Cells and Microscopy

• What are the two types of cell?

  Prokaryotic and Eukaryotic
• What’s the difference between a eukaryotic and a prokaryotic cell?

  A eukaryotic cell contains a nucleus and membrane-bound organelles, a prokaryotic cell does not
• List the components of both plant and animal cells

  • Nucleus

  • Cytoplasm

  • Cell membrane

  • Mitochondria

  • Ribosomes
• How is genetic information stored in a eukaryotic cell?

  Within the nucleus, arranged in chromosomes
• Describe the structure of the cytoplasm


  • Fluid component of the cell

  • Contains organelles, enzymes, dissolved ions and nutrients
• When looking at a cell using a light microscope, why do chloroplasts appear green?

  They contain chlorophyll, a green pigment
• List the organelles found in prokaryotic cells

  • Chromosomal DNA

  • Plasmid DNA

  • Cell wall

  • Cell membrane

  • Ribosomes

  • Flagella
• How is genetic information stored in a prokaryotic cell?

  • Chromosomal DNA (single large loop of circular DNA)

  • Plasmid DNA
• What is the prokaryotic cell wall composed of?

  Peptidoglycan
• What is a flagellum?

  • Long, rotating, ‘whip-like’ protrusion

  • Enables bacteria to move
• What is a haploid cell?

  A cell that contains only one copy of each chromosome

  E.g. 23 chromosomes
• What is a diploid cell?

  A cell that contains two copies of each chromosome

  E.g. 46 chromosomes
• What are gametes?


  • Reproductive cells (e.g. egg and sperm cells)

  • They are haploid cells
• Describe sexual reproduction in terms of chromosome number

  • Two haploid gametes fuse

  • Resulting embryo has two chromosomes for each gene and two copies of each allele

  • Results in diploid
• Describe how egg cells are adapted to their function

  • Haploid nucleus contains genetic material

  • Mitochondria in cytoplasm produce energy for the developing embryo

  • Cytoplasm contains nutrients for the developing embryo

  • Cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid
• Describe how sperm cells are adapted to their function

  • Haploid nucleus contains genetic information

  • Tail enables movement

  • Mitochondria provide energy for tail movement

  • Acrosome contains enzymes that digest the egg cell membrane
• Where are ciliated epithelial cells found?

  Found lining the surface of structures such as the respiratory tract and uterus
• Describe the function of ciliated epithelial cells lining the airways

  Move in synchronised waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed
• What is magnification?


  The number of times bigger an image appears compared to the size of the specimen
• How can the total magnification of an image be calculated from lens powers?

  Total magnification =

  Eyepiece lens magnification x Objective lens magnification
• How can the magnification of an image be calculated?

  Magnification = image size / object size
• What is resolution?


  The smallest distance between two objects that can be distinguished
• How does a light microscope work?

  Passed a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
• What are the advantages of light microscopes?

  • Inexpensive

  • Easy to use

  • Portable

  • Observe both dead and living specimens
• What are the disadvantages of light microscopes?

  Limited resolution
• How does an electron microscope work?

  It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image
• Two types of electron microscope

  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
• What is the advantage of electron microscopes?

  Greater magnification and resolution
• Why do electron microscopes have a greater magnification and resolution?

  They use a beam of electrons which has a shorter wavelength than photons of light
• What are the disadvantages of electron microscopes?

  • Expensive

  • Large so less portable

  • Require training to use

  • Only dead specimens can be observed
• How do you convert m to mm?

  x 10$^3$
• How do you convert from nm to m?

  x 10$^-9$
• Write 10382 in standard form

  1.0382 x 10$^4$
• Convert 1.527 m to μm

  1.527 x 10$^6$