science shorts

• What is the difference between eukaryotic and prokaryotic cells?

  Eukaryotic cells have a nucleus; prokaryotic do not
• What structures can be seen with a light microscope?

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

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

  Actual size = image size / magnification
• What is the function of the cell membrane?

  It keeps everything inside the cell
• What is the composition of the cell wall in plant cells?

  Made of cellulose
• What is the role of mitochondria in a cell?

  Where respiration takes place
• What do ribosomes do in a cell?

  Assemble proteins
• What is the function of chloroplasts in plant cells?

  Site of photosynthesis
• What is a permanent vacuole in plant cells used for?

  Storing sap
• How do bacteria multiply?

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

  • Use aseptic technique
  • Lift lid towards flame
  • Use sterilized equipment
  • Incubate at 25°C
• How do you calculate the area of a circle?

  Area = $\frac{\pi d^2}{4}$
• What is the diploid number of chromosomes in humans?

  46 chromosomes (23 pairs)
• What is the process of mitosis?

  Cell division producing two identical cells
• What are stem cells?

  Undifferentiated cells that can specialize
• Where are stem cells found in humans?

  In embryos and bone marrow
• How can stem cells be used in medicine?

  To treat conditions like diabetes and paralysis
• 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?

  • Cut equal size cylinders from potatoes
  • Weigh and place in sugar solutions
  • Measure change in mass after a day
  • Calculate percentage change in mass
• What is active transport?

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

  1. Cells
  2. Tissues
  3. Organs
  4. Organ systems
• What is the function of bile?

  Neutralizes stomach acid and emulsifies fats
• What are enzymes?

  Biological catalysts that speed up reactions
• What does amylase do?

  Breaks down starch into glucose
• 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 function
• What is the optimum temperature for enzyme activity?

  The temperature at which enzymes work best
• What are the food tests for nutrients?

  • Iodine: turns black for starch
  • Benedict's solution: turns orange for sugars
  • Biuret's reagent: turns purple for proteins
  • Ethanol: turns cloudy for lipids
• What is the role of the respiratory system?

  To provide oxygen for respiration
• What is the pathway of air in the respiratory system?

  Trachea, bronchi, bronchioles, alveoli
• How does oxygen enter the blood from the alveoli?

  By diffusion into blood vessels
• What is the function of hemoglobin?

  To transport oxygen in red blood cells
• What is the structure of the heart?

  It has four chambers: two atria and two ventricles
• What is the role of valves in the heart?

  To prevent backflow of blood
• What is the difference between arteries and veins?

  Arteries carry blood away; veins carry blood to the heart
• What is coronary heart disease (CHD)?

  Blockage of coronary arteries
• What are statins used for?

  To reduce cholesterol levels