Princeton Review MCAT Demo Test Bio/Biochem

Question 5: If a filamentous body were isolated from an infected individual and injected into an uninfected healthy individual what antibodies would be formed? a. anti-core IgM b. anti-eAg IgG c. anti-sAg IgM d. anti-sAg IgG

Answer: C

Question 15: The presence of high concentrations of ATP stimulates production of: a. ribose-5-phosphate b. pyrimidines c. purines d. both pyrimidines and purines

Answer: D

Question 14: Which of the following are products of the pentose phosphate pathway? I. NADPH II. Glycolytic intermediates III. Ribose-5-phosphate

Answer: I, II, III

Question 57: ACE inhibitors are a class of drugs frequently prescribed to treat hypertension. Captopril, a compound that is structurally similar to angiotensin I, was developed in 1975 as the first ACE inhibitor. When patients take Captopril, which of the following is true about the kinetics of their ACE. a. Vmax decreases, Km remains the same b. Vmax remains the same, Km increases c. both Vmax and Km increase d. both Vmax and Km remain the same

Answer B Vmax - maximum velocity of the enzyme competitive inhibition: raises Km only Can only bind to E and not ES. Increase Km by interfering with the binding of the substrate, but does not affect Vmax because the inhibitor does not change the catalysis in ES because it cannot bind ES. uncompetitive inhibition: lowers Vmax and Km Inhibitor that only binds to the ES complex. Both Vmax and Km are reduced by equal amounts. ESI complexes inhibit the formation of product. noncompetitive inhibition: lowers Vmax only, not affect Km Will bind the enzyme on allosteric site (site other than active site). Inhibitor can bind to an enzyme with or without a substrate. Reduces the amount of enzyme available for proper catalysis, which leads to smaller Vmax. Adding more substrate has no effect, unlike in competitive inhibition.

Question 53: Given the role of Pdk4, is its elevation in the mice induced to express HH symptoms consistent with the decreased glucose oxidation seen in diabetic patients? a. No; PDH is needed for gluconeogenesis, and Pdk4 levels should be decreased in diabetic patients b. No; PDH activity should be decreased in diabetic patients due to decreased intracellular glucose concentration c. Yes; high Pdk4 levels will limit glucose oxidation in diabetic patients, who have decreased rates of cellular glucose uptake d. Yes; elevated Pdk4 levels will increase acetyl-CoA production, leading to increased production of ketone bodies, as seen in diabetic patients

Answer C Ketone bodies: always present in blood and their levels increase during fasting and prolonged exercise. In diabetic ketoacidosis, high levels of ketone bodies are produced in response to low insulin levels and high levels of counter-regulatory hormones. Produced by liver from fatty acids during periods of low food intake, starvation, carbohydrate restrictive diets.

Question 29: A genetic regulator is found to contain a lysine that is important for its binding to DNA. If a missense mutation were to occur to this lysine residue, which of the following resulting amino acids would likely be the least harmful to its ability to bind to DNA? a. arginine b. glutamate c. aspartate d. glycine

Answer: A

Question 41: Which of the following best describes why ivabradine is used in patients with cardiac ischemia? a. ivabradine decreases heart rate, reducing the severity of hypoxia b. ivabradine decreases If, increasing intracellular Ca2+ stores for myocyte contraction c. Ivabradine blocks HCN channels, decreasing cAMP concentrations and activating the parasympathetic nervous system d. parasympathetic stimulation causes epinephrine release, activating G-protein coupled receptors that result in elevated cAMP levels

Answer: A Cardiac ischemia: when blood flow to heart is reduced, preventing it from receiving enough oxygen. Usually the result of partial or complete blockage of heart's arteries.

Question 2: An asthmatic reacting to cat dander presents at the ER and the doctor orders an inspiratory chest X-ray. Which of the following is the X-ray most likely to look like during this asthma attach? a. hyperexpanded lung volumes b. normal lung volumes c. areas of pus, derived from dead neutrophils and bacteria d. diminished lung volume

Answer: A Hyperinflated occurs when air gets trapped in the lungs and causes them to overinflate. Hperinflated lungs are often seen in people with chronic obstructive pulmonary disease. Certain lung problems, such as asthama and cystic fibrosis, also cause hyperinflation.

