Question

Arteries, veins, capillaries, xylem vessels, and phloem tubes are all tubes used for transporting substances in mammals and flowering plants. Describe how each of these tubes is adapted for its particular function.

Answer 1

• Arteries, capillaries, and veins are specialized tubes composed of living cells that use water as a medium to transport substances. The concentration of substances transported through these vessels can be controlled and the rate of flow is regulated by vasoconstriction and vasodilation. Respiratory gases, glucose, amino acids, fatty acids, glycerol, vitamins, minerals, and hormones are transported through these tubes.
  
• Xylem vessels and phloem tubes are specialized tubes in vascular plants to transport substances like sucrose, amino acids, fatty acids, glycerol, vitamins, hormones (in the phloem) and minerals and water (in the xylem)using water as a medium. Xylem is composed of live cells while phloem is composed of living cells. The rate of flow in the xylem is controlled by external factors like temperature and humidity via the stomata. The negative pressure built by transpiration helps the flow of water inside xylem against gravity.
• The major function of all the tubes are to transport food molecules around the organism but plants, for instance, do not use the transport system to fight disease.