Topic 1 - Cell Biology

• Eukaryotic cells


  Cells that contain a true nucleus
• Eukaryotic cells


  • Cell membrane wrapped around cytoplasm
  • Contain a nucleus
  • Contain ribosomes
  • Contain mitochondria
  • Plant cells and algae cells have a cell wall made of cellulose
  • Plant cells contain chloroplasts and a permanent vacuole
• Nucleus


  Contains the DNA or genetic material and controls the actions of the cell
• Cytoplasm


  Liquid gel where most chemical reactions in the cell take place
• Cell membrane


  Responsible for controlling what can go into and out of the cell
• Ribosomes


  Used to synthesize protein
• Mitochondria


  Site for aerobic respiration to release energy from glucose
• Cell wall


  Made of cellulose, strengthens and gives support to the cell
• Chloroplasts


  Absorb light and are the site of photosynthesis
• Permanent vacuole


  Storage of cell sap, used to keep the cell rigid and support the plant
• Prokaryotic cells


  • Smaller than eukaryotic cells
  • Lack a nucleus, DNA exists as a single circular chromosome
  • May have small circles of DNA called plasmids
  • Lack membrane-bound subcellular structures like mitochondria or chloroplasts
  • Ribosomes are smaller than in eukaryotic cells
  • Cell walls are not made of cellulose
  • Some have a flagellum to allow movement
• Cells can be specialized, meaning they are adapted structurally to suit their function
• Specialized cells


  • Sperm cell with a tail and many mitochondria
  • Nerve cell with a branched shape
  • Muscle cell packed with mitochondria and ribosomes
  • Palisade cells in leaves with many chloroplasts
  • Root hair cells with an extended shape and no chloroplasts
• Xylem


  Dead hollow tubes reinforced with lignin, transport water and mineral ions from roots to leaves
• Phloem


  Made of living sieve tube elements and companion cells, transport sugars from leaves to rest of plant
• Good conditions for transpiration


  Hot, dry, light, lots of air movement
• Specialized cells are originally derived from unspecialized or undifferentiated stem cells
• Adult stem cells


  Limited in what they can become, e.g. blood stem cells
• Embryonic stem cells


  Can become almost any type of specialized cell
• Therapeutic cloning uses an embryo with the same genes as the patient to harvest stem cells that won't be rejected
• Plants have meristems containing stem cells that can become any cell type, allowing easy cloning
• Resolution


  Smallest measurement that can be made
• Magnification


  How much bigger the image looks than the actual object
• Light microscopes


  • Magnification up to 1500x, resolution down to 0.2 micrometers
  • Can't see ribosomes or other very small structures
• Electron microscopes


  • Much greater magnification (up to 500,000x) and resolution (down to 1 nanometer)
  • Can view mitochondria and subcellular ultrastructure
• Using a light microscope

  1. Start with stage as high as possible

  2. Use lowest power objective lens

  3. Focus first with coarse wheel, then fine wheel

  4. Switch to higher power lens and focus with fine wheel only

  5. Use a stain to see transparent structures
• Troubleshooting a light microscope: adjust focusing wheels, use higher power lens, check lamp and objective lens position
• Chromosomes


  23 pairs in human body cells, contain DNA and genes
• Mitosis


  Cell division used by body cells for growth and repair
• Mitosis


  1. Interphase with DNA replication

  2. Chromosomes pulled to opposite ends

  3. Cell divides once to produce two identical diploid daughter cells
• Diffusion


  Passive movement of particles from high to low concentration
• Diffusion in animals


  • Urea from cells into blood plasma
  • Oxygen from lungs into bloodstream
  • Carbon dioxide from bloodstream into lungs
• Diffusion in plants


  • Carbon dioxide through leaf spongy mesophyll
• Adaptations for faster diffusion

  • Folded structures like alveoli and villi to increase surface area
• Diffusion


  The movement of particles from a region of higher concentration to a region of lower concentration
• Diffusion examples


  • Urea diffuses from cells into blood plasma to be removed
  • Oxygen diffuses from lungs into bloodstream
  • Carbon dioxide diffuses from bloodstream into lungs
• Diffusion is not the same as inhaling and exhaling, which involve physical movement of the diaphragm and ribs
• Diffusion in plants


  Carbon dioxide diffuses through the leaf
• Tissues adapted for diffusion

  • Lungs, small intestines, gills in fish
  • Folded structure to increase surface area
  • Thin membrane for less distance for absorbed substances to travel
  • Good blood supply or ventilation to maintain concentration gradient
• Surface area to volume ratio

  Increasing surface area by cutting or folding an object speeds up transport or chemical reactions