MCAT Biology and Biochemistry Flashcards
1
Q
What will be the effect on a proteins afinity for water if an AA is substituted for a more polar AA?
A
Substituting a more polar amino acid for a nonpolar amino acid will render the protein more hydrophillic (“water-loving”)
2
Q
Where will a protonation occur on histadines side chain?
A
When protonating histadine, the pyradine nitrogen gains the proton. This would not trigger a shift in double bonds in the surrounding structure.
3
Q
What type of reaction happens when a carboxyl group is removed?
A
Decarboxylase reactions occur when they remove a carboxyl group from a molecule.
4
Q
What happens to a molecule above and below its pKa value?
A
Above the pKa (in more basic conditions) the deprotonated form will predominate; and below the pKa (in more acidic conditions) the protonated form will predominate.
5
Q
What is the charge of testosterone?
A
Testosterone is a steroid hormone; it is not charged at all, as evidenced by the fact that it can pass through the plasma membrane and is thus nonpolar.
6
Q
What is the reaction of adding insulin into the bloodstream?
A
Insulin is a peptide hormone that promotes the cells to eat up glucose, causing the glucose levels to decrease in in the body.
7
Q
What structure do steroid hormones typically tend to present in?
A
Non-polar fused -ring structure
8
Q
In addition to myosin motor proteins, what type of fibers are involved in cytokinesis as the contractile ring complex?
A
Actin filaments (microfilaments)
9
Q
What is the effect of adding cholesterol to a phospholipid bilayer?
A
Cholesterol promotes fluidity at low temperatures and increases stability at high temperatures.
10
Q
What is happenign to the cell during G0 phase?
A
G0 is resting phase. There is no cell division occuring at this time.
11
Q
Bacteria contain what size of ribsomes?
A
Bacteria contain an 70S ribosome, which is composed of 30S and 50S subunits.
12
Q
What are negative-sense RNA viruses?
A
These viruses contain RNA that is complementary to mRNA, which needs to be synthesized by an eynzyme known as RNA replicase (which is caried in the viron).
13
Q
What AA does the letter L represent?
A
L = Leucine
14
Q
What is the composition of viral envelope?
A
Viral envelopes are primarily made up of phospholipids and glycoproteins that contribute to recognition and interactions with cell receptors.
15
Q
What happens in terms of protonation state to an amino acid when the pH > pKa?
A
The group in question will be deprotonated
16
Q
What is the estimated isoelectric point of histidine if the pKa = 6?
A
Isoelectric point should be approximately 7.5. Average two most basic pKa values: 6 + 9 / 2 = 7.5
17
Q
What types of AA’s are typically found on the outer plasma membrane vs inner membrane? (i.e. polar/hydrophillic, non-polar/hydrophobic, basic, acidic, )
A
Inner membrane: Non-polar hydrophobic AA’s Outer membrane: Polar hydropilic AA’s
18
Q
What kind of bonding occurs in secondary structure?
A
Hydrogen bonding
19
Q
Intermolecular forces between what two species most directly involved in the formation of the alpha helix backbone?
A
The amine group on one amino acid and the carbonyl group of another
20
Q
What does a value > 1 for a hill coefficient mean?
A
Hill cooperativity reflects cooperativity. A cooefficient > 1 indicates a positive cooperativity, meaning that binding at one position or active site causes binding to take place more easily at the remaining active sites.
21
Q
What is the function of a kinase?
A
Kinases are responsible for transferring a high-energy phosphate group from a donor molecule (typically ATP) to the substrate.
22
Q
In what pathways are allosteric enzyme most prevalent?
A
Allosteric regulation is a ubiquitous phenomenon in the physiology of multicellular eukaryotic organisms. Many metabolic pathways rely on it, in the form of feed-forward regulation, feedback loops and complex multi-factorial systems such as the hormonal regulation of glucose metabolism.
23
Q
Which amino acids are most likely to be phosphorylated by kinases?
A
AA’s that contain -OH groups, which include: serine (S), threonine (T), tyrosine (Y).
24
Q
What is the effect of components of grapefruit juice binding a statin?
A
Bergamottin, a component in grapefruit juice, covalently binds enzyme CYP3A4, which is responsible for metabolizing certain statins. This inhibits the enzyme and increases the systemic concentration of the statin, which can be dangerous
25
What is the term for turn over number in enzyme substrate reactions?
Kcat is also known as the turnover. This is the time it takes one enzyme to tunrover a max amount of substrate molecules per unit time. Kcat = Vmax / [Et]
26
How is catalytic efficiency determined?
Catalytic efficiency is expressed as Kcat / Km. If enzyme concentration is equal among comparative subjects, then Vmax, which is directly proportional to Kcat, can be used to compare efficiency.
27
What is a cofactor?
Cofactors are organic or inorganic molecules that assist in the function of an enzyme.
28
What is a zymogen?
Zymogens are inactive precursors of enzymes that require proteolytic cleavage prior to becoming active.
29
If given mRNA sequence of 5' - AUGAA - 3' what is the sense dsDNA sequence that this corresponds with?
5' - ATGAA - 3' The sense DNA strand should have the same sequence as the mRNA strand produced, except the DNA strand should contain thymine instead of uracil.
30
What are the post-transcriptional modifications in eukaryotes?
