cell biology

• Cell Differentiation


  The process by which a cell changes to become specialised for its job
• Cells


  • They have different structures to suit their different functions
• Cell Differentiation


  1. Cells change

  2. Develop different subcellular structures

  3. Turn into different types

  4. Allows them to carry out specific functions
• Most differentiation occurs as an organism develops
• In most animal cells, the ability to differentiate is then lost at an early stage, after they become specialised
• Lots of plant cells don't ever lose this ability to differentiate
• The cells that differentiate in mature animals are mainly used for supporting and replacing cells, such as skin or blood cells
• Stem cells


  Undifferentiated cells
• SPERM CELLS


  • Specialised for reproduction
  • Have long tail and streamlined head to help swim to egg
  • Have lots of mitochondria to provide energy
  • Carry enzymes in head to digest through egg cell membrane
• NERVE CELLS


  • Specialised for rapid signalling
  • Long to cover more distance
  • Have branched connections at ends to connect to other nerve cells
• MUSCLE CELLS


  • Specialised for contraction
  • Long to have space to contract
  • Contain lots of mitochondria to generate energy for contraction
• ROOT HAIR CELLS


  • Specialised for absorbing water and minerals
  • Grow into long "hairs" that stick to the soil to increase surface area
• PHLOEM and XYLEM CELLS


  • Specialised for transporting substances
  • Form phloem and xylem tubes to transport food and water
  • Phloem cells have very few subcellular structures so stuff can flow through
  • Xylem cells are hollow in the centre
• The process by which cells become more specialised is called differentiation
• Differentiation occurs during embryonic development, but can also occur later on in life.
• Muscle cells are specialized for contraction and movement.
• Red blood cells are specialized for oxygen transport due to their hemoglobin content.
• Neurons are specialized cells that transmit nerve impulses.
• Cells that are not yet fully developed or have lost their ability to divide are called stem cells.
• The process by which cells become more specialised is called differentiation
• Chromosomes


  Contain genetic information
• Chromosomes


  • Coiled up length of DNA molecules
  • Each chromosome carries a large number of genes that control the development of different 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


  Series of stages that body cells in multicellular organisms go through to divide and 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 spread out in long strings

  2. Cell grows and increases subcellular structures

  3. DNA is duplicated 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

  3. Membranes form around each set of chromosomes to become the nuclei of the two new cells

  4. Cytoplasm and cell membrane divide
• The daughter cells contain exactly the same DNA as the parent cell
• Organisms


  Can be Prokaryotes or Eukaryotes
• All living things are made of cells
• Prokaryotic cells


  Smaller and simpler, e.g. bacteria
• Eukaryotic cells


  Complex, include plant and animal cells
• Eukaryotes


  Organisms made up of eukaryotic cells
• Prokaryote


  A single-celled organism with a prokaryotic cell
• Subcellular structures in animal cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Additional subcellular structures in plant cells

  • Rigid cell wall
  • Permanent vacuole
  • Chloroplasts
• Bacterial cells


  • Smaller than eukaryotic cells
  • Don't have a 'true' nucleus, instead have a single circular strand of DNA floating in the cytoplasm
  • May contain small rings of DNA called plasmids