Paper 1

• What is the difference between eukaryotic and prokaryotic cells?

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

  Cells and possibly the nucleus
• What advantage does an electron microscope have over a light microscope?

  It allows us to see finer details of organelles
• How can you calculate the actual size of a cell using a microscope?

  By dividing the image size by the magnification
• What is the function of the cell membrane?

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

  Cellulose
• What is the role of mitochondria in a cell?

  It is where respiration takes place, releasing energy
• What do ribosomes do in a cell?

  They assemble or synthesize proteins
• What is the function of chloroplasts in plant cells?

  They contain chlorophyll and are where photosynthesis occurs
• 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 using aseptic technique?

  • Lift the lid of the dish towards a flame to move microbes away
  • Use sterilized equipment to place bacteria culture on agar
  • Tape the lid partially to allow air in
  • Incubate at 25°C
• How do you calculate the area of a circle in a bacterial culture experiment?

  Using the formula $A =$$\frac{\pi d^2}{4}$
• How many pairs of chromosomes do humans have?

  23 pairs
• What is the process of mitosis?

  It is the duplication of genetic material and division into two identical cells
• What type of cells are gametes and how many chromosomes do they have?

  They are haploid cells with 23 chromosomes
• What are stem cells?

  Cells that have not yet specialized
• Where are stem cells found in humans?

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

  To combat conditions like diabetes and paralysis
• What is diffusion?

  The movement of molecules from high to low concentration
• What is osmosis?

  The diffusion of water across a semi-permeable membrane
• How can the rate of diffusion be increased?

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

  1. Cut equal-sized potato cylinders and weigh them
  2. Place them in varying concentrations of sugar solution
  3. After a day, remove and weigh them again
  4. Calculate percentage change in mass
  5. Plot results against sugar concentration
• What is active transport?

  Movement of substances against a concentration gradient using energy
• What is a tissue?

  A group of similar cells working together
• What is an organ?

  A structure made of different tissues working together
• What is the function of bile?

  To neutralize stomach acid and emulsify fats
• What are enzymes?

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

  Enzymes only work with specific substrates that fit their active site
• What happens to an enzyme at high temperatures?

  It can denature and lose its function
• How do you determine the optimum temperature or pH for an enzyme?

  By plotting the time taken for a reaction against temperature or pH
• What color does iodine turn in the presence of starch?

  Black
• What color does Benedict's solution turn in the presence of sugars?

  Orange
• What color does Biuret's reagent turn in the presence of proteins?

  Purple
• What happens to ethanol when it comes into contact with lipids?

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

  To provide oxygen for respiration and remove carbon dioxide
• What is the pathway of air during breathing?

  From the trachea to bronchi, bronchioles, and alveoli
• What happens to oxygen in the alveoli?

  It diffuses into the 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: right atrium, right ventricle, left atrium, left ventricle