Question 17: Which of the following is likely true of the pentose phosphate pathway? a. It is more active in adipose tissue than in muscle tissue b. NADPH is produced and can be used in the electron transport chain and oxidative phosphorylation to generate ATP c. it is a series of isomerizations of six-carbon sugars d. the inhibition of carbamoyl phosphate synthase by purine nucleotides helps to regulate the production of UTP and CTP

Answer: A NADPH serves as an electron donor in reductive biosynthesis. The pentose phosphate pathway is much more active in adipose tissue than in muscle cells, as large amounts of NADPH are consumed by adipose tissue in the reductive synthesis of fatty acids from acetyl CoA. NADPH: the reduced form of NADP+, which differs from NAD+ in the presence of an additional phosphate group. NADPH is produced in the last step of the electron chain in photosynthesis. Used as the reducing power such as in the Calvin cycle to assimilate carbon dioxide. Major source of NADPH is the pentose phosphate pathway. NADH is used in electron transport chain to obtain energy by converting NADH back to NAD+. NADPH is required as a reducing agent in lipid and nucleic acid synthesis. Role of NADPH is mostly anabolic reactions; NADPH is needed as reducing agent. Role of NADH is mostly catabolic reactions, where NAD+ is needed as oxidizing agent.

Question 21: Which of the following techniques would be LEAST likely to detect a Robertsonian translocation? a. southern blot b. routine karyotype c. high-resolution karyotype d. fluorescent in situ hybridization of chromosomes

Answer: A Southern blot: to detect a specific DNA sequence in DNA samples. Combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. Routine karyotyping: routine chromosome analysis, analysis of metaphase chromosomes. Karyotype: number and appearance of chromosomes in the nucleus of a eukaryotic cell. Also used to describe the complete set of chromosomes in a species or individual. Describes the chromosome count.

Question 49: An adult rat is treated with a sub-lethal dose of TTX via injection. Which of the following is most likely to be observed? a. decreased respiratory rate b. decreased gastrointestinal motility c. neurotoxicity in pancake astrocytes d. voluntary limb movement

Answer: A astrocytes: most numerous cell type within central nervous system. Help with axon guidance and synaptic support to control the blood brain barrier and flow. They are star-shaped. Regulate transmission of electrical impulses within the brain.

Question 35: A patient receiving a liver transplant has immediate post-operative complications, and subsequent blood tests and biopsy results indicate organ failure. Which type of immunity is most likely involved in this process? a. innate b. humoral c. cell-mediated d. complement system

Answer: B Innate immunity - refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. Innate leukocytes include: natural killer cells, mast cells, eosinophils, basophils, macrophages, neutrophils, dendritic cells. Not specific to a particular pathogen; depend on group of proteins and phagocytic cells that recognize conserved features of pathogens and become quickly activated to help destroy invaders. Humoral immunity - mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, antimicrobial peptides. Mediated by antibody molecules secreted by plasma cells. Involves substances found in the humors, or body fluids. Refers to antibody production and Th2 activation and cytokine production. Effector functions of antibodies -- pathogen and toxin neutralization. 1) B Cells mature in bone marrow and gain B-cell receptors, which are displayed on cell surface. Have antibodies specific for antigen detection. Each B cell has a unique antibody that binds with an antigen. Matured B cells migrate from bone marrow to lymph nodes or other lymphatic organs, where they encounter pathogens. B cell activation: when B cell encounters antigen, it is bound to receptor and endocytosed. Antigen is processed and presented on its surface again with MHC-II molecule. B cell proliferation: When Th Cell binds to the complex, cytokines will be released that induce B cells to divide. Daughter B cells become plasma cells or memory cells. Cell-mediated immunity: immune response that does not involve antibodies, but involves activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and release of various cytokines in response to an antigen. Separated into 2 branches: humoral immunity and cellular immunity (T-cell mediated immunity) Complement system: part of immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane.

Question 24: Which of the following is true about the embryo used in the experiments? a. the embryo would have to be post-grastulation and the molecule injected into the blastomeres would have to be single-stranded RNA either with or without introns b. the embryo would have to be pre-grastulation and the molecule injected into the blastomeres would have to be single-stranded RNA without introns c. the embryo would have to be post-grastulation and the molecule injected into the blastomeres would have to be single-stranded DNA generated from RNA d. the embryo would have to be pre-grastulation and the molecule injected into the blastomeres would have to be double-stranded DNA without introns

Answer: B Introns: noncoding regions Exons: coding regions, those that are 'ex'pressed. During transcription, the entire gene is copies into a pre-mRNA which includes both exons and introns. During process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence.

