Topic 1

• Cell types


  • Eukaryotic (animals and plants)
  • Prokaryotic
• Eukaryotic cell


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


  • Does not contain a nucleus or 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
• Cytoplasm


  Fluid component of the cell containing organelles, enzymes and dissolved ions and nutrients
• Function of the cytoplasm

  Site of cellular reactions e.g. first stage of respiration
• Function of the cell membrane


  Controls the entry and exit of materials into and out of the cell
• Function of the mitochondria


  Site of later stages of aerobic respiration in which ATP is produced
• Function of the ribosomes


  Joins amino acids in a specific order during translation
• Organelles found in plant cells only

  • Large, permanent vacuole
  • Cell wall
  • Chloroplasts
• Function of the cell wall

  Provides strength and prevents the cell bursting when water enters by osmosis
• Contents of the permanent vacuole

  A solution of salts, sugars and organic acids
• Function of the permanent vacuole

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

  Site of photosynthesis
• Appearance of chloroplasts 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
• 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, rotating, 'whip-like' protrusion 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 (e.g. egg and sperm cells) that are haploid cells
• 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 ∴ diploid
• Adaptations of egg cells

  • 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
• Adaptations of sperm cells

  • Haploid nucleus contains genetic information
  • Tail enables movement
  • Mitochondria provide energy for tail movement
  • Acrosome contains enzymes that digest the egg cell membrane
• Diploid


  Having two copies of each allele
• Egg cells are adapted to their function
• Egg cells


  • 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
• Sperm cells


  • Haploid nucleus contains genetic information
  • Tail enables movement
  • Mitochondria provide energy for tail movement
  • Acrosome contains enzymes that digest the egg cell membrane
• Ciliated epithelial cells are found lining the surface of structures such as the respiratory tract and uterus
• 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
• Magnification


  The number of times bigger an image appears compared to the size of the specimen
• Resolution


  The smallest distance between two objects that can be distinguished
• How a light microscope works

  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 is limited resolution
• How an electron microscope works

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

  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)