Biology Paper 1

• what are the 2 types of cell


  eukaryotic - plant and animal

  
  

  prokaryotic - bacteria
• differences between eukaryotic and prokaryotic cells


  prokaryotic are smaller

  
  

  eukaryotic contain membrane bound organelles and a nucleus containing genetic material
• how is genetic information stored in a prokaryotic cell


  found freely in the cytoplasm as a single large loop of circular DNA or as plasmid DNA
• what are plasmids


  small circular loops of dna found free in the cytoplasm
• components that are in plant and animals cells


  nucleus

  
  

  cytoplasm

  
  

  cell membrane

  
  

  mitochondria

  
  

  ribosomes
• components that are only in plant cells


  chloroplasts

  
  

  permanent vacuole

  
  

  cell wall
• function of the nucleus

  stores genetic information and controls cellular activities
• structure of he cytoplasm

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

  where chemical reactions occur
• function of cell membrane

  controls the entry and exit of materials in and out of the cell

  
  

  holds cell together
• function of mitochondria


  where reactions for aerobic respiration occur
• functions of ribosomes


  where proteins are made
• what is the plant cell wall made of

  cellulose
• function of plant cell wall

  provides strength

  
  

  prevents cell bursting when water enters by osmosis
• what does the permanent vacuole contains

  cell sap
• function of permanent vacuole


  supports cell, maintaining its turgity
• function of chloroplasts


  site of photosynthesis
• how are sperm cells adapted for their function

  long tail + streamline head helps swim to egg

  
  

  lots of mitochondria in tail to provide energy for tail movement
• how are nerve cells adapted for their function

  long axon - electrical impulses can be transmitted all over the body

  
  

  myelin sheath - insulates axon + speeds up transmission of impulses

  
  

  dendrites - connect to and receive impulses from other nerve cells
• how are muscle cell adapted for their function

  long - have space to contract

  
  

  mitochondria - provide energy for muscle contraction
• how are root hair cells in plants adapted to their funtion

  large SA - to absorb nutrients and water from surrounding soil

  
  

  thin wall - can absorb more
• how are xylem cell adapted to their function

  no gaps between cells - provides continuous route for water to flow

  
  

  thick walls - strengthen their structure and prevent collapse
• how are phloem cells adapted to their function

  sieve plates - let dissolved amino acids + sugars be transported up and down stem

  
  

  few subcellular strictures - stuff can flow through them

  
  

  companion cells - provide energy for active transport of substances
• whats cell differentiation


  process were cells become specialised
• why is cell differentiation important

  allows production of different tissues and organs that perform various vital functions in the human body
• when do most animal cells differentiate

  in an early stage
• how long can plants retain ability to differentiate

  throughout their entire lifecycle
• purpose of cell division is mature animals

  repair + replacement of cells
• how does a cell become differentiated


  acquires subcelluluar structures when enable specific functions to be performed
• what is magnification


  number of time bigger an image appears compared to the size of the real object
• what is resolution

  smallest distance between 2 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 to be observed
• advantages of light microscope

  cheap

  easy to use

  potable

  can observe dead + live samples
• disadvantages of light microscope

  low magnification

  
  

  low resolution
• how does an electron microscope work

  uses a beam of electrons which are focused using magnets

  
  

  electrons hit fluorescent screen which emits visible light producing an image
• advantages of electron microscope

  high magnification

  high resolution
• how have electron microscopes helped scientists

  allowed small suubcellular structures to be observed in detail

  
  

  able to develop more accurate explanations about how cells structure relates to function
• disadvantages to electron microscope

  expensive

  
  

  large - less portable

  
  

  require training to use

  
  

  can only observe dead specimen
• how do bacteria multiply

  binary fission
• how often do bacteria multiply

  every 20 minutes if conditions are optimum