Week 6 (Exam 2): Water & Ion Balance, Renal System; Digestion Flashcards
when is a membrane permeable?
when it allows water or solutes to diffuse through
when is a membrane selectively permeable?
when it allows movement of some molecules but not others
when is a molecule impermeable?
when it blocks diffusion completely
what do aquaporins do?
move water through a membrane
osmosis
the process by which water moves from high concentrations to low concentrations
osmotic pressure
the tendency of water to move from one solution into another by osmosis
what can prevent water movement by osmosis?
hydrostatic pressure
what causes hydrostatic pressure
results from gravity or the stiffness of the container walls
what happens when osmotic pressure = hydrostatic pressure?
net movement of water stops and equilibrium is reached
osmoregulation
the regulation of osmotic pressure
-keeps internal fluids from becoming too concentrated (high osmotic pressure) or too dilute (low osmotic pressure)
high osmotic pressure means internal fluids are:
concentrated
low osmotic pressure means internal fluids are:
dilute
hypotonic
less concentrated
hypertonic
more concentrated
two ways of maintaining homeostasis of water and electrolytes
- by matching their internal osmotic pressure to their external environment
- by using energy to maintain an internal osmotic pressure that is different from the external environment
osmoregulators
an animal that maintains internal solute concentrations that differ from that of its environment
what osmotic problem do salt water osmoregulators have, and how do they solve it?
water loss and electrolyte gain; take in as much water as possible & eliminate excess electrolytes
what osmotic problems do freshwater osmoregulators have, and how do they solve them?
water gain & salt loss; they do not drink water, and they have gill Cl cells that pump Cl- ions into the body (freshwater fish) or take up electrolytes across the skin (amphibians)
what osmotic problem do terrestrial osmoregulators have and how do they solve it?
problem is water loss; they drink hypotonic water
what adaptation do marine birds have that allow them to get rid of salt?
nasal salt glands
excretion
the elimination of waste products & toxic compounds from the body
kidney
paired organs of the renal system that remove waste products & excess fluid; their action contributes to homeostasis
2 functions of excretory functions
- maintain water and electrolyte balance
- eliminate waste products
nitrogenous wastes
wastes in the form of ammonia, urea, and uric acid, which are toxic to organisms and are eliminated
what is ammonia excreted by?
aquatic animals
what is urea excreted by
mammals, amphibians, sharks, some bony fishes
what is urea produced by?
the liver
what is the scale of toxicity of nitrogenous wastes?
ammonia > urea > uric acid
what is the energy expense scale for nitrogenous wastes?
uric acid > urea > ammonia
what are the other forms of nitrogen excretion?
trimethylamine oxide, creatine, creatinine, and amino acids
what are the three functions of excretory organs?
filtration, reabsorption, and secretion
filtration function:
the separation of solids from fluids, as when circulatory pressure pushes fluid containing wastes through specialized filters into an extracellular space
secretion function:
in renal systems, an active process that eliminates substances that were not previously filtered from the blood
-specific but energetically expensive
- active process carried out by protein transporters in the cell membranes of cells lining the tubules
difference between filtration and reabsorption
filtration is used to isolate most wastes, but reabsorption is required to retain filtered compounds the body needs
how do animals with pressurized circulatory systems isolate waste from the blood?
by filtration
-circulatory pressure pushes fluid containing the wastes through filters in extracellular space
-filtered fluid contains waste products along with water, electrolytes, and other soltes
-filtrate drains into excretory tubules that connect to the outside
excretory tubules
a type of tube that drains waste products and connects to the outside of the body
reabsorption function
ions & solutes move from the filtrate into the blood
-cells lining the excretory tubule take up electrolytes, amino acids, vitamins, & simple sugars
-active or passive
2 functions of filtration, reabsorption, and secretion
- isolate wastes that are removed from the body
- allow the organism to adjust the amounts of water and electrolytes required to meet its osmoregulatory needs
protonephridia
excretory organs in flatworms that isolate waste from the body cavity
flatworm waste exchange process
cells w/ cilia move the fluid from the body cavity —> lumen of a tubule —> out of the organism through the excretory pore
do flatworms have a pressurized circulatory system?
no
segmented annelid worm waste excretion system:
filtrate —> metanephridium via a funnel-shaped opening surrounded by cilia —> series of collecting tubules —> out of the animal via an excretory pore
metanephridia
a pair of excretory organs in each body segment of annelid worms that filters the body fluid
insects & other terrestrial arthropod waste excretion system:
hemolymph —> body cavity —> Malpighian tubules —> hindgut —> fluid becomes increasingly acidic as uric acid builds up —> uric acid precipitates when it enters the rectum —> electrolytes reabsorbed —> uric acid & dried digestive wastes are eliminated
Malpighian tubules
one of the tubes in the main body cavity of insects & other terrestrial arthropods through which fluid passes & empties into the hindgut
is the vertebrate excretory system pressurized?
