Cells

Eukaryotic

• Nucleus  
  - Contains DNA > directs synthesis of all proteins required by cell > controls metabolic activities of cell 
  - Contained within nuclear envelope to protect it from damage > contains nuclear pores that allows movement of molecules > DNA transcribed into smaller RNA molecules so it can be exported as DNA is too big to fit through pores
  - DNA associates with histones (proteins) to form chromatin > coils and condenses to form chromosomes 
  
  
• Nucleolus
  - Area within nucleus responsible for producing ribosomes
  - Composed of proteins and RNA > RNA used to produce ribosomal RNA > combines with proteins to form ribosomes
  
  
• Mitochondria
  - Site of final stages of cellular respiration where energy stored in bonds of organic molecules is made available for cell to use by production of ATP
  - Double membrane > inner membrane highly folded to form cristae and fluid interior is called matrix 
  - Contains small amount of mitochondrial DNA ((mt)DNA) 
  - Can produce own enzymes and reproudce themselves
  
  
• Vesicles and lysosomes
  - Vesicles membranous sacs that have storage and transport roles > consist of single membrane with fluid inside 
  - Vesicles used to transport materials inside cell
  - Lysosomes specialised forms of vesicles that contain hydrolytic enzymes > responsible for breaking down waste material in cells > break down pathogens ingested by phagocytic cells
  - Important role in programmed cell death or apoptosis 
  
  
• Cytoskeleton
  - Network of fibres necessary for shape and stability of cell
  - Organelles held in place by cytoskeleton and controls movement of organells within cells
  • Microfilaments - Contractile fibres formed from protein actin. Responsible for cell movement and cell contraction during cytokinesis.
    
  • Microtubules - Globular tubulin proteins polymerise to form tubes used to form scaffold-like structure that determines shape of cell. Also act tracks for movement of organells around cell. Spindle fibres composed of microtubules
  • Intermediate fibres - give mechanical strength to cells and help maintain their integrity
• Centrioles 
  - Composed of microtubules 
  - Two associated centrioles form the centrosome > involved in assembly and organisation of…