B5: THE KIDNEYS + WATER AND NITROGEN BALANCE Flashcards
What is deamination?
breaking down amino acids for excretion
Where does deamination occur?
the liver
Why does deamination occur?
The digestion of proteins results in excess amino acids, which need to be excreted safely. In the liver these amino acids are deaminated to form
ammonia (ammonia is toxic and so it is immediately converted to urea for safe excretion)
What happens if a cell’s water potential is too high?
cell bursts (lysis)
What happens if a cell’s water potential is too low?
cell shrivels/shrinks (crenation)
How are excess water, excess ions and urea lost from the body?
-exhalation (involuntary)
-sweat (involuntary)
-urine (tightly controlled)
What is the role of the kidneys?
removal of urea, excess water and excess ions from the body as urine
What is filtration?
small molecules filtered from the blood into tubules in the kidney
What is selective reabsorption and what is and is not reabsorbed?
-the right amount of water and ions reabsorbed back into the blood depending on the body’s needs
-all glucose is reabsorbed
-no urea is reabsorbed
What is the role of ADH?
-changes permeability of kidney tubules
-controls amount of water reabsorbed (less ADH means kidney tubules are less permeable meaning less water is reabsorbed)
What happens when there’s too much water in blood?
-hypothalamus detects high water levels
-pituitary gland secretes less ADH
-less water reabsorbed by kidneys
-more water lost in urine
-blood water levels return to normal
What happens when there’s too little water in blood?
-hypothalamus detects low water levels
-pituitary gland secretes more ADH
-more water reabsorbed by kidneys
-less water lost in urine
-blood water levels return to normal
What would happen if your kidneys failed?
-waste substances would build up in your blood
-unable to control water conc in body
-unable to control ion levels in blood
-leads to damage to organs and organ systems and could lead to death
How do dialysis machines work?
-blood flows between partially permeable membranes (permeable to small molecules like ions and urea but not large molecules like proteins
-the dialysis fluid has the same conc of dissolved ions and glucose and water as healthy blood so only excess dissolved ions and glucose and water will be lost from the blood
-the dialysis fluid has no urea so all of the urea diffuses from the blood into the fluid
Advs of dialysis
-correct water and ion balance maintained
-less invasive than surgery
