Taxonomy & Evolution
1. A symbiotic relationship developed among the surviving amoebas and the bacteria. Since each originally had been free-living, there were many redundant abilities. It appears that one or more of the redundancies were eliminated so the amoeba was dependent on factors supplied by the bacteria.

2. Genetic recombination occurred between the mitochondria.

3. Heterotrophs would evolve first. The early cells would be metabolizing the organic molecules.

4. The (a) culture has etioplasts that will develop into chloroplasts. The chloroplasts in the (b) culture were destroyed so these cells do not have etioplasts.

5. The discovery of flagella or centrioles possessing DNA and bacteria possessing microtubules are important.

Cell Theory & Microscopy
1. The reporter was unaware of the actual size of the fossils and the magnification of an electron microscope. The oldest fossils are considered bacterial with sizes measured in micrometers.

2. Assuming the limit of resolution is ~300 nm, approximately 37 membranes would be needed.

3. (a) ~9997; (b) ~1

	Bacterial cell	Human liver cell	Plant mesophyll cell
Volume	4.19 µm	41887.90 µm	62831.85 µm

4. The pH of the methylene blue needs to be adjusted to alkaline. Acid methylene blue has a negative chromophore and will be repelled by the negatively-charged cells. At a higher pH, the methylene blue chromophore will be positively charged.

5. Van Leeuwenhoek was an explorer who was interested in discovering the microscopic world, he did not attempt to explain what he saw. Hooke took a scientific approach and tried to provide explanations and look for a unifying concept between this microscopic world and the more familiar, macroscopic life forms.

Cell Structure

1. The organelles are attached to microtubules.

2. ZS patients do not make peroxisomes.

3. Integrins are surface molecules that bind to the extracellular matrix or food particles. If integrins can't bind to a substrate, the white blood cells will not be able to locate and destroy invading bacteria.

4. Nucleus, mitochondrion, chloroplast, flagellum.

5. Peroxisomes destroy toxic forms of oxygen. The defective neutrophils will die and not be available to ingest microbes.

Membranes

1. The membrane is primarily phospholipids and their destruction causes lysis. Phosphatidylserine is on the inner leaflet of the membrane and was not reached by the enzyme. Proteins are not a primary structural component of the membrane

2. The bacteria adhere to a glycolipid on the outsdie of cells. The sugar portion is mannose.

3. Hemolytic anemia could result from a lack of any of the support components of the membrane: spectrin, ankyrin, or band 4.1. This disease is due to a spectrin deficiency. Spectrin is an integrin to which the cytoskeleton is anchored.

4. In the cell that lysed, the solute (substance) was able to diffuse through the membranes. As the solute entered, water followed leading to lysis. The length of time it took for lysis to occur is proportional to the rate of diffusion.

5. They create a hypertonic environment. The osmotic pressure of 10% NaCl and of 20% sucrose are about equal.

Intracellular Traffic

1. Sucrase-isomaltase (SI) should be an integral membrane protein, however, the newly made protein does not make it to the Golgi compex for incorporation in the plasma membrane. The signal sequence is present so SI is appropriately made in the ER. The enzyme may not be glycosylated.

2. These are lysosomal storage diseases. Each disease lacks one enzyme that is being made by the other cells.

3. Membranes can be recycled by endocytosis with vesicles budding off and returning to the Golgi complex.

4. The glycoproteins are made in the rough ER and fused to vesicles in the Golgi complex. Viral nucleoprotein enters the vesicles before they fuse with the plasma membrane. The viruses are released when the vesicles fuse with the plasma membrane.

5. At 37°C, the membrane was randomly invaginating at its normal rate and this brought surface proteins into endocytic vesicles. Normal cell processes are stopped at 10°C.