- 5' cap (7-methylguanylate cap) - 3' poly-A-tail - splicing
31
What DNA enzyme has a "proofreading mechanism"?
DNA polymerase mainly functions to synthesize new DNA strands complementary to a template, but it also is capable of removing mismatched bases and replace them with the correct bases.
32
Where does paracrine signaling occur?
Paracrine signaling occurs between local cells (not cells of distinct tissues) and only lasts for a short amount of time, which is due to fast degradation of the paracrine ligands.
33
How many heavy and light chains does one immunoglobin (Ig) subunit contain?
One immunoglobulin (Ig) subunit contains two heavy chains and two light chains.
34
What type of protein are cadherins classified as? A. Globular proteins. B. Enzymes C. Transmembrane proteins D. Monotopic proteins
Transmembrane proteins. Cadherins are cell adhesion molecules that comprise adheren junctions, which connect cells to each other. So, it makes logical sense that a cadherin would extend through the membrane of a cell into the environment.
35
What is the function of a dynein protein?
Dyneins carry cargo towards (-) end of microtubules (towards the center), which is called retrograde transport.
36
How are G proteins activated and inactivated?
G proteins are activated when a GDP molecule is exchanged for GTP (GDP is NOT simply phosphorylated). G proteins are inactivated by the hydrolysis of GTP, which is accomplished via an intrinsic GTPase activity.
37
What is the goal and what are the parameters for a test cross?
Goal: Discover the genotype of a phenotypically dominant individual. Parameters: Individual with a dominant phenotype is crossed with an individual with the recessive phenotype.
38
What do diseases with a high penetrance exhibit?
Diseases with high penetrance show a high correlation between individuals that have the disease genotype and individuals who exhibit the signs and symptoms of the disease.
39
What is incomplete dominance?
Incomplete dominance is a form of inheritance in which neither allele is completely expressed over the other. Ex: The snapdragon flower. The Homozygous snapdragon flower is either all red or all white, while heterozygotes are blended phenotype of pink.
40
What are saturated phospholipids?
Saturated molecules are those which have no double bonds in their hydrocarbon chains.
41
Where are phospholipids synthesized in the cell?
Phospholipids, like most lipids, are synthesized at the surface of the smooth endoplasmic reticulum (ER).
42
What kind of fat (saturated vs unsaturated) would you add to a membrane to increase fluidity?
Unsaturated fats are more flexible and fluid than saturated fats due to the double bond adding a "kink" into the hydrocarbon tail. Unsaturated fats add fluidity to the membrane, and saturated fats add rigidity as they are much less flexible.
43
What is the name of the process by which long hydrocarbons could be catabolized by the cell?
Beta oxidation is the process by which long chain hydrocarbons are oxidized to acetyl-CoA by enzymes in the mitochondria.
44
What double bond configuration is observed when two high priority groups attached to an alkene are on the same side?
The double bond will be designated cis (for simple alkenes) or Z (on “zee zame zide”).
45
When lactose is present, what does allolactose bind to on the lac operon?
When lactose is present, transcription of structural lac genes takes place. Allolactose binds to the repressor, causing it to dissociate from the operator region. Transcription can take place.
46
Of the following, which are considered to be coding RNAs? I. tRNA
II. siRNA
III. mRNA
IV. miRNA
Messenger RNA (mRNA) is translated, so it is considered coding RNA.
47
What are the major differences between cDNA and DNA coding for the same gene?
cDNA, or complementary DNA, is DNA that is reverse transcribed from the associated mRNA molecule. The resulting cDNA sequence is very similar to the regular DNA sequence, but lacks introns (since mature mRNA does not contain introns). Therefore, a cDNA sequence will be shorter than the associated DNA sequence, assuming that the DNA sequence does include at least one intron.
48
Polymerase chain reaction (PCR) requires use of a thermostable DNA polymerase. The use of such a polymerase is especially important due to which step of the PCR cycle?
Denaturation. The DNA polymerase used in PCR is present throughout the cycle, it must be able to withstand such high temperatures without a significant loss of function. The temperature is raised to approximately 95 degrees to facilitate denaturation and separate the two DNA strands.
49
A cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits (e.g. white flowers crossed with red flowers yield pink flowers)
This is an example of incomplete dominance
50
What is the term that describes the following: clinical symptoms (phenotype) are not always present in individuals who have the disease-causing mutation (genotype)?
Incomplete dominance.
51
In what stage of the cell cycle is chromatin found to be in a dense condensation?
Chromatin is found in this condition when the cell is preparing to undergo mitosis.
52
At the peak of an action potential, what is the state of ions flowing across the neuronal cell membrane?
At peak action potential, the membrane potential is ~ +40 mV. At this point, Na stops flowing into the cell, voltage-gated K channels open to allow K to flow out of the cell.
53
What are the myelinating cells in the CNS and the PNS?
Oligodendrocytes myelinate axons in CNS. Schwann cells myelinate axons in PNS.
54
What is the role of efferent nerves?
Efferent nerves are responsible for carrying out the reflexive action. Example: The patellar reflex is elicited by striking the patellar ligament, which then activates spindle fibers in the muscle. In this case, efferent nerve role is extension of the leg following activation of muscle spindle fibers in the quadricep
55
What type of glial cell functions as macrophages in the central nervous system?
Microglia work as macrophages in the CNS. They provide an active immune defense by clearing out pathogens from the brain.
