B1 - Cell biology

• What are the two main types of organisms based on cell structure?

  Prokaryotes and Eukaryotes
• What is the significance of the first observation of cells through a microscope?

  It led to the discovery of cells as the building blocks of all organisms.
• What is the definition of a prokaryote?


  A prokaryote is a single-celled organism made up of prokaryotic cells.
• What distinguishes eukaryotic cells from prokaryotic cells?

  Eukaryotic cells are complex and include all animal and plant cells, while prokaryotic cells are smaller and simpler.
• What are the main subcellular structures found in animal cells?

  • Nucleus: contains genetic material
  • Cytoplasm: gel-like substance for chemical reactions
  • Cell membrane: controls entry and exit of substances
  • Mitochondria: site of aerobic respiration
  • Ribosomes: where proteins are made
• What additional structures do plant cells have compared to animal cells?

  • Rigid cell wall: made of cellulose for support
  • Permanent vacuole: contains cell sap (sugar and salts)
  • Chloroplasts: site of photosynthesis containing chlorophyll
• What is the function of chloroplasts in plant cells?

  Chloroplasts are where photosynthesis occurs, making food for the plant.
• Why are bacterial cells considered prokaryotes?

  Bacterial cells are smaller and do not have a nucleus, they have a single circular strand of DNA instead.
• What do bacterial cells lack compared to eukaryotic cells?

  Bacterial cells do not have chloroplasts or mitochondria.
• What is the structure of DNA in bacterial cells?

  Bacterial cells have a single circular strand of DNA that floats freely in the cytoplasm.
• What are plasmids in bacterial cells?

  Plasmids are small rings of DNA that may be present in bacterial cells.
• Compare the structures of plant, animal, and bacterial cells.

  • Plant Cells:
  • Rigid cell wall
  • Permanent vacuole
  • Chloroplasts
  • Animal Cells:
  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
  • Bacterial Cells:
  • Cell membrane
  • Cytoplasm
  • Cell wall
  • Circular DNA
  • Plasmids
• What role do enzymes play in the cytoplasm of animal cells?

  Enzymes control the chemical reactions that occur in the cytoplasm.
• What is the gel-like substance in which most chemical reactions occur in animal cells?

  Cytoplasm
• What is the function of the cell membrane in a cell?

  The cell membrane holds the cell together and controls what goes in and out.
• Why are microscopes important for biology?

  They allow us to see things that we can't see with the naked eye.
• What are the main types of microscopes and their functions?

  • Light microscopes: Use light and lenses to magnify specimens, allowing us to see individual cells and large subcellular structures.
  • Electron microscopes: Use electrons to form images, providing much higher magnification and resolution than light microscopes.
• What is the difference between light microscopes and electron microscopes in terms of magnification?

  Electron microscopes have a much higher magnification than light microscopes.
• What does resolution refer to in microscopy?

  Resolution is the ability to distinguish between two points, with higher resolution providing a sharper image.
• What can electron microscopes allow us to see in more detail?

  They allow us to see smaller structures like the internal structure of mitochondria and chloroplasts, as well as ribosomes and plasmids.
• What is the formula for calculating magnification in microscopy?

  • Magnification = image size / real size
  • Ensure that image size and real size are in the same units.
• If a specimen is 50 μm wide, what is the width of the image under a magnification of x 100?

  The width of the image is 5000 μm or 5 mm.
• How can you rearrange the magnification formula to find the real size of an object?

  Real size = image size / magnification.
• How do you convert micrometres to millimetres?

  • Divide the number of micrometres by 1000.
  • Example: 5000 μm = 5 mm.
• What is standard form and why is it useful in microscopy?

  Standard form is a way to express very big or small numbers in a manageable format, useful for tiny objects seen under a microscope.
• How would you write 0.0025 mm in standard form?

  0.0025 mm can be written as $2.5 \times 10^{-3} \text{ mm}$.
• How do you convert a number to standard form?

  You move the decimal point left or right and represent the movement as a power of 10.
• What is the significance of the power of 10 in standard form?

  The power of 10 indicates how many places the decimal point has moved, with positive for left and negative for right.
• What is the first number in standard form required to be between?

  The first number needs to be between 1 and 10.
• What is the purpose of a microscope slide?

  To mount a specimen for viewing under a microscope.
• What is the first step in preparing a slide to view onion cells?

  Add a drop of water to the middle of a clean slide.
• How do you place the epidermal tissue on the slide?

  Using tweezers, place the epidermal tissue into the water on the slide.
• What is the purpose of iodine solution when preparing a slide?

  It is a stain used to highlight objects in a cell by adding color to them.
• What should you do after adding the iodine solution to the slide?

  Place a cover slip on top of the specimen.
• Why is it important to avoid air bubbles when placing the cover slip?

  Air bubbles obstruct your view of the specimen.
• What is the first step in using a light microscope?

  Clip the slide onto the stage.
• What should you do after selecting the lowest-powered objective lens?

  Use the coarse adjustment knob to move the stage up to just below the objective lens.
• How do you achieve a clear image of the specimen?

  Adjust the focus with the fine adjustment knob.
• What should you do if you need to see the slide with greater magnification?

  Swap to a higher-powered objective lens and refocus.
• What are the steps to draw observations under a microscope?

  1. Draw with a sharp pencil.
  2. Ensure the drawing takes up at least half the space.
  3. Avoid coloring or shading.
  4. Draw subcellular structures in proportion.
  5. Include a title and magnification used.
  6. Label important features.