Chemistry Review

1. The animals have cellulose-degrading bacteria in specialized stuctures in the digestive tracts.

2. T. ferrooxidans can oxidize sulfur ("thio") as well as iron ("ferro"). The oxidation of sulfide in pyrite produces sulfuric acid, which dissolves the limestone. Gypsum forms in a subsequent exchange reaction.

3. Since L-isomers are more common in nature, most cells, such as phagocytes, will be able to degrade the L-isomers. D-isomers will be resistant to metabolism by most cells.

4. Amphotericin B would not work against most bacteria because they lack sterols. Fungi have sterols in their membranes and are generally susceptible to amphotericin B. Humans cells have sterols in their membranes.

5. Amino acid changes in a region that is important in the conformation or function of the protein will be more apparent than changes in other regions. The changes in hemoglobin S and Hammersmith hemoglobin change the type of amino acid (e.g., acid to nonpolar) which will change the properties of that region of the peptide. The changes at amino acid #9 from serine to threonine did not change the type of amino acid and thus should not change the binding properties associated with that position.

Energy & Enzymes

1. The enzymes will degrade organic molecules on the clothing. Any stains caused by these molecules will be removed when the molecules are digested.

2. Live bacteria or whole bacterial cells are not being injected. Enzymes are specific for their substrates, so streptokinase will react only with its substrate, fibrin.

3. The ethyl alcohol might compete with methyl alcohol for the active site on the enzyme.

4. Animals do not have the enzyme PEP synthase. Glyphosate-resistant crop plants would be able to grow when glyphosate was used to kill unwanted plants in the field. The unwanted plants compete with the crop for nutrients and interfere with harvesting.

5. The glycogen made by von Gierke's cells is normal but the enzyme needed to degrade glycogen is not correctly made.

Catabolism

1. Hydrolysis splits the starch to release glucose and maltose, no energy is produced. Fermentation uses glycolysis to produce 2 ATPs from each glucose subunit.

2. Streptococcus is only capable of fermentation, which yields to two molecules of ATP and two molecules of NADH for each molecule of glucose consumed. The NADH is reoxidzed in fermentation when electrons are transferred to pyruvic acid (reducing pyruvate to lactate).

3.

Pseudomonas	Glycolysis, Krebs cycle, electron transport chain
Lactobacillus	Glycolysis, fermentation
Alcaligenes	Hydrolyzes proteins, oxidized amino acids in Krebs cycle
Escherichia	Glycolysis, Krebs cycle, ETC or glycolysis, fermentation

4. In eukaryotes, the 2 NADH made in the cytosol during glycolysis enter the electron transport chain at a lower energy level when they are carried into the mitochondrion.

5. (a) More electron carriers means that more energy can be released by the transfer of electrons. (b) The energy will be released as heat rather than stored in ATP.

Photosynthesis

1. Only violet and blue light are available below this depth. The red light used by green and grown algae is absorbed by the water. Photosynthesizing organisms must red to absorb the violet and blue light.

2. Both use an electron transport chain to generate ATP. In oxidative phosphorylation, electrons come from a substrate (such as glucose or iron). In photophosphorylation, electrons are released from chlorophyll by light.

3. The high salt concentration is hypertonic and cells lose water by osmosis. Halobacterium bacteria can use a proton pump to move Na+ into the cells so water will passively follow.

4. Electrons from the hydrogen atoms in a reduced compound go to NADP+ which can also pick up the protons. The NADPH is used in the Calvin Cycle.

5. The 680 nm wavelength is stimulating photosystem II which splits water to produce oxygen.

Molecular Genetics

1.

(d) No change.
(e) Cysteine susbstituted for arginine.
(f) Proline substituted for threonine (missense mutation).
(g) Frameshift mutation.
(h) Adjacent thymines might polymerize.
(i) ACT.

2. The promoter is shown in blue. The structural gene is highlighted in green. The termination sequence is highlighted in red.

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3. The cell does not regulate the rate at which DNA is synthesized, but it regulates the rate at which replication forks on the chromosome are initiated. The cell initiates multiple forks so that a daughter cell will inherit a complete chromosome plus additional portions from multiple replication forks. Chromosome replication begins during or immediately after division.

