Animal Structure and Function

Keywords: importance of size, scaling, collagen, ascorbate, hydroxyproline Reading = Ch. 40 in Campbell 6th edition

Objectives of the second half of the course Learn how animals, plants, and bacteria work. Understanding of relationship between organism function and physical principles Linkages between biochemistry/cell biology and whole organism function/ecology

In the second half will discuss the basic functional needs of organisms What is an animal – animal diversity circulation and gas exchange nutrition control of internal environment chemical signaling reproduction nervous systems sensory and motor mechanisms

This section introduces overall themes we will come back to: 1) Organisms have similar functional needs 2) Organisms must obey physical laws 3) Understanding how an organism works involves consideration of biochemistry, cell biology, physiology, ecology and evolution

1. Organisms have similar functional needs

bacterium

Sea anemone

Example: Size Does Matter (scaling effects)

What is it like for a mayfly to hatch out of a stream?

E. coli swimming in water -- is like a human swimming in hot asphalt

How do insects cling to vertical surfaces?

Example: scaling of skeletons Is it possible to have 12 foot tall humans? Have to consider scaling effects

Cross sectional area = πr 2 Mass increases to the third power of the linear dimension What happens if you double the linear dimension of an animal? tissue skeleton

To avoid weaker skeletons on large animals, the skeleton size increases disproportionately This Not This

The relationship between skeleton size and body mass for a variety of mammals

Body weight Skeleton weight 1:1 relationship actual mouse rat man elephant

A mouse-sized elephant would have a skeleton around 5 times heavier than a mouse Body weight Skeleton weight 1:1 relationship actual mouse rat man elephant

3) To understand how the functional needs of organisms are met, we need to integrate information about: Biochemistry Cell biology Physiology Evolution and Ecology

Collagen most abundant protein of mammals skin, bone, tendon, cartilage, and teeth Great tensile strength 3 helical polypeptides nearly 1000 residues long repeated (...glycine-x-x-glycine-x-x … ) amino acid sequence Often Glycine-proline-hydroxyproline

Structure of collagen

What happens when there is faulty collagen: Scurvy Jacques Cartier 1536 exploration of the Saint Lawrence River “ Some did lose all their strength, and could not stand on their feet.. Others also had all their skins spotted with spots of blood of a purple colour then did it ascend up to their ankles, knees, thighs, shoulders, arms, and necks. Their mouths became stinking, their gums so rotten, that all the flesh did fall off, even to the roots of the teeth, which did also almost all fall out. ”

Why did this happen? Primates and guinea pigs cannot synthesize ascorbate (Vitamin C) Ascorbate is vital for the enzymatic conversion of proline (pro) to hydroxyproline (hyp) In scurvy patients, collagen has an amino acid sequence of gly-X-pro rather than gly- X-hyp

Why does the improper amino acid sequence have deleterious effects? Collagen of scurvy patients has a low melting temperature Melting temp = 24° C for gly-X-pro in scurvy patients compared with 58° C for gly-X-hyp in normal people

The pompeii worm Alvinella pompejana

What about animals living at high temperatures? The pompeii worm lives on undersea volcanoes at temperatures reported to be as high as 80°C making it the hottest living metazoan (multicellular animal) known. This is well above the melting temperature for normal collagen -- efforts are underway to determine the biochemical basis for high temperature collagen in these worms.

Summary 1) Organisms have similar functional needs, but have developed diverse ways of meeting them 2) Organisms must obey physical laws 3) Understanding how an organism works involves consideration of biochemistry, cell biology, physiology, ecology and evolution