Animals cells

• Nucleus

  = contains coded genetic information, and controls metabolic activities in the cell.

  • nuclear envelope= double membrane allows transport of proteins+ mRNA into and out of the nucleus.
  • chromatin= uncondensed DNA (chromosomes) in a complex with histones.
  • nucleolus= manufactures ribosomes, composed of proteins and RNA.
• Nucleus

  nucleus

  
• mitochondria

  = site of respiration.

  • produce their own enzymes+ reproduce themselves.
  • matrix= contains enzymes.
  • double membrane= inner membrane is folded to form cristae.
  • cristae= large surface area for attachment of protein and enzymes for respiration.
• mitochondria

  mitochondria

  
• Endoplasmic reticulum

  = network of membranes enclosing flattened sacs called cristernae.- connected to outer membrane of the nucleus.

  • smooth endoplasmic reticulum= responsible for lipid+ carbohydrate synthesis and storage.
  • rough endoplasmic reticulum= has ribosomes bound to the surface and is responsible for the synthesis and transport of protein.
• golgi apparatus

  = compact, formed of cristernae

  • modify proteins and packaging them into vesicles.
• protein production

  1. proteins synthesised on ribosomes bound to rough endoplasmic reticulum.
  2. passed into it's cristernae and packaged into transport vesicles.
  3. vesicles move towards golgi apparatus via transport function of the cytoskeleton.
  4. vesicles fuse with the cis face of the golgi body and proteins enter.- they are structurally modified before leaving in secretory vesicles from the trans face.
  5. vesicles carry proteins to be released from the cell. Vesicles fuse with the membrane releasing proteins by exocytosis. Some vesicles form lysosomes.
• protein production

  protein production

  
• lysosomes

  = specialised vesicles containing hydrolytic enzymes for the breakdown of waste materials within a cell.

  • formed in endoplasmic reticulum and transported to golgi body via vesicles.
  • hydrolytic enzymes= digest and breakdown lipid, protein or carbohydrate.
• flagella and cilia

  -both whip/hair like extensions.

  • flagella are longer but cilia present in large numbers.
  • flagella used to enable cell movement or as sensory-detecting chemical changes in the cells environment.
  • cilia can be stationary= surface of cells, sensory organs or mobile= beat in rhythmic manner creating a current causing fluids or objects adjacent to the cell to move.
  • each cilium contains 2 central microtubules surrounded by 9 pairs of microtubules arranged in a wheel. Pairs of parallel microtubules slide over each other causing a beating motion.
• the cytoskeleton

  -microfilaments= contractile fibres formed from actin- cell movement and contraction during cytokinesis.

  -microtubules= globular tubulin proteins polymerise to form tubes- scaffolding that determines the shape of the cell. Act as tracks for movement of organelles.

  -intermediate fibres= give mechanical strength to cells and help maintain their integrity.
• functions of cytoskeleton

  -maintaining the shape of the cell

  -securing some organelles in specific positions

  -allowing cytoplasm and vesicles to move within the cell

  -enabling cells within multicellular organisms to move
• centrioles

  = component of cytoskeleton, composed of microtubules.

  • 2 associated centrioles form the centrosome involved in assembly and organisation of spindle fibres.
• eukaryotic cell