7.3: Excreting Wastes Control and Regulation of Metabolic Wastes Waste products must be removed from the body to maintain life processes. Examples: Lungs remove CO 2. Large intestine removes toxic wastes. Liver Transforms toxins such as alcohol and heavy metals into soluble compounds. Transforms products of protein metabolism into metabolites. Kidneys remove waste, balance blood pH and maintain water balance.

What happens to excess Protein? Converted into carbohydrates Amino group must be removed from the body – Deamination

Deamination Occurs in the liver Byproduct is ammonia, which is water soluble and extremely toxic Ammonia combines with CO 2 to form urea, which is times less toxic Uric Acid is formed by the breakdown of nucleic acids Ammonia, Urea and Uric Acid are all removed by the Kidneys

Excretion in Unicellular Organisms Waste moves directly out of the cell. Excess water is regulated by contractile vacuoles that pump out excess water. Multicelluar organisms need specialized cells and structures to get rid of waste.

Removal of Metabolic Wastes WasteOrigin of wasteOrgan of excretion Ammonia Deamination of a.a.s by the liver Kidneys Urea Deamin. Of a.a.s by the liver Ammonia combined with CO2 kidneys Uric acid Product of breakdown of nucleic acids kidneys CO2 Waste product of cellular resp. Lungs Bile pigments Breakdown of hemoglobin Liver Lactic acid Product of anaerobic resp. Liver Solid waste By product of digestible and indigestible material Large intestine

Some Key Terms: Deamination  the breaking up of amino acids (removal of an amino group from an organic compound) –(NH3 = toxic and must be further processed) Urea  2 molecules of highly insoluble, toxic ammonia (NH3) mixed with one molecule of CO2 = soluble (made in liver) –(waste product of amino acid – NH3) Uric acid  waste product formed from the breakdown of nucleic acids Liver  responsible for removing/breaking down waste in the blood which is then sent to the kidneys to be filtered into the bladder Section 7.3 Questions, pp. 345, # 1-4

7.4: The Urinary SystemThe Urinary System

online.com/objects/AP2 504/AP2504.swf

Nephrons online.com/objects/AP2204 /AP2204.swf

Cortex: Bowman’s capsule, efferent and afferent arterioles are located here Medulla: Loop of Henle descends into this portion. *See kidney above. *Concentration of solute in the interstitial fluid increases from the cortex down to the medulla – this facilitates movement of water and solutes during reabsorption. Section 7.4, pp. 348, #1-4 mad.com/resource s/kidney.swf

7.5: Formation of Urine There is a lot going on here! The main point is that the nephron is able to expel unneeded or harmful substances and retain or reabsorb substances useful to the body. You would be rather dysfunctional and have to pee a lot if this didn’t happen! nephron For every 120 mL of fluid (amount filtered by kidneys each minute), 1 mL of urine is formed, 119 mL of fluid and solutes need to be reabsorbed. Urine is formed by: 1.filtration of the blood 2.reabsorption into the blood 3.secretion from the blood

Filtration Structures involved – glomerulus and Bowman’s capsule  pressure in capillary bed = 2 kPa, pressure in glomerulus = 8 kPa Blood moves from the afferent arteriole into the glomerulus (high pressure filter) Dissolved solutes such as H 2 O, NaCl & H+ pass into the Bowman’s capsule Large molecules such as protein, blood cells and platelets cannot pass through the glomerulus.

Reabsorption Structures: convoluted tubules, loop of henle Selective reabsorption occurs by both active and passive transport Carrier molecules move Na+ ions across cell membranes, negative ions (Cl-) follow Reabsorption occurs until the threshold level is reached. Excess salt remains in the nephron and is excreted with the urine.

Reabsorption On average, 600 mL of fluid in kidney/minute ~ 120 mL of that fluid is filtered into the nephrons 1 mL of urine is formed and 119 mL of fluid is reabsorbed by active and passive transport into the blood stream reabsorption occurs until the threshold level is reached (maximum amount of material that can be moved across the nephron)

Reabsorption Continued Glucose and amino acids attach to carrier molecules, which drives them out of the nephron and into the blood. Solutes actively transported out of the nephron create an osmotic gradient that draws water from it. A second osmotic force is created by proteins helps reabsorption. Proteins remain in the blood stream and draws water from interstitial fluid into the blood.

Reabsorption Continued As water is reabsorbed from the nephron, remaining solutes become more concentrated. Urea and uric acid diffuse from the nephron back into the blood but less is reabsorbed than was originally filtered. On average 600 ml of fluid flows through the kidneys every minute Approx. 120 ml of that fluid is filtered into the nephrons. 1 ml of urine is formed and 119ml of fluid is reabsorbed by active and passive transport into the blood stream.

Secretion Occurs in distal/proximal tubule Wastes from the blood move into the nephron Nitrogen-containing wastes, excess H+ and K+ secreted Cells loaded with mitochondria line the distal tubule Tubular secretion occurs by active transport therefore require mitochondria.

SiteProcess 1.glomerulus/Bow man’s capsule *FILTRATION  The movement of fluids from the blood into the Bowman's capsule of the nephron  blood plasma forced through walls of glomerulus into Bowman’s capsule by pressure  water and dissolved solutes (Na + Cl -, glucose, proteins, amino acids, H + ) move out of blood via fluid pressure into Bowman’s Capsule REABSORBTION takes place in the region – Loop of Henle 2. proximal tubule *REABSORBTIONREABSORBTION  The transfer of essential solutes and most water back into the blood stream.  passive: water by osmosis, K+  active: NaCl (Na+, Cl- follows), HCO3-, Glucose, Amino acids  Na + ions leave (active) … take –ve ions with them (attraction)  As solutes are drawn out of the nephron into the cells surrounding the nephron they create an osmotic gradient. Summary of Urine Formation

3. descending limb (permeable to water ) *REABSORBTION  water follows (passively) due to concentration gradient, ions actively pumped from nephron –  (as water leaves) salt becomes concentrated in filtrate at bottom of descending loop 4. ascending limb (permeable to salt ) *REABSORBTION  thin portion of ascending is permeable to salt – salt leaves with concentration grad. (passively)  Salt continues to leave in thick segment of loop (actively pumped) 5. distal tube *REABSORBTION  More substances transported out of the nephron into the blood (i.e. bicarbonate – for pH adjustment )  water follows – more leaves with the concentration grad.  Drugs, poisons can be removed from blood into filtrate here too.  The stuff left in the nephron that is not reabsorbed is the filtrate

*SECRETION  Formation of urine … purpose  to release any toxins and drugs that have not been filtered  Maintain the electrolyte balance of the body (if positive sodium ions are reabsorbed then positive ions like potassium must be secreted to keep the balance).  Acid-base balance (usually it is an acid being secreted, essentially a proton plus whatever it is attached to). Note : Acidic juices like cranberry cause our urine to be quite acidic which helps protect against UTIs and prevent kidney stones. Note: The bicarbonate ion is never secreted since it is used as a buffer in the maintenance of our blood pH.  Wastes removed from body – sent to bladder via 6. collecting duct What is a kidney stone? = hard mass developed from crystals that separate from the urine within the urinary tract. Do not normally form due to inhibitors in urine. Common type of stone contains calcium in combination with either oxalate or phosphate /Links/Animations/Flash/0 041-swf_micturition_re.swf

Section 7.5, pp. 352, # 2-6 Target Practice Quiz: Kidney