B1.9 / 1.10

• How does active transport differ from diffusion?


  Active transport moves molecules against their concentration gradient, while diffusion moves them down their gradient
• What is diffusion?


  The process by which substances move down their concentration gradient
• Why is diffusion considered a passive process?


  Because it does not require any energy from the cell
• What does active transport require from the cell?


  Energy
• What type of proteins are involved in active transport?


  Special proteins that sit in the membrane
• Where does the energy for active transport come from?


  Cellular respiration
• What is the role of mitochondria in active transport?

  Mitochondria break down glucose to release energy
• What molecule stores energy for the cell?

  ATP
• What are specialized exchange surfaces?


  Parts of an organism over which they exchange substances with their environment
• What are the main specialized exchange surfaces in humans?

  The alveoli and the villi
• What is the function of alveoli in the lungs?


  To exchange oxygen and carbon dioxide between the air and the blood
• What role do villi play in the small intestine?


  They help absorb nutrients like glucose and amino acids
• What specialized exchange surface do plants have to absorb water and minerals?


  Root hair cells
• How do leaves function as specialized exchange surfaces in plants?


  They help absorb carbon dioxide from the air
• What are the common features of specialized exchange surfaces?


  • Large surface area
  • Very thin surfaces
  • Permeable to exchanged substances
  • Good blood supply (internal medium)
  • Good supply of external medium
• Why is a large surface area important for specialized exchange surfaces?


  It allows many molecules to diffuse across at the same time, increasing the rate of diffusion
• Why are specialized exchange surfaces usually very thin?


  To minimize the distance for substances to diffuse across
• What does it mean for exchange surfaces to be permeable?


  They allow substances to diffuse across rather than blocking them
• How does a good blood supply benefit exchange surfaces?

  It helps maintain a concentration gradient for efficient diffusion
• What is the role of the external medium in specialized exchange surfaces?

  It provides the necessary substances for exchange, like air for alveoli
• What are the five main features of specialized exchange surfaces?


  1. Large surface area
  2. Very thin surfaces
  3. Permeable to exchanged substances
  4. Good supply of blood (internal medium)
  5. Good supply of external medium (e.g., air)
• What is the purpose of breathing in relation to alveoli?


  To maintain a good supply of air for oxygen absorption
• How does a concentration gradient facilitate diffusion in exchange surfaces?


  A higher concentration of a substance on one side promotes its movement to the area of lower concentration
• What is the significance of having hundreds of millions of alveoli?


  It provides a huge area for oxygen absorption