Exchanging substances

• What is the concept of surface area to volume ratio important for?


  It is important for exchanging substances.
• What type of organisms continuously carry out chemical reactions?

  Single-celled organisms.
• How does the surface area to volume ratio change as organisms get larger?


  The surface area to volume ratio decreases.
• Why do larger organisms have less surface area compared to their volume?


  Because as organisms grow, their volume increases faster than their surface area.
• What is the surface area to volume ratio like in bacteria?


  Bacteria have a high surface area to volume ratio.
• Why can bacteria rely on diffusion across their surface?


  Because they are small and have a high surface area to volume ratio.
• Why can't humans rely on diffusion for substance exchange?


  Because humans have a low surface area to volume ratio.
• What are examples of specialized exchange surfaces in humans?


  Lungs and intestines.
• How do specialized exchange surfaces increase the surface area to volume ratio?


  By providing extra surface area inside the body.
• What structures in the lungs increase surface area for gas exchange?

  Millions of alveoli.
• What is the purpose of the large surface area in the lungs?


  To absorb oxygen and get rid of CO₂.
• What structures in the intestines increase surface area for nutrient absorption?

  Villi.
• How does diffusion distance change as organisms get larger?


  The diffusion distance increases.
• What happens to diffusion in larger organisms?


  Diffusion will be slower.
• What do larger organisms often have to transport substances?


  Transport systems, such as a circulatory system.
• How do transport systems benefit larger organisms in terms of substance exchange?


  They transport substances to parts of the body that need them.
• What are specialised exchange surfaces?


  Parts of an organism over which they exchange substances with their environment
• What is the function of alveoli in the lungs?


  Gas exchange of oxygen and CO2 between air and blood
• How many alveoli are present in the lungs?


  Millions of alveoli
• Where are villi found?


  Inside the lining of the small intestine
• What is the primary function of villi?


  To absorb nutrients such as glucose and amino acids
• What type of organisms are plants classified as?


  Large multicellular organisms
• What do root hair cells absorb?


  Water and minerals from the soil
• What is the role of leaves in plants?

  To absorb CO2 and facilitate gas exchange
• What is a stoma?


  A pore that lets gases in and out of the plant
• What are the common features of specialised exchange surfaces?


  • Large surface area for diffusion
  • Thin membranes for short diffusion distance
  • Permeable to substances being exchanged
• Why is a large surface area important for exchange surfaces?


  It allows many molecules to diffuse across at one time and increases the rate of diffusion
• Why are exchange surfaces usually thin?


  To provide a short diffusion distance for substances to diffuse across
• What is the significance of permeability in exchange surfaces?


  They allow substances to diffuse across as needed
• How does a good blood supply benefit exchange surfaces in animals?

  It maintains a concentration gradient for efficient absorption
• What happens to glucose after it is absorbed into the blood?


  It is transported away, replaced by blood with lower glucose levels
• Why is a good supply of external medium important for exchange surfaces?


  It maintains the concentration gradient between air and blood in alveoli
• What are the five main features of specialised exchange surfaces?


  1. Large surface area
  2. Surfaces are permeable
  3. Surfaces are thin
  4. Good supply of blood (internal medium)
  5. Good supply of external medium
• What is the main topic of the study material?

  Exchanging Substances
• Why is the surface area to volume ratio important for single-celled organisms?


  It allows enough substances to pass across the outer surface to meet the organism's needs
• What are the four key features of exchange surfaces in single-celled organisms?


  1. A large surface area for diffusion
  2. A thin membrane for short diffusion distance
  3. An efficient blood supply in animals
  4. Ventilation for gas exchange in animals
• What is the first feature of exchange surfaces in single-celled organisms?


  A large surface area
• Why is a thin membrane important for exchange surfaces?


  It provides a short diffusion distance
• What is the third feature of exchange surfaces in animals?


  An efficient blood supply
• Why do multicellular organisms need exchange surfaces and transport systems?


  To meet the needs of every cell that is too far from the outer surface