Cell anatomy

• Cytoskeleton:

  • contains a network of fibres made of protein
  • provides the internal framework(structure)
  • actin fibres move against each other, moving organelles around inside the cell
  • Microtubules are cylinders of the protein tubulin
  • They may be used to move organism through a liquid
  • Other proteins known as microtubule motors move organelles along the fibres
• Nucleus:

  • large organelle
  • surrounded by the nuclear envelope
  • nuclear pores go through these envelopes
  • when stained the nucleus shows darkened patches (the chromatin)
  • contains genetic material)
  • dense spherical structure within the nucleus called the nucleolus
  • nucleolus make RNA and ribosomes
  • the nucleus have tiny holes to allow MRNA to pass through (not DNA)
• endoplasmic reticulum (ER):

  • consists of a series of flattened membrane bound sacs called cisternae
  • they are continuous with the outer nucleus membrane
  • 2 different types of ER; rough ER and smooth ER
• Rough ER:

  • studded with ribosomes and transports proteins that were made by the attached ribosomes.
  • some of these will be placed on the cells surface membrane and some will be secreted from the cell
• Smooth ER:

  • contains no ribosomes
  • produces lipids
• Golgi apparatus:

  • a stack of membrane bound flattened sacs
  • receives proteins from the ER and modifies them
  • Golgi then packages the protein into vesicles that can be transported
  • some may be secreted from the surface of the cell
• Mitochondria:

  • two membranes separated by fluid filled space
  • inner membrane folded to form cristae
  • central part is called the matrix
  • site of respiration where most ATP in produced
• chloroplasts:

  • found in green plants (and algae)
  • two membranes separated by fluid filled space
  • inner membrane is continuous with a network of flattened membrane sacs called thylakoids
  • a stack of thylakoids are called a granum
  • chlorophyll molecules present on thylakoid membranes
  • site of photosynthesis
• lysosomes:

  • spherical sacs surrounded by a single membrane
  • contain powerful digestive enzymes
  • their role is to break down materials (foreign invaders)
• ribosomes:

  • tiny organelle (18-22 nanometers)
  • some found in cytoplasm and some bound to ER
  • each ribosome consists of 2 subunits
  • site of protein synthesis in the cell
• Centrioles:

  • small tubes of protein fibres (microtubules)
  • there is a pair of centrioles next to the nucleus of animal cells
  • take part in cell division
  • form fibres known as the spindle which move chromosomes during nuclear division
  • not observed inside of animal cells
• Cillia and Flagella:

  • • Structurally the same
  • • Hair like extensions that stick out from the surface of the cell
  • • Cylinders containing 9 microtubules in a circle and 2 microtubules in a central bundle. 
  • • Cilia are short and flagella are longer.
  • • Involved in movement of the cell or of substances across the cell surface. 
  • • Similar to centrioles.