56
What is the neurotransmitter that is released by somatic neurons in order to induce muscle contraction?
Acetylcholine facilitates muscle contraction. Inhibition of acetylcholine results in less of it being available to bind to the receptor in the neuromuscular junction, thereby reducing the ability of the muscle to contract.
57
A hormone that acts on neighboring cells is best described as what?
A paracrine hormone acts on nerby cells.
58
Increased secretion of what mineralocorticoid acts on the distal tubules and collecting ducts of the kidney nephron to stimulate sodium retention, potassium secretion and thus water retention?
The mineralocorticoid aldosterone
59
What type of four ring structured hormone passes directly through plasma membranes of cells and encounters the nucleus where it affects gene transcription, resulting in long lasting physiological effects?
Steroid hormones
60
What type of neuron would relay a message from a C-fiber nociceptor?
Nociceptor refers to neurons that convey sensations of pain to the central nervous system. So, these are sensory and afferent neurons.
61
What effect does insulin have on the process of glycogenesis or glycogen synthesis?
Insulin stimulates glycogen or glycogenesis
62
What is the effects of LH being present in males and females?
In males: LH binds to receptors on Leydig cells, which stimulates testosterone synthesis and secretion. In females: LH causes mature follicles on the ovary to undergo ovulation, which often occurs between days 11 and 21 of the menstrual cycle.
63
What is the condition of a spinal cord in which the nerves that run inside the vertebral column are damaged, which interupts efferent signals to reach their destination?
Transection of the spinal cord
64
What do non-overlapping error bars represent?
It suggests that there is a statistically significant difference present between two variables.
65
In general, what are the abilities of a stem cell (this is a concern for people who undergo chemotherapy and are trying to eliminate cancer stem cells)?
Stem cells have the ability to undergo self-renewal. Cancer stem cells may be responsible for reocurrence after chemotherapy, which implies that they can resist chemo, replicate, and then differentiate.
66
What is the process of binding complementary nucleotides?
This process is called hybridization
67
What type of enzyme removes a phosphate from a substrate?
A phosphatase removes phosphates from substrates.
68
All other things being equal, in what type of solute conditions can we infer that aquaporins, will localize to the plasma membrane to a greater extent? (In hypotonic, isotonic, hypertonic conditions?)
Hypotonic conditions would provide the most beneficial conditions for increasing the concentration of aquaporins in a plama membrane.
69
What method of passing on genetic information maintains genetic integrity? (meiosis vs mitosis)
Meiosis functions in genetic recombination to create genetic diversity in offspring. Mitosis maintains genetic integrity.
70
What enzyme is used to alter the configuation of atoms, while keeping the same atomic ingredients?
Isomeraze is an enzyme that will modify a molecule in this way
71
What are the responses in the body to an insulin injection?
1. Halt production of new sugar 2. Begin storing sugar as glycogen 3. Begin building fatty acids into fats for storing energy
72
What is the function of acylcarnitine translocase?
This enzyme is essential for the catabolism of fatty acids. If there is a deficiency then there will be an abundance of fatty acids in the body and less energy available.
73
The mitotic spindle is composed of what structures, which are cytoskeletal components.
Mitotic spindle is composed of microtubules, which are made of tubulin.
74
What is the term for a structure that evolved independently to carry our the same function?
These are called analogous structures
75
How do humans (males with XY and females with XX) regulate potential gene imbalances?
As the X chromosome carries more genes than Y chromosomes, in order to balance the genetic load with the males, one of a females XX chromosomes is inactivated, which balances the male XY set.
76
Why are trisomy pregnancies involving multiple copies of the X chromosome not terminated?
Due to the X chromosome carrying the majority of the genetic load for sexual differentiation, vs Y chromosome holding fewer genes, the additional two X chromosomes can simply be shut down via methylation.
77
Who would be more at risk of inherating MELAS, a mitochondrial disorder that affects many of the body's systems, the daughter of a male or the son of a female who has the disease?
The son is more likely to inherit the disease, as mitochondrial disorders are inherited maternally.
78
What does a low recombination frequency suggest about two genes?
A low recombination frequency suggests that the two genes are physically close.
79
In what stage do homologous chromosomes separate?
Homologous chromosomes separate during meiosis I, which cause the daughter cells generated in this process to be haploid prior to meiosis II.
80
What may be a result of a dysfunctional synaptonemal complex?
The synaptonemal complex is a protein based linkage that arises during meiosis and connects homologous chromosomes, and if it is dysfunctional then = issues with recombination and synapsis
81
Heavy smokers often experience SOB, what comound and binding mechanism is most likely responsible for the SOB?
Carbon Monoxide (CO) has a 250 x greater affinity for hemoglobin than Oxygen does. CO is a direct competitive inhibitor.
82
How does having hemoglobin that are able to bind bicarbonate at the a1b2 interface enable a crocodile to hold their breath for a long time?
When an crocodile binds bicarbonate it stabalizes the "tense" state of hemoglobin and decreases the affinity of that molecule for O2, which then releases O2.
83
What metal cofactor helps carbonic anhydrase function as a catalyst for the conversion H2O -> CO2? A. Pt B. Fe C. Zn D. Mg
The active site of carbonic anhydrase contains a zinc molecule, which helps it catalyze the reversible reaction between CO2 and H2O.
