Paper 1

• Give the function of each part of the cell

  1. Cell Membrane - Controls what substances go in and out of the cell
  2. Cytoplasm - Where most of the chemical reactions take place
  3. Nucleus - Controls the activities of the cell and contains genetic material

  
• Give one difference between prokaryotic and eukaryotic cells, other than their size

  Eukaryotic cells have mitochondria, prokaryotic cells do not
• How do magnification and resolution compare between electron and light microscope?

  Electron microscopes have a higher magnification and a higher resolution than light microscopes
• Explain how electron microscopy has increased understanding of sub cellular structures.

  More cell structures can be seen under an electron microscope and they can be seen with greater detail.
• The student wants to see the cells at a greater magnification. Describe the steps that she should take.

  She should select the x40 or x10 objective lens and use the adjustment knobs to bring the sample back into focus
• Explain how the structure of a sperm cell helps it to achieve its function.

  It has a tail to enable it to swim to the egg. It has lots of mitochondria to give it more energy. It has a streamlined head to help swimming. The head contains enzymes to help the sperm penetrate the egg.

  
• Describe what is happening to cell D

  The cytoplasm is dividing. The cell membrane is dividing.

  
• You can produce cloned plants from plant stem cells.

  Describe three benefits of producing cloned plants from stem cells.

  Plants can be produced quickly and cheaply. Rare species can be cloned to protect them from extinction. Large number of identical crop plants with features like disease resistance can be grown for farmers
• Describe the ethic issues surrounding the use of embryonic stem cells in medicine and research.

  Some people feel that embryonic stem cells from human embryos shouldn’t be used since each embryo is a potential human life. Some people may argue that there are other sources of stem cells that scientists could use, so using embryos to create stem cells is unjustified. Some people argue that many embryonic stem cells are sourced from unwanted embryos from fertility clinics which would probably be destroyed anyways.
• Define diffusion in terms of the particles of a gas.

  The spreading out of particles of a gas, resulting in net movement from an area of higher concentration to an area of lower concentration.
• Define Osmosis

  The movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration.
• Define Active transport

  The movement of a substance from a more dilute solution to a more concentrated solution against a concentration gradient
• Explain why plants are not able to rely on diffusion to absorb mineral ions from the soil.

  The concentration of minerals is higher inside the plant cells than in the soil so the minerals would move out of the plant cells by diffusion.