Bio mod 1 exam

• Organelles in cells


  • Nucleus
  • Mitochondria
  • Chloroplast
  • Endoplasmic reticulum
  • Ribosomes
  • Golgi body
  • Lysosome
• Nucleus


  Large spherical structure in cytoplasm, stores information to control all cell activity, double nucleus membrane with tiny pores that regulate passage of substance between nucleus and cytoplasm
• Mitochondria


  Produces energy via cellular respiration, combines oxygen and glucose to make carbon dioxide, water and ATP, number depends on energy consumption
• Chloroplast


  Green colour due to chlorophyll, surrounded by double membrane to allow substances to pass between cytoplasm and chloroplast, liquid part in stroma which contains stacks of membranes called thylakoids
• Endoplasmic reticulum (E.R)


  Rough ER: Ribosomes attached, processes proteins made by cell, can synthesise lipids. Smooth ER: No ribosomes attached, main site of lipid production
• Ribosomes


  Made of RNA & Proteins, follows 'instructions' of DNA for protein production, amino acids join together to form a chain, polypeptides, the structural units of protein
• Golgi body/ Golgi apparatus


  Processes, packages and sorts cell products
• Lysosome


  Formed by the golgi body, contain digestive enzymes that split chemical compounds into simpler ones, sometimes destroy entire cell (apoptosis)
• Examples of Prokaryotes


  • Bacteria
  • Archaea
• Bacteria


  A unicellular prokaryote, first type of living organism on Earth, have diverse metabolic systems, found in moist, low salt environments of moderate temperature, obtains energy via photosynthesis or by chemosynthesis, have a cell wall made up of a substance called peptidoglycan
• Gram staining


  Involves adding a purple dye (crystal violet) to bacterial cells, the dye interacts with the cell walls which alters the colour
• Gram positive bacteria


  • Purple colour, thicker layer of peptidoglycan that retains the stain, e.g. Staphylococcus & Streptococcus
• Gram negative bacteria


  • Pink colour, thinner layer of peptidoglycan that does not retain the stain, e.g. cyanobacterium
• Archaea


  In the domain extremophiles, can live in extreme conditions such as areas of high temperatures (thermophiles), acidic environments (acidophiles), salty environments (halophiles), cell membranes composed of lipids allows archaea to live in harsh environments, the lipids remains fluid and selectively permeable over a wide range of temperatures
• 1 nanometre= 0.001mm, 1000 nanometre= 1mm
• Working out the size of a cell

  1. Field of view (mm)/ number of cells= length of each cell (mm)

  2. Measured length (mm)/magnification= Actual length of cell (mm)
• Light microscope


  Passes light through a thin specimen magnified by a convex glass lens
• Advantages of light microscope

  • Allows living cells to be observed in colour
  • Slide preparation is simple and quick
  • Different components of cells can be highlighted via staining through substances like iodine
• Disadvantages of light microscope

  • Only 2D images
  • Not all organelles are visible
  • Cannot see sample if too thick
• Techniques used in light microscopy

  • Whole mounts
  • Smears
  • Sections
• Fluorescence microscopy


  Wavelengths "excite" these molecules to emit light, used to examine cells, cellular structures or any material such as stains, dyes or antibodies with fluorescent molecules, allows us to visualise, target and detect specific particles
• Confocal microscopy


  Involves a laser passing through a small segment of the specimen, allows scientists to obtain 'optical sections' of a cell or tissue, stained with fluorescent markers, without sectioning (keeping the original form) or slicing the cells, can obtain high-resolution images
• Electron microscopy


  Uses an electron beam maintained by electromagnetic lenses to allow the molecules to absorb the electrons, allows for a much higher resolution, greater depth of field
• Fluid mosaic model


  Model displaying a 'lipid sea' with 'many and various proteins floating on and in it', phospholipid bilayer composed of hydrophilic heads and hydrophobic tails, cell membranes can form and reform due to their composition, 40% lipid, 60% proteins
• Proteins in cell membrane

  • Receptors for chemical messengers
  • Identification markers
  • Helping chemicals move through the membrane
• Integral proteins


  Embedded through both sides of the phospholipid bilayer
• Peripheral proteins


  Attached to the integral proteins, and can be either outside or inside
• Cell membrane permeability


  The ability of molecule to pass through the cell membrane, important for intake of essential substances and removal of wastes
• Types of transport

  • Passive diffusion
  • Active diffusion
  • Osmosis
  • Endocytosis
  • Exocytosis
• Passive diffusion


  Diffusion of substances from high to low following a concentration gradient, diffusion of substances into the cell through proteins (carrier molecules) in the membrane, oxygen and water diffuse directly through the bilayer
• High concentration gradient


  Rapid diffusion
• Low concentration gradient


  Slower diffusion
• Osmosis


  The diffusion of water across a semipermeable membrane, equalises the concentration of the molecules by moving along a concentration gradient into a fixed ratio between solute and solvent
• Active diffusion


  Movement of molecules from low concentration to high concentration, requires a carrier protein to move chemicals from low-high concentration via ATP
• Endocytosis


  Cell membrane creates a vesicle to surround large molecules (macromolecules) and engulfs it, phagocytosis engulfs solid particles
• Exocytosis


  Membrane-bound vesicles moves to & fuses to cell membranes to release wastes
• Osmosis


  • Hypotonic solution
  • Isotonic solution
  • Hypertonic solution
• What is a hypotonic solution

  An external solution that has a low solute concentration and high water concentration causing the cell to expand
• What is a isotonic solution

  AN external solution that has the same solute concentration and water concentration causing it to stay the same size as it absorbs and releases the water equally
• What is a hypertonic solution?

  An external solution that has a high solute concentration and low water concentration causing it to shrink