84
Hemoglobin's O2 binding affinity is affected by the pH of it's environment and CO2 concentration, what conditions of pH and CO2 concentration are conducive for hemoglobin and O2 binding?
Low CO2 levels and high pH levels. (Since CO2 in the plasma lead to formation of carbonic acid, low CO2 leads to basic blood.
85
How does the binding of one oxygen molecule change the affinity / availability of that hemoglobin?
The binding of one oxygen molecule to a hemoglobin promotes changes in the position of the central iron ion, which facilitates the binding of additional O2 molecules.
86
Where does glycolysis occur in the cell?
Glycolysis occurs in the cytoplasm.
87
What are the three enzymes that catalyze the three irreversible steps in glycolysis?
-Hexokinase, phosphofructokinase, pyruvate kinase
88
How is step 1 of glycolysis regulated?
Step 1 of glycolysis is regulated by the negative feedback loop. When the product of step one is in excess it will inhibit the forward reaction.
89
What is the term for the reaction that uses water to synthesise a product?
Hydration reaction
90
What are the products of the Krebs cycle?
Products: ATP, citrate, NADH
91
In humans, where does gluconeogenesis take place?
Gluconeogenesis mainly takes place in the liver, but also occurs in the kidneys to a smaller extent.
92
In what phase of the cell cycle would the pentose phosphate pathway be most active?
In the synthesis phase (S), as ribose 5-phosphate is a product of PPP. This plays an important role in nucleic acid synthesis.
93
What is the meaning of multipotency when it comes to progenitor cells?
Multipotent progenitor cells have the gene activation potential to differentiate into multiple, but limited cell types. Ex: a multi blood stem cell can differentiate into other blood cells, but not to cells of other lineages.
94
What is the second law of thermodynamics?
A spontaneous reaction or cyclic process must yield a net entropy increase. (AKA: entropy of the universe should be continually rising)
95
What species has the greatest energetic yield in the Kreb's Cycle? A. ATP B. GTP C. FADH2 D. NADH
As NADH drops off electrons at COmplex I of the ETC each mol of NADH contributes enough energy to synthesize 2.5 ATP mols.
96
What aspect of light does not change when it moves between media of different refractive indicies?
Frequency always remains constant.
97
Polypeptides are formed via what type of reaction?
Polypeptides are formed via dehydration synthesis reactions.
98
In ion-exchange chromatography with a negatively- charged stationary phase, what type of compound will elute first?
As the stationary phase is negative, positive compounds will interact more and stay in this phase longer. Therefore, negatively charged (or less positively charged) coumpounds will elute faster.
99
Describe a circumstance where an AA incurs many entropic penalties.
This would be when an AA is exposed to an environment in which it displays poor solubility. Example: High entropic penalties would be incurred if a largely hydrophilic AA were placed in the interior of a protein (non-aqueous environment).
100
Why would the substitution of Gly for Cys change the tertiary structure of a theoretical protein?
Tertiary structure is driven by side chain interations such as hydrogen bonding and disulfide bridges. So replacing a Gly with a Cys AA would most likely alter the tertiary structure due to possible breakdowns in disulfide bridges.
101
What type of reagent would break the disulfide linkages that form part of a proteins tertiary structure?
A reducing reagent; by adding hydrogen back to the sulfur atoms.
102
What are the aromatic AAs?
W - Tryptophan, Y - Tyrosine, F - Phenylalanine
103
NAD+ -> NADH Is this an oxidation or reduction?
This is a reduction, because it involves the gaining of an H bond.
104
Gram-positive organisms stain dark purple while gram-negative organisms stain pink. Why is this?
Gram-pos organisms posses a thick peptidoglycan wall, which attaches to crystal violet particles and prevents them from leaving when washed. Gram-neg organisms have think cells wall that does not bind to the violet stain and result in pink color.
105
What type of organism does not have membranous organelles?
Archea - which are classified as prokaryotes.
106
What is the transfer of material from a phage to a bacterial cell called?
Transduction is the process by which DNA is transferred from one bacterium to another by a virus.
107
Where is insulin produced in the body?
Insulin (a peptide hormone) is produced by the beta cells of the pancreas.
108
In the lac operon, which segment of the DNA binds the repressor?
The operator binds the repressor.
109
What type of structural proteins are compose eukaryotic flagella and cilia?
Bundles of microtubules compose eukaryotic cilia and flagella.
110
What occurs during the S phase of the cell cycle?
DNA synthesis / DNA replication
111
What is it called when heterozygous mixing of the new allele with the recessive allele causes the expressed phenotype to be a mix of the dominant trait and the recessive trait, rather than one or the other?
This is known as Incomplete dominance.
112
Cortisol is classified as an immunosuppressant, true or false?
Glucocorticoids such as cortisol are immunosuppressants.
113
What cytoskeletal structure is keratin composed of?
Keratin is an intermediate filaments
114
What two AA would likely bind Calcium ions ?
As Calcium ions are positively charged, the AAs that would bind to them would more likely be negatively charged: aspartate and glutamate.
115
If a cell is said to have negative membrane potential, where is the majority of the negativity?
The membrane potential is always measured in terms of the inside of the cell relative to the extracellular fluid. So... the inside of the cell is neg compared to the extracellular fluid.
116
What is the result of fluidity on a cholesterol embedded membrane is placed in a heated environment?
Cholesterol decreases membrane fluidity when in heated environments.
