Cells and microscopes

• The cytoskeleton in cells consists of microtubules and microfilaments.
• Describe the roles of the cytoskeleton.

  1 (whole) cell, support / stability / scaffolding /

  maintain shape ;

  2 movement of, cilia / flagella / undulipodia OR use

  of cilia / flagellum / undulipodium to move cell ;

  3 changing shape of cell / cytokinesis / pseudopodia /

  phagocytosis / endocytosis / exocytosis /

  muscle contraction ;

  4 (named) organelles, moved / held in place ;

  5 movement of, chromosomes / chromatids / (m)RNA ;
• **Bacterial cells don't have centrioles because genetic material flows freely in the cytoplasm**
• Transport of vesicles not movement
• What is the magnification of the light and electron microscope’s?

  light microscope ................. 1500x

  transmission electron microscope …….. 500,000x
• Definition of resolution

  resolution : in detail and distinguish objects as separate.
• **Suggest two processes inside cells that rely on the cytoskeleton for movement.**

  for RNA molecule movement and cytokinesis
• **Structures C and E are examples of the same organelle.

  Suggest why E looks so different to C.**

  (mitochondria) vary in shape ;

  longer than wide ;

  cut in different planes / angles / AW ;

  just divided / growing ;

  artefact / deformed during preparation of section ;
• True or false- scanning electron microscopes allow you to see 3D shape?

  TRUE
• Purpose of vacuole?

  vacuoles purpose is to take up water/ become turgid in a guard cell also one side is slightly thicker so that the stomata can open
• What is the resolution of a light and TEM microscope?

  light 50 - 200 nm ;

  TEM 0.05 - 1.0 nm ;
• **why 2 cells cytoplasm reacts differently to the stain:**

  1 C (is, blue / purple, so) has (more) nucleic acid ✓

  2 (C has) (m / t / r) RNA ✓

  3 D (is red so) has (more) protein ✓

  4 (D has) enzyme / antibody / immunoglobulin ✓

  5 idea that different cells have different, roles /

  (concentrations of) biochemicals / levels of activity ✓
• 1. **Which of the stains, A to D, would be chosen to bind to the phosphate group of DNA (negatively charged) to make chromosomes more visible when using a light microscope?**

  A carbolfuchsin – a non-polar dye

  B nigrosin – a negatively charged dye

  C methylene blue – a positively charged dye

  D Sudan 111 – a lipid-soluble dye

  C
• **why stain is imp?**

  contrast is high(er) (1)

  more (internal) structures visible (1)

  some (named) organelles / cell components more

  visible, because they bind to stain (1)

  clearer image can be obtained (1)
• How to calculate the length of the nucleus using a microscope?

  use eyepiece graticule ✓

  calibrate graticule, using stage micrometer / detail of

  calibration / calculate the length of one epu ✓

  measure the diameter of the nucleus in, epu / graticule

  units ✓

  take repeat measurements and calculate a mean

  diameter (in epu) ✓

  use calibrated epu to calculate diameter (of nucleus) (in

  μm) / described ✓
• LSCM allows you to see different depths of the live sample (coloured images produced)
• microtubules are not part of the 9+2 arrangement in bacteria flagellum
• nucleus synthesises RNA
• pilli only found in a bacteria and not found in root hair cell.
• Golgi apparatus and secretory vesicles are not found in bacteria
• What is the type of division yeast cells undergo?

  Budding
• Explain why early eukaryotes were able to grow more quickly than cells that did not possess

  mitochondria.

  1 would be able to respire aerobically ✓

  2 (this) produces more ATP ✓

  3 ATP needed for , active transport / cell division

  / protein synthesis / DNA replication ✓

  4 more ATP allows faster metabolic , processes

  / reactions ✓
• **Outline the process and organelles involved in the translation of these proteins from RNA.**

  (m)RNA transported out of nucleus (1)

  (m)RNA transported to / associates with

  ribosome (1)

  translation / protein synthesis, occurs at

  ribosome (1)

  (t)RNA brings specific amino acids or (t)RNA

  described (1)

  peptide bonds form between adjacent amino

  acids or peptide bonds described (1)

  polypeptide / protein processed through Golgi

  apparatus (1)
• Peroxisomes are vesicles that usually contain enzymes such as catalase.

  Explain how peroxisomes can be moved around inside the cell.

  attach to cytoskeleton (1)

  moved by, protein motors / dynein (1)