Cell structure and microscopy

• Explain why it is not possible to determine the identity of organelles using an optical microscope.

  1. Resolution too low;

  2. Because wavelength of light is too long;
• U. marinum cells ingest bacteria and digest them in the cytoplasm.

  Describe the role of one named organelle in digesting these bacteria.

  1. Lysosomes;

  2. Fuse with vesicle;

  3. Releases hydrolytic enzymes;
• Give structures found in all prokaryotic cells and in all eukaryotic cells.

  1. Cell-surface membrane;

  2. Ribosomes;

  3. Cytoplasm;

  4. DNA;
• All prokaryotic cells contain a circular DNA molecule and some prokaryotic cells contain plasmids.

  Scientists have found that the rate of plasmid replication is faster in cells growing in a culture with a high concentration of amino acids than in a culture with a lower concentration of amino acids.

  Suggest explanations for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration.


  1. Amino acids used in protein synthesis; so more enzymes for plasmid replication

  2. Amino acids used in respiration so more ATP for plasmid replication
• Describe how a sample of chloroplasts could be isolated from leaves.

  1. Break open tissue and filter

  2. In cold, same water potential pH controlled solution;

  3. Centrifuge and remove nuclei alongside cell debris;

  4. Centrifuge at higher speed, chloroplasts settle out;
• Give one feature of the chloroplast that allows protein to be synthesised inside the chloroplast and describe differences between this feature in the chloroplast and similar features in the rest of the cell.

  1. DNA is not associated with histones but nuclear DNA is;

  2. Chloroplast ribosomes are smaller than cytoplasmic ribosomes;
• Assume there is a transmission electron micrographs of two cells, one animal cell and one prokaryotic cell. Contrast the structure of the two cells that would be expected to be noticed

  1. Magnification figures would show animal cell is bigger than prokaryotic cell;

  2. Animal cell has a nucleus whereas prokaryote cell as free DNA;

  3. Animal cell has mitochondria whereas prokaryote cell does not;

  4. Animal cell has Golgi body and endoplasmic reticulum whereas prokaryote cell does not;

  5.Animal cell has no cell wall whereas prokaryotic cell has a mureincell wall;

  6. Animal cell has no capsule whereas prokaryotic cell has a capsule;

  7. Animal cell has DNA is bound to histones whereas prokaryotic cell has DNA not associated with histones

  8. Animal cell has larger ribosomes;
• Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells. Do not include details of transcription and translation in your answer.

  1. DNA in nucleus is code for protein;

  2. Ribosomes on the rough endoplasmic reticulum produce protein;

  3. Mitochondria produce ATP for protein synthesis;

  4. Golgi apparatus modify and glycoprotein produced by Golgi apparatus;

  5. Vesicles transport;

  6. Vesicles fuse with cell-surface membrane;
• The image below is a transmission electron micrograph of a plant cell. Suggest why a nucleus is not visible in above image

  Only a section so nucleus in another part of cell

  OR

  Nucleus not stained;
• Give one advantage of viewing a biological specimen using a transmission electron microscope compared with using a scanning electron microscope

  Higher resolution

  OR

  View internal structures;
• The detail shown in the diagram above would not be seen using an optical microscope. Explain why.

  1. Light has longer wavelength;

  2. So lower resolution;
• Name an organelle found in both a chloroplast and a prokaryotic cell

  70S Ribosome;
• A biologist separated cell components to investigate organelle activity. She prepared a suspension of the organelles in a solution that prevented damage to the organelles. Describe three properties of this solution and explain how each property prevented damage to the organelles.

  1. Ice cold to prevent enzyme activity;

  2. Buffered to prevent denaturing of enzyme;

  3. Same water potential to prevent lysis which is the bursting of organelle;
• Name the main biological molecule in a prokaryote's:

  W- cell surface membrane

  X- cell wall

  W - Phospholipids;

  X - Murein / glycoprotein;
• Name the process by which prokaryotic cells divide

  Binary fission;
• What part of the plant cell has stacked membranes arranged in parallel and contains DNA?

  Chloroplast
• Which part of the plant cell is made out of polysaccharide?

  Cell Wall
• What part of the plact cell is an organelle and is NOT surrounded by two membranes?

  Golgi Apparatus
• Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells.

  1. TEM use electrons and optical use light;

  2. TEM allows a greater resolution;

  3. So with TEM smaller organelles can be observed

  4. TEM view only dead specimens and optical can view live specimens;

  5. TEM does not show colour and optical can;

  6. TEM requires thinner specimens;

  7. TEM requires a more complex preparation;

  8. TEM focuses using magnets and optical uses glass lenses;
• Name structures present in plant cells that are not present in animal cells.

  1. Chloroplasts

  2. Cell wall

  3. Cell vacuole

  4. Starch grains
• DNA and RNA can be found in bacteria. Give two ways in which the nucleotides in DNA are different from the nucleotides in RNA.

  1. DNA contains thymine and RNA contains uracil;

  2. DNA contains deoxyribose and RNA contains ribose.
• The cell-surface membrane can be seen with a transmission electron microscope but not with an optical microscope. Explain why.

  Electron microscope has higher resolution than optical microscope.
• No organelles are visible in the cytoplasm of this red blood cell. Suggest why.

  Cytoplasm of red blood cell filled with haemoglobin.
• Before the cell was examined using the electron microscope, it was stained. This stain caused parts of the structure of the cell-surface membrane to appear as two dark lines. Suggest an explanation for the appearance of the cell-surface membrane as two dark lines.

  1. Membrane has phospholipid bilayer;

  2. Stain binds to phosphate;

  3. On inside and outside of membrane.
• Name structures in a eukaryotic cell that cannot be identified using an optical microscope.

  Mitochondrion

  ribosome

  endoplasmic reticulum

  lysosome

  cellsurface membrane
• Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope.

  1. Add drop of water to glass slide;

  2. Obtain thin section of plant tissue and place on slide

  3. Stain with iodine in potassium iodide.

  4. Lower cover slip using mounted needle.
• Give the function of the chloroplast

  Site of photosynthesis

  Has chlorophyll which absorbs light energy and converts it to chemical energy
• Give the function of the nucleus

  contains DNA of cell.
• A transmission electron microscope was used to produce the image in the figure above. Explain why.

  1. High resolution;

  2. Can see internal structure of organelles.
• A biologist separated cell components to investigate organelle activity. She prepared a suspension of the organelles in a solution that prevented damage to the organelles. Describe three properties of this solution and explain how each property prevented damage to the organelles.

  1. Ice cold to prevent enzyme activity;
  2. Buffered to prevent denaturing of enzyme;
  3. Same water potential to prevent lysis which is the bursting of organelle;