cell biology

• Cell differentiation


  How a cell changes and becomes specialised
• Animal cell differentiation


  • Occurs in early stages of development for repair and replacement only
• Plant cell differentiation


  • Occurs in all stages of life, the stem/undifferentiated cells are grouped together in meristems (active regions of the stem and roots)
  • Mitosis takes place until the cells elongate and grow before they finally differentiate
• Cell structures for animal


  • Cytoplasm
  • Nucleus
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Cytoplasm


  Where most chemical reactions happen
• Nucleus


  Contains genetic material which controls the cell's activities
• Cell membrane


  Controls the movement of substances in and out of the cell
• Mitochondria


  Where most energy is released in respiration
• Ribosomes


  Where protein synthesis happens
• Additional plant cell structures


  • Chloroplasts
  • Cell wall
  • Permanent vacuole
• Chloroplasts


  Absorb light energy for photosynthesis
• Cell wall


  Strengthens the cell and supports the plant
• Permanent vacuole


  Filled with cell sap to help keep the cell turgid
• The cell cycle


  1. Cell growth

  2. DNA synthesis

  3. Temporary cell resting period or cell stops dividing

  4. Cytoplasm depocates, two cells formed

  5. Mitosis, chromosomes are now double stranded

  6. Further growth occurs and the DNA is checked for errors
• Active transport


  The process that moves molecules against a concentration gradient and requires energy
• Active transport examples


  • Moves mineral ions into plant roots
  • Moves glucose from gut into intestinal cells, from where it moves into the blood
• osmosis RQP

  1. Set up one with distilled water to act as the control

  2. Make one each tube its labelled with the concentration

  3. weigh the potato cylinders and make sure to not mix up their masses

  4. Place the potato cylinders into the boiling tubes and leave for 30 minutesuse forceps to remove each potato strip

  5. dry and measure mass gain
• Stem cell


  An unspecialized cell that has not undergone differentiation
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
• disadvantages of Embryonic stem cells

  • Expensive
  • Ethical issues
• adv and disadv of Adult stem cells

  • Cheap
  • Give permission
  • Develop into most other cells
  • Divide every 30 minutes
  • Low chance of rejection
  • Considered a safe procedure
  • More research
• Cell division stages


  1. Prophase - nuclear membrane breaks up

  2. Metaphase - chromosomes line up

  3. Anaphase - chromosomes move to sides

  4. Telophase - new nuclear membranes made
• Osmosis


  The movement of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration
• Dilute solution contains a high concentration of water molecules
• Concentrated solution contains a low concentration of water molecules
• Magnification


  A measure of the size of an image compared to the size of the object
• Cell structures of a bacterial cell


  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Plasmids
• Eukaryotic cells


  Animal and plant cells, have a cell membrane, cytoplasm and genetic material in the nucleus
• Prokaryotic cells


  Bacteria, have cytoplasm and a cell membrane surrounded by a cell wall, genetic material not enclosed in a nucleus, may contain plasmids
• Eukaryotic cell size is 5um - 100um
• Prokaryotic cell size is 0.2um-2um
• Specialized cell


  • sperm
  • muscle cell
  • nerve cell
  • root hair
  • palisade cell
• Sperm

  • Tall to swim to the ovum and fertilise
  • Lots of mitochondria to release energy from respiration
• Muscle cell


  • Contains protein fibres, which can contract to make the cell shorter
  • Contains lots of mitochondria to release energy from respiration, allowing the muscles to contract
• Nerve cell


  • Branched endings, called dendrites, to make connections with other neurones or effectors
  • Myelin sheath insulates the axon to increase the transmission speed of the electrical impulses
• Root hair


  • Long projection speeds up the absorption of water and mineral ions by increasing the surface area of the cell
  • Lots of mitochondria to release energy for the active transport of mineral ions from the soil
• Palisade cell


  • Lots of chloroplasts containing chlorophyll to absorb light energy
  • Located at the top surface of the leaf where it can absorb the most light energy
• Prokaryotic cells (Bacteria)


  • Single-celled
  • No nucleus - have a single loop of DNA
  • Have small rings of DNA called plasmids
  • Smaller than eukaryotic cells
• Light microscope


  • Uses light to form images
  • Living samples can be viewed
  • Relatively cheap
  • Low magnification
• Electron microscope


  • Uses a beam of electrons to form images
  • Samples cannot be living
  • Expensive
  • High magnification
  • Low resolution
  • High resolution