Edexcel IGCSE Biology 复习笔记 2.2.2 Specialised Cells

• The structural differences between different types of cells enables them to perform specific functions within the organism
• Cell differentiation is an important process by which a cell changes to become specialised
• As an organism develops, cells differentiate to form different types of cells
• Almost all of the cells in a multicellular organism will contain the same genetic information (the same genes or alleles), but depending on what role a particular cell needs to have, only some of the genes in a particular cell are used/expressed to control its development
• When a cell differentiates, it develops a structure and composition of subcellular structures which enables it to carry out a certain function
  • For example, to form a nerve cell the cytoplasm and cell membrane of an undifferentiated cell must elongate to form connections over large distances

   

Diagram showing the possible differentiation of a human cell into two different cell types

Differentiation and development

• As a multicellular organism develops, its cells differentiate to form specialised cells
  • In an animal, most cells differentiate at an early stage of development
  • As a result, animal cells lose their ability to differentiate  early in the life of the organism

   

• Specific cells in various locations throughout the body of an animal retain the ability to differentiate throughout the life of the animal
  • These undifferentiated cells are called adult stem cells and they are mainly involved in replacing and repairing cells (such as blood or skin cells)

   

• Plants differ from animals in that many types of plant cells retain the ability to fully differentiate throughout the life of a plant, not just in the early stages of development

Specialised cells in animals and plants

• Specialised cells are those which have developed certain characteristics in order to perform particular functions. These differences are controlled by genes in the nucleus
• Cells specialise by undergoing differentiation: this is a process by which cells develop the structure and characteristics needed to be able to carry out their functions
• Some examples of specialised animal and plant cells are shown in the table and images below

Examples of Specialised Cells in Animals Table

Ciliated epithelial cells

A nerve cell

Red blood cells

Sperm cell

Egg cell

Examples of Specialised Cells in Plants Table

Root hair cell

Palisade mesophyll cell

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