B2.3  Cell Specialization

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• What are the roles of stem cells in multicellular organisms?
• How are differentiated cells adapted to their specialized functions? 

​​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• What are the advantages of small size and large size in biological systems?
• How do cells become differentiated? ​

B2.3.1— Production of unspecialized cells following fertilization and their development into specialized cells by differentiation.

• State that a zygote is an unspecialized cell produced from fertilization. 
• Outline the impact of chemical gradients on gene expression within an early-stage embryo. ​

B2.3.2— Properties of stem cells.

• Outline two properties of stem cells. 
  

B2.3.3—  Location and function of stem cell niches in adult humans.

• Define stem cell niche.
  
• Outline the location and function of two types of multipotent stem cells in an adult human body.​​

B2.3.4— Differences between totipotent, pluripotent and multipotent stem cells.

• Define totipotent, multipotent and pluripotent.
• List an example of a totipotent, multipotent and pluripotent stem cell. 
• Explain why pluripotent stem cells are most prevalent in the early embryonic development of a multicellular organism.​

​​B2.3.5— Cell size as an aspect of specialization.

• Relate the relative cell size to the specialized function of sperm, egg, red blood cell, white blood cell, neuron and striated muscle fibers.​

B2.3.6- Surface area-to-volume ratios and constraints on cell size.

• Outline the activities occurring in the volume and at the surface of the cell.
• Calculate the surface area, volume and SA:V ratio of a cube.
• Explain the benefits and limitations of using cubes to model the surface area and volume of a cell.
• Describe the relationship between cell size and the SA:V ratio of the cell.
• Explain why cells are often limited in size by the SA:V ratio.

AHL ​​B2.3.7— Adaptations to increase surface area-to-volume ratios of cells.

• List two examples of cells that are specialized for exchange of materials and have adaptations to increase the SA:V ratio.
• Outline three adaptations of cells that maximize the SA: volume ratio.

AHL ​​B2.3.8- Adaptations of type I and type II pneumocytes in alveoli.

• Define “alveolar epithelium.”
• Outline the structure and function of type I pneumocytes.
• Outline the structure and function of type II pneumocytes.
• Describe two functions of the fluid secreted by type II pneumocytes.
• Label the following structures on a micrograph of lung tissue:  type 1 pneumocyte, type 2 pneumocyte, capillary endothelium, basement membrane and blood cells.

AHL ​​B2.3.9- Adaptations of cardiac muscle cells and striated muscle fibers.

• List three types of muscle tissue found in the human body.
• Outline the relationship between skeletal muscles, muscle fibre cells and myofibrils.
• Label a diagram of a  skeletal muscle fibre cell, including the sarcolemma, nuclei, sarcoplasmic reticulum and mitochondria.
• Compare and contrast cardiac muscle tissue and skeletal muscle tissue.
• Describe how the branching and intercalated discs of cardiac muscle cells allow for propagation of the stimulus to contract.

AHL ​​B2.3.10- Adaptations of sperm and egg cells.

• State the function of gamete cells.
• Compare the size, and motility of egg and sperm cells.  
• State the function of each of the following egg structures:  haploid nucleus, binding proteins, zona pellucida, cortical granules, yolk, mitochondria and centrioles.
• State the function of each of the following sperm structures:  head, acrosome, plasma membrane receptors, binding proteins in the acrosome, haploid nucleus, midpiece, helical mitochondria, microtubules and tail.