4. The Pseudomonas will (a) not respond, (b) emit light; and (c) lactose won't affect the lux operon and you can't tell from this information whether Pseudomonas can degrade lactose.

5. (a) Chloroquine interferes with transcription; erythromycin interferes with translation; acyclovir interferes with DNA replication.

(b) Erythromycin is specific for bacteria ribosomes.

(c) Acyclovir is effective against viruses because a viral enzymes tried to use it as a DNA nucleotide

Biotechnology

1. (a) Use a two-stage production. Grow the cells in Medium 1 until stationary phase, then transfer them to Medium 2 so as to maximize bacteriocin production.
(b) Bacteriocins are toxins produced by bacteria that kill other bacteria.
(c) Bacteriocines against Salmonella could be useful in food production or storage to prevent Salmonella infections.

2. You probably used a few plant cells in a Petri plate for your experiment. You can grow these cells on a plant-cell culture medium with tetracycline to isolate the plant cells that actually have the new Ti plasmid.

3. A gene for antisense RNA complementary to the mRNA for the enzyme that synthesizes ethylene has been introduced into tomatoes. This antisense RNA binds with the mRNA and prevemts protein synthesis.

4. "Normal" DNA polymerase is denatured by the heating step, so a technician would have to add DNA polymerase to the reaction vessel every 2 minutes. DNA polymerase from Thermus is not denatured by 90°C, so fresh DNA polymerase does not have to be added every 2 minutes.

5. A positive sample will show a band of DNA in the electrophoresis land. A negative sample will not have a band. V. cholerae ingested by oysters is a source of diseases for humans. The PCR doesn't require isolation and additonal incubation for test results.

Ecology

1. The source of his recurrent infection was a biofilm on his pacemaker. The infection was cured with antibiotics because freed cells were sensitive to antibiotics; however, antibiotics couldn't penetrate the biofilm to eliminate the source.

2. Nitrates, phosphates, oxygen, or water may not be present in sufficient amounts for bacterial growth. The naturally occurring bacteria may be able to degrade the hydrocarbons.

3. Accumulation of BOD and loss of dissolved oxygen would be much less in a fast-moving river. Continual aeration caused by the river's movement would result in rapid oxidation of organic matter.

Type of sewage	BOD	Rate of eutrophication	Dissolved oxygen
Untreated	3+	3+	+
Secondary tx	+	+	3+

4.

Process	Chemical Reactions	Microorganisms
Ammonification	-NH2 -> NH3	Proteolytic bacteria
Nitrification	NH3 -> nitrite ion Nitrite ion -> nitrate ion	Nitrosomonas Nitrobacter
Denitrification	Nitrate ion -> N2	Bacillus
Nitrogen fixation	N2 -> NH3	Rhizobium

5. In the sulfur cycle, microbes degrade organic sulfur compounds, such as amino acids to release hydrogen sulfide, which can oxidized by Thiobacillus to sulfate ion. This ion can be assimilated into amino acid by plants and bacteria- or reduced by Desulfovibrio to hydrogen sulfide. Hydrogen sulfide is used by photoautotrophic bacteria as an electron donor to synthesize carbohydrates. The sulfur-containing by-product of this metabolism is elemental sulfur.

Growth

1. You can determine when S phase begins. The cells will incorporate the labeled thymidine in their nuclei during S phase.

2. During normal development RA cells die in the female's brain. Estrogen prevents cell death.

3. Ubx inhibits expression of Anpt and abd inhibits Ubx. It appears that homeotic genes expressed in more posterior regions reduce transcription of homeotic genes that are expressed more anteriorly.

4. Auxin promotes cell growth and so these cells will grow without dividing and become too large to function; uncontrolled growth takes resources from other necessary aspects of plant physiology.

