osmoregulation 3

Question 1

nitrogen excretion problem

-N excretion forms

Answer 1

Amino acids are essential for functions like protein building and regulating metabolism

• but ammonia produced during aa and protein breakdown is toxic and must be excreted
• nitrogen can be excreted as ammonia, uric acid, or urea

Question 2

ammonia excretors are found..

Answer 2

• in water

- mostly invertebrates and aquatic molluscs, as well as fishes

Question 3

uric acid found in..

Answer 3

terrestrial molluscs/arthropods, reptiles and birds

Question 4

urea excretors

Answer 4

some larval bony fish, mammals

NOTE all species can produce any of these nitrogenous compounds due to common genetics, some just have preffered methods

Question 5

ammonia excretion adv/dis

Answer 5

adv: directly released by breakdown of aa and proteins
dis: highly toxic, requires large volumes of water to store and excrete
- requires large amount of water to dilute its toxic affects, thus not suitable for terretrial animals

Question 6

ammonia solutions

Answer 6

1. repackaged as glutamate for storage and turned back to ammonia during excretion
2. excreted across epithelium, at skin or gills

Question 7

uric acid excretion

Answer 7

adv: few toxic effects
-can be excreted in small volume of water as anhydrous white crystals
dis: expensive to produce, requiring many (18) enzymes
(can be further broken down into urea

Question 8

urea excretion

Answer 8

urea produced via ornithine-urea cycle, starting with glutamine and requires 5 enzymes

• urea is made in liver and transported to blood, then excreted via kidneys or gills
  adv: slightly toxic, inexpensive, but moreso than uric acid, though less protein is lost (more effecient for protein recovery)
  dis: urea is a perturbing solute

Question 9

urea as anaosmolyte

Answer 9

• stored in fish to increase osmolarity, excreted when moving to less saline water to maintain osmolarity
• perturbing effects countered by methylamines

Question 10

kidney functions

Answer 10

multiple cell types form tubelike structures to aid

1. ion balance
2. osmotic balance
3. blood pressure
4. pH balance
5. excretion of metabolic wastes and toxins
6. hormone production

Question 11

kidney ion balance

Answer 11

Na+-extracellular fluid osmolarity

K+=muscle contractions Ca+, iron, trace metals

Question 12

kidney osmotic balance

Answer 12

kidneys determine volume f urine produced and urine excreted

-dehydration (low BP) vs fluid buildup (high BP, edema)

Question 13

kidney and blood pressure

Answer 13

• hyper/hypoe tension
• longterm changes in blood volume regulate bp
• volume of extracellular fluid under control of kidney

Question 14

kidney and pH balance

Answer 14

• maintains pH of extracell fluids by retaining or excreting H and HCO3
• important for proper enzymatic function and transport of solutes
• also pH balance tied to nitrogenous waste disposal as many pathways involve acid or base production

Question 15

kidney excretion of metabolic wastes and toxins

Answer 15

nitrogenous wastest and byproducts

-removal of water soluble toxins

Question 16

kidney hormone production

Answer 16

renin=controls BP (b vessel restriction, thirst via hypothalamus
erythropoeitin-regulates RBC synthesis

Question 17

nephron

Answer 17

• functional unit of kidney

- composed of renal tubule and vasculature

Question 18

renal tubule

Answer 18

-lined with transport epithelium, a single layer of cells of which various segments have specific transport functions

Question 19

vasculature

Answer 19

=glomerulus: ball of capillaries that are surrounded by the bownmans capsule of the renal tubules, where fluids are delivered to become primary urine
-capillary beds surrounding renal tubule are important for solute gradients, transport of fluid and solutes

Question 20

vasculature path along nephron

Answer 20

renal artery, afferent arteriole, glomerulus, efferent arteriole, cap network, venous system

Question 21

urine production processes

Answer 21

flitration: filtrate of blood formed at glomerulus
reabsorption: specific molecules in filtrate removed
secretion: specific molecules added to filtrate
excretion: urine excreted from the body

Question 22

filtration

Answer 22

liquid part of blood fills lumen of bowmans capsule
-water and small solutes gross
-blood cells and large solutes do not
glomerular cap are very porous
mesangial cells control bp and filtration within glomerulus
-filtrate flows from bowmans capsule into proximal tubule

Question 23

reabsorption

Answer 23

primary urine: initial filtrate filtered in bowmans capsule that is isosmotic to blood
-most water and salt in primary urine reabsorbed using transport proteins and energy
-rate of reabsorption limited by number of transporters=RENAL THRESHOLD
-conc of solute will overwhelm reabsorptive cap, and stay in tubule
each zone of nephron has transporters for specific solutes

Question 24

reabsorption of glucose

Answer 24

• reabsorbed by secondary active transport

- brought back to blood

Question 25

secretion

Answer 25

similar to reab, but in reverse - molecules removed from blood transported filtrate - includes K+, NH4+, H+, pharmaceuticals, and water-soluble vitamins - requires transport proteins and energy