Cell Structure

• What is in a cells structure?

  • Cells are separated from their surrounding environment by a cell membrane
  • Within the cell membrane is the cytoplasm
  • Eukaryotic cells have organelles contained within their cytoplasm
  • Organelles are subcellular compartments where specific processes take place within the cell
  • Within the cytoplasm of eukaryotic cells the following organelles are present
  • Nucleus
  • Mitochondria (singular mitochondrion)
  • Ribosomes
• What are additional structures plant cells have.

  • Cell wall
  • Chloroplasts
  • Permanent vacuole
• Diagram of a animal and plant cell :

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• Cell structures and functions table pt1

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• Cell structure and function table pt2

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• What are sub-cellular structures in animals?

  • The nucleus: contains genetic material
  • Cell membranes: controls what enters and leaves the cell
  • Mitochondria: site of aerobic respiration
  • Ribosomes: site of protein synthesis
  • Cytoplasm: chemical reactions take place in this jelly-like substance
• In addition to the sub-cellular parts found in animal cells, plant cells have:

  • A cell wall made of cellulose: gives the cell shape and protection
  • A permanent vacuole filled with cell sap: pushes the cytoplasm against the cell wall, keeping the cell turgid
  • Plant cells found in the leaf and stem may also contain chloroplasts: the site of photosynthesis
• Plant cell and structure table:

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• Cell differentiation


  An important process by which a cell changes to become specialised
• Cell differentiation

  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)
• 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
• Cell differentiation


  • A cell develops a structure and composition of subcellular structures which enables it to carry out a certain function
• Structural differences between different types of cells


  Enables them to perform specific functions within the organism
• Diagram showing the possible differentiation of a human cell into two different cell types


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• Differentiation


  As a multicellular organism develops, its cells differentiate to form specialised cells
• Animal cells


  • Most cells differentiate at an early stage of development
  • Lose their ability to differentiate early in the life of the organism
• Specific cells in animals

  • Retain the ability to differentiate throughout the life of the animal
• Adult stem cells

  Undifferentiated cells mainly involved in replacing and repairing cells (such as blood or skin cells)
• Differentiation


  As a multicellular organism develops, its cells differentiate to form specialised cells
• Animal cells


  • Most cells differentiate at an early stage of development
  • Lose their ability to differentiate early in the life of the organism
• Specific animal cells


  • Retain the ability to differentiate throughout the life of the animal
  • Called adult stem cells
  • Mainly involved in replacing and repairing cells (such as blood or skin cells)
• Plant cells

  • 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
• As a multicellular organism develops

  Its cells differentiate to form specialised cells
• Specialised cells in plants and animals

  • 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:


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• Ciliated epithelial cells


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• A nerve cell

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• Red blood cells


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• A sperm cell

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• Egg cells

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• Examples of Specialised Cells in Plants Table


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• Diagram of a root hair cell:


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• Diagram of a Palisade mesophyll cell

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• What is a stem cell?

  • A stem cell is an undifferentiated cell of an organism that is capable of dividing to produce many more cells of the same type (undifferentiated stem cells)
  • In addition, stem cells can also give rise to other cell types through the process of differentiation
• Stem cell table 


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• Why is embryonic stem cells important?

  • Embryonic stem cells are important as they help to form all of the different tissues and organs needed during development to form a whole new individual - they are totipotent
• What is the role of adult stem cells?


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• What are meristem cells?

  • In plants, meristem cells are unspecialised cells that can differentiate into the cells needed by the plant in regions wheregrowth is occurring
  • For example, meristem cells in the roots can differentiate into root hair cells as well as other cells required in this part of the plant
  • The stem cells found in the meristems of plants retain the ability to differentiate into any type of plant cell throughout the life of the plant
• Stem cells in medicine

  Cells that can differentiate into most types of specialised cells