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 where protein is made
  • Contain mitochondria
  • Plant cells and cells of algae have a cell wall made from cellulose
  • Plant cells contain green chloroplasts full of chlorophyll which absorb light for photosynthesis
  • Plant cells contain a permanent vacuole full of cell sap
• Nucleus


  Contains the DNA or genetic material and is responsible for controlling the actions of the cell
• Cytoplasm


  The liquid gel where most of the 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


  The site for aerobic respiration which is used to release energy from glucose
• Cell wall


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


  Absorb light and are where photosynthesis takes place
• Permanent vacuole


  A storage of cell sap used to keep the cell rigid to support the plant
• Prokaryotic cells


  Smaller than eukaryotic cells, lack a nucleus, and lack membrane-bound subcellular structures like mitochondria or chloroplasts
• Prokaryotic cells have a single circular chromosome and may also have small circles of DNA called plasmids
• Prokaryotic cells have smaller ribosomes than eukaryotic cells
• Bacterial cell walls are not made of cellulose
• Some bacteria have a flagellum which acts like a tail and allows the bacteria to move around more easily
• Cell specialization


  • Cells are adapted structurally to suit their function, involving changes in shape or the presence of more or fewer subcellular structures
  • Sperm cells have a tail and are packed with mitochondria
  • Nerve cells have a very branched shape
  • Muscle cells are packed with mitochondria and ribosomes
• Plant cell specialization


  • Plant cells specialize much later than animal cells and plants retain unspecialized stem cells throughout their lifetime
  • Palisade cells in leaves have lots of extra chloroplasts
  • Root hair cells have an extended shape to increase surface area and actively transport minerals
• Xylem


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


  Living cells that transport sugar from leaves to other parts of the plant
• Phloem are made from sieve tube elements that carry contents and companion cells that supply energy
• Xylem and phloem are found in the vascular bundles of leaves
• Conditions for good transpiration


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


  Relatively few and limited in what they can become
• Embryonic stem cells


  Can differentiate into many cell types
• 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 from cuttings
• Resolution


  The smallest measurement that can be made
• Magnification


  How much bigger the image looks than the actual object
• Light microscopes have a maximum magnification of around 1500x and a resolution of 0.2 micrometers
• Light microscopes


  • Compound microscopes with an eyepiece lens and objective lens
  • Use light to focus on the object
• Electron microscopes


  • Have much greater magnification (up to 500,000x) and resolution (down to 1 nanometer)
  • Use a beam of electrons rather than light
• Using a light microscope

  1. Start with stage as high as possible

  2. Use lowest power objective lens

  3. Focus first with coarse focusing wheel, then fine focusing wheel

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

  5. Use a stain to see transparent structures
• Magnification formula


  Magnification = Size of image / Size of actual object
• There are 1000 micrometers in a millimeter and 1000 nanometers in a micrometer
• Mitosis


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


  • Occurs as part of the normal cell cycle following interphase
  • Involves DNA replication and then separation of chromosomes to opposite ends of the cell, producing two identical diploid daughter cells
• Diffusion


  The passive movement of particles from an area of high concentration to an area of low concentration
• Diffusion occurs in both gases and solutions, with or without a membrane
• Diffusion in animals


  • Urea diffuses from cells into blood plasma
  • Oxygen diffuses from lungs into bloodstream, carbon dioxide diffuses in opposite direction