Cell biology

• What is the function of a ribosome?

  Protein synthesis
• How have microscopes developed over the years?

  Increased magnification, Increased resolution
• Which of the following is an advantage of the transmission electron microscope compared with the light microscope?

  Higher magnifications are possible with the transmission electron microscope owing to the shorter wavelengths of the electron compared with visible light.
• Which of the following is the correct sequence for setting up a microscope on high power?

  Focus on low power with the coarse adjustment, move the high power objective in line with the specimen, refocus on high power with the fine adjustment
• How is a muscle adapted to its function?

  It contains protein filaments that slide over each other and cause contraction
• Which of the following is a feature of eukaryotic cells not present in prokaryotic cells?

  Mitochondria
• If the actual size of a cell is 100 μm, and 10 cm in a book, what is the magnification of the image in the book?

  1000
• A type of white blood cell called a macrophage measures 5 x 10-5 m. What does it measure in micrometres?

  50 μm
• If a cell called a megakaryocyte measures 1 x 10-4 m, and a neutrophil measures 1 x 10-5 m, what is the difference in order of magnitude?


  1
• Which of the following is an adaptation to the transport of substances in the xylem?

  There are no end walls, and the side walls are thickened
• Which of these correctly describes the role of specialised cells in the excretory system?

  Remove waste products and regulate the water content of the body
• Which statement is correct about the cells produced by mitosis?

  Two daughter cells are produced, each has the same number of chromosomes as the parent cells
• Which of the following is an ethical consideration about the use of embryonic stem cells?


  In some cases embryos are being produced just so that stem cells can be extracted for research on therapies.
• 
  

  Plant stem cells occur in meristems
• Why are meristematic cells grown in a sterile culture medium?

  To avoid the growth of microorganisms
• A gene is a short section of DNA that codes for a protein
• Embryonic stem cells can differentiate into different cell types
• What happens in the stage that is before mitosis in the cell cycle?


  A period of growth, during which time DNA is checked for errors
• A scientist observes 100 cancer cells with a microscope. If 16 cells are undergoing mitosis, and the length of the cell cycle is 400 hours, what is the length of mitosis?

  64 hours
• What are guard cells in plants specialised to do?


  Open and close to let carbon dioxide into the leaf for photosynthesis
• What is the surface area to volume ratio of a cube with sides 7 cm?

  0.86
• The mass of a cylinder of beetroot was 2.5 g. If its final mass in an osmosis experiment was 2.7 g, what was the increase in mass in per cent?

  8
• What will happen if a spray of perfume is released into one corner of a room?


  Particles of the perfume will diffuse until they are spread evenly through the room
• Water moves from a region of high concentration to a low concentration across a partially permeable membrane - osmosis
• If the decrease in mass of a cylinder of beetroot was 0.62 g in 48 minutes, what was the rate of water loss?

  0.78 g h-1
• Which factor will decrease the rate of diffusion across a membrane?


  Decreasing the temperature
• What happens to red blood cells when they are placed in water?

  the cells swell up and burst
• Why does a mouse experience more problems with heat loss than an elephant?

  The mouse has a larger surface area to volume ratio