cells and microscoopy

• Cell types


  Eukaryotic (animals and plants)<|>Prokaryotic
• Eukaryotic cell


  • Contains a nucleus and membrane-bound organelles
• Prokaryotic cell


  • Does not contain a nucleus and membrane-bound organelles
• Components of plant and animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Genetic information storage in eukaryotic cells

  Within the nucleus, arranged in chromosomes
• Function of the nucleus

  Controls cellular activities
• Function of the cytoplasm

  Site of chemical reactions in cell
• Function of the cell membrane


  Controls the entry and exit of materials into and out of the cell
• Organelles found in plant cells only

  • Large, permanent vacuole
  • Cell wall
  • Chloroplasts
• Cell wall composition


  Cellulose
• Function of the cell wall

  Provides strength<|>Prevents the cell bursting when water enters by osmosis
• Function of the permanent vacuole

  Supports the cell, maintaining its turgidity
• Function of the chloroplasts

  Site of photosynthesis
• Chloroplast appearance under a light microscope

  Appear green due to containing chlorophyll, a green pigment
• Organelles found in prokaryotic cells

  • Chromosomal DNA
  • Plasmid DNA
  • Cell wall
  • Cell membrane
  • Ribosomes
  • Flagella
  • cytoplasm
• Genetic information storage in prokaryotic cells

  Found free within the cytoplasm as chromosomal DNA (single large loop of circular DNA) and plasmid DNA
• Plasmids


  Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA, carrying genes that provide genetic advantages e.g. antibiotic resistance
• Flagellum


  Long, 'whip-like' tail that enables bacteria to move
• Haploid cell


  A cell that contains a single copy of each chromosome (half the number of chromosomes)
• Diploid cell


  A cell that contains two copies of each chromosome (full set of chromosomes)
• Gametes


  Reproductive cells of an animal or a plant (e.g. egg and sperm cells) that are haploid cells
• Sexual reproduction in terms of chromosome number

  1. Two haploid gametes fuse

  2. Resulting embryo has a full set of 46 chromosomes ∴ diploid
• Describe how egg cells are adapted to their function

  1. Haploid nucleus contains genetic material

  2. Mitochondria in cytoplasm produce energy for the developing embryo

  3. Cytoplasm contains nutrients for the developing embryo

  4. 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

  1. Haploid nucleus contains genetic information

  2. Tail enables movement

  3. Mitochondria provide energy for tail movement

  4. Acrosome contains enzymes that digest the egg cell membrane
• Ciliated epithelial cells


  Cells lining the surface of structures such as the respiratory tract and uterus with hair (cilia ) on them
• 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
• How does a light microscope work?

  Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
• Advantages of light microscopes

  • Inexpensive
  • Easy to use
  • Portable
  • Observe both dead and living specimens
• Disadvantage of light microscopes

  Limited resolution
• Advantage of electron microscopes

  Greater magnification and resolution
• How have electron microscopes enabled scientists to develop their understanding of cells?

  1. Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail

  2. Enable scientists to develop more accurate explanations about how organelle structure relates to function
• Disadvantages of electron microscopes

  • Expensive
  • Large so less portable
  • Require training to use
  • Only dead specimens can be observed
• How do you convert from m to mm?

  × 1000 (× 103)

  
• How do you convert from m to µm?

  × 1 000 000 (× 106)

  
• How do you convert from m to nm?

  × 1 000 000 000 (× 109)
• How to you convert from nm to m?

  ÷ 1 000 000 000 (× 10-9)
• How do you convert from m to pm?

  × 1 000 000 000 000 (× 1012)
• Convert 1.527 m to µm. Write your answer in standard form (higher)

  1.527 m × 1000000 = 1527000 µm
• function of ribosome

  site of protein synthesis in cell
• function of mitochondria

  releases energy in the cell , site of respiration in the cell