cell biology

• The compound microscope uses two lenses to magnify the specimen – the eyepiece and an objective lens.
• Magnification of the microscope = magnification of eyepiece × magnification of objective
• magnification = size of image/ real size of specimen
• What is the role of the nucleus in a cell?


  To control cell activities and contain DNA for protein synthesis.
• What is the function of the cytoplasm in a cell?


  It is where chemical reactions take place.
• What is the typical size range of most animal and plant cells?


  0.01 - 0.10 mm
• What does the cell membrane do?


  It controls what goes in and out of the cell and is partially permeable.
• What is the smallest size that can be seen with the naked eye?


  About 0.05 mm
• What are ribosomes responsible for?


  Making proteins from amino acids.
• What is the main component of the plant cell wall?

  Cellulose
• What is the function of chloroplasts in plant cells?


  To absorb sunlight for photosynthesis.
• What is the best unit to measure most cells?

  Micrometre, symbol µm
• What distinguishes prokaryotic cells from eukaryotic cells?


  Prokaryotic cells have no nucleus or membrane-bound organelles.
• For which structures is it best to use the nanometre as a unit of measurement?


  For sub-cellular structures like ribosomes and organisms like viruses
• What is the role of plasmids in prokaryotic cells?

  They are small rings of DNA that contain a few genes. they can carry the genetic code for antibiotic resistance and can be exchanged between bacteria
• What are the divisions of a metre in terms of millimetres, micrometres, and nanometres?


  • 1 metre = 1000 millimetres (mm)
  • 1 metre = 1,000,000 micrometres (µm)
  • 1 metre = 1,000,000,000 nanometres (nm)
• What is the approximate size of an animal cell?

  About 10 micrometers.
• What is the approximate size of a plant cell?

  About 50 micrometers.
• How is a metre divided in standard form?


  • 1 mm = \(1 \times 10^{-3}\) m
  • 1 µm = \(1 \times 10^{-6}\) m
  • 1 nm = \(1 \times 10^{-9}\) m
• What is the approximate size of a prokaryotic cell?


  About 5 micrometers.
• What is the purpose of a coverslip when viewing a slide with a microscope?

  It protects the microscope and prevents the slide from drying out
• How should a coverslip be placed over a specimen?

  It should be lowered gently to avoid trapping air bubbles
• What is cell differentiation and specialization?

  • Process where undifferentiated cells become specialized cells.
  • In animals: nerve cells, muscle cells, sperm cells.
  • In plants: xylem, phloem, root hair cells.
• What is the function of nerve cells?

  To transmit impulses around the body.
• Why are stains used when viewing cells under a microscope?

  To add contrast and highlight specific structures
• What is the role of mitochondria in sperm cells?

  To provide energy for the tail to move.
• What precautions should be taken when using a microscope?

  • Be careful with bright illumination
  • Handle microscope stains with care
  • Handle coverslips and slides carefully
• What does the acrosome in a sperm cell contain?

  Enzymes for penetrating the egg cell membrane.
• What should be included in a low power diagram when examining cells or tissues?

  • Arrangement of distinct regions of the tissue
  • Outline of individual cells if the tissue is uniform
• What is the function of muscle cells?

  To contract and allow movement of the body.
• What is the resolution of a light microscope?


  About 0.2 µm or 200 nm
• What is the structure of xylem cells?

  Long tube-shaped cells with no end plates and no cytoplasm.
• How does the resolution of a light microscope affect the visibility of details?

  It determines the ability to see two points as separate rather than merged
• What is the role of lignin in xylem cells?


  To support the xylem cells and prevent collapse.
• What is the maximum magnification of a transmission electron microscope (TEM)?


  Around 1,000,000
• What is the structure of phloem cells?


  Elongated cells with end plates and some cytoplasm.
• What is the function of companion cells in phloem?


  To provide energy for the transport of sugars.
• What is the main difference between scanning electron microscopes (SEM) and transmission electron microscopes (TEM)?


  SEM examines surface structures, while TEM examines thin slices of specimens
• What is the function of root hair cells?


  To absorb water and mineral ions from the soil.
• What structures are visible under a light microscope?

  Cytoplasm, nucleus, ribosome, and cell membrane