excretion

Question 1

nitrogenous waste

Answer 1

byproduct of protein/nucleic acid metabolism

Question 2

ammonia

Answer 2

• small, easy to synthesize, water soluble, toxic!
• released by
  
  • diffusion across gills–freshwater/marine
  • lots of dilute urine–freshwater

Question 3

urea`

Answer 3

• mammals and adult amphibians
• less toxic, conserves water
• excreted in urine

Question 4

uric acid

Answer 4

• terrestrial arthropiods, birds, reptiles
• reactions convert from ammonia
• non-toxic
• excreted as paste–insoluble
• requires energy
• get rid of nitrogen while losing little water

Question 5

production of nitrogenous waste relates to

Answer 5

• habitat
  
  • tadpoles/aquatic/bony fishes species excrete amonia (aquatic species)
  • mammals/amphibians/cartilaginous fishes excrete urea to lose less water
  • uric acid–birds/reptiles in dry habitats

Question 6

insect excretory systems adaptations

Answer 6

• high sa/v ration so water loss is a threat
• ability to close spiracles minimizes water loss from the tracheae
• wax (cuticle) layer on the insect minimizes evaporative water loss
  *

Question 7

open circulatory system

Answer 7

• hemolymph is running through body cavity
• malpighian tubules form filtrate from hemolymph
  
  • this is pre-urine that passes through the hind gut where it is processed and modified before excretion

Question 8

hindgut selectivity

Answer 8

insects that are osmotically stressed due to water/electrolyte shortage reabsorb electrolytes and filtrate from the hindgut back to the hemolymph, while uric acid remains in the hindgut

Question 9

insect and vertebrate excretion

Answer 9

1. water moves only by osmosis
   
   • osmotic gradients set up by active transport of ions
2. formation of filtrate is not selective– same molecules present in hemolymph are present in malpighian tubules
3. reabsorption is selective
   
   • protein pumps and channels select certain ions/molecules
   • waste molecules do not pass through hindgut membrane
4. reabsorption is regulated
   
   • membrane pumps and channels are activated/deactivated to respond to osmotic stress

Question 10

hindgut reabsorption

Answer 10

• H+ pump creates electrochemical gradient in hindgut so K+ can move back into cell–active
• Cl- is moved in via H+/Cl- symporter
• Na+/K+-ATPase pumps Na+ into hemolymph and Na+ flows out of hindgut from high to low
• Cl- and K+ move into hemolymph from high to low
  
  • H2O moves as well in response

Question 11

where does human excretion occur

Answer 11

kidney

Question 12

nephron

Answer 12

• basic functional unit of the kidney
• maintains water and electrolyte ballance

Question 13

Filtration

Answer 13

• renal corpuscle filters blood–size selective
  
  • no cells or proteins exit blood
• passive–blood pressure causes the force to push fluid through filter from closed circulatory system

Question 14

glomerus

Answer 14

cluster of capillaries that bring blud to the nephron from the renal artery

Question 15

bowman’s capsule

Answer 15

region of nephron that surrounds the glomerus

Question 16

renal corpuscle

Answer 16

glomerus and bowman’s capsule

Question 17

proximal tubule

Answer 17

filtrate leaves bowman’s capsule and enters proximal tubule to start reabsorption

Question 18

reapsorption active transport

Answer 18

• occurs in epithelial cells
• microvilli expand the SA and provides space for proteins to act as pumps
• exiting pre-urine isotonic to blood

Question 19

ion and water movement for reabsorption

Answer 19

1. na+/K+ atpase removes na+ from interior of cell and creates a gradient for entry of NA+ from lumen
2. apical membrane, na+ dependent cotransporters use this gradient to remove vitamins, cl-, and glucose selectively from the filtrate
3. solutes diffuse across basolateral membrane into interstitial fluid and blood vessels
4. water follows the movement of ions through aquaporin

• whole process selectively retrieves important nutrients

Question 20

loop of henle

Answer 20

• uses osmotic gradient

1. fluid down the descending limb loses water to interstitial fluid surrounding nephron, b/c descending limb is permeable to water
2. fluid inside nephron loses Na+ and Cl- passively along concentration gradients in thin ascending limb
3. additional Na+ and Cl- ions actively transported out of nephron in thick ascending limb

• exiting pre urine hypotonic to blood

Question 21

vasa recta

Answer 21

• network of blood vessels that runs along loop and joins with small veins in kidney
• water and salt that move out of the loop of henle diffuse into this

Question 22

distal tubule/collecting duct

Answer 22

• additional reabsorption occurs
• urine formation and reabsorption is regulated by hormones

Question 23

aldosterone

Answer 23

• activation of sodium-potassium pumps and reabbsorption of Na+ in distal tubule
• water follows by osmosis
• aldosterone saves sodium and water

Question 24

ADH

Answer 24

• saves water
• triggers insertion of aquaporins into apical membrane, making it more permeable to water and leads to reaabsorption
• increaes permeability to urea, which is reabsorbed
  
  • creates a concentration gradient favoring reabsorption of water from filtrate