yes
vertebrate waste excretion system
blood from the heart —> paired renal arteries —> specialized capillary filters (glomerules) —> extracellular space surrounded by Bowman’s capsule —> renal tubules —> collecting ducts as uring —> ureter —> bladder
glomerulus
a tufted loop of porous capillaries in the vertebrate kidney that filters blood
renal tubules
a tube in the vertebrate kidney that processes the filtrate from the glomerulus to the collecting duct by reabsorption & secretion to produce uring
ureter
brings urine from the kidneys to the bladder
bladder
a hollow organ for the storage & elimination of urine
nephron
the functional unit of the kidney, consisting of the glomerulus, Bowman’s capsule, renal tubules, & collecting ducts
-perform 3 basic steps of excretion & osmoregulation
3 basic steps of excretion & osmoregulation
-filtration of blood passing through the glomerulus
-reabsorption of key electrolytes & solutes from the renal tubule & return of these substances to the bloodstream
-secretion of additional wastes & electrolytes via cells lining the renal tubules
interstitial fluid
the liquid surrounding the cells, tubules, & ducts of the kidneys
mammalian urine concentration steps:
generating concentrated interstitial fluid deep in the kidney —> filtrate passes through connecting ducts —> water moves out of collecting ducts & inter interstitial fluid by osmosis —> concentrated urine is now in the collecting ducts
kidney cortex
the outer layer
kidney medulla
the inner layer
mammalian kidney structure
-nephrons organized in wedge-shapes
-each nephron’s glomerulus is located in the renal cortex of the medulla
-glomerulus —> renal tubule —> dips into the medulla at the base of the wedge —> loops back to the cortex
Bowman’s capsule
a membranous sac that encases the glomerulus in the kidney
-capillary wall & Bowman’s capsule act as the filter
3 layers of the glomerulus filtration barrier
- endothelial cells
- basal lamina
- podocytes
podocytes
cells with footlike processes
3 major sections of the renal tubule
- the proximal convoluted tubule
- the loop of Henle
- the distal convoluted tubule
proximal convoluted tubule function
reabsorbes electrolytes and nutrients into the blood
-leaves water and urea
proximal convoluted tubule characteristics
-has microvilli
-permeable to water
loop of Henle function
-acts as a counter current multiplier to create a concentration gradient from the cortex to the medulla
-produces concentrated urine
how does the interstitial fluid of the cortex compare to the interstitial fluid of the medulla?
the cortex interstitial fluid is less concentrated than the medulla interstitial fluid
characteristics of the loop of Henle
-two limbs run in parallel but opposite directions
-thick part of ascending limb is impermeable to water but not electrolytes
-descending limb is permeable to water
what path does the filtrate take through the loop of Henle
fiiltrate —> descending limb —> ascending limb
counter current multiplier
a system that generates a concentration gradient but in opposite directions
distal convoluted tubule function
-secretes additional wastes
-K+ ions secreted from the blood into the tubule
-Na+ and Ca2+ ions are reabsorbed into the blood
-regulates pH
distal convoluted tubule characteristics
-located in the cortex
-filtrate entering is dilute
-filtrate leaving is dilute and contains urea
where is the final concentration of urine determined in the mammalian excretory system?
in the collective ducts
-under hormonal control
what controls the permeability of the collecting ducts?
ADH
when is ADH secreted?
when solute concentration is high
juxtaglomerular apparatus:
the structure formed by specialized cells of the efferent arterioles by leaving the glomerulus of each nephron, which secretes renin into the bloodstream
when is renin secreted?
when there is a drop in blood pressure
what does renin do?
converts angiotensinogen —> angiotensin I
what does angiotensin-converting enzyme (ACE) do?
converts angiotensis I —> angiotensin II (active form)
what does angiotensin II do?
causes arterioles to constrict
-stimulates release of aldosterone from the adrenal glands
aldosterone
stimulates distal convoluted tubules & collecting ducts to increase reabsorption of electrolytes & water into the blood
what are the three main classes of molecules for animal nutrition?
carbs, fats, and proteins
ATP
a molecule composed of the base adenin, the 5-carbon sugar ribose, and 3 phosphate groups
-provides energy in a form that all cells use to perform their work
catabolic
the set of chemical reactions that break down molecules into smaller units & produce ATP to meet the energy needs of the cell
anabolic
the set of chemical reactions that build molecules from smaller units utilizing an input of energy, usually in the form of ATP
-result in net energy storage
what does glycolysis do?
partially breaks down glucose without O2
-occurs in the cytoplasm
-1 molecule of glucose = 2 molecules of pyruvate, 2 molecules of ATP, & 2 molecules of NADH
-if oxygen is not present, pyruvate is converted by fermentation into lactic acid
anaerobic metabolism
energy metabolism in the absence of oxygen
aerobic metabolism
energy metabolism that uses O2 to oxidize organic compounds, generating ATP, found in Bacteria, Archaea, & the mitochondria of eukaryotic organisms
what are lipids broken down into?
glycerol and free fatty acids, which enter glycolysis or the citric acid cycle to yield ATP by oxidative phosphorylation
-or they can be stored as fat
what is the order that molecules are broken down?
carbs —> lipids —> protein
