Unformatted text preview: Exam #1 Concepts
1. What does it mean to say science is provisional and that proof is relative to the evidence available
at that time? You should be able to relate this to several of the topics discussed this term. i s provisional because there are no absolutes in science. Nothing can be
proven with absolute certainty, but supported with evidence. Proof is relative to the
evidence available at the time because technology is advancing and as this
happens ideas became more accepted than before because there is more certain
evidence to back it up. Robert Hooke had limited technology compared to
Theodore Schwann (every part of animal looked at was made of cells) and
Matthias Schleiden (every part of plant looked at was made out of cells) who had
improved microscopes, sites, and staining.These advancements allow the cell
theory to develop because there was evidence to support that cells were the basic
unit of life and all living things were composed of cells. This is compared to Hooke
who used technology to view the water passages in the cork involved in plant
growth, but could calculate from his work what the cell was composed with.
Science Our understanding of life is constantly changing as t echnology and collaboration allow for new means to answer old questions. What we know today and think, may change
tomorrow. This is due to technology, improvements in technology helps us think in
different ways, ways we view DNA today was not possible 15 years ago. For example,
now we can sequence our own genes today, before we couldn’t. Science is an ongoing
process. a. Relating to the Cell Theory: A specific example of this comes with the nerve cells,
they were thought to be an outlier during the development of the cell theory due
to its complexity. When golgi used the black reaction he discovered the structure
of a neuron and thought that the cells were directly connected to one another.
But the development of the electron microscope, scientists discovered the
synapses between nerve cells . This is a demonstration of the process of
scientific discovery. Science is provisional because it is based on facts and
observable truths that can only happen when the proper experiment and tools
needed for an experiment are available. 2. Scientific evidence suggests that all living things share a common ancestor (the unity of life). What
evidence supports this statement that all living organisms are related? a. -Darwin saw anatomical similarities
b. -similarities between alive and extinct species c. -Most evidence that all life is all related has to do with our DNA and RNA, since
all things have it. RNA is very critical to life but evolves very slowly, giving
scientists the opportunity to go back and look at homologies or relationships
between distantly related organisms. Also with modern technology we are able to
go back and compare DNA. Both DNA and RNA, this has made looking at our
genes very useful for determining evolutionary relationships.
● All living organisms have DNA/RNA (use the same code)
All living organisms use ATP - ATP synthase
All living things have cell membranes (ex. Phospholipid bilayer)
All living things have ribosomes and synthesize proteins s aw anatomical similarities between diverse species that were alive/extinct.
Despite this, most evidence to support the unity of life comes from our DNA/RNA.
As we know RNA is very critical to life but has evolved very slowly. This has
allowed scientists to go global and look at similarities between distantly related
organisms, make genes very useful for determining evolutionary relationships.
Additionally we are now able to look at DNA sequences for comparison.
Darwin the biggest unifying characteristic among all domains is that they all share a genetic code. They use
the same letters and if you put them in certain sequences, they have the same results. Living things
also have the same building blocks in common (amino acids) and they use ATP for energy.
These characteristics show that life evolved from one single cell because living organisms all seem
to be a variation of the same building blocks. Some are simpler, and others are more complex, but
the more complex ones must have evolved over a long period of time through mutations that just
happened to help those organisms thrive in their environment. It is unlikely that any complex
organism magically arranged themselves into a functioning self-sustaining and self-replicating
system, when nature favors disorder. They must have come from simpler organisms, the simplest
one being the cell. 3. Discuss the general steps needed for life to emerge from inorganic molecules. -(CO2) inorganics to organic (CH) Hydrothermal events (gradient): right next to the hydrothermal vents it
was too hot, and too far from the hydrothermal vents it was too cold, life
could have potentially arose at a certain distant from the vents which
provided an ideal temp and environment. (Goldilocks effect)
● Extraterrestrial: meteorites brought life, crash would result in new
compounds/molecules (form new bonds and break bonds)
● Lightning striking the oceans- Stanley miller recreated this:electrical
voltage. Empirical evidence. Reducing Environment (favoring synthesis)
● Deep Sea Vents - underwater volcanoes
○ Has potentially favorable temperatures
○ Is a reducing environment
○ Heat in the form of volcanoes/gas
-Simple to complex
● Clays, tide pools; tide comes in washing up simple organic matter, water
evaporates now you have concentration of simple organic particles.
