Chapter 1: cell biology and transport

• Microscopy


  The use of microscopes
• How light microscopes work

  1. Light from the room hits the mirror

  2. Reflected upwards through the object

  3. Passes through the objective lens

  4. Passes through the eyepiece lens

  5. Into the eye
• Object


  The real object or sample that you're looking at
• Image


  The image that we see when we look down the microscope
• Magnification


  How many times larger the image is than the object
• Magnification = image size / object size
• Resolution


  The shortest distance between two points on an object that can still be distinguished as two separate entities
• Higher resolution


  More details can be seen, less blurry the image
• The images have the same magnification (100x) but different resolutions
• Specialized animal cells


  Cells that have adaptations which help them to carry out a particular function
• Differentiation


  When cells become specialized
• Sperm cells


  • Long tail to swim to ovum
  • Packed with mitochondria to provide energy for swimming
  • Contain enzymes to digest outer layer of ovum
• Fertilization


  The process where the genetic information of the ovum and sperm combine
• Sperm cells only contain half the genetic information of a normal adult cell
• Nerve cells


  • Long axon to transmit electrical impulses
  • Axon covered in myelin to insulate and speed up transmission
  • Dendrites to increase surface area for connections
• Axon


  Part of nerve cell that transmits electrical impulses
• Synapses


  Junctions that allow impulses to pass from one nerve cell to another
• Muscle cells


  • Contain protein fibers that can contract and shorten
  • Packed with mitochondria to provide energy for contraction
• Muscle cells work together to form muscle tissue
• Differentiation


  The process where cells become specialized
• Root hair cells


  • Increase the surface area of the root to absorb water and dissolved minerals more effectively
  • Do not contain chloroplasts
• Xylem cells


  • Have very thick walls containing lignin to provide support
  • Have no internal structures like nucleus, cytoplasm, vacuole or chloroplasts to allow easy flow of water and dissolved minerals
• Phloem cells


  • Consist of two types: phloem vessel cells with no nucleus and limited cytoplasm, and companion cells with mitochondria to provide energy to the phloem vessel cells
  • Phloem vessel cells have porous end walls called sieve plates to allow flow of dissolved sugars
• Specialized plant cells include root hair cells, xylem cells, and phloem cells
• Diffusion


  The net movement of particles from an area of higher concentration to an area of lower concentration
• Diffusion


  1. Molecules move about randomly

  2. Molecules spread out over time

  3. Molecules become evenly distributed
• Diffusion can happen in both gases and liquids
• Partially permeable membrane


  Only some molecules can diffuse through, like water, glucose, and amino acids. Larger molecules like proteins and starch cannot fit through.
• Diffusion is a passive process that does not require energy from the cell
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Larger concentration gradient


  Higher rate of diffusion
• Higher temperature


  Higher rate of diffusion
• Larger surface area


  Higher rate of diffusion
• Osmosis


  The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• Water concentration


  The amount of water as compared to the other molecules like sugars or salts that are dissolved in that water
• Solutes are the dissolving molecules in water
• Higher solute concentration


  Lower water concentration
• Lower solute concentration


  Higher water concentration
• Osmosis in cells


  Water particles diffuse from outside the cell (higher water concentration) down the concentration gradient into the cell (lower water concentration)
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