Question 23: The Goosecoid protein would contain which of the following? a nuclear localization signal and disulfide bonds b. nuclear localization signal and DNA binding motifs c. signal sequence and disulfide bonds d. signal sequence and DNA binding motifs

Answer: B Nuclear localization signal: or sequence, is an amino acid sequence that tags a protein for import into the cell nucleus by nuclear transport. Typically consists of one or more short sequences of positively charged lysines or arginines exposed on the protein surface. DNA binding motifs: motifs are short, recurring patterns in DNA that are resumed to have a biological function; usually indicate sequence-specific binding sites for proteins Signal sequence: function to prompt a cell to translocate the protein, usually to the cellular membrane

Answer 45: Rank the following metals in order of increasing oxidation potential: I. Sr(s) II. Cs(s) III. Fe(s) IV. Ca(s) A. III<II<I<IV B. III<IV<I<II C. II<I<IV<III D> IV<I<III<II

Answer: B Oxidation potential - measure of tendency of chemical species to give away electrons and be oxidized. Cs is most likely to give away electrons, so has the most oxidation potential.

Question 13: Synthesis of which of the following are subject to end-product inhibition? a. AMP, GMP, CTP only b. AMP, GMP, CTP, UTP c. AMP, GMP d. UTP, CTP

Answer: B Read the passage carefully!

Question 19: With which of the following processes is a double-stranded DNA break NOT typically associated? a. recombination b. mitosis c. balanced Robertsonian translocation d. unbalanced Robertsonian translocation

Answer: B Recombination: During meiosis, involves the pairing of homologous chromosomes. Transfer of information between chromosomes Translocation: chromosome abnormality; rearrangement of parts between nonhomologous chromosomes. Balanced: an even exchange of material wit no genetic information extra or missing, ideally full functionality. Unbalanced: exchanges of chromosome material is unequal resulting in extra or missing genes.

Question 12: Sodium laurel sulfate, a common ingredient in hand soap, functions due to the combination of its hydrophobic tail. This amphipathic nature allows for the removal of hydrophobic substances with water. Which of the following would most likely increase the effectiveness of sodium laurel sulfate? a. benzene b. dilute aqueous sodium bicarbonate c. aqueous phosphoric acid (pH = 1.9) d. lemon juice

Answer: B Sodium bicarbonate: baking soda, NA+ -OCOOH Would raise the pH level Amphoteric compound, aqueous solutions are mildly alkaline due to the formation of carbonic acid and hydroxide ion. Can be used as wash to remove any acidic impurities. Saponification: chemical reaction between acid and base to form a salt. When you make soap, you mix an oil or fat (your acid) with Lye (which is the base) to form soap (the salt).

Question 54: Palmitic acid has the chemical formula, C16H32O2. Which of the following best describes the appropriate product distribution after 4 rounds of beta-oxidation? a. 1C12H24O2; 4 NADH, 4 acetyl-CoA; 4 FADH2 b. 1C8H16O2; 4 NADH; 4 acetyl-CoA; 4 FADH2 c. 1C8H16OSCoA; 4 NADH; 4 acetic acid; 4 FADH2 d. 1C6H12O2; 5 NADH; 5 acetyl-CoA; 5 FADH2

Answer: B beta-oxidation: catabolic process by which fatty acid molecules are broken down (cytosol in prokaryotes, mitochondria in eukaryotes) to generate acetyl-CoA, which enters into citric acid cycle, and NADH and FADH2 which are used in electron transport chain. acetyl-CoA has two carbons

Question 6: Which of the following would be detected in the blood of a person chronically infected with hepatitis B? a. anti-core IgG, anti-sAg b. HBsAg, anti-core IgM, anti-core IgG c. HBsAg, anti-core IgG d. HBsAg, anti-core IgG, anti-sAg

Answer: C

Question 44: Phosphofructokinase (PFK) is the rate-limiting enzyme in glycolysis. Which of the following conditions would negatively regulate PFK activity? a. low cellular ATP/ADP b. low cellular NADH/NAD+ c. high citric acid levels d. high cellular Mg2+ levels (a cofactor for the PFK reaction)

Answer: C Glycolysis extracts energy from sugars and store it in ATP and NADH. The end product of glycolysis is pyruvate. A high ratio of ATP to ADP will inhibit PFK. Glucose -> glycolysis Pyruvate -> pyruvate oxidation Acetyl CoA -> Citric acid cycle -> oxidative phosphorylation 3rd step of pathway: catalyzed by enzyme PFK -- this is the first committed step, making PFK a central target for regulation of the glycolysis pathway AMP: positive regulator of PFK; when cell is low on ATP, it will convert more ATP and AMP so high levels of AMP means that cell needs energy. Citrate: the first product of the citric acid cycle, can also inhibit PFK. If citrate builds up, this is a sign that glycolysis can slow down, because the CAC is backed up and doesn't need more fuel.

