paper one

• What can be seen with a normal light microscope?

  Cells and possibly the nucleus
• What does an electron microscope allow us to see?

  Finer details of organelles
• How can we calculate the actual size of a cell?

  Image size divided by magnification
• What are the two main groups of cells?

  Eukaryotic and prokaryotic cells
• What do eukaryotic cells contain?

  A nucleus with DNA
• Where is DNA found in prokaryotic cells?

  In a ring called a plasmid
• What is the function of the cell membrane?

  Keeps everything inside the cell
• What is the role of the cytoplasm?

  Site of most chemical reactions
• Where does respiration take place in a cell?

  In the mitochondria
• What do ribosomes do?

  Assemble or synthesize proteins
• What do chloroplasts contain?

  Chlorophyll for photosynthesis
• What is stored in the permanent vacuole of plant cells?

  Sap
• How do bacteria multiply?

  By binary fission
• What is the procedure for culturing bacteria on agar?

  • Use aseptic technique to avoid contamination
  • Lift the lid of the dish towards a flame
  • Use sterilized equipment to place bacteria
  • Tape the lid partially to allow air in
  • Incubate at 25°C
• How do you calculate the area of a circle?

  Use $\pi r^2$ or $\frac{\pi d^2}{4}$
• How many pairs of chromosomes do humans have?

  23 pairs
• What type of cells are diploid?

  Cells with 23 pairs of chromosomes
• What type of cells are haploid?

  Gametes with 23 chromosomes
• What process do new cells undergo for growth and repair?

  Mitosis
• What is the process of mitosis?

  1. Genetic material duplicates
  2. Ribosomes and mitochondria double
  3. Nucleus breaks down
  4. Chromosomes pulled to opposite sides
  5. New nuclei form
  6. Two identical cells result
• What are stem cells?

  Cells that haven't specialized yet
• Where are stem cells found in humans?

  In embryos and bone marrow
• What can stem cells be used for?

  To combat conditions like diabetes
• What is diffusion?

  Movement from high to low concentration
• What is osmosis?

  Diffusion of water across a membrane
• How can the rate of diffusion be increased?

  By increasing concentration difference, temperature, or surface area
• What is the practical procedure for osmosis using potatoes?

  1. Cut equal size potato cylinders
  2. Weigh and place in sugar solutions
  3. After a day, weigh again
  4. Calculate percentage change in mass
  5. Plot against sugar concentration
  6. Determine concentration with no mass change
• What is active transport?

  Movement against a concentration gradient using energy
• What are the levels of organization in biology?

  • Cells form tissues
  • Tissues form organs
  • Organs form organ systems
• What is the function of bile?

  Neutralizes stomach acid and emulsifies fats
• What are enzymes?

  Biological catalysts that speed up reactions
• What is the lock and key principle in enzymes?

  Substrate fits into the enzyme's active site
• What happens to enzymes at high temperatures?

  They denature and lose their shape
• What is the optimum temperature for enzyme activity?

  The temperature at which the maximum rate occurs
• What is the practical procedure for testing enzyme activity with amylase?

  1. Mix amylase with starch
  2. Vary temperature or pH
  3. Remove drops every 10 seconds
  4. Test with iodine for starch presence
  5. Calculate time for starch breakdown
  6. Plot results to find optimum conditions
• What color does iodine turn in the presence of starch?

  From brown to black
• What color does Benedict's solution turn in the presence of sugars?

  From blue to orange
• What color does Biuret's reagent turn in the presence of proteins?

  From blue to purple
• What happens to cold ethanol in the presence of lipids?

  It turns cloudy
• What is the role of the respiratory system?

  To provide oxygen for respiration