Cell biology

• What is differentiation?


  The process by which a cell changes to become specialised for its job
• How does differentiation work?

  As cells change they develop different subcellular structures and turn into different type of cells. This allows them to carry out specific functions

  
  

  Mostly occurs as an organism develops

  
  

  Animal cells lose ability to differentiate in early stages after being specialised whereas plants don't lose it
• What are the main reasons for cells that differentiate in mature animals?

  For repairing and replacing cells, like skin or blood cells
• What are stem cells ?

  Undifferentiated cells
• What are the 5 examples of specialised cells?

  Sperm cells, nerve cells, muscle cells, root hair cells, phloem and xylem cells
• How are sperm cells specialised?

  For REPRODUCTION

  long tail and streamline head to help it swim to the egg

  Lot of mitochondria in the cell to provide the energy needed

  Carries enzymes in its head to digest through the egg cell membrane
• How are nerve cells specialised?

  For RAPID SIGNALLING

  To carry electrical signals

  Long - cover more distance

  Branched connections at their ends to connect to other nerve cells and form a network throughout the body
• How muscle cells specialised ?

  FOR CONTRACTION

  Cells are long (space to contact) and contain lots of mitochondria for energy
• How are root hair cells specialised?

  For absorbing WATER and MINERALS

  Long - big surface area to absorb these from soils
• How are phloem and xylem cells specialised?

  For TRANSPORTING SUBSTANCES

  Form tubes which transport food and water around the plants

  The cells are joined end to end

  Xylem cells are Hollow

  Phloem cells have Very few subcellular structures so stuff can flow through them
• Chromosomes


  Contain genetic information
• Chromosomes


  • Coiled up lengths of DNA molecules
  • Each chromosome carries a large number of genes control development of characteristics
  • Body cells normally have two copies of each chromosome, one from the 'mother' and one from the 'father'
• The diagram shows the 23 pairs of chromosomes from a human cell
• Cell cycle


  A series of stages that body cells in multicellular organisms go through to produce new cells for growth, development and repair
• Mitosis


  The stage of the cell cycle when the cell divides
• Multicellular organisms use mitosis to grow or replace cells that have been damaged
• The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes
• Growth & DNA Replication

  1. DNA is all spread out in long strings

  2. Cell grows and increases subcellular structures such as mitochondria and ribosomes

  3. Cell duplicates its DNA, forming X-shaped chromosomes with identical 'arms'
• Mitosis

  1. Chromosomes line up at the centre of the cell

  2. Cell fibres pull the chromosomes apart, with the 'arms' going to opposite ends

  3. Membranes form around each set of chromosomes, becoming the nuclei of the two new cells (nucleus is divided)

  4. Cytoplasm and cell membrane divide, producing two new daughter cells
• The daughter cells contain exactly the same DNA as the parent cell
• Mitosis can seem tricky at first, but should be understood step-by-step