Eukaryotic cell structure

• Organelles are structures within the cells that perform specific functions
• Eukaryotic cells have a distinct nucleus and membrane-bound organelles
• The nucleolus is the site of ribosomal RNA and ribosomal synthesis
• Nuclear pores allow for the diffusion of large molecules out of the nucleus
• Chromosomes only become visible during cell division
• Mitochondria is the site of aerobic respiration and is the site of ATP synthesis
• Ribosomes are the site of polypeptide synthesis
• Ribosomes are made of a small and large subunit
• Ribosomes exist as two sizes

  • 80S - found in eukaryotic cells
  • 70S - found in prokaryotic cells
• Rough endoplasmic reticulum has ribosomes attached for protein synthesis and provides a pathway for the transport of materials
• Smooth endoplasmic reticulum is the site of lipid and carbohydrate synthesis, store and transport
• Golgi apparatus is a series of flattened membrane-bound sacs that are involved in the modification and packaging of proteins
• Golgi apparatus

  • combine carbohydrates and proteins
  • process enzymes
  • secrete carbohydrates
  • transfer, modify and store lipids
  • forms lysosomes and golgi vesicles
• Lysosomes are vesicles produced by the golgi appartus
• Lysosomes contain hydrolytic enzymes called lysozymes which digest unwanted material in the cell
• Lysozymes digest pathogens, worn out organelles and the cell after it dies
• Protein and lipid modification

  • vesicle containing phagosome fuses with lysosome
  • soluble products from hydrolysis diffuse out of the vesicle
  • vesicle membrane moves inwards
  • vesicle from rough endoplasmic reticulum containing polypeptides arrives at the golgi apparatus
  • insoluble molecules egested from the cell as vesicle fuses with cell surface membrane
  • lysosomes containing lysozymes released from the golgi apparatus
  • lysozymes hydrolyse the pathogen/molecules
• Cell surface membrane

  • controls entry and exit of substances into and out of the cell
  • made from a phospholipid bilayer
  • proteins and other molecules embedded which are able to move
• Cell walls in plants and algae are made from cellulose/glycoproteins
• Cell walls in fungi are made from chitin/glycon/glycoproteins
• Cell walls provide strength and allow water to pass through
• Vacuoles are fluid filled sacs that store food and waste products
• Function of vacuoles

  • give cells turgidity
  • sugars and amino acids act as temporary food store
  • pigments give colour