bio paper 1

• Eukaryotic cells


  Cells that contain a true nucleus
• Eukaryotic cells


  • Contain a 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 plant cells
• 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, their 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
• Flagellum


  Allows bacteria to move around more easily
• Cell specialization


  • Cells are adapted structurally to suit their function
  • Can involve changes in shape or presence of subcellular structures
  • Sperm cells have a tail and many mitochondria
  • Nerve cells have a branched shape
  • Muscle cells are packed with mitochondria and ribosomes
• Plant cell specialization


  • Occurs later in development compared to animals
  • Plants retain unspecialized stem cells throughout their lifetime
  • Palisade cells in leaves have many chloroplasts
  • Root hair cells have an extended shape to increase surface area and absorb water and minerals
• Xylem


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


  Made of living cells, transport sugars from leaves to rest of plant
• Good conditions for transpiration


  Hot, dry, light, lots of air movement
• Stem cells


  Unspecialized cells that can differentiate into specialized cell types
• Adult human stem cells

  • Relatively few, limited in what they can become
  • Embryonic stem cells can become almost any cell type
• Therapeutic cloning


  Creating an embryo with the same genes as the patient, to harvest stem cells that won't be rejected
• Plant meristems


  Contain stem cells that can become any cell type, allowing easy cloning of plants
• Resolution


  Smallest measurement that can be made
• Magnification


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


  • Existed since 16th century, give basic understanding of cells
  • Maximum magnification around 1500x, resolution around 0.2 micrometers
  • Cannot see very small structures like ribosomes
• Electron microscopes


  • Use electron beams instead of light
  • 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 objective and focus with fine wheel only

  5. Use stain to see transparent structures

  6. Troubleshoot if image is out of focus or too small
• Chromosomes


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


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


  Part of the cell cycle where the cell grows and carries out normal metabolism
• Mitosis


  1. DNA replication

  2. Chromosomes pulled to opposite ends of cell

  3. Cell divides once, producing two identical diploid daughter cells
• Diffusion


  Passive movement of particles from high to low concentration, down the concentration gradient
• Diffusion in animals


  • Urea diffuses from cells into blood plasma
  • Oxygen diffuses from lungs into bloodstream, carbon dioxide diffuses the opposite way
• Diffusion in plants


  • Carbon dioxide diffuses through leaf
• Adaptations for faster diffusion

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


  The movement of molecules 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 shorter distance
  • 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