biology

• All organisms are composed of one or more cells. Cells are the smallest living units of all living organisms. Cells arise only by division of a previously existing cell.
• Magnification


  How much bigger a sample appears to be under the microscope than it is in real life
• Resolution


  The ability to distinguish between two points on an image i.e. the amount of detail
• Common types of microscopes

  • Light (optical) microscopes
  • Electron microscopes
• Light Microscope


  Specimens are illuminated with light, which is focused using glass lenses and viewed using the eye or photographic film
• Compound Light Microscope


  Uses several lenses to obtain high magnification
• Total Magnification


  How much bigger a sample appears to be under the microscope than it is in real life
• Eyepiece graticule


  Transparent scale, generally with 100 divisions placed in the microscope eyepiece
• Stage micrometer


  Miniature transparent ruler placed on the microscope stage

  
• Measuring Cells


  Magnification = Size of image / Actual size of the specimen

  
• Electron Microscope


  Uses a beam of electrons to "illuminate" the specimen
• Types of Electron Microscopes

  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
• Label the components of the light microscope.
• The initial development of the cell theory, during the mid-17th century, was made possible by advances in microscopy
• The three parts to the cell theory

  • All living organisms are composed of one or more cells
  • The cell is the basic unit of structure, function, and organization in all organisms
  • All cells come from preexisting, living cells
• Rudolf Virchow - New cells come from existing cells


  1855
• Matthias Schleiden - Cell theory; Plants are made of cells


  1838
• Theodor Schwann - Cell theory; Animals are made of cells


  1839
• Cells are the basic unit of living things.
• Types of cells


  • Prokaryotic cells
  • Eukaryotic cells
• Features common to all cells

  • All membranes have the same lipid bilayer
  • All cells use membranes to form boundaries
  • Membranes are semi-permeable barriers controls the passage of molecules
  • The membranes separate the cell contents from the external environment
  • Cytoplasm is the jelly-like material filling the cell interior
  • All cells store genetic information as DNA
  • Central dogma (information flows from DNA to protein); Replication, Transcription, Translation
• Nucleoid


  Region where the cell's DNA is located (not enclosed by a membrane)
• Organelles in eukaryotic cells

  • Nucleus
  • Mitochondria
  • Chloroplast
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Vacuole
  • Ribosomes
  • Centrioles
  • Flagellum & cilium
  • Cytoskeleton
• Nucleus


  The control centre of the cell and the site where hereditary information is stored
• Nucleolus


  Dark region inside the nucleus where you can find chromatins
• The nucleolus is not bounded by a membrane.
• Organelles


  • Membrane
  • Nucleus
  • Mitochondria
  • Chloroplast
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Vacuole
  • Ribosomes
  • Centrioles
  • Flagellum & cilium
  • Cytoskeleton
• Nucleus


  • Found in all cells except prokaryotic cells, red blood cells and mature sieve tubes
  • The largest organelle and roughly spherical in shape
  • The control centre of the cell and the site where hereditary information is stored
• The nucleolus is not bounded by a membrane
• Nuclear envelope


  • Consists of an inner membrane and an outer membrane
  • Nuclear pores (40-100nm diameter, 3000/nucleus) are found where the two membranes pinch together
  • Nuclear pores are lined with proteins and act as molecular channels
• Nucleoplasm


  The space between the nuclear envelope and nucleolus, a semi-fluid medium containing chromatins
• Chromatins


  Chromosomes in their non-dividing state, have a thread-like appearance, made of DNA and proteins
• During cell division, chromatins condense to form thick rod-like structures called chromosomes
• Mitochondria


  • Bound by two membranes: outer membrane and inner membrane
  • The inner membrane is folded to form projection structures called cristae
  • The surface of the inner membrane is embedded with proteins that carry out oxidative metabolism
  • Matrix mitochondria contains DNA, ribosome, RNA, respiration enzyme, proteins and etc.
• Intermembrane space


  The space between the inner membrane and the outer membrane of mitochondria
• Mitochondria has its own DNA, it is not replicated through cell division but replicates by itself
• Chloroplast


  • Distributed at high level plants, can be found at mesophyll especially palisade mesophyll
  • Plastids are organelles that conduct photosynthesis and store starch
  • Diameter: 8-10µm
  • Stroma is the matrix of chloroplast, contains starch, DNA, lipid globule, ribosome and photosynthetic enzyme
• Chloroplast structure


  • Has outer membrane and inner membrane
  • A closed compartment of stacked membranes called grana (granum)
  • The granum may be made up of many stacked, disk-shaped structures called thylakoids
  • Chloroplasts contain the photosynthetic pigment called chlorophyll which located in the thylakoid membranes
• Vacuole


  • A sac surrounded by a single lipoprotein membrane, spherical in shape
  • The lipoprotein membrane surrounding the vacuole is called tonoplast
  • It contains a solution of water, sugars, ions and pigments called the cell sap
  • There are 3 types of vacuole: sap or central vacuole, food vacuole, contractile vacuole
• Endoplasmic reticulum (ER)


  • It is an extension of the outer nuclear membrane with which it is continuous
  • Membranes forms a series of sheets which enclose flattened sacs called cisternae
  • The rough ER is studded with 80S ribosomes and is the site of protein synthesis
  • Smooth ER is a network of tubules without ribosome on its surface, involved in lipid and steroid synthesis, regulation of calcium levels, and breakdown of toxins