Cell Biology

• Animal Cells

  • Nucleus
  • Cytoplasm
  • Cell Membrane
  • Mitochondria
  • Ribosomes
• Plants Cells

  • Nucleus
  • Cytoplasm
  • Cell Membrane
  • Mitochondria
  • Ribosomes
  • Rigid Cell Wall
  • Permanent Vacuole
  • Chloroplasts
• Eukaryotic Cells

  • Complex
  • Include animal and plant cells
• Prokaryotic

  • Smaller
  • Simpler
• Nucleus


  Controls activities of the cell.
• Cytoplasm


  Contains emzymes, most chemical reactions happen here.
• Cell Membrane


  Holds the cell together and controls what goes in and out.
• Mitochondria


  Most reactions for aerobic respiration take place here.
• Ribosomes


  Where proteins are made in the cell.
• Rigid Cell Wall


  Made of cellulose, supports the cell and strengthens it.
• Permanent Vacuole


  Contains cell sap, a weak solution of sugar and salts.
• Chloroplasts


  Where respiration occurs, contains chlorophyll.
• Bacteria Cells

  • Prokaryotes
  • Cell Membrane
  • Cytoplasm
  • Cell Wall
  • Plasmids
  • No nucleus, chloroplasts or mitochondria
• Plasmids


  Small rings of DNA.
• Light Microscopes


  Use light and lenses to form an image of a specimen and magnify it.
• Electron Microscopes


  Use electrons to form an image, have a higher magnification and resolution than light microscope.
• Formula for Magnification


  Image Size ÷ Real Size = Magnification

  
• Using a Light Microscope (Practical)

  1. Clip the slide you've prepared onto the stage.
  2. Select the lowest-powered objective lens (i.e. the one that produces the lowest magnification)
  3. Use the coarse adjustment knob to move the stage up to just below the objective lens.
  4. Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
  5. Adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide.
  6. If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus.
• Differentiation


  Process by which a cell changes to be specialised for its job.
• How Sperm Cells differentiate


  Specialised for reproduction, long tail and streamlined head to help it swim to the egg, lots of mitochondria to provide energy, and carries enzymes in its head to digest through the egg cell membrane.
• How Nerve Cells differentiate


  Specialised for rapid siganlling, cells and long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
• How Muscle Cells differentiate


  Specialised for contraction, cells are long (so they have space to contract) and contain lots of mitochondria to generate the energy needed for contraction.
• How Root Hair Cells differentiate


  Specialised for absorbing water and minerals, grow into long "hairs" that stick out into the soil (this gives the plant a big surface area for absorbing water and mineral ions from the soil).
• How Phloem and Xylem Cells differentiate


  For phloem and xylem tubes which transport substances (such as food and water) around plants, cells are long and joined end to end to form tubes, xylem cells are hollow and phloem cells have very few subcellular structures (so stuff can flow through them).
• Chromosomes

  • Genetic material in nucleus
  • Coiled up lengths of DNA molecules
  • Carries a large number of genes - different genes control the development of different characteristics
  • Body cells normally have 2 copies of each chromosome (one from the organism's 'mother' and one from its 'father') - so humans have two copies of chromosome 1 and two copies of chromosome 2
• Cell Cycle

  • Makes new cells for growth, development and repair
  • Body cells in multicellular organisms divide to produce new cells as part of a series of stages
  • When cells divide it is called mitosis
  • Multicellular organisms use mitosis to grow or replace cells that have been damaged
  • The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes
  • 2 main stages: - growth & DNA replication - mitosis
• Cell Cycle - Growth and DNA Replication (Stage 1)

  1. In a cell that's not dividing, the DNA is spread out in long strings.
  2. Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes.
  3. It then duplicates its DNA - so there's only one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
• Cell Cycle - Mitosis (Stage 2)

  1. Once its contents and DNA have been copied, the cell is ready for mitosis.
  2. The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.
  3. Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided.
  4. The cytoplasm and cell membrane divide.
  5. The cell has nkw produced two new daughter cells. The daughter cells contain the same DNA and it is also identical to the parent cell.
• Where are Stem Cells found in adults?


  Bone marrow, embryo, adipose tissue, and blood are common sources of adult stem cells.
• What can Stem Cells turn into?

  Any type of cell.
• What can Stem Cells be used for?

  To cure many diseases (e.g. replacing faulty blood cells, nerve cells, could make insulin- producing cells).
• Risks of using Stem Cells in Medicine


  Stem cells grown in the lab can become contaminated with a virus which could be passed on to a patient and make them sicker.
• Reasons some people are against Stem Cell Research 


  Some people feel that human embryos are potential human lifes.
• Stem Cells in Plants


  Found in the meristems, meristem tissues can differentiate into any type of plant cell, these stem cells can b used to make clones of the plant and can be used to grow more plants of rare species or crops of identical plants with certain features.
• What is Diffusion?


  The movement of particles from an area of high concentration to an area of low concentration.
• Where does Diffusion happen?


  Both solutions and gases b/c the particles in these substances are free to move about randomly.
• What is Osmosis?


  The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
• Active Transport - Movement of particles from an area of low concentration to an area of high concentration
• How Osmosis occurs?


  Water molecules pass both ways through the membrane during osmosis due to random movement of water molecules. There are more water molecules on one side than on the other so there is a steady net flow of water into the region with fewer water molecules. Therefore the strong sugar solution gets more dilute. The water acts like its trying to "even up" the concentration on either side of the membrane.
• Observing the Effects of Sugar Solutions on Plant Tissue

  1. Place identical cylinders of potatoes into beakers with different sugar solutions (e.g pure water, very concentrated).
  2. Measure the mass of each cylinder and leave them for 24 hours.
  3. Take them out, dry them with a paper towel and measure the masses again.
  4. Increase in mass means water has been drawn in. Decrease means water has been drawn out. Calculate the % change in mass.
  5. The dependent variable is chip mass. The independent variable is the concentration of the sugar solution. All other variables must remain the same.