Cells and specialised cells

• Eukaryotes


  Organisms that have cells with a nucleus and membrane-bound organelles
• Prokaryotes


  Organisms that have cells without a nucleus or membrane-bound organelles
• Parts of a cell

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  • Contains genetic material that controls the activities of the cell
• Mitochondria


  • Where most of the chemical reactions for an organism's energy production take place
• Ribosomes


  • Involved in the translation of genetic material in the synthesis of proteins
• Plant cells have all the basic structures that animal cells have, plus a few additional structures
• Cell wall


  Made of cellulose, it surrounds the cell and strengthens it
• Vacuole


  Large sacs that contain a dilute solution of sugars and salts, which maintain the cell's water pressure to support the cell
• Chloroplasts


  Where photosynthesis occurs, which makes food for the plant
• Bacterial cells


  • Have no nucleus, but have circular DNA, ribosomes, cell membrane, and plasmid DNA
• Flagellum


  A long, hair-like structure that rotates to make the bacterial cell move
• Cells aren't all the same - they have different structures depending on the job they do
• Function of egg cells

  1. Carry female DNA

  2. Nourish the developing embryo in early stages
• Function of sperm cells

  1. Transport male DNA to the egg

  2. Provide energy for the long journey to the egg

  3. Contain enzymes to digest through the egg's membrane
• Ciliated epithelial cells


  • Line the surfaces of organs
  • Have cilia (hair-like structures) that beat to move substances in one direction along the surface of the tissue
• SPERM CELLS


  Specialised for REPRODUCTION
• Sperm cells


  • Have a long tail and a streamlined head to help it swim to the egg
  • Have a lot of mitochondria to provide the energy needed
  • Carry enzymes in its head to digest through the egg cell membrane
• NERVE CELLS


  Specialised for RAPID SIGNALLING
• Nerve cells


  • Are long to cover more distance
  • Have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• MUSCLE CELLS


  Specialised for CONTRACTION
• Muscle cells


  • Are long so that they have space to contract
  • Contain lots of mitochondria to generate the energy needed for contraction
• ROOT HAIR CELLS


  Specialised for absorbing WATER and MINERALS
• Root hair cells


  • Grow into long "hairs" that stick out into the soil, giving the plant a big surface area for absorbing water and minerals
• PHLOEM and XYLEM CELLS

  Specialised for TRANSPORTING SUBSTANCES
• Phloem and xylem cells

  • Form phloem and xylem tubes to transport substances such as food and water around plants
  • Xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them
• Plants transport food substances from the leaves to growing parts of the plant through phloem tubes