in 1590 and further refined during the 1600s
• Cell walls were first seen on dead cells of oak bark by Robert Hooke in 1665 and living cells by Antoni van Leeuwenhoek a few years later
• Functions of a microscope

  Produce a magnified image, separate details to make it clearer, render details visible to the human eye

  
• Compound/Light microscope


  Light-illuminated, uses lenses to refract light and magnify the image, produces a 2D image

  
• Electron microscope


  Uses a beam of electrons to illuminate the specimen, produces a 3D image, higher magnification and resolution

  
• Transmission electron microscope (TEM)


  Aims an electron beam through a thin section of the specimen, uses heavy metal stains to enhance contrast

  
• Microscopes use electromagnets as lenses to bend the paths of electrons, focusing the image onto a monitor

  
• Cell components


  • Plasma membrane
  • Cytoplasm
  • Nucleus
• Plasma membrane


  Outermost layer, semi-permeable, maintains cell shape and size, protects internal contents, regulates entry and exit of substances
• Plasma membrane modifications

  • Microvilli, glycocalyx, cell wall in plant cells
• Cell wall

  Found in plants and bacteria, provides shape, strength, rigidity, protects from pathogens
• Nucleus


  Control center, contains genes and hereditary information, separated from cytoplasm by nuclear membrane, contains nucleoplasm, nucleolus, and chromatin fibers
• Cytoplasm


  Area between nucleus and plasma membrane, contains cytosol and organelles

  
• Endoplasmic reticulum (ER)


  Network of tubular and vesicular structures, some connected to nuclear and cell membranes, rough ER synthesizes proteins, smooth ER synthesizes lipids

  
• Golgi bodies


  Modify, sort, and pack materials synthesized in the cell, deliver materials to targets inside and outside the cell
• Lysosomes


  Membrane-bound sacs filled with hydrolytic enzymes, break down large molecules, destroy foreign invaders, degrade worn out organelles, perform autolysis

  
• Peroxisomes


  Break down excess fatty acids, help produce cholesterol and phospholipids, convert fatty acids and lipids to sugars in germinating seeds
• Vacuoles


  Storage of various substances, help maintain water balance and rigidity in plant cells, store food in amoeba
• Mitochondria


  Powerhouse, site of ATP synthesis and cellular respiration
• Plastids


  Double membrane-bound organelles in plant cells, involved in photosynthesis, synthesis of amino acids and lipids, storage of materials

  
• Chromoplasts


  Brightly colored plastids that act as the site of pigment accumulation
• Vacuoles


  In plant cells, help maintain water balance and rigidity of cells. In amoeba, function in food storage
• Mitochondria


  The powerhouse of the cell, bound by two membranes, functions in the synthesis of ATP which provides energy for cell activities, site of cellular respiration

  
• Plastids


  Double membrane-bound organelles in plant cells, involved in manufacture and storage of food, photosynthesis, synthesis of amino acids and lipids, storage of various materials

  
• Leucoplasts


  Non-pigmented plastids located in non-photosynthetic plant tissues, specialized for bulk storage of starch, lipid or protein, also provide essential biosynthetic functions
• Chloroplasts


  Plant cell organelles that convert light energy into chemical energy via photosynthesis, provide green color to leaves and stems, have grana and stroma regions