BBio 352 Test / April 29, 2015
NAME: ______[9 points for your name]_________
1. Would each of the following characteristics more likely be found in a ruminant, non-ruminant, both, or
neither? For lines A through H, check the appropriate column(s), if any. [1 point per line]
Ruminant?
Non-ruminant?
X
a. More likely to engage in coprophagy
X
b. Can survive on relatively low-nutrient food, like grass
X
c. Complex multi-chambered stomach
X
X
d. Has bacteria living in digestive tract
X
e. Large cecum and/or large large intestine relative to overall body size
f. Obtain maximal benefit from microbial digestion of cellulose (even in
X
the absence of coprophagy)
g. Very acidic stomach (pH < 5)
X
h. Significant nutrient absorption takes place in the stomach
X
2. What sort of calcium-related adjustments might go on in a young salmon leaving a freshwater environment
for a marine environment? Briefly explain. [3 points]
We said in class that seawater is high in calcium, potentially overloading marine creatures with calcium. It is
reasonable to imagine that a rise in blood calcium upon reaching the sea would increase calcitonin levels
and/or lower parathyroid hormone (PTH) levels, causing increased calcium deposition by osteoblasts,
decreased calcium uptake by the gills and intestines, and/or decreased calcium retention by the kidneys. 1
point off for a correct answer that did not mention the likely hormones involved.
3. Would each of the following characteristics most likely be found in a skeletal muscle optimized to pull its
load with high force, high speed, both, or neither? For lines A through H, check the appropriate column(s), if
any. [1 point per line]
High FORCE?
High SPEED?
X
a. High Fi compared to Fo
(X)
X
b. High rate of ATP use
c. Long out-lever (Lo) compared to in-lever (Li)
X
d. Long tendons
X
e. Parallel (NOT pennate) muscle fascicles
X
f. Small angle of insertion onto the bone (far from 90°; not close to
being perpendicular to the bone)
g. Striations, when viewed under the microscope
X
X
h. High mechanical advantage
X
4. Define the Krogh principle and provide 2 examples of it, briefly explaining WHY these examples illustrate the
principle. [3 points]
The Krogh Principle states that, for any given problem or adaptation, there is an organism (or small number of
organisms) in which it can be most conveniently studied. For example, we said that squid were used in 1940’sera studies of neurons because their giant axons could be probed with the primitive equipment available at the
time. Many other examples are possible.
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5. Assume that the top and bottom
parts of the figure at left portray
sections of 2 muscles that were
identical until stretched to 2
different lengths. Then imagine that
both muscles are electrically
stimulated for 1 minute while being
held at constant length, i.e., they are
contracting isometrically.
a. During the 1 minute of contraction, which muscle’s myosin will use more ATP? (Choices: top, bottom,
or both equal.) Briefly explain your choice. [3 points]
In the bottom muscle, there is more overlap between actin and myosin, so more of the myosin will be able
to go through its contractile cycle and use ATP.
b. During the 1 minute of contraction, which muscle’s release of calcium from the SR will use more ATP?
(Choices: top, bottom, or both equal.) Briefly explain your choice. [3 points]
Release of calcium from the SR is passive (calcium diffuses down its concentration gradient), so this process
doesn’t use any ATP in either muscle.
c. During the 1 minute of contraction, which muscle’s uptake of calcium back into the SR will use more
ATP? (Choices: top, bottom, or both equal.) Briefly explain your choice. [3 points]
Since calcium release will be the same in both muscles – it is independent of sarcomere length – ATPdependent calcium uptake will also be the same in both muscles, so both will use the same amount of ATP
for this purpose.
5. Of the following, which is the strongest evidence that repeated practice can change one’s brain? [2 pts.]
a. Taxi drivers tend to have larger posterior hippocampi than control subjects.
b. The size of the body of the hippocampus is similar for taxi drivers and control subjects.
c. The size of the posterior hippocampus correlates with number of years of taxi-driving.
d. Experienced taxidermists make more money than taxi drivers.