117
What type of protein facilitates proper protein folding and inhibits the formation of nonfunctional protein aggregates?
These are called chaperone proteins.
118
How does a transmembrane protein enter the endomembrane system?
Transmembrane proteins enter the endomembrane system by docking at the rough ER, which is facilitated by using a signal sequence.
119
When concentrated urine is being produced, what region of the kidney will the glomerular filtrate reach its highest concentration?
The glomerular filtrate will be most concentrated in the medullary portion of the collecting duct, in comparison to other kidney structures.
120
What is the function of the Na+K+ ATPase during a neuronal action potential?
The Na+K+ATPase functions to restore the resting membrane potential by moving ions against their concentration gradients.
121
In which direction does the Na+K+ ATPase transport ions across the cell membrane upon ATP hydrolysis?
3 Na+ ions are transported out of the cell and 2 K+ ions into the cell with each ATP hydrolyzed.
122
What is a cyclic oligosaccharide composed of?
It is composed of carbohydrates
123
What structural filament facilitate chromosomal movements in cell division?
Microtubules facilitate chromosomal moements in cell division.
124
The initial filtration in the glomerulus is due to what?
The initial filtration in the glomerulus occurs as blood pressure forces the fluid from the glomerulus into the lumen of the bowman's capsule.
125
Enzymes alter the rate of a chemical reaction by all of the following except: A co-localizing substrates, B altering local pH, C altering substrate shape, D altering substrate primary structure.
Enzymes cannot alter the primary structure of a protein, as this is the amino acid sequence of the protein.
126
What occurs during interphase?
Interphase is the phase of the cell cycle between cell divisions and is the phase in which the cell obtains nutrients, grows, and reads its DNA and other normal cell functions.
127
Why would viruses not be able to grow if they were inoculated on a noncellular agar-based medium?
This is due to the fact that they are obligate parasites and require a host cell to reproduce.
128
Why are telomeres not important to most prokaryotes/bacterial cells?
This is because most prokaryotes have circular DNA and therefore do not have repetitive non-coding nucleotide sequences.
129
What role does insulin play in the uptake of glucose in the liver?
Insulin stimulates the first step in the glycolytic pathway in the liver, which decreases the cellular conc. of glucose. This results in the increased uptake of glucose to maintain cellular conc. of glucose.
130
Where does cleavage of secreted proteins such as insulin take place?
Cleaving of insulin into a mature form takes place withiin the endomembrane system.
131
The sodium pump would be most active in cells of which of the following structures?
A. Veins
B. Loop of Henle
C. Lungs
D. Bone marrow
Of those listed, Na+ reabsorption is most important to the Loop of Henle. Here, Na+ is reabsorbed from the filtrate moving through the nephron. This is the mechanism that kidneys use to concentrate urine. This is dependent on Na+ for primary function.
132
How many molecules of ATP are produced per glucose molecule in glycolysis?
Glycolysis produces two ATP molecules per glucose molecule.
133
What is the relationship between leukocytes and inflammation ?
Leukocytes gravitate toward an inflammation.
134
Blood plasma and lymph are two examples of what?
Blood plasma and lymph are two examples of extracellular fluid.
135
What is transformation, the recombinant process?
In transformation bacteria take up DNA from their surroundings, the media in which they are immersed.
136
What is transduction, the recombinant process?
Transduction is the process whereby genes are transferred by a virus.
137
What is conjugation, the recombinant process?
The process of conjugation involves production of a special conjugation pilus (sex pilus) by one bacterium and transfer through it of DNA to another bacterium.
138
Inflation of the lungs in mammals is accomplished by what action?
Negative action casuses lung inflation.
139
What is the function of a phosphatase?
Phosphatase is an enzyme that removes a phosphate group from its substrate.
140
What structural filament is compsed of actin?
Microfilaments are composed of actin.
141
By keeping enzyme concentration constant, varying substrate concentration, and either including or excluding the inhibitor, the effect of the inhibitor on the Vmax and apparent Km of the reaction can be determined. What will be the result on Vmax and Km for a competitive inhibitor?
A competitive inhibitor will increase the apparent Km and not affect the Vmax.
142
What is the average molecular weight of an amino acid?
The average weight of an AA is 110 Da = .11 KDa.
143
Guanosine tri-phosphate (GTP) belongs to which family of biomolecules?
It is part of the nucleotide family.
144
The GTPase activating protein (GAP) catalyzes the conversion of Arf1-bound GTP to GDP and inorganic phosphate. What class of enzyme does GAP belong to?
GAP is a phosphatase, which are responsible for the cleavage of phosphate bonds and utilize water to remove a mol of inorganic phosphate.
145
If a protein is encapsulated and is currently in the Golgi apparatus and it is to undergo retrograde transport, where would it be headed?
It would return the protein to the ER where it was translated prior to entering the Golgi.
146
What enzymes are used to overcome the three irreversible steps in gluconeogenesis?
Enzymes: glucose-6-phosphatase, fructose 1,6-biphosphatase, PEP carboxykinase, and pyruvate carboxylase
147
In oxidative phosphorylation, how many electrons can cytochrome c carry?
Cytochrome c is a heme protein that only cycles between a ferrous and ferric state during oxidative phosphorylation. So, only single e- transfers are possible.
148
What is known about the composition of DNA primers ?
