B2.3 Cell Specialisation


  • B2.3.1 cell specialization 

Stem cells: 



What are Stem Cells?

  • Stem cells are undifferentiated cells, meaning they do not have a specific job or function. They are unspecialized and do not have a specific role or job to play yet.




Characteristics of Stem Cells

  • Have the potential to become all other kinds of cells in the body

  • Can make more of themselves (self-renewal)

  • Can change into other cells (differentiation)



Regenerative Medicine

  • Regenerative medicine involves using stem cells to replace damaged bodily tissue. This type of medicine aims to create new tissue to replace the parts of organs damaged by injury or disease.



Examples of Regenerative Medicine

  • Treating patients with blood diseases, such as leukemia, a form of cancer that affects the bone marrow

  • Replacing damaged bone marrow with healthy stem cells to create new blood cells





  • B2.3.2 Properties of stem cells

Functions: 



Self-renewal:

  • They can constantly divide and replicated



Potency:

  • They can differentiate into specialized cell types (ability to change into new cells)





  • B2.3.3 location and function of stem cell niches



Stem cell niches:

  • Sites within the body where a pool of adult stem cells are maintained in preparation for future proliferation and differentiation 

    • They can be located in the: bonw marrow, hair follicles, heart, intestines, and brain 



  1. Bone marrow

  • I.e. haemopoietic stem cells are located within the bone marrow and give rise to different types of blood cells 

  • Bone marrow transplants used to replace the haemopoietic stem cell niche following chemotherapy for leukemia 



  1. Hair follicles 

  • Contain a range of epidermal stem cells that are involved in cyclic bouts of hair growth, skin innervation, vascularisation and wound repair 

  • Could potentially be harvested and used to regenerate skin tissue in burns 





  • B2.3.4 differences between totipotent, pluripotent, and mutipotent stem cells

Three main types of stem cells present at various stages of human development: 



  1. Totipotent (early embryonic stem cells):

  • Can become any type of cell.

  • Can grow into a whole new organism.




  1. Pluripotent:

  • Can become almost any type of cell.

  • Can't form a whole new organism on its own.




  1. Multipotent (stem cells in adult tissue- i.e bone marrow):

  • Can become a few types of related cells.






Morphogen: 

  • Causes stem cells to turn into other cells

  •  Different concentration leads to different cells 

  • Closer to source (higher concentration) 





  • B2.3.5 cell size as an aspect of specialization

Examples:



  1. Red blood cells (7-8 micrometers):

  • Carry oxygen throughout the body



  1. Neurons (10 micrometer):

  • Transmit signals through the body



  1. Striated muscle fiber (12 cm)- loaded with mitochondria:

  • Consist of fused muscle cells (two contractile proteins- actin and myosin)



  • Cardiac muscle

    • Causes fast contraption (faster signal)

    • Contains a lot of mitochondria 

    • Dont stop working (don't tire)



  • Skeletal muscle

    • Get tired




  • Smooth muscle




  1. Human ovum

  • Largest cell with a diameter of 120 micrometers

  • Half number of chromosomes (23 chromosomes)






  • B2.3.5 cell size as an aspect of specialization



Cell size limited by their surface area to volume ration:

  • As cell grows

    • Volume increases faster than surface are (decrease in SA:Vol ratio)