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• The Cell Cycle and Mitosis

  1. Cell grows and replicates its contents

  2. Cell splits into two by Mitosis
• Mitosis


  When a cell reproduces itself by dividing to form two identical offspring
• Mitosis


  • DNA forms chromosomes
  • Chromosomes line up at the centre of the cell
  • Cell fibres pull the chromosomes apart
  • Membrane forms around each set of chromosomes
  • Cytoplasm divides
• After mitosis, the new cells contain the same DNA as the parent cell - they are genetically identical
• The cell cycle has nothing to do with bikes in prison
• Mitosis can seem tricky at first, but it's best to go through it step-by-step
• Calculating percentage of cells undergoing mitosis

  1. Count cells undergoing mitosis

  2. Count cells not undergoing mitosis

  3. Calculate percentage of cells undergoing mitosis
• The student can tell if a cell is undergoing mitosis by looking for the characteristic stages of mitosis under the microscope
• Cell differentiation


  The process by which a cell becomes specialised to perform a particular function
• Specialised cells


  • Nerve cells
  • Muscle cells
  • Red blood cells
• Specialised cells


  • Adapted for their specific job
  • Contain structures to carry out their function
• Stem cells


  Unspecialised cells that can divide by mitosis to produce daughter cells that then differentiate
• Embryonic stem cells can differentiate into any cell type, adult stem cells can only produce certain specialised cell types
• In animals, adult stem cells are used to replace damaged cells, e.g. to make new skin cells
• Meristems


  Regions of plant tissue containing stem cells that allow the plant to grow
• Meristems are found at the tips of plant shoots and roots
• Meristems produce cells that can divide and differentiate into any cell type in the plant
• Diffusion


  The movement of particles from an area of high concentration to an area of low concentration
• Active transport


  The movement of particles against a concentration gradient, requiring energy
• Active transport allows nutrients to be taken into the blood even when the concentration is higher in the blood than the gut
• Diffusion is the movement of particles down a concentration gradient, without requiring energy
• Osmosis


  The diffusion of water molecules through a partially permeable membrane from an area of high water concentration to an area of low water concentration
• If a piece of potato is placed in a solution with lower water potential than the potato cells, the potato will shrink as water moves out of the cells
• Water moves from an area of higher water potential to an area of lower water potential during osmosis
• Surface area to volume ratio

  The ratio of an organism's surface area to its volume, which affects its ability to exchange substances with the environment
• The larger an organism, the smaller its surface area to volume ratio
• A smaller surface area to volume ratio makes it harder for an organism to exchange substances with its environment
• The blood acts as a transport system, carrying substances around the body
• Components of blood


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma
• Plasma


  The liquid part of blood that transports various substances around the body
• Red blood cells


  • Biconcave disc shape
  • Contain haemoglobin to carry oxygen
  • No nucleus, more space for carrying oxygen
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• Plasma


  The Liquid Bit of Blood