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
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•
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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
What happens if you double the
linear dimension of an animal?
tissue
skeleton
Cross sectional area = πr2
Mass increases to the third power of the linear dimension
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
Skeleton weight
elephant
1:1 relationship
man
actual
rat
mouse
Body weight
The
relationship
between
skeleton size
and body
mass for a
variety of
mammals
Skeleton weight
1:1 relationship
man
actual
rat
mouse
Body weight
A
mouse-sized
elephant
elephant
would have a
skeleton
around 5 times
heavier than a
mouse
3) To understand how the
functional needs of organisms
are met, we need to integrate
information about:
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•
Biochemistry
Cell biology
Physiology
Evolution and Ecology
Collagen
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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 glyX-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