Primers have a high GC content and have G or C base paris at the 5" and 3" ends.
149
In which phase of meiosis does nondisjunction occur?
Nondisjunction is the failure of homologous chromosomes to separate during anaphase I of meiosis or failure of sister chromosomes to separate during anaphase II of meiosis.
150
What is euchromatin and why would the GAPDH gene be found here?
Euchromatin is in a loose conformation and readily accessible for transcription, which is good for a continuously expressed housekeeping gene.
151
A fatty acid is comprised of a long hydrocarbon tail and a head consisting of:
Fatty acids contain a carboxylic acid head group and a hydrocarbon tail.
152
What does the term "wild type" refer to?
"Wild type" refers to the traits an animal typically posses when found in nature.
153
What are some indications of an X-linked condition?
The fact that more male and female offspring express this trait, coupled wiht the idea that males never seem to inherit it from their fathers.
154
What is genetic drift?
Genetic drift is simply the change in allele frequency due to random processes. (Random chance plays a role in determining which alleles are inherited by offspring from thwir parents.)
155
What is a frameshift mutation?
Frameshift mutations occur whenever nucleotides are inserted or deleted in numbers other than multiples of three.
156
What is disruptive selection?
Disruptive selection theory states that only the extreme phenotypes are evolutionarily favored.
157
What is sympatric speciation?
Sympatric speciation occurs without a physical barrier. Ex: a population that diverges into two separate species in a single cave.
158
What is convergent evolution?
COnvergent evolution is when entirely separate lineages gradually appear more similar over time. Ex: Bats, birds, and butterflies are very distantly related, but all evolved to possess wings differently.
159
What is commensalism?
Commensalism involves a benefit to only one participating species; the other species is unaffected.
160
What is the result of an additional S phase of a cell cycle?
This results in an additional doubling of the DNA. This would minimize fluctuations only if DNA levels were low.
161
Could an antisense drug help individuals with a genetic disorder that eliminates its enzymatic activity?
No, an antisense drug works to prevent the expression of undesirable genes but does nothing to remedy the problem of a gene that produces an ineffective product.
162
If oligonucleotides, like mRNA, are not degraded rapidly, what process would be affected?
The destruction of mRNA prevents continuous protein production, allowing the cell to change its protein expression over time. The coordination of cell differentiation during development is extremely sensitive to the timing of mRNA turnover.
163
Ture or false: an increase in urine production be casued an increase in blood pressure due to adrenaline, released in respomse to excitement or anxiety.
True.
164
Heart rate is controlled by which part of the brain?
Brainstem
165
Muscle coordination is controlled by which part of the brain?
Cerebellum
166
Appetite is controlled by which part of the brain?
Hypothalamus
167
```
Which of the following characteristics clearly marks fungi as eukaryotes?
A. They have cell walls.
B. They contain ribosomes.
C. They contain mitochondria.
D. They exhibit sexual reproduction.
```
One characteristic the distinguishes between eukaryotic and prokaryotic cells is the presence of membrane-bound organelles like mitochondria in eukaryotes.
168
In what stage of mitosis and meiosis does "splitting of the centromeres" occur?
Mitosis: During anaphase of mitosis, sister chromatids are pulled apart at the centromeres. Meiosis: During anaphase II of meiosis II the centromere is split and the sister chromatids separate.
169
Inbreeding can reduce the fitness of a population in the short term because it causes an increase what?
The chances of getting a pair of deleterious recessive genes increase enormously when a mate is a relative, because relatives are likely to have a similar genotype
170
What is the effect of low blood pressure on glomerular filtration rate?
Low BP decreases glomerular filtration rate, which allows more time for reabsorption. BP is source of energy that forces fluid into capsular space.
171
The two primary factors that normally determine the level of blood pressure are:
Two factors that normally determine the blood pressure are the cardiac output and the resistance to blood flow.
172
```
Accumulation of DDT in the testes may cause reduced fertility in males because the uncoupling of oxidative metabolism from ATP production may reduce:
A. glucose concentration of semen.
B. testosterone concentration of semen.
C. blood circulation in the testes.
D. sperm motility.
```
Sperm motility requires large amounts of ATP. Therefore, reduced sperm motility is most likely to result from reduced ATP levels.
173
How would low fluidity impact the recovery time after a photobleaching event?
Membranes with low fluidity would recover less rapidly after a photobleaching event. (Low fluidity = long recovery time)
174
What is the result on membrane fluidity if it has a high composition of unsaturated fatty acids?
Unsaturated fatty acids increase the fluidity of the membranes.
175
What does the fluid mosaic model mean?
The fluid aspect refers to the ability of component molecules to travel laterally within the bilayer. The word mosaic denotes the presence of proteins and other molecules scattered in a mosaic within its structure.
176
What would increase the membrane fluidity of a membrane at cold temperatures?
The addition of unsaturated fatty acids would increase fluidity in general, and addition of cholesterol would increase fluidity at low temperatures (but decrease at high temps)
177
A scientist has a beaker with 1 L of water in it, there is permeable membrane that divides it in half. If the scientist adds 3 moles of glucose on one side and adds 5 moles of AgCl on the other, what will happen to the water?
Since AgCl is insoluble, leaving that side ion-less, the water will flow to dilute the glucose side.