Answer 46: At what pH would the net charge on a 3.0 M solution of the amino acid asparagine (pKa alpha-COOH = 2.0, pKa alpha-NH3+ = 8.8) be effectively minimized? a. 1.0 b. 2.0 c. 5.0 d. 9.0

Answer: C Net charge is minimized when there is no charge. alpha-COOH: at pH higher than 2.0, it will be COO- alpha-NH3+: at pH lower than 8.8, it will be NH3+ total charge will be 0. Only option that matches this is c.

Question 33: Certain lung cancers can secrete PTHrP (parathyroid hormone related-protein), which, while distinct from PTH, binds and activates PTH receptors. Which of the following laboratory findings would be consistent with a patient that had a PTHrP-secreting tumor? a. decrease Serum [calcium], increase PTH, decrease risk of nephrolithiasis b. increase Serum [calcium], increase PTH, increase risk of nephrolithiasis c. increase Serum [calcium], decrease PTH, increase risk of nephrolithiasis d. decrease Serum [calcium], decrease PTH, increase risk of nephrolithiasis

Answer: C Parathyroid hormone (PTH) is released by parathyroid gland. When calcium in our blood goes too low, the parathyroid glands make more PTH. Increased PTH causes the body to put more calcium in the blood. Increased PTH causes the bones to release their calcium into the blood.

Question 16: The reaction of glucose-6-phosphate to ribulose-5-phosphate is a(n): a. carboxylation of G6P b. reduction of G6P c. oxidation of G6P d. isomerization of G6P

Answer: C The pentose phosphate pathway begins with the oxidation of a glucose-derived carbon atom to CO2 and concomitantly generates NADPH. Carboxylation: carboxylic acid group is formed -- not the case here

Question 8: Which of the following mutations would most likely lead to a virus incapable of infecting liver cells? a. missense mutation in pre-S2 b. nonsense mutation late in S c. single base pair insertion in pre-S1 d. three nucleotide deletion early in S

Answer: C There are multiple in-frame start codons, so the shift may not really affect the virus. Nonsense mutation: codon is changed to a premature stop codon that results in truncation of resulting protein. Missense mutation: point mutation in which single nucleotide change results in a codon that codes for a different amino acid. Start codon: always codes for methionine in eukaryotes: AUG 3 stop codons: UAG, UGA, UAA

Question 42: The process by which the autonomic nervous system activates HCN channels is best described by which of the following? a. sympathetic stimulation causes acetylcholine release, thereby activating cardiac tyrosine kinase receptors, resulting in elevated cAMP levels b. parasympathetic stimulation causes acetylcholine release, thereby activating tyrosine kinase receptors, resulting in elevated cAMP levels c. sympathetic stimulation causes epinephrine release, thereby activating G-protein coupled receptors, resulting in elevated cAMP levels d. parasymphathetic stimulation causes epinephrine release, thereby activating G-protein coupled receptors, resulting in elevated cAMP levels

Answer: C Tyrosine kinase receptors: bind to peptide/protein hormones. Ligand binding leads to activation of kinase activity

TTX has been detected in pufferfish, newts, red alga, crabs, starfish, octopus, and many types of worms. Question 48: TTX-producing bacteria have been found in symbiotic relationships with: a. animals only b. animals and worms c. plants, worms, and fish d. animals and at least one other kingdom to eukaryotes

Answer: D

Question 36: Exogenous corticosteroids would have what effect on the hypothalamic-pituitary-adrenal axis? a. increase in both CRH and ACTH b. increase in CRH and decrease in ACTH c. decrease in CRH and increase in ACTH d. decrease in both CRH and ACTH

Answer: D ACTH: adrenocorticotropic hormone. ACTH stimulates secretion of glucocorticoids and has little control over secretion of aldosterone. ACTH is secreted from anterior pituitary in response to corticotropin-releasing hormone from hypothalamus.

