UNT BIOL 4505 - Final Exam Study Guide (3 pages)

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Final Exam Study Guide

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Final Exam Study Guide


Covering the last lectures 33 - 38 for BIOL 4505 for the final exam.

Study Guide
University of North Texas
Biol 4505 - Comp Animal Physiology
Comp Animal Physiology Documents

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BIOL 4505 1st Edition Final Study Guide Lectures 33 38 Lecture 33 November 19 Animals that synthesize ammonia or urea as their primary nitrogenous end product are termed respectively ammonotelic or ureotelic Animals that synthesize mainly uric acid or urates are uricotelic Ammonotelism is the primitive condition and is seen in most water breathing aquatic animals Ammonia has the advantage of costing no extra ATP to produce It is toxic however Thus for an animal to be ammonotelic the animal must have a means to void ammonia reliably as fast as it is produced so that blood levels are kept low Aquatic animals void ammonia into the ambient water across their gills or general body surfaces Ureotelism is more costly than ammonotelism because producing urea has an ATP cost Urea is far less toxic than ammonia however Ureotelism has evolved principally in certain groups of vertebrates in which it usually serves one or more of three possible functions reducing the water requirement of routine nitrogen excretion e g terrestrial amphibians and mammals adjusting the blood osmotic pressure in advantageous ways e g elasmobranch fish and detoxification of waste nitrogen during periods when water stressed animals cease urine production Although uricotelism is even more costly per nitrogen atom than ureotelism uric acid and related compounds have the advantage that they are so poorly soluble that they are low in toxicity can be excreted in little water and can be accumulated in the body indefinitely Most groups of terrestrial animals including invertebrates e g insects and vertebrates e g birds lizards and snakes are uricotelic or produce predominantly other purines e g guanine or purine derivatives Lecture 34 November 21 Primary urine is formed by ultrafiltration or by active solute secretion During ultrafiltration fluid is driven by elevated hydrostatic pressure from the blood plasma into the kidney tubules through intervening epithelia and basement membranes that act as a filter

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