B1

• What is the function of the nucleus in eukaryotic cells?

  It contains genetic material.
• Where do most chemical reactions occur in a cell?

  In the cytoplasm.
• What additional structures do plant cells have compared to animal cells?

  • Cell wall made of cellulose
  • Chloroplasts for photosynthesis
  • Permanent vacuole containing cell sap
• What is the role of ribosomes in a cell?

  They are where proteins are made.
• What is the function of mitochondria in cells?

  They are where most reactions for aerobic respiration take place.
• What is the function of the cell membrane?

  It controls what goes in and out of the cell.
• What is the role of chloroplasts in plant cells?

  They are where photosynthesis occurs.
• What does a permanent vacuole contain?

  Cell sap.
• What is a characteristic of prokaryotic cells?

  They don’t have a true nucleus.
• What is the difference in size between prokaryotic and eukaryotic cells?

  Prokaryotic cells are tiny compared to eukaryotic cells.
• What is the formula for magnification?

  Magnification = image size / real size.
• Why were electron microscopes invented later than light microscopes?

  They have a higher magnification and resolution.
• What is the significance of using standard form for small numbers?

  It simplifies the representation of very small numbers.
• What are the three main stages a cell goes through before dividing?

  1. Grows in size.
  2. Increases the amount of subcellular structures.
  3. Duplicates its DNA.
• What is mitosis?

  It is the stage of the cell cycle when the cell divides.
• What happens to the DNA during mitosis?

  The cell's DNA has been doubled.
• What is the outcome of mitosis?

  Two identical cells are formed.
• What is binary fission?

  It is the simple cell division process by which bacterial cells replicate.
• How often can binary fission occur under suitable conditions?

  Every 20 minutes.
• What is differentiation?

  It is the process by which a cell changes to become specialised for its job.
• What are five types of specialised cells and their functions?

  1. Sperm cell — reproduction.
  2. Nerve cell — rapid signalling.
  3. Xylem and phloem — transporting substances.
  4. Muscle cell — contraction.
  5. Root hair cell — absorbing water and minerals.
• What are stem cells?

  They are undifferentiated cells that can divide and differentiate into many types of cells.
• What can stem cells from adult bone marrow become?

  Many kinds of cells, e.g., blood cells.
• What can stem cells from a human embryo become?

  Any kind of human cell.
• What can stem cells from plant meristems become?

  Any kind of plant cell.
• What are the uses of stem cells in medicine?

  • Producing nerve cells to treat paralysis.
  • Creating insulin-producing cells to treat diabetes.
  • Therapeutic cloning to avoid rejection.
• What is a risk associated with using stem cells from the lab?

  They could get a virus, which could be transferred to the patient.
• How can stem cells be used in plants?

  • Produce clones of whole plants quickly and cheaply.
  • Grow more plants of a rare species.
  • Clone crops with desired features.
• What is diffusion?

  The spreading out of particles from an area of higher concentration to an area of lower concentration.
• What types of molecules can diffuse through cell membranes?

  Only very small molecules, e.g., oxygen and glucose.
• What is osmosis?

  The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
• What factors increase the rate of diffusion across a cell membrane?

  1. A high concentration gradient.
  2. A high temperature.
  3. A large surface area.
• What is active transport?

  The movement of a substance against the concentration gradient, requiring energy from respiration.
• What are two examples of active transport in cells?

  Absorbing mineral ions into root hair cells and glucose into the bloodstream from the gut.
• What are the four characteristics of exchange surfaces?

  1. A large surface area.
  2. A thin membrane.
  3. An efficient blood supply (in animals).
  4. Ventilation (in gas exchange in animals).
• What are four organs adapted for exchange and their functions?

  1. Leaves — gas exchange.
  2. Gills — gas exchange in fish.
  3. Small intestine — absorption of food molecules.
  4. Alveoli in lungs — gas exchange.
• How do leaves facilitate gas exchange?

  They have a flat shape and stomata that let gases in and out.
• How do gills facilitate gas exchange in fish?

  Oxygen and carbon dioxide move between water and blood through lamellae with lots of capillaries.
• How does the small intestine facilitate absorption?

  It has a single layer of surface cells covered in villi and a capillary network.
• How do alveoli facilitate gas exchange in the lungs?

  They have thin walls and a capillary network, allowing air to move in and out.