cell biology

• eukaryotic cells


  are plant and animal cells
• prokaryotic cells


  are bacterial cells
• differences between eukaryotic and prokaryotic cells

  • prokaryotic cells are much smaller than eukaryotic cells
  • eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotic cells do not
• prokaryotic cell wall


  composted of peptidoglycan
• genetic information storage in prokaryotic cells

  found free within the cytoplasm as: chromosomal DNA (single large loop of circular DNA), plasmin DNA
• plasmids


  small, circular loops of DNA found free in the cytoplasm and separate from the main DNA, carry genes that provide advantages e.g. antibiotic resistance
• order and magnitude


  a power to the base 10 used to quantify and compare size
• centimeter


  1 x 10-2 meteres
• millimetre


  1 x 10-3 meters
• micrometre (μm)


  1 x 10-6 meteres
• nanometer (nm)


  1 10-9 meters
• components of both plant and animal cells

  • nucleus
  • cytoplasm
  • cell membrane
  • mitochondria
  • ribosomes
• additional cell components found in plant cells

  • chloroplasts
  • permanent vacuole
  • cell wall
• function of the nucleus (other than storing genetic information)

  controls cellular activites
• structure of the cytoplasm

  fluid component of the cell, contains organelles, enzymes and dissolved ions and nutrients
• function of the cytoplasm

  site of cellular reactions e.g. first stage respiration, transport medium
• function of the cell membrane

  controls the entry and exit of materials in 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 animo acids in a specific order during translation for the synthesis of proteins
• function of the plant cell wall

  provides stength, prevents the cell bursting when water enters by osmosis
• contents of the permanent vacuole

  cell sap (a solution of salts<sugars and organic acids)
• function of the permanent vacuole

  supports the cell, maintaining its structure
• function of chloroplast 


  site of photosynthesis
• adaptations of the sperm cell in animals

  • haploid nucleus contains genetic information
  • tail helps them swim
  • mitochondria to provide energy for tail movement
  • acrosome contains enzymes that digest the egg cell membrane
• adaptations of nerve cells in animals

  • long axon allows electrical impulses to be transmitted all over the body from the central nervous system
  • dendrites from the cell body connect to receive impulses from other nerve cells, muscles and glands
  • myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell
• adaptations of muscle cells in animals

  • arrangement of protein filaments allows them to slide over each other to produce muscle contraction
  • mitochondria to provide energy for muscle contraction
  • merged cells in skeletal muscle allow muscle fiber contraction in unison
• adaptations of root hair cells in plants

  • large surface area to absorb nutrients and water from surrounding soil
  • thin walls that do not restrict water absorbsion
• adaptations of xylem cells in plants

  • no upper or lower margins between cells to provide a continuous route for water to flow
  • thick, woody walls strength their structure and prevent collapse
• adaptations of phloem cells in plants

  • sieve plates let dissolved amino acids and sugars to be transported up and down the stem
  • companion cells provide energy needed for active transport of substances along the phloem
• cell differentiation 


  the process by which cells become specialised
• importance of cell differentiation

  allows production of different tissues and organs that perform variou vital functions in the human body
• timing of cell differentiation in animals

  early in their life cycle
• timing of cell differentiation in plants

  throughout their entire life cycle
• purpose of cell division in mature animals

  repair and replacement of cells
• changes during cell differentiation

  becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell
• magnification


  the number of times bigger an image appears compared to the size of the real object
• cell division in mature animals

  repair and replacement of cells
• cell differentiation


  cells become specialised through acquisition of different sub-cellular structures to enable a specific function to be performed
• resolution

  the smallest distance between two objects that can be distinguished
• advantages of light microscopes

  • inexpensive
  • easy to use
  • portable
  • observe both dead and living specimens