biology topic 1

• What is cell differentiation?


  process were unspecified cells become specialized
• Why do cells divide?


  growth, repair, reproduction
• explain cell division


  the cell begins to divide and the dna replicates itself to form two copies of each chromosome. One set of chromosome is pulled to each end of the dividing cell and the nucleus divides. The cell membrane divides into two identical daughter cells.
• what are the advantages of an electron microscope


  Greater magnification and resolution
• what are the advantages of a light microscope


  Inexpensive

  Easy to use

  Portable

  Can view living/dead specimens

  Can view larger organelles with staining, eg nucleus

  Used in schools, hospitals and research labs
• what are the disadvantages of a light microscope?


  Limited magnification and resolution
• what is cellular differentiation?


  when cells express specific genes that characterize a certain type of cell, that cell has been differentiated.
• what is binary fission?


  A form of asexual reproduction in which the parent divides into two approximately equal parts, only occurs in prokariyotic cells
• describe how a root hair cells in plants are adapted to their function


  large surface area: to absorb nutrients and water from surronding soil.

  thin walls: so it doesnt restrict water absorption
• what are the disadvantages of an electron microscope?


  expensive

  large so less portable

  only dead specimens can be observed
• explain what are the three stages of the cell cycle.


  Growth phase (chromosome doubling and subcellular structures increase)

  Mitosis

  Cytokinesis (division of cytoplasm and the cell membrane)
• how many chromosomes are found in the nucleus of human body cells


  46
• what are the two main things a bacterial cell needs to do before it divides


  grow and replace genetic material
• explain the steps of binary fission


  1) Genetic material is replicated

  2) The cell grows larger in size . Each set of geentic materisl begins to move to each oppsite ends of the cell

  3) The cell wall and memebrane begin to divide into seperate sets of dna

  4) The cell walls and cells membranes close around each set of dna

  5) The cell slips to form two identical duaghter cells
• where does binary fission happen?


  binary fission happens in prokaryotic cells
• what are the ethical issues for embryonic stem cells


  some people think embryos have the potential for human life
• explain the process when repairing cells with embroynic stem cells

  extract embryonic stemm cells from early embryos

  grow them

  stimulize them to grow into whatever cell we want.

  give them to the patient
• what do stem cells help with?


  stem cells help repair/replace fault damaged cells
• what is the difference between a plant stem cell and an embryonic stem cell


  plant stemm cells resist for the plants entire life, unlike embyronic stem cells, which disappear by the time there fully developed.
• where are the plant stem cells found?


  meritsems
• what can adult stem cells differentiate into.


  platlets, red blood cell, white blood cells
• What are embryonic stem cells?


  stem cells from embryos that can differentiate into any specialised cell
• label the sperm cell and there functions.


  flagellum- helps the sperm cell swim.

  midpiece- has alot of mitchondria, gives energy for the stem cell to move

  acrosome (headpiece)- contains genetic material for fertillisation.
• other then genetic information what is the function of the nucleus?


  control cellular activties.
• what is a plasmid?


  a small ring of dna
• what is a eukaryotic cell?


  a cell where the dna is embedded in a nucleus.
• what is a prokaryiotic cell?


  a cell where the dna isnt embedded in a nucleas.
• state the equation for maginfication.

  mag= size of image/ real size of image
• what are the differences between eukaryotic and prokaryotic cells


  prokayotic cells are much smaller then eukaryotic cells

  eukaryotic cells have the dna in a nucleus whilst prokaryotics dont
• how has a red blood cell adapted for its function


  thin outer membrane, diffusion happens quicker. no nucleus, can carry more haemoglobin. biconcave shape helps the cell to absorb more oxygen

  
  

  very felxible can move through narrow blood vessels

  hameglobin carrys pigment that carries oxygen
• What are stem cells?


  Stem cells are cells that can divide to produce many types of cell. There are two kinds of stem cell; embryonic and adult stem cells.
• explain the need for differentiation in a multicellular organism


  differntaited cells are important in a multiceullular organism because they are able to perfom a specilised function in the body
• what is the difference between differntiation in plants then in animals


  plant cells retain their ability to differntiate throughout there life, whereas animal cells, differeniate at an early stage making it restricted to repair and replacement in later life
• What are meristems?


  The areas in plants where growth occurs, because of unspecialised cells dividing by mitosis, differentiating and becoming specialised.

  
  

  meristems are regions of unspecilised cells in plants that are capable of cell division
• What is active transport?


  active transport is the movemement of substance from a high to low concentration against a concentration gradient,

  this requires energy
• what happens to a plant in water

  concentrated solution

  highly concentrated solution

  in pure water the cell wil expand as water is going in my osmosis

  in a concentrated solution the plant cell shrinks, it is becoming plasmofiyed.

  in a high concentrated solution the cell undergoes full plasomolysis and shrinks
• what is osmosis


  osmosis is the diffustion of water molecules from a region of high to low concentration through a partially permeable membrane.
• what factors affect the rate of diffusion


  greater difference in conc grafient the quicker rate

  the higher the temperature, the quicler the particles will move.

  the greator surface area to volume ration, faster rate

  distance
• define diffusion


  movement of molecules from high concentration to low concentration