Cell structure

• What is the structure that surrounds the nucleus of a cell?

  The nuclear envelope
• How is the outer membrane of the nuclear envelope related to the endoplasmic reticulum?

  It is continuous with the endoplasmic reticulum of the cell
• What is the function of the nuclear envelope?

  It controls the entry and exit of materials in and out of the nucleus
• What are nuclear pores and what do they allow?

  Nuclear pores allow the passage of large molecules, such as messenger RNA, out of the nucleus
• How many nuclear pores are typically found in each nucleus?

  About 3000 pores
• What is the diameter range of nuclear pores?

  40-100 nm
• What is nucleoplasm?


  Nucleoplasm is the granular, jelly-like material that makes up the bulk of the nucleus
• What do chromosomes consist of?

  Protein-bound, linear DNA
• What is the nucleolus?

  The nucleolus is a small spherical region within the nucleoplasm
• What is the primary function of the nucleolus?

  It manufactures ribosomal RNA and assembles the ribosomes
• Can there be more than one nucleolus in a nucleus?

  Yes, there may be more than one nucleolus in a nucleus
• What are the main functions of the nucleus?


  • Acts as the control centre of the cell through the production of mRNA and tRNA, facilitating protein synthesis
  • Retains the genetic material of the cell in the form of DNA and chromosomes
  • Manufactures ribosomal RNA and ribosomes
• What is the main reason cells in multicellular organisms are specialized?


  To perform a particular role effectively
• How do specialized cells differ from one another?

  They have evolved different organelles and structures to suit their specific roles
• What happens to the first group of cells in an embryo as it matures?

  Each cell takes on its own individual characteristics
• What is the process by which all cells in an organism are produced?

  They are produced by mitotic divisions from the fertilised egg
• How do cells become specialized despite containing the same genes?

  Only some genes are switched on (expressed) in any one cell at any one time
• What varies among different specialized cells besides their shape?

  The numbers of each of their organelles
• Why do muscle and sperm cells have many mitochondria?

  Because they require a lot of energy for their functions
• What is the function of lysosomes in white blood cells?


  They help in breaking down waste materials and cellular debris
• How have the cells of multicellular organisms evolved?


  They have become more suited to one specialized function
• What is a tissue?

  A collection of similar cells that perform a specific function
• What are some examples of tissues in multicellular organisms?

  • Epithelial tissues: sheets of cells lining surfaces of organs
  • Muscle tissues: responsible for movement
  • Connective tissues: support and bind other tissues
  • Nervous tissues: transmit signals
• What is the role of epithelial tissues in animals?

  They line the surfaces of organs and often have a protective or secretory function
• What type of epithelial tissue lines the alveoli of the lungs?

  Thin, flat cells that facilitate diffusion
• What is the function of ciliated epithelium in the trachea?

  To move mucus over the surface
• What are the characteristics of epithelial tissues?


  • Composed of sheets of cells
  • Can be specialized for protection or secretion
  • Vary in shape (e.g., flat, cuboidal, columnar)
  • Can have cilia for movement of substances