5.3.3 Maintaining Water & Nitrogen Balance in the Body

• What happens to cells if they gain or lose too much water by osmosis?

  They do not function efficiently.
• How does water leave the body?

  Via the lungs during exhalation and through sweat.
• How are water, ions, and urea removed from the body?

  Through the kidneys in urine.
• Can the body control water, ion, or urea loss via the lungs or skin?

  No.
• What happens to excess amino acids from protein digestion?

  They are deaminated in the liver to form ammonia, which is toxic and is immediately converted to urea for safe excretion.
• What is the function of the kidneys in maintaining water balance?

  They filter the blood and selectively reabsorb useful substances like glucose, some ions, and water.
• What are the key processes in the kidneys?

  Filtration of blood and selective reabsorption of useful substances.
• What hormone controls the water level in the body?

  ADH.
• Where is ADH released from?

  The pituitary gland.
• What does ADH do in the kidneys?

  It increases the permeability of the kidney tubules, allowing more water to be reabsorbed back into the blood.
• How is the release of ADH controlled?

  By negative feedback.
• How can people with kidney failure be treated?

  By organ transplant or kidney dialysis.
• What is kidney dialysis?

  Kidney dialysis is a treatment that removes waste, excess ions, and water from the blood when the kidneys fail. It uses a dialysis machine to filter the blood, acting as an artificial kidney.