Cell divisions

• What type of cell division occurs in eukaryotic cells ?

  mitosis or meiosis
• What type of cell division occurs in prokaryotic cells ?

  binary fission
• Haploid cell = one copy of each chromosome
• diploid = two copies of each chromosome
• example of haploid cell ?

  gametes
• what happens in G1?

  protein synthesis occurs and organelles replicate
• What happens at g1 checkpoint ?

  checks cell is correct size and no DNA has been damaged
• What happens in s phase ?

  DNA is replicated
• G2 = cell grows and energy stores are replenished
• G2 checkpoint = check for copying errors in DNA
• Cytokinesis = cytoplasm splits inot two genetically identical cells
• Prophase = chromatin condenses into visible chromosomes, centrioles move to opposite poles of nucleus and spindle fibres form between them. Nuclear envelope and nucleolous break down.
• Metaphase = chromosomes line up along equator of cell
• Telophase = nuclear envelope reforms around new sets of chromosomes, mitotic spindles break down and cytokinesis begins
• Anaphase = sister chromatids separate from each other and pulled towards the poles by microtubules
• Meiosis = reductional division - produces haploid gametes with half the number of chromosomes as parent cell
• Mitosis is important because it allows organisms to grow and repair damaged tissues
• Meiosis has two rounds of division with one round of DNA replication
• What is the result of meiosis ?

  4 genetically different haploid daughter cells
• Which processes cause variation in meiosis ?

  Crossing over and independant assortment
• Crossing Over = Exchange of genetic material between non-sister chromatids (chromosomes) during prophase I
• independant assortment = random position of paternal/maternal chromosomes when lining up at the equator of the cell in metaphase 1
• stem cells = undifferentiated cells
• Tolipotent cells = divide and produce any type of body cells, including the placenta. They occur for a limited time and can be found the embryo
• Pluripotent cells = can form most types of cells in the body, found in the embryo.
• Multipotent = form limited number of cells. E.g if found in bone marrow can form any type of blood cell
• Unipotent cell = form one type of specific cell
• Name 3 uses of stem cells ?

  repairing damaged tissues

  treatment of neurological conditions

  research into developmental biology
• What is an ethical issue surrounding the use of stem cells ?

  People consider embryos as alive beings, so when they are extracted and used for research of treatment it is argued they are murdering them
• Name 2 ways the erythrocytes are specilised ?

  Biconcave shape to increase surface area for more efficient diffusion

  No nucleus to increase the space to hold more haemoglobin to increase oxygen transport.
• Where are neutrophils made ?

  Bone marrow
• Name 3 adaptations of neutrophils ?

  Lobed nucleus to help surround and engulf the pathogen

  Flexible, surround the pathogen and fit through small capillaries

  Lysosomes filled with digestive enzymes to destroy pathogens
• Name 2 adaptations of the sperm cell ?

  Many mitochondria in the flagella to release energy for locomotion of the tail to move towards the egg faster

  Digestive enzymes in the acrosome of the head to digest the membrane of the egg cell so the sperm can penetrate it and fertilise the egg
• Where are palisade cells located ?


  In the mesophyll tissue layer of the leaves
• Name 3 adaptations of the palisade cell?

  Thin cell wall to reduce the diffusion distance of carbon dioxide

  Many chloroplasts to maximise light absorption and photosynthesis

  Rectangular, so can tighly pack together to maximise photosynthesis
• Name an adaptation of guard cells?

  Walls are uneven thickness on each side to allow it to open/close when turgid/flaccid.
• Give an example of squamous epithelial cells?


  lining of the lungs
• Name 1 adaptation of squamous epithelial cells ?

  Single layer of flattened cells to provide a short diffusion distance
• Goblet cells = produce mucus to trap dust and bacteria
• Ciliated epithelial cells = hairlike projections to sweep dust and debris away from airways or move eggs along the oviduct.