Question 4: Which of the following is a true statement about the diaphragm? a. it contains both skeletal and smooth muscle cells b. its effector neurotransmitters are norepinephrine and acetylcholine c. it is innervated by the phrenic nerve and autonomic nervous system d. it receives neural signals from the cerebral cortex and the brain stem

Answer: D Diaphragm is classified as a skeletal muscle. Most of the time it is under involuntary control but we can move it voluntarily at will. Efferent connections: In nervous system, refer to those that send signals from the CNS to the effector cells of the body such as muscles and glands. Efferent nerves are also referred to as motor neurons. Phrenic nerve: nerve that originates in the neck and passes down between the lung and heart to reach the diaphragm. Important for breathing since it passes motor information to the diaphragm and receives sensory information from it. There is a left and right phrenic nerve. Contains motor, sensory, and sympathetic nerve fibers.

Question 28: In a culture of mammalian skeletal muscle cells, the consumption of oxygen and glucose is measured. Which of the following would occur in response to inhibition of electron transport? a. oxygen consumption will increase, and glucose consumption will decrease b. oxygen consumption will increase and glucose consumption will increase c. oxygen consumption will decrease and glucose consumption will decrease d. oxygen consumption will decrease and glucose consumption will increase

Answer: D Electron transport chain: series of complexes that transfer electrons from electron donors to electron acceptors via redox reactions and couples this electron transfer with the transfer of protons across a membrane. Synthesizes ATP

Question 31: A decreased TmP/GFR value would result in which of the following? I. Hypophosphatemia II. Increased 1,25-dihydroxy vitamin D production III. Hyperphosphatemia

Answer: I and II only Vitamin D from the diet or skin synthesis is biologically inactive; enzymatic conversion in the liver and kidney is required for activation.

Question 52: In order to obtain the data in Table 1, various tissues from rats were collected. What other experimental step(s) were required? I. Lysis of cells, and removal of protein and lipid components II. Isolation and stabilization of genomic DNA III. Isolation and stabilization of RNA, and generation of cDNA

Answer: I and III only cDNA is synthesized from single stranded RNA template in a reaction catalyzed by enzyme reverse transcriptase. Often used to clone eukaryotic genes in prokaryotes.

Question 11: Which of the following statements about bile is/are true? I. Bile emulsifies lipids for easier digestion II. The amphipathic nature of bile allows it to digest lipids III. Bile is produced by the liver and gallbladder

Answer: I only Bile is a complex fluid containing water, electrolytes and organic molecules including bile acids, cholesterol, phospholipids, and bilirubin. Bile contains bile acids. Bile acids are amphipathic, which allows them to emulsify lipids, and are able to be lipid carriers and solubilize many lipids by forming micelles Bile is produced by the liver and stored in the gallbladder.

Which of the following statements is/are true with regard to the mechanics of skeletal muscle contraction? I. Reduced ATP levels could result in high intracellular calcium and persistent contraction II. Calcium binds to calmodulin and allows actin and myosin to interact III. The shorter the sarcomere length, the stronger the contraction

Answer: I only Sarcomere: During contraction, A bands do not change length; I-bands and H-zone shorten, causing Z lines to come closer together. Muscle contraction: ends when Ca2+ ions are pumped back into the sarcoplasmic reticulum, allowing the contractile apparatus and muscle cell to relax.

Question 7: Viral infection would lead to an increase in which of the following cellular pathways? I. Aerobic respiration II. Pentose phosphate pathway III. cAMP mediated protein kinase activation

Answer: I, II only Infection by viruses can significantly affect cellular respiration and ability of cells to produce ATP. cAMP-dependent pathway: activated Gs alpha subunit binds to and activates enzyme adenyly cyclase, which catalyzes the conversion of ATP into cAMP. Increase in cAMP leads to activation of exchange proteins, enzyme protein kinase A (PKA), cyclic nucleotide-gated ion channels. Once PKA is activated, it phosphorylates other proteins including converting glycogen to glucose, enzymes that promote muscle contraction in heart (increased heart rate), transcription factors. Different cell responses mediated by cAMP: increase in heart rate, cortisol secretion, breakdown of glycogen and fat. Essential for maintenance of memory in brain, relaxation in the heart, and water absorbed in the kidney. This pathway activates enzymes and regulates gene expression. Activated GPCRs cause conformational change in the attached G protein complex, results in alpha subunit exchanging GDP for GTP and separation of beta and gamma subunits. ---------- Pentose phosphate pathway: generation of reducing equivalents in form of NADPH and production of ribose-5-phosphate, used in synthesis of nucleotides and nucleic acids. Consists of aerobic and anaerobic part. Significance: main source of synthesis of NADPH. Fatty acid synthesis is a NADPH dependent process.

