cell biology

• What are the two types of cells?

  • eukaryotic
  • prokaryotic
• Difference between prokaryotic and eukaryotic cells

  • prokaryotic cells are much smaller than eukaryotic cells
  • eukaryotic cells have a nucleus but prokaryotic cells don't
• how is genetic information stored in prokaryotic cells?

  • chromosomal DNA (single loop of DNA loose in the cytoplasm)
  • plasmid
• plasmids

  • small, circular loops of DNA found free in the cytoplasm and separate from the main DNA
  • Carry genes that provide genetic advantages eg. antibiotic resistance
• components of both plant and animal cells

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

  • chloroplasts
  • permanent vacuole
  • cell wall
• other than storing genetic information, what is the function of the nucleus?

  • controls cellular activities
• function of cytoplasm

  • where chemical reactions take place
• function of cell membrane

  controls the entry and exit of materials in and out of the cell
• function of mitochondria


  site of aerobic respiration
• function of ribosomes


  joins amino acids in a specific order during protein synthesis
• what is the plant cell wall made of?

  cellulose
• plant cell wall function

  • provides strength
  • prevents the cell bursting when water enters by osmosis
• what does the permanent vacuole contain?

  cell sap (solution of salts,sigars and organic acids)
• permanent vacuole function


  supports the cell
• function of chloroplasts


  site of photosynthesis
• how are sperm cells adapted to their function?

  nucleus - contains genetic info

  tail - movement

  mitochondria - provides energy for movement

  acrosome - contains enzymes that digest egg cell membrane
• how are nerve cells adapted to their function?

  • long axon - allows electrical impulses to be transmitted all over the body and the central nervous system
  • dendrites - connect to and 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
• how are muscle cells adapted to their function?

  • 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 to allow muscle fibre contraction in unison
• how are root hair cells adapted to their function?

  • large surface area to absorb nutrients and water from the surrounding soil
  • thin wall - no restriction of water absorption
• Describe how xylem cells are adapted to their function

  • no upper or lower margins between cells - provides a continuous route for water flow
  • thick,woody side walls strengthen their structure and prevent collapse
• phloem cells adaptations


  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
• cell differentiation


  process of cells becoming specialied
• purpose of cell division

  repair and replacement of cells
• advantages of light microscopes

  • cheap
  • easy to use
  • portable
  • observe both dead and living specimens
• disadvantage of light microscopes

  limited resolution
• advantages of electron microscope

  greater magnification and resolution
• disadvantages of electron microscope

  • expensive
  • less portable - large
  • requires training to use
  • only dead specimens can be observed
• magnification =


  size of image / real object size
• how do bacterial multiply?

  binary fission
• 2 ways in which bacteria can be grown

  • nutrient broth solution
  • colonies on an agar gel plate
• why must petri dishes and culture media be sterilised before use?

  to kill bacteria already present
• why must inoculating loops be sterilised by passing them through Bunsen burner flame?


  to kill bacteria present
• why must the petri dish lid be secured with adhesive tape and the whole dish stored upside down?

  stops bacteria in the air contaminating the culture

  the lid not fully sealed to prevent the growth of anaerobic bacteria

  upside down to prevent the condensation from forming and dripping down onto the colonies
• why must cultures be incubated at 25 degrees Celsius in school labs?

  harmful pathogens are less likely to grow at this temperature
• three main stages of the cell cycle

  • replication of DNA and synthesis of organelles
  • mitosis
  • division of cell
• why is mitosis important?

  • produces identical cells which all have the same genetic info
  • produces additional cells for growth + repair
• first stage of cell cycle

  longest stage - cells grow and increase in mass, replicate DNA and synthesis more organelles
• second stage of cell cycle

  each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides
• third stage of the cell cycle

  the cytoplasm and cell membrane divide - two identical daughter cells are produced