● Increase concentration
-complex to life
● Self replication
● 4. Compare and contrast Eukarya, Bacteria, and Archaea and discuss why horizontal gene transfer
makes using molecular data to determine evolutionary relationships between these domains
challenging. 5. Using examples, explain the concept “structure suggests function” as it relates to biological
molecules and cells. 6. Explain the endosymbiotic theory used to explain the origin of mitochondria and chloroplasts. You
should be able to list several lines of evidence supporting this theory. Endosymbiosis is the process in which certain unicellular organisms engulf other cells,
Which become organelles in the host cell. Structural, biochemical, and DNA sequence
data indicate that the first eukaryotes acquired mitochondria by engulfing an aerobic prokaryote.
The endosymbiosis theory states that cells were created by engulfing mitochondria and by using
the excess power that they produced, created the other organelles that are present in
Eukaryotic cells today.
● A double membrane in mitochondria
● Mitochondria has bacterial DNA (circular)
● Mitochondria divides by binary fission
● Mitochondria have 70-S ribosomes, but eukaryotes have 80-S
● Mitochondria are used for energy Mitochondria came first, before chloroplasts; we have reason to believe this is the case because
all eukaryotic cell contains mitochondria, but not every one contains chloroplasts.
7. Explain how substrate concentration affects the rate of an enzyme-catalyzed reaction. Describe
how this response to substrate concentration is affected by competitive and noncompetitive
inhibitors. 8. Describe how allosteric regulators may inhibit or stimulate the activity of an enzyme and how this
can be used by the cell to regulate metabolic pathways.
-By inducing shape change so something can’t bind to active site.
Glycolysis=pyruvate--->acetyl coa--->citric acid cycle (produces NADH and FADH2) -->oxidative
phosphorylation= ATP-------> if nothing is taking ATP, ATP can bind with phosphofructokinase Exam #2 Concepts
9. Explain how various molecules (hydrophobic, small/large charged or polar, etc.) are transported
across membranes. The cell transports CO2 Ca and other small/ nonpolar substances through simple diffusion.
Transport of larger molecules like glucose AA, and ions require transport proteins and facilitated
diffusion. Transmembrane proteins create a water filled pore through which ions and small
hydrophilic molecules can pass via diffusion with their concentration gradient. There channels
can be opened or closed based off of the needs of the cells. Transmembrane porters (transporters)
use active transport which requires ATP to force ions or small molecules through the membrane
against their concentration gradient.
Simple Diffusion (a): passive, no ATP, concentration grad is potential energy used. Small,
nonpolar molecules (Oxygen, nitrogen, carbon dioxide)
Channel-mediated Facilitated Diffusion (b): Transport proteins with hydrophilic core all
diffusion of polar molecules (water) to pass, no ATP, cell regulated
Carrier-mediated Facilitated Diffusion (c): Transport protein changes shape when large polar
molecules (glucose) bind to active site. ● Hydrophobic small molecules are passively transported through the nonpolar membrane ● Large molecules are often rejected from moving through the membrane in any way
● Small m
olecules usually get across is one of the three ways (passively, through a canal,
or actively through transport proteins)
● Hydrophilic molecules need canals with a polar inside or transport proteins to move
● Charged molecules (ions) need canals and transport proteins as well
10. Using examples, describe facilitated diffusion, primary active transport, and secondary active
transport (antiporter/symporter). Relate these to the structure and function of carriers and channels. 11. Explain how cells establish, maintain, and use electrochemical gradients. Relate this to cellular
energy and cell signaling. 12. Compare and contrast the structures and functions of microtubules, intermediate filaments, and
actin filaments. 13. Explain how the cell uses cytoskeletal elements (microtubules or actin filaments) and motor
proteins (dynein/kinesin or myosin) in intracellular transport and muscle contractions. 14. Discuss muscle contractions as an example of the interconnectedness of cellular structures and
processes. You should be able to relate intracellular transport, membrane structure/transport,
protein structure/function/regulation, cellular energy, and cell signaling to muscle contractions.
