Kidneys/maintaining nitrogen and oxygen balance

• What results from the digestion of proteins in the diet?

  Excess amino acids
• Why must excess amino acids be excreted?

  They need to be excreted safely
• What process occurs in the liver involving amino acids?

  Amino acids are deaminated to form ammonia
• What is ammonia converted into for safe excretion?

  Urea
• Why is ammonia converted to urea?

  Ammonia is toxic and needs safe excretion
• What happens to food after it is eaten?

  It is digested by the body
• How are proteins broken down in the body?

  By protease enzymes into amino acids
• Where does the digestion of proteins occur?

  In the stomach and small intestines
• What happens to excess amino acids after digestion?

  They are transported to the liver
• What role does the liver play regarding amino acids?

  The liver controls amino acid concentration
• Can the body store proteins or amino acids?

  No, the body cannot store them
• What is the consequence of ammonia accumulation in the body?

  It is highly toxic and dangerous
• How is excess ammonia handled in the body?

  Converted into urea
• What happens to urea after it is formed in the liver?

  It is released into the bloodstream
• Where is urea transported after leaving the liver?

  To the kidneys for filtration
• What do the kidneys do with the blood?

  Filter it and remove waste
• What substances do the kidneys remove from the blood?

  Excess water, salt, and urea
• How is blood transported to the kidneys?

  Through the renal artery
• What pressure is the blood filtered at in the kidneys?

  High pressure
• What happens to useful materials during kidney filtration?

  They are selectively reabsorbed
• What is the function of the renal vein?

  Returns purified blood to circulation
• What is produced by the kidneys?

  Urine
• How do the kidneys help maintain water balance?

  By producing urine
• How is urine transported from the kidneys to the bladder?

  By the ureters
• What is the function of the bladder?

  Stores urine until expulsion
• What is the difference between ureters and urethra?

  Ureters carry urine; urethra expels it
• What does urine contain?

  Water, urea, and salts
• How is urea produced in the liver?

  From the breakdown of excess amino acids
• What is the main waste product removed in urine?

  Urea
• What is the role of nephrons in the kidneys?

  Cleaning the blood by removing waste
• What are the components of each nephron?

  A tubule responsible for filtration
• What do nephrons remove from the blood?

  Urea, excess water, and mineral ions
• Stage 1 - Filtration

  blood passes through the nephron inside the kidneys. There are many capillaries inside the kidney and the blood is under high pressure at the start of the nephron which aids the ultrafiltration of the blood. Small molecules are filtered out and pass into the nephron tubule. These molecules include urea water ions and glucose. However, large molecules such as blood proteins are too big to fit through the capillary wall and remain in the blood.
• What is the process called where the kidneys reabsorb essential molecules?

  Selective reabsorption
• Why do kidneys filter out small essential molecules from the blood?

  To reabsorb needed molecules and excrete waste
• What happens to molecules that are not needed by the body after filtration?

  They pass out in the urine
• What types of molecules do the kidneys selectively reabsorb?

  Only those needed by the body
• Which molecule is completely reabsorbed by the kidneys?

  Glucose
• How much water do the kidneys reabsorb?

  As much as the body needs
• What is the purpose of reabsorbing ions in the kidneys?

  To maintain a constant balance of mineral ions