178
Manganese ions are moved into a cell until it reaches a concentration equilibrium, at which point transport stops. What can be inferred about the transportation used to pass through the membrane?
Transport is passive and manganese uses a protein channel to pass through the membrane.
179
The sodium-potassium pump moves what in and what out of the cell?
It pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell.
180
The Na+ / Ca2+ exchanger moves what ions in and what ions out of the cell?
Since sodium tends to be more highly concentrated outside the cell, it will flow inward when allowed to move down its gradient. Ca2+ will then be moved out of the cell.
181
After a molecule has been engulfed via endocytosis, what order does it progress through membrane-bound compartments before it is degraded?
Endocytosis: Vesicle -> early endosomes -> late endosomes -> lysosomes
182
```
Pinocytosis involves the engulfment of extracellular fluid and any associated solutes by one or more vesicles. It can be classified as which of the following:
I. passive transport.
II. active transport.
III. phagocytosis.
IV. endocytosis.
```
Pinocytosis is a specific form of endocytosis. As such, it requires large amounts of ATP and is certainly classified as active transport.
183
If an unknown organism has its DNA sequenced and rRNA is found, what cellular structures are present in these cells?
Ribosomes are present, as rRNA = ribosomal RNA.
184
The presence of multiple linear chromosomes is a unique quality to eukaryotic or prokaryotic cells?
Only eukaryotes possess linear chromosomes in a true nucleus.
185
What is the function of the Golgi apparatus?
It receives proteins from the endoplasmic reticulum and packages them into vesicles. Also, lysosomes are formed from vesicles that bud off the Golgi’s larger structure.
186
What would be the result of removing the endoplasmic reticulum?
The removal would greatly diminish overall nuclear integrity and likely cause the organelle to lyse. - Thus, cause apoptosis.
187
What is the function of the rough ER?
The rough ER has bound ribosomes that produce a variety of proteins.
188
What is the function of the nucleolus?
The nucleus is vital for the synthesis of ribosomes from protein and rRNA.
189
What is the function of a peroxisome?
Small membrane-bound organelles that break down lipids.
190
What is the function of a lysosome?
Lysosomes facilitate the enzymatic catabolism of protein.
191
What cytoskeletal polymer is crucial to macrophage function?
Actin filaments
192
What cytoskeletal protein contributes to most of the skin's resistance to stretching and tearing?
Keratin fibers, As a type of intermediate filament, keratin possesses high tensile strength; it can form a network of fibers that distribute mechanical stress among the cells of an epithelial layer
193
What type of cytoskeletal protein fiber is used in cytokinesis to pinch the two daughter cells apart?
A contracting ring of actin microfilaments helps pinch the two daughter cells apart.
194
If the ETC is shut down and unable to produce ATP, how would the cell then produce ATP?
If ATP is no longer produced through the ETC, then glycolysis would be the next major pathway for ATP production.
195
In an experiment studying complexes I, II, III, and IV, why would their activity need to be determined independently?
Studying the complexes all together would lead to erroneous results because inhibition of I and II affects activity of III, which affects activity of IV.
196
Moving an ion into a cell against their concentration gradient requires energy, what is the term that describes this process?
Active transport
197
What is the result on the propigation of an electrical signal if voltage-gated potassium channels are blocked?
If potassioum channels are blocked, then the membrane would fail to repolarize and extend the length of the action potential.
198
What type of chemical reaction breaks disulfide bridges?
The presence of reducing agents will break disulfide bridges.
199
What are micelles?
Phospholipid-bound liposomes
200
What is the result of a protein forming a membrane-spanning channel?
This will alter the permeability of the inner membrane, thus dissipating the proton gradient.
201
What is the molecule that GAPDH reversibly converts from glyceraldehyde-3-phosphate?
1,3-biphosphoglycerate
202
What does a Western blot analyze?
Proteins
203
Vasopressin regulates the insertion of aquaporins into the apical membranes of the epithelial cells of what renal structure?
The collecting duct
204
What are the primary myelin-forming cells in the peripheral nervous system?
Schwann cells are the myelin-forming cells in the peripheral nervous system.
205
What is a prion?
A prion is an abnormally folded protein that induces a normally folded version of the protein to also adopt the abnormal structure, which is often deleterious.
206
What is the function of LH and where is it produced??
LH is produced in the anterior pituitary gland and it stimulates sex hormone production by the gonads in both sexes and triggers ovulation in females.
207
What is the function of endosomes ?
Endosomes fold inward with the cells plasma membrane to surround macromolecules or other matter diffusing through the extracellular fluid
208
What is the function of a protease?
Proteases function to digest proteins into smaller fragments.
209
Under anaerobic conditions, how many net molecules of ATP are produced by the consumption of 5 moles of glucose?
Under anaerobic conditions, 2 moles of ATP are produced from each mole of glucose. Thus, 10 moles of ATP would be generated from 5 moles of glucose. Since there are 6 × 1023 molecules per mole, 10 moles of ATP is equal to 6 × 1024 molecules.
210
What are lysosomes?
Lysosomes are defined as membrane-bound organelles that contain hydrolytic enzymes activated by a low pH, which are capable of degrading many kinds of biomolecules.
211
Where do microtubules originate?
Microtubules are cellular structures that originate from centrosomes.
212
How do cytotoxic T lymphocytes target virus-infected cells?
Cytotoxic T lymphocytes target virus-infected cells by recognizing the viral antigen presented on the cell surface.
