Cell structure

• Structure of the nucleus:

  • Nuclear envelope: a double membrane that surrounds the nucleus, controlling the entry and exit of materials
  • Nuclear pores: allow the passage of large molecules like mRNA
  • Nucleoplasm: granular, jelly-like material that makes up the bulk of the nucleus
  • Chromosomes: proteins (histone) bound linear DNA
  • Nucleolus: manufactures RNA and assembles ribosomes
• Function of the nucleus

  • site of DNA replication and transcription of mRNA
  • contains the genetic code for each cell
• Structure of smooth Endoplasmic reticulum

  made from folded membranes on the Cisternae
• function of SER

  synthesis and store lipids carbohydrates and steroids.
• structure of RER

  folded membranes called Cisternae

  have ribosomes on the Cisternae
• function of RER

  protein synthesis
• structure of Golgi apparatus

  folded membranes making Cisternae

  secreting vesicles pinch of from the Cisternae
• function of Golgi apparatus 


  Organelle of eukaryotic cells that is responsible for transporting, modifying and packaging proteins and lipids

  molecules are labelled with their destinations

  finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents are released by exocytosis.
• structure of lysosomes

  bags of digestive (hydrolytic) enzymes
• function of lysosomes

  hydrolyse phagocytic cells

  exocytosis - release enzymes to outside of cell to destroy material

  digest worn out organelles for reuse of materials.
• Structure of mitochondria

  Double membrane

  inner membrane - Cisternae

  fluid centre called the mitochondrial matrix

  loop of mitochondria DNA
• function of mitochondria

  site of aerobic respiration

  site of ATP production
• structure of ribosomes

  small, made up of two sub-units of protein and rRNA

  80s - large ribosomes found in eukaryotic cells

  70s - smaller ribosomes found in prokaryotic cells, mitochondria and chloroplast
• function of ribosomes 


  Site of protein synthesis
• structure of vacuole

  filled with fluid surrounding by a single membrane called a tonoplast
• function of vacuole 


  make cells turgid and therefore provide support

  temporary store of sugars and amino acids
• structure of chloroplast

  surrounded by a double membrane

  grana - stacks of thylakoids (folded membranes embedded with chlorophyll) joined by lamellae

  fluid filled stroma contains enzymes for photosynthesis
• function of chloroplast

  site of photosynthesis
• structure of cell wall

  In plants and fungi

  plants - made of micro fibrils of the cellulose polymer (form hydrogen bonds between cellulose molecules)

  fungi - made of chitin
• function of cellulose

  Provide structural strength to the cell to prevent cell lysis by osmotic gain
• function of phospholipid balayer

  Controls the entry and exit of molecules
• What is the structure of a prokaryotic cell

  Capsule

  Cell wall - (murein)

  cell surface membrane

  cytoplasm

  circular DNA

  ribsomes

  plasmids

  pilli

  flagellum
• prokaryotic vs eukaryotic

  size - 0.5 -5 um diameter : up to 100um diameter

  genome - DNA circular with no associated proteins : DNA is associated with histone proteins formed into a chromosome

  cell division - binary fission : mitosis and meiosis

  ribosomes - 70s : 80s

  organelles - no membrane bound organelles : lysosomes, Golgi apparatus, cell surface membrane, chloroplast, mitochondria, nucleus

  cell wall- murein : plants (cellulose), fungi (chitin)
• structure of viruses

  viruses are non-living infectious particles (parasitic - only reproduce by infecting living cells)

  a nucleic acid core - dna or rna genetic code

  attachement proteins

  lipid envelope