2.1.3 Common Cellular Structures

• Cytoplasm

  Jelly-like liquid that makes up the bulk of the cell and contains the organelles
• Nucleus

  Organelle containing the nucleic acids DNA (the genetic material) and RNA, as well as protein, surrounded by a nuclear envelope with pores
• Protoplasm

  Cytoplasm + nucleus
• Ultrastructure

  Detailed organisation of the cell, only visible using the electron microscope
• Intracellular

  Inside the cell
• Chromatin

  Granular combination of DNA bonded to protein found in the nucleus when the cell is not actively dividing`
• Nucleolus

  Extra dense area of almost pure DNA and protein found in the nucleus involved in the production of ribosomes and control of growth and division
• Mitochondria

  Rod-like structures with inner and outer membranes that are the site of aerobic respiration
• Cristae

  The infoldings of the inner membrane of the mitochondria which provide a large surface area for the reactions of aerobic respiration
• Eubacteria

  True bacteria (prokaryotic organisms)
• Endosymbiotic theory

  Theory that suggests that mitochondria and chloroplasts originated as independent prokaryotic organisms that began living symbiotically inside other cells as endosymbionts
• Centrioles

  Bundles of tubules found near the nucleus and involved in cell division by the production of a spindle of microtubules that move the chromosomes to the ends of the cell
• Spindle

  Set of overlapping protein microtubules running the length of the cell, formed as the centrioles pull apart in mitosis and meiosis
• Cytoskeleton

  Dynamic, 3D web-like structure made up of microfilaments and microtubules that fills the cytoplasm and gives it structure, keeping the organelles in place and enabling cell movements and transport within the cell
• Microfilaments

  Protein fibres that make up part of the structure of the cytoskeleton
• Microtubules

  Tiny protein tubes about 20nm in diameter that make up part of the structure of the cytoskeleton
• Vacuole

  Fluid filled cavity within the cytoplasm of a cell surrounded by a membrane
• Contractile vacuoles

  Vacuoles that can fill and empty to help control the concentration of the cytoplasm of simple freshwater animals