Topic 1

• Describe differentiation 


  Process by which a cell changes to become specialised
• Animal cell differentiation 


  Lost at early stage
• Plants can differentiate… 


  throughout their whole life
• what are stem cells

  undifferent cells
• How are sperm cells specialises to perform their functions

  1. long tail
  2. lots of mitochondria
  3. streamlined head
  4. enzymes to digest through egg cell membrane
• How are nerve cells adapted

  1. Long to cover more distance
  2. branched connections to connect to other cells
• How are muscle cells adapted

  1. Lots of mitochondria to generate energy for contractions
  2. long So they have space to contract
• How are root hair cells specialised

  1. Large surface area for absorbing water and mineral ions
  2. hairs that stick into soil
• How are the phloem and xylem adapted

  1. the Cells long and joined end to end
  2. xylem is hollow in centre
  3. phloem has very few sub-cellular structures so more stuff can flow through
• What can embryonic stem cells turn into

  Any type of cell
• What can adult stem cells that are found in bone marrow turn into


  Replace faulty red blood cells
• Embryonic stem cells can…

  1. replace faulty cells
  2. insulin producing cells for diabetes
  3. nerve cells for paralysis
• Therapeutic cloning wont cause the body to reject embryo why?

  Embryo will have the same genetic information
• Risks of therapeutic cloning 


  Virus can be passed onto patient
• Stem cells in plants are found


  In the meristems
• what stage of the cell cycle comes before mitosis?

  growth and DNA replication
• before a cell divides it....?

  1. grows and increases the number of sub-cellular structures
  2. duplicates its DNA
• Describe the process of mitosis?

  1. chromosomes line up and cell fibres pull them apart and the two arms of each chromosome go to opposite ends
  2. membranes from on each side to divide the nucleus
  3. cytoplasm and cell membrane divide
  4. two identical daughter cells are produced (a set of chromosomes in each cell are identical)
• Describe the process of Binary fission?

  1. plasmids and circular DNA replicated
  2. The cell gets bigger and DNA moves to opposite poles
  3. cytoplasm begins splits to form new cell walls
  4. once it has split two daughter cells with one copy of the DNA and variable num. of plasmid copies
• how to calculate divisions of bacteria?$total time/mean time$

  total time/ mean time
• Define diffusion

  the spreading out of particles from an area from a higher concentration to a lower concentration
• How does a bigger concentration gradient effect diffusion?

  increases the rate of diffusion
• How does temperature affect diffusion ?

  increases it as the particles gain more energy
• how to grow bacteria in a lab?

  1. grown in culture medium with all the nutrients needed to grow
  2. use agar jelly or nutrient broth
  3. use inoculating loop or sterile dropping pipette to add microorganisms
• why are cultures of microorganism not kept above 25 degrees?

  to prevent harmful pathogens growing.
• how to prevent contamination when culturing microorganisms?

  1. seal petri dish
  2. place an inoculating loop in fire to sterilise
  3. sterilise surface working on
  4. sterilise petri dish and agar jelly
  5. store it upside down to prevent condensation falling onto jelly
• Describe how to carry out the experiment when testing different antibiotics/cleansers?

  1. soak paper discs in different or different concentrations of antibiotics and place them on agar jelly
  2. antibiotics will diffuse into agar jelly and the resistant strains of bacteria will stay
  3. the non resistant strains will die and create inhibition zone+
  4. leave for 48 hrs in 25 degrees
  5. use a control disc to show an accurate difference of effectiveness
  6. the one with the largest inhibition zone is the most effective
• Describe how to do the microscopy practical?

  1. prepare slide
  2. add slide to stage
  3. select the lowest power objective lens
  4. use a coarse knob to move stage and fine knob to focus image
  5. look into eyepiece
• The larger the surface area of the membrane the.......

  higher rate of diffusion
• what molecules do cell membranes let in?

  small like: oxygen, amino acids, glucose and water
• what do cell membranes not allow into cell?

  big molecules like: starch and proteins
• Define osmosis?


  The movement of water molecules across a partially permeable membrane from an area from a higher concentration to an area of a lower concentration
• Is osmosis active of passive?

  passive
• How do you carry out the practical osmosis?

  1. measure initial mass of potato and leave in solutions for 24 hrs
  2. take them out and pat till dry (otherwise excess will add more mass than actual)
  3. measure final mass
• Define active transport?


  The absorption of minerals from a dilute solution (lower concentration) to a higher concentration. against the concentration gradient.
• How are exchange surfaces adapted to maximise effectiveness:

  1. thin membrane to decrease distance of diffusion
  2. large surface area so lots of substances can diffuse at once
  3. exchange surfaces in animals have lots of blood vessels so lots can go in and out of blood quickly
  4. gas exchange surfaces in animals are often ventilated
• How does gas exchange happen in the lungs?

  1. transfer oxygen to blood and remove carbon dioxide
  2. has millions of alveoli where this takes place
• How are alveoli specialised to allow maximum diffusion?

  1. an enormous surface area
  2. a moist thin lining to dissolve gasses
  3. very thin walls
  4. large blood supply
• How are villi adapted to assist the small intestines in digesting food?

  • single layer of surface cells decreases the distance for diffusion
  • good blood supply for quick absorption
• How are leafs adapted to maximise diffusion?

  1. flattened shape increases surface area
  2. stomata allows oxygen, water vapour and carbon dioxide to diffuse in and out