IHS / IB Biology 2
25 Questions KEY!
1.
One can apply a two-tailed t-test to analyze data from an
experiment if the data are normally distributed (think: bellshaped curve) and if N is at least 10. (You won’t be
expected to calculate t, but you will need to use a t-value
and statistical tables to determine if two sets of data (e.g.
control and experimental) are significantly different.
2.
About 68% of all the data in a set fall within one standard
deviation, if the data are normally distributed. Remember,
you want to put the standard deviation of the sample (s)
button, not the total population’s standard deviation (sigma
button), on your calculator.
3.
Roles for
a. Sulfur: part of some amino acids
b. Calcium: muscle contraction, neurotransmitter
exocytosis in animals
c. Phosphorus: DNA, RNA, ATP
d. Iron: hemoglobin in animals
e. Sodium: Na/K pump, Na channels in excitable animal
cells
4.
A condensation reaction between two amino acids pulls
the H from the amino group of one a.a. and the OH from the
carboxyl group of the other a.a. and forms water, in the
process linking the amino acids with a covalent bond called
a peptide bond.
5.
Lactose free milk is produced by pre-treating milk
(containing lactose disaccharide) with lactase, the enzyme
that hydrolyzes lactose into glucose and galactose. People
who are lactose intolerant (whose bodies have stopped
producing lactase) can then consume the lactose free milk
without developing tummy troubles. The lactase to pretreat the milk is a product of biotechnology (the gene for
lactase was transferred to cells in culture).
6.
Four proteins’ names and jobs:
a. Hemoglobin – carries oxygen within blood cells
b. Amylase – digests starch, made by salivary glands and
pancreas
c. Silk – structural protein in spider webs
d. Collagen – structural protein in hair, nails
7.
Cells are so small because it maximizes their surface area
to volume ratio. The rates of exchange of food and wastes is
a function of a cell’s surface area, while the rates of food
consumption and waste production are a function of a cell’s
volume.
Examples of
a. Competitive inhibition (inhibitor resembles substrate and
competes for active site): Example - Ethanol is oxidized in
the body to acetaldehyde, which is in turn further oxidized
to acetic acid by aldehyde oxidase. Normally, the second
reaction is rapid so that acetaldehyde does not accumulate
in the body. A drug, disulfiram (Antabuse) inhibits the
aldehyde oxidase, which causes the accumulation of
acetaldehyde with subsequent unpleasant side effects
(nausea, vomiting). This drug is sometimes used to help
8.
people overcome a drinking habit.
b. Noncompetitive inhibition (inhibitor does not resemble
substrate; binds elsewhere on enzyme but in so doing still
affects shape of active site): Compounds containing heavy
metals such as lead, mercury, copper or silver are
poisonous. This is because ions of these metals are noncompetitive inhibitors for several enzymes. For instance,
silver ions react with –SH groups in the side groups of the
amino acid cysteine in a protein chain.
9.
Labeled prokaryote drawing should include a cell wall,
plasma membrane, cytoplasm, pili, flagella, ribosomes, and
a region of cytoplasm containing the prokaryote’s DNA (the
nucleoid). Prokaryotes tend to be spherical, rod-shaped, or
spiral-shaped, so that could be included.
10. In
interphase, there are three different sets of activities in
cells. In the first part of interphase, G-1, cells are
synthesizing proteins and carrying out all their moment-tomoment metabolic reactions. In the middle of interphase, S,
cells replicate their DNA. That’s all they do! In the third
portion of interphase, G-2, which is typically fairly short,
cells resume protein synthesis, especially for proteins that
would be needed in cell division (like tubulin, which is part
of microtubules). Also during interphase the cells’
organelles must be roughly doubled. Mitochondria and
chloroplasts divide on their own during interphase.
11. Chlorophyll
molecules’ structure enables them to
absorb red and blue, primarily. They do not absorb green.
Green is reflected, giving plants their green color. We
would be aware of these differences in absorption by
inspecting the absorption spectrum of chlorophyll.
Memorize: wavelength of blue light about 400 nm,
wavelength of green light about 550 nm, wavelength of red
light about 700 nm.
12. A
nucleosome is a bead of 8 histone proteins on which
DNA is “wound.” Nucleosomes help “package” a large
amount of DNA into a tiny space, the nucleus (eukaryotic
cells). There is a ninth kind of histone found between
nucleosomes. While a gene is being transcribed, it is
temporarily loosened or released from its nucleosomes.
13. Transfer
RNA (tRNA) molecules have a
three-dimensional, “L” shape. Although
fundamentally they are a string of
nucleotides, they coil up and internally
base pair. The shape of a tRNA is
recognized by a tRNA-activating enzyme,
which puts amino acids on the top of their corresponding
tRNA molecules. The sequence CCA appears at the 3’ end,
the end at which the appropriate amino acid is attached to
the ribose of the last adenine – in red on picture). The loop
with the anticodon is at the opposite end of the L shape,
green in picture. tRNAs are re-used.