Remember that this example was used to tie these complex processes together. 15. Explain how an energetically favorable reaction can be used to drive an energetically unfavorable
reaction. Be able to relate this concept to other aspects of cell/molecular biology. 16. Summarize each step in cellular respiration (glycolysis, pyruvate processing, citric acid cycle, ETC)
and photosynthesis (light reaction and Calvin cycle) highlighting the flow of energy (ΔG) and
describe where in the cell it occurs. 17. Explain in general terms how redox reactions are involved in energy exchanges. Relate this to cell
respiration and photosynthesis. 18. Describe the similarities and differences between oxidative phosphorylation (mitochondria) and
photophosphorylation (chloroplasts). 19. List and briefly describe, using examples, the three stages of cell signaling. 20. Explain how one signal can promote different responses in different cells. For example, epinephrine
causes the heart to beat faster while causing the liver to release glucose. Genetic Material
21. Explain how the experiments performed by the following scientists provided evidence that DNA is
the genetic material: a. Frederick Griffith: He did the whole experiment with bacteria and mice. Used two strains
of bacteria, R and S. His purpose was to develop a vaccine against pneumonia. Tried
injecting mice with heat-killed S bacteria. The heat killed S bacteria don't cause disease in
mice. When harmless R bacteria was combined with harmless heat-killed S bacteria and
injected into a mouse, the mouse developed pneumonia and died, but also found the blood in
the mouse contained living S bacteria. So, he concluded that the R-strain bacteria must have
taken up a transforming principle from the heat killed S bacteria which allowed them to
transform into smooth coated bacteria and become harmful.
b. Oswald Avery, Maclyn McCarty, and Colin MacLeod: Wanted to identify “transforming
principle.” Began with large cultures of heat killed S cells and purified the the transforming
principle by washing away, separating out, or destroying other cellular components. They
were able to obtain a small amount of highly purified transforming principle which they were
able to analyze. They suggested that it was DNA. What they found out:
● The substance gave a negative result in chemical test known to detect
proteins, but a positive result in chemical test known to detect DNA. ● The elemental composition of the purified transforming principle closely
resembled DNA in its ratio of nitrogen and phosphorus. ● Protein and RNA degrading enzymes had little effect on the transforming
principle, but enzymes able to degrade DNA eliminated the transforming
activity. Result: everything pointed to DNA as the transforming principle. c. Alfred Hershey and Martha Chase: used radioactive isotopes to label proteins vs. DNA -studied bacteriophage (virus that targets bacteria) phage has protein capsule and DNA
in middle. Learned that genetic material goes into host and the capsule stays behind
Batch 1: radioactive sulfur-->in protein but not DNA/ radioactive phosphorus--->in DNA, but
not in protein. Now they can tag these and see which goes where. They found that the sulfur
was up in the supernatant (proteins always on top) and DNA was found in the bottom.
d. Erwin Chargaff: A=T, C=G
1. Base composition varies between species
2. Within a
species, the number of A and T bases are equal and the number of C and G bases are
*basis remained unexplained until discovery of the double helix 22. Explain how Watson and Crick deduced the structure of DNA and describe the evidence they used.
Explain the significance of the research of Rosalind Franklin. Watson saw x-ray diffraction image of DNA (Rosalind Franklin’s)
Discovered double helix structure of DNA since Watson was familiar with the type of x-ray
diffraction pattern that helical molecules produce. They began building models that would
conform to the x-ray measurements. From Franklin’s research, they knew she concluded that the
sugar-phosphate backbones were on the outside of the DNA molecule
Model for DNA replication:
a.) parent molecule: has two complementary strands of DNA. Each base paired by hydrogen
bonding with its specific partner, A-T and C-G
b.) separation of strands: each parental strand can now serve as a template that determines the
order of nucleotides along a new, complementary strand
c.) “daughter” DNA molecules, each consisting of one parental strand and one new strand:
complementary nucleotides line up and are connected to form sugar-phosphate backbones of new
strands. Each “daughter” DNA molecule has one parental strand and one new strand
23. Describe the structure of DNA. Explain the base-pairing rule and describe its significance. DNA Replication and Repair
24. Describe the classic experiment by Matthew Meselson and Franklin Stahl. For each hypothesis
(semiconservative, conservative, and dispersive) explain the predicted results. They tested if DNA replication followed a conservative, semi-conservative or dispersive model. They
began with a flask with cultured bacteria in a liquid with a heavy isotope, N15. the bacteria was then
transferred into another flask with a lighter isotope, N14. From that flask they extracted DNA from
the bacteria and centrifuged each DNA sample to separate the different densities of DNA. After the
first replication, the DNA sample results in a single strand about mid way between the test tube.
After the second replication, there were two s...
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- Spring '14