213
When an initially heterozygous macronucleus undergoes repeated binary fission, the result will be:
A. The loss of macronuclear chromosomes.
B. An increased rate of crossing over in the macronucleus.
C. The production of a macronucleus with a genetic origin distinct from the micronucleus.
D. A variable allele distribution in the macronucleus.
The amitotic division of the macronucleus will result in uneven distribution of chromosomes, hence an unpredictable genome and the allele distribution will be uneven.
214
What recombinant processes depends on the F factor plasmid?
Conjugation requires special genes for a sex pilus and these are usually present on a plasmid, a separate extragenomic strand of DNA not incorporated into the bacterium’s own DNA. This plasmid is referred to as the fertility or F factor.
215
If an IV infusion causes a sharp rise in serum level of albumin, what will be the result of this on the circulatory system?
An increase in plasma albumin will upset the osmotic balance because the blood will become hypertonic with respect to the tissue. Water will have to flow into the bloodstream to reestablish equilibrium.
216
What steroid causes Na+ reabsorption by kidney tubules, which decreases Na+ levels in the urine?
Aldosterone, which is produced by the adrenal cortex
217
What is the function of activated vitamin D?
Activated vitamin D acts on the small intestine to stimulate the absorption of calcium into the bloodstream.
218
What is the function of osteoclast activity?
Osteoclasts break down bone cells.
219
What is hypocalcemia and what are the ramifications of this on the body?
Hypocalcemia is a condition of low blood calcium. This would cause increased neuromuscular excitability due to the change in membrane potential. A person may die from severe respiratory muscle spasms.
220
What changes in blood volume and pressure would be expected as a result of aldosterone deficiency?
This deficiency would result in a decreased blood volume and a decreased blood pressure.
221
In which organelle of a eukaryotic cell is the pyramidine uracil incorporated into as a nucleic acid?
Uridine is incorporated into RNA in the nucleus where transcription of DNA into RNA takes place.
222
What are significant differences between fast and slow twitch fibers?
Compared to fast-twitch fibers, slow-twitch fibers are adapted for aerobic exercise (long-dist run) and so they have (1) increased capillary density, (2) higher #s of mitochondria, and (3) higher levels of oxygen-binding protein.
223
What type of evolution is exhibited whereby distantly related organisms independently evolve similar traits to adapt to similar needs?
This process is called convergent evolution
224
How are two different proteins created from a single mRNA strand?
An operon containing two genes is prokaryotic cells is transcribed from a single promoter upstream of the first gene in the operon.
225
What is the function of histone acetylase (HAT)?
Histone acetylation typically promotes transcription and uncoiling of the chromatin structure.
226
What is the function of histone deacetylase (HDAC)?
HDAC promotes a condensed structure of the chromatin and decreased transcription at these genes.
227
What processes does fasting and prolonged fasting lead to?
Fasting leads to glycogen breakdown and gluconeogenesis. Continued fasting leads to the production of ketone bodies by sustained fatty acid oxidation.
228
What metabolic pathway is phosphoglucose isomerase involved in?
Phosphoglucose isomerase is an enzyme involved in glycolysis.
229
Why would tubulin be used as a loading control to test for equal amounts of protein in a Western blot under hypoxic conditions?
This is because tubulin are stable under most conditions, including hypoxia.
230
What is one way that a virus, which containes RNA as their genetic material, replicates themselves?
RNA viruses require a type of transcriptase (reverse transcriptase) to replicate themselves.
231
If large amounts of protein are cound in the urine of a person, what portion of the nephron is malfunctioning?
In healthy individuals the glomerular capillaries prevent the entry of large molecules, like proteins, into the filtrate.
232
What is the optimum temperature for enzymes to function at their apex?
The optimum temperature is 37 C
233
How might the action of serotonin on the postsynaptic receptors be terminated?
The action would be terminated by removal of serotonin from the synaptic space. This could occur by transport of serotonin back into the presynaptic terminal. (An action that SSRIs block)
234
SSRIs most likely relieve depression by doing what?
SSRIs treat depression by blocking reuptake in the presynaptic neuron. Blocking the reuptake in the presynaptic neurons would increase the amount of time that serotonin is available in the synaptic cleft to bind to postsynaptic neurons.
235
What is the result of Villi atrophy on the body?
Villi atrophy results in a decrease in the surface area of the small intestine, leading to a decrease in nutrient absorption.
236
Excess unabsorbed fats most likely have what effect within the intestines?
An excess of unabsorbed fats in the intestines inhibits normal water and electrolyte absorption, resulting in increased osmotic pressure and diarrhea.
237
What is the function of osteoclasts and osetoblasts?
Osteoblasts function to build and repair bone. Osteoclasts break down bone.
238
In a preterm neonate that is coping with collapsing alveoli, what can they do to improve the atelectasis?
They can grunt which causes expiration against a positive end-expiratory pressure (in other words, causing the alveolar pressure to be comparatively low) forces air into the alveoli, keeping them open and allowing gas exchange to continue.
239
An effective and efficient method for the delivery of an antisense gene could be:
Deliver the antisense gene into the cells of the individual by infecting an embryo with a virus that carries the antisense gene. The appropriate virus could become incorporated into the genome of the embryonic cells, thus causing all cells derived from these embryonic cells to contain the antisense gene
