biology p1 topic 1 - cell biology

• Stem cell


  An undifferentiated cell which can give rise to more cells of the same type and can differentiate into other types of cells
• Fertilization


  1. Sperm cell joins with ovum

  2. Fertilized ovum undergoes mitosis

  3. Forms a ball of cells called an embryo

  4. Cells continue to undergo mitosis and begin to form specialized cells
• Differentiation


  The process where cells specialize into different cell types
• Embryonic stem cells


  Undifferentiated cells in the early stage embryo that can differentiate into any type of body cell
• Adult stem cells


  Stem cells found in adult organisms that cannot differentiate into any other type of cell, e.g. bone marrow stem cells
• Bone marrow transplant


  1. Patient's existing bone marrow is destroyed

  2. Patient receives transplant of donor bone marrow

  3. Stem cells divide and form new bone marrow and blood cells
• Problems with bone marrow transplants

  • Donor must be compatible with patient
  • Risk of viruses being passed from donor to patient
• Therapeutic cloning


  1. Embryo is produced with same genes as patient

  2. Stem cells from embryo can be transplanted into patient without being rejected

  3. Stem cells can then differentiate to replace malfunctioning cells
• Therapeutic cloning could be useful for a range of medical conditions such as diabetes or paralysis
• Some people have ethical or religious objections to therapeutic cloning procedure
• Plant stem cells (meristem)


  • Found at the tips of roots and buds
  • Can differentiate into any type of plant tissue at any point in the plant's life
• Using plant stem cells


  Can be used to quickly and cheaply clone rare plants or produce cloned crop plants
• Mitochondria are responsible for producing energy through respiration.
• Ribosomes are where protein synthesis occurs.