All of igcse bio

• What is the basic unit of life?

  Cells
• What does an electron microscope allow us to see?

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

  By dividing the image size by the magnification.
• What are the two main groups of cells?

  Eukaryotic cells and prokaryotic cells.
• What is a characteristic of eukaryotic cells?

  They have a nucleus containing DNA.
• Where is DNA found in prokaryotic cells?

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

  It keeps everything inside the cell and is semi-permeable.
• What do plant cells and most bacteria have that provides a rigid structure?

  A cell wall made of cellulose.
• What is the cytoplasm?

  The liquid that makes up the cell where most chemical reactions occur.
• Where does respiration take place in a cell?

  In the mitochondria.
• What is the role of ribosomes in a cell?

  They assemble or synthesize proteins.
• What do chloroplasts contain and what is their function?

  They contain chlorophyll and are where photosynthesis takes place.
• What is a permanent vacuole in plant cells used for?

  To store sap.
• What are stem cells?

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

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

  To combat conditions like diabetes and paralysis.
• What ethical considerations are associated with cloning?

  Cloning raises ethical arguments regarding its implications and consequences.
• What is diffusion?

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

  The diffusion of water across a semi-permeable membrane.
• How does the concentration gradient affect diffusion and osmosis?

  A greater difference in concentrations increases the rate of diffusion and osmosis.
• What factors can increase the rate of diffusion and osmosis?

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

  1. Cut equal size cylinders from a potato.
  2. Weigh them and place in test tubes with varying sugar concentrations.
  3. After a day, remove and dab excess water.
  4. Reweigh and calculate percentage change in mass.
  5. Plot percentages against sugar concentration.
• What is active transport?

  The movement of substances against a concentration gradient using energy.
• What is the function of tissues in the body?

  To organize similar cells together.
• How do organs function in an organ system?

  They work together to perform specific functions.
• What is the role of the stomach in digestion?

  It breaks down food using acid.
• What is the function of bile in digestion?

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

  Biological catalysts that speed up chemical reactions.
• How do enzymes work on substrates?

  They bind to specific substrates at their active site to form a complex.
• What happens to an enzyme when it denatures?

  The active site changes shape, preventing substrate binding.
• What is the optimum temperature for enzyme activity?

  The temperature at which the enzyme works best.
• What is the role of carbohydrates in a balanced diet?

  To provide energy.
• What are the consequences of vitamin C deficiency?

  It can lead to scurvy, affecting gums and hair.
• What is the function of calcium in the body?

  To maintain healthy bones.
• What is the role of fiber in the diet?

  To keep the digestive system working properly.
• What is the function of the respiratory system?

  To facilitate breathing and gas exchange.
• How does oxygen enter the blood during respiration?

  It diffuses from the alveoli into the blood vessels.
• What is the role of hemoglobin in red blood cells?

  To bind oxygen for transport.
• What happens to carbon dioxide produced during respiration?

  It diffuses into the lungs and is exhaled.
• What is the structure of the heart?

  It has four chambers: right atrium, right ventricle, left atrium, and left ventricle.