Cell structure

• What are the two types of cells?

  Eukaryotic (plant and animal)

  prokaryotic(bacteria)
• What are the 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 don’t
• What is the prokaryotic cell wall composed of?

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

  Found free within the cytoplasm as:

  chromosomal DNA (single large loop of circular DNA)

  plasmid DNA
• What are plasmids?


  Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA

  carry genes that provide genetic advantages e.g. antibiotic resistance
• What is order of magnitude ?

  A power to the base 10 used to quantify and compare size
• What is a micrometer ?

  1 x 10^-6 meters
• What’s a nanometer 


  1 x 10^-9 meters
• List the components of both plant and animal cells

  Nucleus

  cytoplasm

  cell membrane

  mitochondria

  ribosomes
• List the components only found in plant cells

  Chloroplast

  permanent vacuole

  cell wall
• Function of the nucleus

  storing genetic information

  controls cellular activities
• 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

  transport medium
• 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 for the synthesis of proteins
• What’s a plant cell wall made of

  Cellulose
• Function of the plant cell wall

  Provides strength

  prevents the cell bursting when water enters by osmosis
• What does the permanent vacuole contain ?

  Cell sap ( a solution of salts, sugars , and organic acids)
• Function of the permanent vacuole

  Supports the cell, maintainimg its turgidity
• Function of chloroplasts 


  Site of photosynthesis
• Describe how sperm cells in animals are adapted for 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
• Describe how nerve cells in animals are adapted to their function

  • Long axon allows electrical impulses to be transmitted all over the body from the central nervous system
  • dendrites from the cell body connect to and relieve impulses from other nerve cells , muscles and glands
  • myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell
• Describe how muscl cells in animals are adapted to their function

  • Arrangemen of protein filaments allows them to slide over each other to produce muscle contractions
  • mitochondria to provide energy for muscle contractions
  • merged cells in skeletal muscle allows muscle fibre contraction in unison
• Describe how root hair cells in plants are adapted to their function

  • Large surface area to absorb nutrients and water from surrounding soil
  • thin walls that do not restrict water absorption
• Describe how xylem cells in plants are ada to their function

  • No upper or lower margins between cells to provide a continuous route for water to flow
  • thick,woody side walls strengthen their structure and prevent collapse
• Describe how phloem cells in plants are adapted to their function

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

  The process by which cells become specialised
• Why is cell differentiation important

  Allows production of different tissues and organs that perform various vital functions in the human body
• At What point in their life cycle do mist animal cells differentiate

  early in their life cycle
• For how long do plant cells retain their ablility to differentiate 


  Throughout their entire life cycle
• Whats the purpose of cells division in mature animals

  Repair and replacement of cells
• What change does a cell go through as it differentiates 


  Becomes specialised through acquisition of different sub cellular structure to enable a specific function to be performed by the cell
• Define magnification 


  The number of times bigger an image appears comapred to the size of the real object
• define resolution 


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

  Passes a beam of light through a specimen which travels through the eyepiece lens allowing the specimen the be observed
• What are the advantages of a light microscope

  • 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 magnet. The electrons hit a fluorescent screen which emits visible light, producing an image
• Advantages of an electron microscope

  Greater magnification and resolution