6. A given structure’s surface area, relative to its volume, can be maximized if the structure is [2 pts.]
a. very flat
b. highly branched
c. highly folded
d. perfectly (or almost perfectly) spherical
e. A, B, or C
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7. Is each of the following characteristics true of an endoskeleton, exoskeleton, hydrostatic skeleton, or more
than one? For lines A through F, check the appropriate column(s). [1.5 points per line]
HYDROSTATIC
EXOSKELETON ENDOSKELETON
SKELETON
a. resists deformation and/or transfers mechanical
X
X
X
force from one part of the body to another
b. muscles achieve movement by changing the angle
X
X
at a joint
c. muscles achieve movement by changing the volume
of the skeleton
d. includes “pin” joints, which do not scale up well and
X
thus limit animal size
e. usually a composite of inorganic materials
X
X
(minerals) and organic materials
f. chordates and echinoderms have this
X
X
8. You are studying a pennate muscle whose total force generated by the muscle (in the direction parallel to
the muscle’s fibers and fascicles) is 200 Newtons. Explain what information you would need to calculate the
force exerted in the direction of the muscle’s line of action (parallel to the tendon or apodeme), and how you
would do this calculation. Would the force in the muscle’s line of action be greater than, equal to, or less than
200 Newtons? [3 points]
 You need to know the angle of pennation, i.e., the angle that the muscle fibers make with the tendon or
apodeme.
 The force along the line of action will be equal to 200 Newtons times cos Θ where Θ is the angle of
pennation.
 The force along the line of action will be less than 200 Newtons, since cos Θ will be less than 1.
9. The graph at left (from wikibooks.org) concerns muscle
physiology. What is being graphed here, i.e., what are the Y axis
and X axis? (Choices: force, velocity, sarcomere length, ATP use,
power, # of motor units recruited, force per motor unit, etc.)
EXPLAIN YOUR REASONING. [3 points]
This could be interpreted as a graph of power (Y axis) versus
velocity (X axis), power (Y axis) versus force (X axis), force (Y axis)
versus sarcomere length (X axis), or ATP use (Y axis) versus
sarcomere length (X axis). In each of these cases, Y values are
greatest at intermediate values of X. Articulate reasoning is
needed for full credit.
10. Osteoblasts and osteoclasts help regulate blood calcium levels via negative feedback. Explain. Are they
best considered sensors, comparators, setpoints, or effectors of this negative feedback system? Why? [3 pts.]
If blood calcium gets too low, osteoclasts break down existing bone tissue and release calcium into the blood,
push blood calcium levels back up toward the setpoint. If blood calcium gets too high, osteoblasts use some of
that blood calcium to build new bone, pulling blood calcium levels back down toward the setpoint. In both
cases, this is called negative feedback because the response negates the change that stimulated it. Osteoblasts
and osteoclasts are effectors because they move the regulated variable back toward the setpoint.
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11. Is each of the following characteristics more true of skeletal muscle or smooth muscle? For lines A through
E, check the appropriate column. [1 point per line]
SKELETAL
SMOOTH
X
a. relatively slow to contract
X
b. relatively good endurance
c. a significant fraction of ATP production is glycolytic
X
d. found along most of the digestive tract
X
e. calcium promotes force production by binding to troponin, which then
X
moves tropomyosin out of the way
12. You are studying muscle mechanics in lab when your lab partner brusquely announces that he must leave
to watch the new Star Wars trailer, and cleans up your station before you are done. Before this interruption,
you have been able to determine Fi (150 Newtons) and Fo (300 Newtons) but not Li or Lo. Are you able to
calculate the mechanical advantage of this muscle? Explain. [3 points]
Mechanical advantage is equal to Li/Lo and is also equal to Fo/Fi. Since you know both Fo and Fi, you can
calculate the mechanical advantage as 300 Newtons divided by 150 Newtons, or 2 (unitless).
13. Add a line or curve to the plot at left to
show the typical relationship between
recruitment order and motor unit strength.
Briefly explain what your graph shows.
[3 points]
The exact shape of the curve is not crucial,
but it should show that force is highest in the
motor units that are recruited last.
14. Sperm whales have auditory skeletal structures called bullae that consist mostly of minerals, with very
little organic material such as collagen. What type of force is most commonly faced by the bullae? Briefly
explain your reasoning. [3 points]
Minerals are good for resisting compression, while organic materials like collagen are good for resisting
tension. Since the bullae are mostly minerals, they are probably subjected mostly to compression rather than
tension.
