pls

• Magnification


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


  The ability to distinguish between 2 separate points
• Types of microscopes


  • Light Microscope
  • Scanning Electron Microscope (SEM)
  • Transmission Electron Microscope (TEM)
• Light Microscope


  • Resolution is 200 nm
  • Magnification x 1500 to x 500,000
  • Limit of resolution: half the wavelength
  • Ribosomes (25 nm) can't be seen
• Electron microscopes


  • Require a vacuum
  • Sample must be dehydrated
• Cell


  All living things are built around cells. The relationships between these cell structures demonstrate how cells transfer energy, produce biological products, and proteins.
• Golgi body


  • Consist of stack of flattened membranes enclosing hollow sacs called cisternae
  • Not continuous with nuclear membrane
  • Modifications and packaging of proteins and lipids
• Nucleus


  • Largest organelle of Eukaryotic cells
  • Surrounded by a double membrane called nuclear envelope
  • Contains chromosomes and chromatin
  • Nucleolus makes ribosomes, rRNA and tRNA
• Endoplasmic reticulum (ER)


  • Rough ER has ribosomes on outer surface and transports proteins
  • Smooth ER produces and stores lipids and steroids
• Mitochondria


  • Have a double membrane
  • Cristae provide large surface area for aerobic respiration
  • Matrix contains enzymes for Krebs cycle
• Chloroplast


  • Site of photosynthesis
  • Have a double membrane envelope
  • Stroma contains enzymes, ribosomes and DNA for light-independent reactions
  • Thylakoids and grana for light-dependent reactions
• Lysosomes


  • Contain hydrolytic enzymes to digest old organelles, pathogens, toxins and foreign objects
• Ribosomes


  • 80S in eukaryotes, 70S in prokaryotes, chloroplasts and mitochondria
  • Sites of protein synthesis
• Plasmodesmata


  • Pores in plant cell walls that allow transfer of water, sucrose, amino acids, ions, minerals, salts, hormones and ATP between cells
• Tonoplast


  • Phospholipid bilayer surrounding the cell vacuole
  • Selectively permeable to control exchange of materials
• Cell vacuole


  • Large fluid-filled space that gives the cell turgidity and supports the cell
• Cell wall


  • Made of cellulose, gives plant cells shape and prevents bursting
  • Has a middle lamella that cements adjacent cells
• Structural features of a prokaryotic cell

  • Unicellular
  • Generally 1–5 µm diameter
  • Peptidoglycan cell walls
  • Circular DNA
  • 70S ribosomes
  • Absence of organelles surrounded by double membranes
• Animal and plant cells are types of eukaryotic cells, bacteria are prokaryotes
• Prokaryotes have a cellular structure distinct from eukaryotes; their genetic material is not packaged with a membrane bound nucleus and is usually circular
• Prokaryotes are smaller than eukaryotes and have smaller 70S ribosomes compared to 80S in eukaryotes
• Structures sometimes present in prokaryotes


  • Flagellum
  • Capsule
  • Infoldings of cell surface membrane
  • Plasmid
  • Pili
• Structures always present in prokaryotes

  • Cell wall
  • Cell surface membrane
  • Cytoplasm
  • Circular DNA
  • Ribosomes
• Eukaryotic cells


  Animal and plant cells
• Prokaryotes


  Cellular structure distinct from eukaryotes, genetic material not packaged with a membrane bound nucleus, usually circular
• Structures sometimes present in Prokaryotes

  • Flagellum
  • Capsule (for protection)
  • Infoldings of cell surface membrane (may allow photosynthesis or carry out nitrogen fixation)
  • Plasmid (small circle of DNA)
  • Pili (for attachment to other cells or surfaces, involved in sexual reproduction)
• Structures always present in Prokaryotes

  • Cell wall
  • Cell surface membrane
  • Cytoplasm
  • Circular DNA
  • Ribosomes
• ATP


  Energy currency used by all organisms to maintain their cells and stay alive
• ATP


  • Required for anabolic reactions, transport across cell membrane, muscle contraction, nerve impulse transmission, and many other cellular processes
  • Produced from respiration and used to transfer energy in all energy-requiring processes in cells in all known forms of life
• Viruses


  Non-cellular/acellular, made up of a protein coat called capsid, either have a DNA or RNA strand, replicate inside host cells only, show no characteristics of living organism, symmetrical shape the virus DNA/RNA takes over the protein synthesising machinery of the host cell which helps to make new virus particles, all viruses are parasitic
• All living organisms are made of C, H, O and N molecules
• Monosaccharide


  A molecule consisting of a single sugar unit and with the general formula (CH2O)n, examples include hexoses (glucose, fructose and galactose) and pentoses (ribose and deoxyribose)
• Disaccharide


  A sugar molecule consisting of two monosaccharides joined together by a glycosidic bond, examples include sucrose (formed by joining of glucose and fructose), maltose (formed by joining of two glucose units)
• Polysaccharide


  A polymer whose subunits are monosaccharides joined together by glycosidic bonds, examples include amylose, amylopectin, glycogen and cellulose
• Glycosidic bond


  A C-O-C link between two sugar molecules, formed by a condensation reaction, a covalent bond
• Condensation reaction


  A chemical reaction in which two molecules join together to form a complex molecule with the removal of a molecule of water
• Hydrolysis


  A chemical reaction in which a chemical bond is broken by the addition of a molecule of water, commonly used to break down complex molecules into simpler molecules
• Monomer


  A relatively simple molecule which is used as a basic building block for the synthesis of a giant complex molecule called polymer, many monomers bond together by covalent bonds to form the polymer (condensation reaction)
• Polymer


  A giant molecule made from many similar repeating subunits (monomers) joined together in a chain, examples include polysaccharides, proteins, nucleic acids
• Macromolecule


  A large molecule such as a polysaccharide, protein or nucleic acid