Ch. 43 Water & Electrolyte Balance in Animals Flashcards
electrolyte
any compound that dissociates into ions when dissolved in water
- (in nutrition) any of the major ions necessary for normal cell function
- active ions
- dissipate quickly
(ie) Na, Cl, K & Ca
diffusion
the movement of substances from regions of higher concentration to regions of lower concentration, along their concentration gradients
SUBSTANCES
osmosis
the diffusion of water through a selectively permeable membrane from areas of higher water concentration to areas of lower water concentration
WATER
solutes
dissolved substances
- move down their concentration gradients across a selectively permeable membrane via diffusion
concentration gradient
difference across space (ie. membrane) in the concentration of a dissolved substance
osmolarity
the concentration of dissolved substances in a solution, measured in moles per liter
osmotic stress
occurs when the concentration of dissolved substances in a cell or tissue is abnormal
osmoregulation
process by which a living organism controls the concentration of water and salts in its body
(ie) living organisms control the concentration of water and salt in their bodies through osmoregulation
osmoconformer
an animal that does not actually regulate the osmolarity of its tissues but conforms to the osmolarity of the surrounding environment
- make inside same as outside (in between)
(ie) jellyfish make tissue concentration equal to water (isotonic)
osmoregulator
an animal that actively regulates osmolarity inside their bodies to achieve homeostasis
- required in marine vertebrates because their tissues are hypotonic to salt water
- lose water by osmosis
- gain electrolytes by diffusion
(ie) most marine fish by removing/gaining water or salt
hypotonic
solution inside the cells contains fewer solutes than the solution outside
- cells gain water through osmosis
- lose electrolytes by diffusion
ways land animals lose water
when they produce urine/sweat or pant
passive transport
diffusion of a substance across a membrane
- driven by diffusion along an electrochemical gradient
- does not requireATP
- type: facilitated difussion
- transport smaller substances
facilitated diffusion
passive movement of substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins
active transport
the movement of of ions or molecules across a membrane against an electrochemical gradient
- requires energy (ATP)
most important type of pump in animals
sodium-potassium pump (Na+/K+-ATPase)
secondary active transport
transport of an ion or miolecule in a defined direction that is often against its electrochemical gradient, in company with an ion or molecule being transported along its electrochemical gradient
- once a pump establishes a concentration gradient, secondary active transport can occur
cotransporter
a transmembrane protein that facilitates diffusion of an ion down its previously established electrochemical gradient and uses the energy of that process to transport some other substances, in the same or opposite direction, AGAINST its concentration gradient
- energy released when a solute is transported along its concentration gradient can be used by a cotransporter to transport another molecule against its concentration gradient
types of cotransporters
1) symporter
2) antiporter
sympoter
move solutes in the same direction
anitporter
move solutes in the same direction
rectal gland
a salt-secreting gland in the digestive system of sharks, skates, and rays
- ions can be concentrated only if they are actively transported against a concentration gradient
location of sodium-potassium pumps in shark
epithelial cells along the inner surface, or lumen, of the shark rectal gland
ouabain
a plant defense compound that is toxic to animals
- prevents Na+/K+-ATPase from functioning
Na+/K+-ATPase
essential for salt secretion
common molecular mechanism of salt extension
1) drink salt water, excrete NaCl via glands in their nostrils
2) marine fish excrete salt from their gills
3) mammals transport salt in their kidneys
cystic fibrosis transmembrane regulator (CFTR)
80% identical to the shark chloride channel
hypothesis for cause of cystic fibrosis
defect in a chloride channel
how do insects minimize water loss from the body surface?
1) tracheae connects to spiracles, which can open or close as needed to minimize water loss
2) exoskeleton/chitin + wax
tracheae
any of the small air-filled tubes that extend throughout the body and function in gas exchange
- an extensive system of tubes that functions as the insect’s respiratory organ
spiracle
a small openings that connects air-filled tracheae to the external environment, allowing for gas exchange
chitin
a tough polysaccharide, and layers of protein
- part of insect exoskeleton
- prevents water loss
cuticle
a protective coat secreted by the outermost layer of cells of an animal or a plant
- FCN: reduce evaporative water loss
ammonia (NH3)
- by-product of catabolic reactions
- a strong base
- readily gains a proton to form ammonium ion (NH4)
- high water solubility
- high water loss required for excretion of waste
- low energy cost (amount of ATP required)
- high toxicity
- groups where it is the primary waste: bony fishes, aquatic invertebrates
- method of synthesis: product of breakdown of amino acids & nucleic acids
- method of excretion: in urine, diffuse across gills
ammonium ion (NH4)
toxic to cells
ways to get rid of ammonia (NH3)
from least expensive (most water) to most expensive (least water):
1) fish dilute to a low concentration & excrete as watery urine
2) fresh-/saltwater fish diffuse across gills into water along a concentration gradient
3) humans convert to less toxic urea & excrete it in urine
4) birds, reptiles, and terrestrial arthopods convert to uric acid & excrete as dry paste