B2.3

• What are the roles of stem cells in multicellular organisms?

  Stem cells can divide indefinitely and differentiate into specialized cell types.
• What is fertilization?


  Fertilization is a multi-step process where a sperm and egg fuse to form a zygote.
• What happens to the zygote after fertilization?

  The zygote divides by mitosis to form an embryo composed of genetically identical cells.
• What type of cells are present in the zygote and embryo?

  The cells in the zygote and embryo are unspecialized stem cells.
• What is cell specialization?

  Cell specialization allows cells to perform a function with increased efficiency.
• How do differentiated cells adapt to their specialized functions?

  Differentiated cells develop specific shapes and sizes and create proteins needed for metabolic reactions.
• What is differentiation in cells?

  Differentiation is the development of specialized structures and functions in cells.
• How does gene expression relate to differentiation?

  Differentiation occurs when different cell types express different genes.
• What is the process of gene expression?


  Gene expression is the process by which information encoded in a gene is turned into a function.
• What role do morphogens play in embryonic development?

  Morphogens are signaling molecules that impact gene expression and cell differentiation.
• What is retinoic acid's role in embryonic development?

  Retinoic acid is a morphogen that influences cell growth, differentiation, and organ development.
• What is a stem cell?

  A stem cell is an undifferentiated cell that can divide indefinitely and differentiate into specialized cell types.
• Where are adult stem cells found in humans?

  Adult stem cells are found in specific areas called stem cell niches within various tissues and organs.
• What is the function of stem cell niches?

  Stem cell niches provide physical and chemical signals that influence the fate of stem cells.
• What happens to stem cells during tissue injury?

  Conditions in the stem cell niche allow adult stem cells to differentiate and divide rapidly during tissue injury.
• What is the hematopoietic stem cell niche?

  The hematopoietic stem cell niche in bone marrow is where multipotent adult stem cells give rise to various blood cells.
• What is the hair follicle stem cell niche?

  The hair follicle stem cell niche is where multipotent adult stem cells differentiate into various skin cells.
• How are stem cells categorized based on their differentiation potential?

  Stem cells are categorized as totipotent, pluripotent, multipotent, and unipotent based on their differentiation potential.
• What are totipotent stem cells?

  Totipotent stem cells can become any body cell, including the placenta in placental mammals.
• What are pluripotent stem cells?


  Pluripotent stem cells can become any body cell but not the placenta and are found in the inner cell mass of a blastocyst.
• What are multipotent stem cells?

  Multipotent stem cells are partially differentiated and can become multiple related cell types.
• What is the significance of iPSC?

  Induced pluripotent stem cells (iPSC) are reprogrammed adult cells that can develop into any type of human cell for therapeutic purposes.
• How do iPSC relate to diabetes treatment?

  iPSC can be induced to become beta islet cells to treat diabetes.
• How does cell size relate to specialization?

  Cell specialization allows cells to develop specific shapes and sizes that maximize their ability to perform specialized functions.
• What is an example of cell size and specialization in human sperm cells?

  Human sperm cells are large (50 µm) and narrow with a long flagellum for propulsion.
• What is the benefit of the size specialization of human sperm cells?

  The size specialization of sperm cells reduces resistance as they move towards the egg.
• What is an example of cell size and specialization in human egg cells?

  Human egg cells are large (110 µm) spherical cells that store materials for embryo development.
• What is an example of cell size and specialization in red blood cells?

  Red blood cells are biconcave disk-shaped cells (6-8 µm wide and 1 µm thick) adapted to transport oxygen.
• How does the shape of red blood cells maximize their function?

  The biconcave shape of red blood cells maximizes their surface area to volume ratio for efficient oxygen transport.
• What is an example of cell size and specialization in B-lymphocytes?

  1. lymphocytes are small (10 µm) when inactive but increase in size (30 µm) during active infection.
• What is the benefit of size specialization in B-lymphocytes during infection?

  The increase in size during infection allows B-lymphocytes to produce and secrete antibodies more effectively.
• What is the significance of endless cell division in stem cells?

  Stem cells can divide indefinitely, allowing for continuous regeneration and repair of tissues.
• What is pluripotency in stem cells?

  Pluripotency is the ability of stem cells to differentiate into various cell types along specific pathways.
• How do stem cell niches contribute to regeneration?

  Stem cell niches provide signals that dictate when and how stem cells should differentiate for tissue repair.
• What is the difference between totipotent, pluripotent, and multipotent stem cells?

  Totipotent stem cells can become any cell type, pluripotent stem cells can become almost any cell type, and multipotent stem cells can differentiate into related cell types.
• How does the potency of stem cells change as an organism develops?

  The potency of stem cells declines as the organism grows and cells become specialized along specific pathways.
• What is the size of a red blood cell?

  A red blood cell is approximately 8 µm in width.
• What is the size of a B-lymphocyte when inactive?

  A B-lymphocyte is approximately 10 µm in diameter when inactive.
• What is the size of a B-lymphocyte when activated?

  A B-lymphocyte can increase in size to approximately 30 µm during active infection.
• What is the size of a human sperm cell?

  A human sperm cell is approximately 60 µm in length, including the tail.