Chapter 17: Ion and Water Balance

What is necessary for homeostasis

solute and water balance

Osmotic regulation

control of tissue osmotic pressure (driving force of water across cell membrane)

Ionic regulation

control of ion concentration which translates to control of ion balance in the ECF and ICF

Nitrogen excretion

excretion of ammonioa (end product of protein catabolism) which is toxic

How is nitrogen excreted

ammonia, urea, uric acid

Osmolarity

collection of solutes in solution

What do cells do in response to osmotic gradient

cells change volume

review tonicity

What forms the barrier between animal and environment

epithelial tissue

Paracellular transport

transport between epithelial cells

Transcellular transport

transport through epithelial cells

What organ helps regulate ion and water balance in vertebrates

kidneys

Extrarenal structures

structures that assist the kidney in ion and water balance

What regulates the movement of water across membranes

ionic concentrations and osmotic pressure

What are terrestrial animals challenged with

constant water loss

What is obtained from the diet for terrestrial animals

water and ions

What is osmoregulation in a marine fish like

gain of water and salt ions from food

excretion of salt ions from gills

osmotic water loss through gills and other parts of body surfaces

gain of water and salt ions from drinking seawater

excretion of salt ions and small amounts of water in scanty urine from kidneys

What is osmoregulation like in a freshwater fish

gain of water and ions from food

uptake of salt ions by gills

osmotic water gain through gills and other parts of body surface

excretion of salt ions and large amounts of water in dilute urine from the kidneys

Conformers

internal conditions similar to external conditions

Ionoconformer

little control over ionic concentration of ECF

Ionregulator

controls levels of most ions in ECF

Osmoconformer

ECF osmolarity similar to external environment

Osmoregulator

ECF levels controlled intrinsically

Stenohaline

ability to tolerate narrow range of salt concentrations

Euryhaline

ability to tolerate wide range of salt concentrations

Dietary water

obtained from plant and animal tissues

Why can't all water be obtained from dietary water

because feces has to have consistency to move through GI tract

Metabolic water

water generated as a bi-product of oxidative phosphorylation

Perturbing solutes

disrupts macromolecule function at normal concentratoins

What is important about the concentrations in perturbing solutes

they are different in ECF than in ICF

Compatible solutes

little effect on macromolecule function and can accumulate in high levels

Example of compatible solutes

glycerol, glucose, uncharged amino acids

Counteracting solutes

antagonistic relationship between two solutes

What weakens hydrophobic interactions

urea

What strengthens hydrophobic interactions

methylamines

What do bony fish use

ionregulators and osmoregulators

What happens for bony fish in saltwater

gain water, lose ions

What happens for bony fish in freshwater

lose water, gain ions

What structures help transfer water and ions between fish/environment

gills, gut, skin

Why do saltwater fish drink water

account for water loss and pump ions out of gills

How do freshwater fish uptake ions

through gills and gets rid of excess water through kidneys

Diadromoous

part of life in freshwater, part of life in seawater

Anadromous

adult life in seawater, migrate to freshwater for reproduction

Catadromous

adult life in freshwater, migrate to saltwater for reproduction

What comes with terrestriality

need to limit amount of water loss

cannot exchange ions with environment

cannot excrete metabolic waste into water

integument prevents water loss

different modalities of ammonia excretion

What does the integument do

limit water permeability with specialized epithelial tissue

What is the surface of the integument covered with

hydrophobic molecules such as mucous

What does mucus do for the integument

traps water between mucus and integument

What are keratinocytes

secrete keratin to form dense hydrophobic ECM

includes stratum corneum and cornification

What is the glycolipid layer

involved in integument and covers stratum corneum-most prominent in birds and mammals

What can preformed water be stored in for desert animals

water stored in food and plants can be obtained through diet

How is water consumed by desert animals

in excess

How much can camels drink

100kg (100liters) of water in 10 minutes

What is special about the integument of a desert animals

thicker stratum corneum

What is a problem for homeotherms

cutaneous water loss

How is water lost in homeotherms

evaporative cooling

What is special about desert antelopes

allow body temps to rise to 104*F

What causes respiratory water loss

can be reduced through countercurrent heat exchanger through enlarged nose

Ammoniotelism

excretion of ammonia as ammonia

What does ammoniotelism occur in

fish and amphibians

Ureotelism

excretion of ammonia as urea

What does ureotelism occur in

mammals

Uricotelism

excretion of ammonia as uric acid

What does uricotelism occur in

birds/reptiles

How is ammonia formed

in the liver by deamination of amino acids

What excretion causes the least expenditure of energy

ammonia

Which excretion is the most toxic

ammonia

What excretion is highly soluble in water

ammonia

What excretion is excreted the slowest

uric acid

What excretion is excreted the fastest

ammobnia

What excretion causes concentrated urine

urea

What excretion causes a thick paste like urine/semi-solid

uric acid

Which excretion causes dilute urine

ammonia

Which excretion is non toxic

uric acid

Which excretion is formed in the liver by orinthine cycle

urea

What excretion is formed in the liver by the ionosinic pathway

uric acid

Which excretion has the highest expenditure of energy

uric acid

How much water is needed to eliminate 1 gm of urea

50ml

How much water is needed to eliminate 1 gm of ammonia

500ml of water

How much water is needed to eliminate 1 gm of uric acid

10ml of water

What is ammonia used for

used in synthesis of amino acids and released in breakdown of amino acids

Why are amino acids broken down for

energy metabolism

What is deamination

removal of ammonia

How are some amino acids deaminated

directly

What do most amino acids ammonia transferred to

glutamate and then its deaminated; energetically more expensive

What gas can dissolve in water

NH#3

What is NH3 dependent on

partial pressure, solubility, and temp

What happens when NH3 dissolves

becomes NH4 and reaction is dependent on pH

What is most ammonia

in NH4 form

How does NH3 pass through membranes

passive diffusion

How does NH4 pass through

NH4/H+ antiport channels

T/F NH4 can pass through K+ channels

Na+/K+ ATPase

Ammoniotales do what

excrete NH3 and NH4 through epithelial tissues

What is most common in aquatic vertebrates

passive processes drive diffusion of ammonia because of the amount of NH3/NH4 in surrounding water

What can accumulate without toxic effects

uric acid

T/F uric acid can be converted to urea in some animals

True

Where is urea production high

protein rich diets

How much does it cost to transfer 1 mol of urea

5 moles of ATMp (2.5 ATP/nitrogen)

How much does it cost to transfer 1 mole of uric acid

1 mol urea to 7 mol ATP

(1.75 ATP/Nitrogen)

Why does urea accumulate

to maintain osmotic pressure

What increases 20 fold with exposed to high salinity

crab-eating frog urea