Structural organisation of cells

• What are the learning objectives?

  5:

  
• What are nuclear pores used for?

  RNA, ribosomes, macromolecules selectively transported into cytoplasm

  Proteins & macromolecules selectively transported into nucleus (selective permeability)
• What does the nucleus contain?

  Code for all the cell's enzymes & other proteins

  Molecular machinery to replicate DNA

  Chromosomes & chromatin

  Synthesises & processes all types of RNA
• Which is usually the largest organelle in the cell?

  Nucleus (usually found in centre of cell)
• In which type of cells is the nucleus found?


  Eukaryotic cells
• What is the nuclear envelope?


  Double membrane surrounding nucleus

  Inner & outer membranes fuse to form nuclear pores at many points

  Outer membrane continuous with rough endoplasmic reticulum.
• What is chromatin?


  Delicate filaments formed from dispersed chromosomes

  During cell division, chromatin becomes densely coiled to form chromosomes

  Packages DNA to fit inside nucleus
• What does RNA polymerase do during transcription?


  Uses DNA as template to produce pre-mRNA transcript

  pre-mRNA processed to form mature mRNA that's translated to build protein polypeptide encoded by gene
• What is the nucleolus?


  Found in nucleus- has no membrane

  Forms to maximise interactions between specific DNAs, RNAs & proteins

  Makes ribosomes

  Active cells have a big nucleolus

  Inactive cells have no nucleolus
• What are ribosomes?


  Sites of protein synthesis

  Leave nucleus via nuclear pore

  Consist of ribosomal RNA (rRNA) & proteins

  Has large subunit & small subunit

  Float free in cytoplasm
• What are lysosomes?


  • Membrane-bound sacs containing lysozymes
  • Lysozymes digest material taken in by cell by phagocytosis & endocytosis + destroy worn-out organelles in cell & cell itself
• Where is mitochondria found in abundance?


  Cells active in energy consumption e.g, skeletal