True or False:
Beacuse most metabolic wastes must be dissolved in water to be excreted from the body, the type and quantity of waste products may have a large impact on an animal's water balance.
True
In this regard, some of the most significant waste products are the nitrogenous breakdown products of proteins and nucleic acids. When proteins and nucleic acids are broken apart for energy or converted to carbs or fats, enzymes remove nitrogen in __. __ is very toxic, in part because its ion, __, interferes with __. Although some animals excrete __ directly, many species expend energy to convert it to less toxic compounds prior to excretion.
ammonia x2
ammonium
ammonia
Animals exrete nitrogenous wastes as __, __ or __. These differnet forms vary significantly in their toxicity and the energy costs of producing them.
ammonia
urea
uric acid
Because __ can be tolerated only at very low concentrations, animals that excrete nitrogenous wastes as __ need access to lots of water. Therefore, __ excretion is most common in aquatic species. Being highly soluble, __ moleucules easily pass through membranes and are readily lost by diffusion to teh surrounding water. In many invertebrates, __ release occurs across th whole body surface. In fishes, most of the __ is lost as NH4+ across the epithelium of the gills; the kidneys excrete only minor amts of nitrogenous waste.
ammonia x6
Although __excretion works welll in many aquatic species, it is much less suitable for land animals. __ is so toxic that it can be transported and excreted only in large volumes of very dilute solutions. As a result, most terrestrial animals and many marine species (those that tend to lose water to their environment by osmosis) simply do not have access to sufficient water to routinely excrete __.
ammonia x3
Instead, mammals, most adult amphibians, sharks, and some marine bony fishes and turtles mainly excrete a differnet nitrogenous waste, __. Produced in the vertebrate liver, __ is the product of a metabolic cycle that combines ammonia with carbon dioxide.
urea x2
Insects, land snails and many reptiles, including birds, excrete __ as their primary nitrogenous waste. __ is relatively nontoxic and does not readily dissolve in water. In therefore can be excreted as a semisolid paste with very little water loss. This is a great advantage for animals with little access to water, but there is a cost:
--- What is it? ---
uric acid x2
uric acid is even more energetically expensive to produce than urea, requiring considerable ATP for synthesis from ammonia
Many animals including humans, produce a small amt of __ as a product of purine breakdown. Diseases that disrupt this process reflect the problems that can arise when a metabolic product is insoluble .
uric acid
True or False:
In general , the kind of nitrogenous wastes excreted depend on an animal's evolutionary history and habitat, especially the availabilty of water.
true
Regardless of the tyype of nitrogenous waste, the amt produced by an animal is coupled to the energy budget. __, which use energy at high rates, eat more food and produce more nitrogenous waste than __. THe amount of nitrogenous waste is also linked to diet.