14. Cloning
for therapeutic purposes (creating cells to
replace a patient’s diseased cells) involves isolating a
nucleus from one of the patient’s differentiated cells (like a
skin cell), putting it into an egg cell from which the nucleus
has been removed, and getting the egg to start dividing,
often with a mild electrical shock. As the egg-and-diploid
nucleus “embryo” divides, it therefore produces a bank of
cells that could be chemically treated to differentiate in a
certain way to cause them to differentiate into the cell type
needed (heart, brain, etc.), and then given to the patient.
15. An
energy pyramid is pyramid-shaped because it is made
by stacking the energy available to successive trophic levels
(TL), with producers on the bottom and carnivores at the
top. Since only 10% of the energy available to one TL
becomes available to the next TL, the stack sharply narrows.
Photosynthesis captures only a fraction of the sun’s energy;
respiration is less than 50% efficient; and, energy is
expended to catch and eat prey. Units of an energy pyramid
typically = kJ or kCal per m2 per year.
16. How
global temperature rise is impacting the arctic
(way more than just four consequences!)
a. It is causing ice melt, which deprives animals like polar
bears of places to hunt/rest
b. It is causing permafrost to thaw, which increases
decomposition rate of previously-frozen detritus, thereby
releasing more CO2 to the atmosphere
c. By melting ice, it is causing sea levels to rise, displacing
people and wildlife
d. Some temperate zone species like grizzlies are expanding
their ranges northward
17. An
S shaped population growth curve has 3 phases:
exponential or steep initial phase, transitional phase, and
leveling off at K or carrying capacity, the plateau phase.
18. An
apical meristem is perpetually embryonic (ie mitotic)
tissue at the tips of roots and shoots, increasing their
length, while a lateral meristem is perpetually embryonic
tissue around the sides of a shoot or root, increasing their
girth. The vascular cambium is a lateral meristem.
19. Abscissic
acid or ABA promotes the closure of a plant’s
stomata. It is synthesized when a plant is experiencing
drought stress.
20. Phytochrome
comes in two shapes, Pr and Pfr. Pr is
synthesized from scratch. In sunlight (which includes red
light), Pr is converted to Pfr. In darkness, Pfr slowly reverts
to Pr. Pfr promotes flowering in long-day (short night)
plants, and inhibits flowering in short-day (long night)
plants.
21. Cells’
jobs and locations:
a. Blastocyst cells (aka blastomeres) are undifferentiated
(unspecialized) cells of an embryo. As development
proceeds, blastocyst cells divide and divide – their
progency become differentiated as muscle cells, brain
cells, etc.
b. Leydig cells (aka interstitial cells) produce and secrete
testosterone. They are located in the spaces between
seminiferous tubules in the testes. (“Interstices” are
crevices.) Leydig cells respond to commands from LH,
secreted by the pituitary.
c. Polar bodies are haploid cells produced during meiosis of
a primary oocyte. Their job is to remove excess
chromosomes so that the final egg cell (in humans) has
23, unreplicated chromosomes. They are found in the
ovary.
d. Sertoli cells are the cells that nourish developing
spermatogonia all the way to spermatozoans. They are
stimulated by FSH, secreted by the pituitary.
22. Crossbridges
are formed by the heads of myosin
molecules, which as a group constitute a thick filament in
the myofibril of a muscle fiber. They attach to exposed
actin molecules (on thin filaments) when calcium presence
has removed a blocking molecule away from the thin
filaments. (When a nerve impulse tells a muscle fiber to
contract, calcium is released within the fiber.) By spending
ATP to detach and re-set the crossbridges, which bend like
rowing boat oars, thick filaments slide between thin
filaments and contraction (shortening) of the fibers occurs.
23. In
contralateral processing of visual stimuli, the “wiring”
from the retinas of both eyes to the occipital lobes is such
that light received by the left visual field is projected to the
right visual cortex, while the light received by the right
visual field is projected to the left visual cortex. (It is NOT
true that light received by the left eye goes to the right
visual cortex and vice versa. Both eyes’ neural impulses go
to both the left and right visual cortices.)
24. One
effect of THC on synapses in the brain is to inhibit
neurons that were inhibiting VTA neurons. As a result,
there is more dopamine in the nucleus accumbens (the
pleasure or reward center of the brain). THC mimics
naturally occurring endocannabinoids that, when binding
to receptors, affect appetite, pain sensation, mood,
and memory.
25. Bluegills
(a type of sunfish) forage optimally, as it turns
out, for prey like Daphnia. Daphnia are small arthropods
related to crabs and lobsters. In a famous series of
experiments conducted in the 1970’s, scientists discovered
that, in low density prey conditions, bluegills take small,
medium, and large Daphnia. However, when prey is
abundant, bluegills spend the extra search time to forage
for and consume mostly large Daphnia. See figure 9.4
below.