5. cAMP accumulare which causes hypersecretion of Cl-, K-, and associated water molecules out of intestinal cells.

Cancer

1. Radiation causes mutations. A few mutations may result in malignant transformations. In radiation therapy, the radiation dosage is sufficiently large to cause a number of potentially lethal mutations. Activity growing cells such as cancer cells will be more suceptible to expression of these mutations than normal cells which may be arrested.

2. BCRA I is a tumor suppressing gene. It might encode a transcription factor that suppresses transcription.

3. Malaria and AIDS depress the normal immune response, consequently, immune surveillance or other tumor-suppressing mechanisms that destory cancer cells are impaired.

4. The longer mRNA contains stop codons (UAA) and so translation is terminated before a protein can be made. The mistake occurs in splicing where an exon is skipped.

5. The oncogene would be the gene coding for PDGF. PDGF binds to a cell-surface receptor to produce second messengers [Ca(2+) and DAG] which activate protein kinase. Protein kinase can activate the transcription factor to activate transcription of fos and jun. Jun and Fos are joined as a leucine zipper to form the API transcription factor; API binds DNA to cause cell growth and division.

Cell Communication

1. Growth factors; specifically nerve growth factor.

2. vWD platelets do not produce the necessay adhesion molecules (von Willebrand Factor, vWF) in their extracellular matrix. The adhesion molecule is not produced during embryonic development but only after cell differentiation.

3. Acetylcholine will accumulate. Symptoms of nicotinic acetylcholine stimulation include skeletal muscle spasms; symptoms of muscarinic stimulation include slowing the heart rate. The usual treatment is atropine.

4.

Toxin	Effect on neuron
Batrachotoxin	Depolarization
Pumilotoxin B	Prolongs release of neurotransmitter
Histrionicotoxin	Prolongs release of neurotransmitter

5. The Na+ doesn't diffuse in or out.

Viruses

1. The cells were lysed by a bacteriophage.

2. A virus is small and cannot hold as much DNA as a cell. Genes that code for proteins that serve two functions conserve space on a viral nucleic acid.

3. These two diseases provide animal models for the study of acquired immunodeficiencies and treatments. Study of the (simian and feline) viruses can provide more information regarding the evolution of retroviruses.

4. A prophage, provirus, or plasmid begins as a strand of DNA outside the cell's chromosome that can be integrated into the chromosome. Like a plasmid, a prophage carries genes that can be used by the cell but are not essential. Prophages and proviruses are replicated with the cell's chromosome and remain in progeny cells. Prophage DNA will form a circle and replicate itself in the cell's cytoplasm. Unlike a plasmid, prophages and proviruses are not transferred by conjugation, and when they replicate themselves, viruses are produced that can destroy the host cell.

5. These people acquired hepatitis from contaminated ice-slushes.

Picornaviridae Hepatitis A	Ingestion	+RNA, ss	Nonenveloped
Hepadnaviridae Hepatitis B	Injection	DNA, ds	Enveloped	Reverse transcriptase
Flaviviridae Hepatitis C	Injection	+RNA, ss	Enveloped

Immunity

1. The drug acts as a hapten and complement-fixing antibodies attach to the drug.

2. Bone marrow transplants are done to give T cells and B cells to an immune-deficient patient. The recipient has an immune deficiency and will not mount an immune response against the new tissue. The donor cells are immunologically competent and recognize the new host's MHCs as foreign antigens.

3. (a) An immediate hypersensitivity.
(b) The mediators of anaphylaxis (e.g., histamine, prostaglandins)
(c) Skin tests
(d) Some workers will not produce IgE engibodies against the conidiospores

4. Epinephrine is used to treat symptoms of type I hypersensitivity, systemic anaphylaxis. People with hypersensitivity to eggs may experience anaphylaxis from this vaccine.

5. Lacking IgA antibodies. Suppressor T cells kill B cells producing IgA antibodies.