Diffusion

-movement of substances from region of high[ ] to

low [ ]

-pertains to solutes

Osmosis

-movment of water from high to low [ ] across a selectively permeable memebrane

(phospholipid bilayer)

Osmotic Stress

-when [ ] of dissolved subtances in cell/tissue is abnormal

-not at the set point

osmoregulating

-control [ ] of water/salts

-respond to osmotic stress

isotonic

[ ] of solutes inside = outside

osmosis/diffusion have no effect

osmoconfomers

-conform to environmnet

-set point of water/salt [ ] closely match envior

Osmoregulators

-actively regulate osmolarity

-marine fish

hypotonic

-solution inside contains fewer solutes than out

Marine Fish

 -lose water and gain salt

-hypotonic (fewer solutes inside than out-lose H20)

-epithelium gills need to be in direct contact w/ seawater

-drink lots of water to get water-actively pumps out ions

*trade off btwn gas exchange&water/electrolyte balance

Freshwater fish

 -lose salt and gain water

-hypertonic (more inside than outside-lose electrolytes)

-epithelia cells gain H20 via osmosis

-excrete large amnts of water in urine and do not drink

*trade off btwn gas exchange and osmoregulation

hypertonic

more solutes inside than outside

osmotic stress for land animals

-due to evaporation

-epithelia cells = moist & air = dry therefore evaporation

lose water via urine/sweat

gain water via drinking, ingesting, metabolic H20

*trade off btwn breathing and water/electrolyte balance

Passive Transport

diffusion along electrochemical gradient

- no require of ATP

-facilitated diffusion

facilitated diffusion

-occurs through CHANNELS

-->proteins that form a hole and selectively diffuse ions

-occurs via carriers

-->transmembrane proteins bind to ion and allow conformational change to allow to cross membrane

Active transport

-ATP power movemtn against electrochem gradient

-takes place via membrane proteins

PUMPS

SECONDARY ACTIVE TRANSPORT 

pumps

-active transport/some passive

-change conformation when they bind ATP or are phosphorylated

-allows them to transport ions or moleucles against their [ ]

secondary active transport

-can occur once a pump has been established an electrochemical gradie

cotransporter

-can use energy released when ion is transported along the electrochem gradient of a secondary active transport

to transport a diff solute agains the electrochem gradien

symporter

-cotransporter that moves solutes in same direction

antiporter

-cotransporter that moves solutes in opposite directions

rectal glands

-secretes a [ ]ed salt solution

-requires active transport

Na+/K+ -ATPase

-protein in plasma membrane of epithelial cells that is actively pumping Na+ Cl- or both

ouabin

-molecule is toxic to animals b/c bind to Na+/K+ -ATPase and prevents it from functioning

-prevents homeostasis

4 steps in salt excretion

1-Na+/K+ - ATPase pumps Na+ out of epithelial across basolateral surface and into the extracellular flupid

-->pump creates electrochm gradient favoring diffusion of Na+ into the cell

2-Na+ Cl- and K+ all enter cell powered by the Na+ master gradient (via contransporter)

3-As Cl- builds up inside cell, chloride channel locate in apical mem allows Cl- to diffuse down its [ ] gradient into lumen of gland

4-Na+ diffuses into lume of gland through spaces btwn cells

How do freshwater fish osmoregulate?

they lose electrolytes therefore have to actively transport ions back into body across gill epithelium

chloride cells

-in MARINE fish

-specialized cells in gill epithelium

-move salts

-when sal water in these cells-->cells abundant and active

-excrete salt

freshwater version of classical chloride cell

-moves ions in opp direction

-import electrolytes

difference btwn the Na+/Cl-/K6 cotransporters in seawater/freshwater fish

seawater-cotransporter protein located on basolateral membrane of chloride cells

freshwater-cotransporter protein located on apical membrane

how do insects breath

is it problematic?

-thin layer of epithelium exposed to atmosphere

O2/CO2 diffuse

water constantly leaks via evaporation

(LARGE SA to a SMALL V)

trachea

-extensive system of tubes

-lined w/epithelia

-connects w/ atmosphere via spiracles

spiracles

pore in epithelium

-muscles open/close 

cuticle

-combination of chintin and protein

-includes layer of wax on its surface

-HIGHLY HYDROPHOBIC-thus highly IMPERMEABLE to water

ammonia

-strong base, readily gains proteon

toxic to cells b/c at HIHG [ ] raises pH of intracellular and extracellular fluids

Ammonia characteristics

-solubility in water = HIGH

-amnt water required for excretion of wastes = HIGH

-ATP required = LOW

Toxicity = HIGH

Urea characteristics

-solubility in water = HIGH

-amnt water required for excretion of wastes = Medium

-ATP required = HIGH

Toxicity = MEDIUM

Uric Acid Characteristics

-solubility in water = Low

-amnt water required for excretion of wastes = Low

-ATP required = HIGH

Toxicity = Low

groups that secrete ammonia

-fish, aquatic invertebrates

groups that secrete urea

mammals and sharks

groups that secrete uric acid

-birds, other reptile

most terrestrial insects

Synthesis of ammonia

-breakdown of a.a. and nucelic acids

synthesis of urea

-synthesized in liver, starting w/ amino gropu from a.a.

synthesis of uric acid

-synthesis starts w/a.a. and nucleic acids

methods of excretion for 

ammonia

urea

uric acid

-in urine and diffuses across gills for 

ammonia and urea

for uric acid-in feces

tradeoff for types of wastes

-energetic cost of excreting urea/uric acid and benefit of conserving water

-->ammonia requires large water loss but little energy

-->uric acid almost no water loss but very energy demanding

hemolymph

blood like fluid

-pumped by heat and transports electrolytes, nutrients, oxygen, and wastes products 

(in insects)

malpighian tubules

-excretory organ

-on their hindgut -posterior porteion of their digestive tract

-large SA and direct contact w/hemolymph

-empty into hindgut

-form filtrate from hemolype