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L.C. Rome et al., PNAS 1996
15. The figure below reports cytoplasmic calcium levels for 3 types of muscle fibers present in the toadfish –
white (w) fibers, red (r) fibers, and swimbladder (s) fibers – after 1 action potential delivered by the motor
neurons. “Free calcium” is calcium concentration in the cytoplasm.
a. Based on these measurements, which muscle fiber type (swimbladder, white, or red) is likely to have the
SMALLEST fraction of its cellular space devoted to sarcoplasmic reticulum (SR)? Briefly defend your answer. [3
points]
More SR enables a faster uptake of calcium and thus a shorter period of elevated calcium levels (think of the
rattlesnake tailshaker muscles); conversely, less SR corresponds to a slower uptake of calcium and more
prolonged elevations of calcium. Since red muscle has the most prolonged period of high calcium levels, it
probably has the least cellular space devoted to SR.
b. Which fiber type would you predict to exert the LOWEST amount of force per unit of cross-sectional area?
Briefly explain. [3 points]
Swimbladder muscle has such a brief spike in calcium that it must have lots of cellular space devoted to SR, and
thus relatively less devoted to contractile proteins, so its force per cross-sectional area should be lowest.
16. Trypsin. What is it? What does it do? Where is it made? Where does it become active, and why? What is
its ultimate fate (excretion in feces? reabsorption by the gut?). Go! [3 points]
 Trypsin is an enzyme (0.5), specifically a protease that digests proteins (0.5).
 Trypsin is made by the acinar cells of the pancreas (0.5).
 Trypsin becomes activated in the duodenum (0.5) after being cleaved by another protease
(enterokinase, present in the brush border of the duodenum).
 Trypsin is digested by other proteases and its amino acids are reabsorbed in the small intestine (0.5).
17. Bile salts. What are they? Where are they made? What do they accomplish? Go! [3 points]
 Bile salts are amphipathic molecules (partly hydrophobic, partly hydrophilic).
 Bile salts are produced by the liver.
 Bile salt break huge globs of lipids up into smaller globs, thus facilitating transport through the gut and
giving lipase better access to more of the lipid molecules.
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18. What sorts of mouth, skull, and/or facial features would you expect to see in a mammalian carnivore such
as a tiger? Briefly explain at least 3 features, covering both the animal’s mammal-ness and its carnivore-ness.
[3 points]
 Expected mammalian features: palate separating nasal cavity and mouth cavity, allowing simultaneous
breathing and chewing; diverse specialized teeth that come together precisely (precise occlusion) and
are rarely replaced, to enable thorough chewing of food.
 Expected carnivore features: sharp teeth for subduing and slicing prey; prominent temporalis muscle;
jaw joint in line with upper row of teeth; high jaw stability but limited mobility (e.g., lateral movement).
19. Draw a simple diagram and annotate it (with words) to explain the general concept of secondary active
transport. [3 points]
 Nutrients such as glucose and amino acids are co-transported into cells with sodium, which is more
concentrated outside the cell.
 This co-transport process does not itself use ATP.
 This co-transport process depends on the sodium/potassium pump to keep intracellular sodium low (so
that diffusion of sodium into the cell is a “downhill” process).
20. In large quantities, alcohol can be toxic to cells. Explain why the liver is an organ frequently damaged in
people who drink too much alcohol. [3 points]
 The hepatic portal system brings all substances absorbed from the gut to the liver first before they go
into the general circulation, where they can be detoxified. [1 point off if the “liver first” point was not
made; 0.5 points off if the term “hepatic portal system/vein” was not used.]
 The liver thus helps protect the rest of the body from toxins like alcohol, but may itself be damaged by
high levels of these toxins.
21. What physiological process is represented by the
picture at left (from your textbook)? Where does it
occur, and what does it accomplish?
[3 points]



This is called endochondral ossification, in
which cartilage is replaced by bone.
Endochondral ossification occurs in the long
bones of the body, especially at the
epiphyseal plates.
Endochondral ossification promotes growth
of the long bones until the end of puberty.
Bonus question! Provide an example of a physiological trade-off. Use the form of a haiku (a 3-line poem,
generally non-rhyming, with 5 syllables on the 1st line, 7 syllables on the 2nd line, and 5 syllables on the 3rd
line). I may share some favorites with the class; if it is OK to share yours, please check here: ______.
 1 point for any attempt at this.
 2 points for a really good haiku (correct format syllable-wise, clearly captures a trade-off).
 3 points for true poetic brilliance.
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