Cell Sub-Structures

  1. What do eukaryotic cells contain?
    • A distinct nucleus
    • Membrane-bounded organelles
  2. What are the functions of a nucleus?
    • Contains genetic material in the form of DNA + chromosomes
    • Acts as control centre through production of mRNA and tRNA, hence protein synthesis
    • Manufactures ribosomal RNA + ribosomes
  3. What is the structure of a nucleus?
    • Nuclear envelope - double membrane. Outer membrane is continuous with ER and has ribosomes
    • Nuclear pores - allow passage of large molecules eg RNA. 3000 pores
    • Nucleoplasm is granular, jelly material that makes up bulk
    • Chromosomes have protein-bound, linear DNA
    • Nucleolus - small spherical region. Manufactures ribosomal RNA + assembles ribosomes
  4. What are the functions of a mitochondrion?
    • Sites of aerobic respiration
    • Produce ATP from substrates e.g. glucose
  5. What is the structure of a mitochondrion?
    • Double membrane - controls exit/entry of material. Inner membrane is folded to form cristae
    • Cristae - extensions of inner membrane, provide large SA for attachment of enzymes/proteins for increased rate of respiration
    • Matrix - space containing protein, lipids, ribosomes, DNA, enzymes
  6. Where are many mitochondria found?
    • In cells that have a high level of metabolic activity so require lots of ATP
    • e.g. muscle cells, epithelial cells -> need lots of ATP in active transport when absorbing substances from intestines
  7. What is the structure of a chloroplast?
    • Chloroplast envelope - double plasma membrane that controls exit/entry of materials
    • Grana - stacks of thylakoids, containing chlorophyll, where light absorption for PSN takes place
    • Stroma - fluid-filled matrix where synthesis of sugars for PSN takes place
  8. What are the functions of a chloroplast?
    Carries out PSN by absorbing sunlight
  9. How is a chloroplast adapted to its functions?
    • Granal membranes - provide large SA for attachment of substances that carry out PSN
    • Fluid of stroma - has enzymes needed to make sugars in 2nd stage of PSN
    • Contains DNA = ribosomes - to quickly manufacture proteins needed for PSN
  10. What is the structure of an ER?
    • 3D system of sheet-like membranes spreading through cytoplasm
    • Membranes enclose network of tubules + flattened sacs called cisternae
  11. What are the functions of an RER?
    • Has ribosomes
    • Large SA for synthesis of proteins
    • Provide pathway for transport of materials through cell
  12. What are the functions of the SER?
    • Synthesise, store + transport lipids
    • Synthesise, store + transport carbohydrates
  13. Where are extensive ERs found?
    • In cells that manufacture + store large quantities of carbohydrates, proteins, lipids
    • e.g. liver, secretory cells (epithelial)
  14. What is the structure of a Golgi apparatus?
    Stacks of membranes that make up flattened sacs called cisternae, with small rounded hollow structures called vesicles
  15. What are the functions of a Golgi apparatus?
    • Modifies + sorts proteins
    • They are transported in vesicles which are pinched off from ends of cisternae
  16. What is the structure of a lysosome?
    • Formed when vesicles produced by Golgi contain enzymes such as proteases/lipases
    • Contain enzymes that hydrolyse some cell walls
  17. What are the functions of a lysosome?
    • Hydrolyse material ingested by phagocytic cells
    • Release enzymes to outside of cell
    • Digest worn out organelles to be reused
    • Completely break don cells after they've died
  18. What is the structure of a ribosome?
    • Small cytoplasmic granules
    • Occur in cytoplasm or with RER
    • 80S - eukaryotic
    • 70S - prokaryotic (smaller)
    • One large unit, one small, containing ribosomal RNA + protein
  19. What is the function of a ribosome?
    The site of protein synthesis
  20. What is the structure of a cell wall?
    • Has microfibrils made of cellulose embedded in matrix
    • Thin layer called middle lamella marking boundary between adjacent cell walls
  21. What are the functions of a cell wall?
    • Provide strength to prevent cell bursting from osmotic gain of water
    • Provide strength to whole plant
    • Allow water to pass along it
  22. What is the structure of a vacuole?
    Fluid-filled sac bounded by a single membrane called a tonoplast
  23. What are the functions of vacuoles?
    • Support plants by making cells turgid
    • Sugars + amino acids act as temporary food store
    • Pigments may colour petals to attract insects
  24. What is the structure of a bacterium?
    • Prokaryotic
    • Cell wall - made of murein
    • Capsule - (some bacteria) slime wall for protection
    • Cell-surface membrane - with 70S ribsomes
    • Circular DNA 
    • Plasmids - extra loops of DNA
  25. What is a prokaryotic cell?
    • Smaller
    • No nucleus
    • No nuclear envelope
  26. What is a virus?
    • Acellular
    • Non-living particles
    • Smaller than bacteria
    • Contain nucleic acids - DNA/RNA - within capsid, a protective protein coat
    • Only multiply inside living host cells
    • Lipid envelope - (some) if not then attachment proteins to allow virus to attach to host cell
  27. What are the relative sizes of cell types to each other?
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Card Set
Cell Sub-Structures
Ultrastructure of eukaryotic and prokaryotic cells.