Question 3: Which of the following medications are used to treat asthma? I. Salbutamol (short acting Beta-agonist) II. prednisolone (glucocorticoid) III. Cromolyn sodium (mast cell stabilizer) IV. Propranolol (long acting beta-antagonist)

Answer: I, II, and III only Glucocorticoid: any of a group of corticosteroids (e.g., hydrocortisone) that are involved in the metabolism of carbohydrates, proteins, and fats and have anti-inflammatory activity. Interrupts inflammation by moving into cells and suppressing the proteins that go on to promote inflammation. Mast cell stabilizers: chromone medications used to prevent or control certain allergic disorders. They block mast cell degranulation, stabilizing the cell and thereby preventing the release of histamine and related mediators.

Question 18: It can be inferred from the passage that TTP is made from: I. Glutamine II. Carbomoyl phosphate III. Intermediate 1 IV. Intermediate 2

Answer: I, III, IV Purines are A and G -double rings Pyrimidines: T and C and U -single rings Pairings: A/T, G/C RNA represented by A, G, C, U Pairings: A/U, G/C

Question 37: Which statement(s) is/are true regarding antigen-presenting cells? I. The only MHC proteins they express are class II II. They have a direct role in all types of rejection III. A dendritic cell is one type of APC

Answer: III only APC are immune cells that mediate cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. APCs include dendritic cells, macrophages, Langerhans cells, and B cells.

Question 40: CNG channels are likely utilized in which of the following regulatory pathway(s): I. ADH regulation of water retention II. aldosterone regulation of sodium and water retention III. regulation of olfactory neuronal depolarization

Answer: III only CNG channels only affect depolarization and hyperpolarization of cells.

Citric acid cycle

Entry into citric acid cycle is largely controlled through pyruvate dehydrogenase, the enzyme that produces acetyl CoA. Isocitrate dehydrogenase controls the first of these 2 steps, turning 6-C molecules into 5-C molecules. This enzyme is inhibited by ATP and NADH, but activated by ADP. alpha-ketoglutarate dehydrogenase: turns 5C compound into 4C compound bound to CoA (succinyl CoA). This enzyme is inhibited by ATP, NADH, and other molecules, including succinyl CoA.

Pyruvate oxidation

Pyruvate is converted to acetyl CoA (irreversible in many organisms) and controls how much acetyl CoA fuel enters the citric acid cycle. Pyruvate dehydrogenase is the enzyme that catalyzes this reaction. ATP and NADH make the enzyme less active, while ADP makes it more active. So more acetyl CoA is made when energy stores are low. Pyruvate dehydrogenase is activated by its substrate pyruvate, and inhibited by its product, acetyl CoA. Ensures that acetyl CoA is made only when it's needed.

Question 30: If size exclusion chromatography (SEC) were used to separate a mixture of ethylene glycol oligomers, as shown below, with fractions further purified by gas chromatography (GC), what might be expected? a. the use of nonpolar solvents in SEC will lead to good separation and efficient purification by GC b. the use of ether-type solvents in SEC will lead to poor separation, and subsequently to inefficient purification by GC c. oligomers with long retention times on the SEC column have long GC retention times d. oligomers with short retention times on the SEC column will have long GC retention times

SEC: method in which molecules in solution are separated by their size, and in some cases molecular weight. Usually applied to large molecules or macromolecular complexes. The large particles cannot enter the pores, and the smaller molecules are trapped in the pores. The smaller the molecule, the longer the retention time. The larger molecules will flow through the column more quickly. ethylene glycol - OHCH2Ch2OH Gel-filtration chromatography: fractionation of proteins and other water-soluble polymers Gel permeation chromatography: used to analyze the molecular weight distribution of organic-soluble polymers Gel electrophoresis: electric field is used to pull or push molecules through the gel depending on their electrical charges.

Sympathetic nervous system vs Parasympathetic nervous system

SNS: vasoconstriction, fight or flight Preganglionic neurotransmitter: Acetylcholine ACh, binds to nicotinic ACh receptors on postganglionic neuron Postganglionic neurotransmitter: Norepinephrine, binds to adrenergic receptors PNS: vasodilation, rest and digest The ganglia of the parasympathetic NS are referred to as terminal ganglia as they lie close to, or within, the organs that they innervate. Preganglionic neurotransmitter: ACh, then binds to nicotinic receptors Postganglionic neurotransmitter: ACh, then binds to muscarinic receptors