TPR 5

Saponification of triglycerides will produce what?

1 glycerol and 3 fatty acid salts. B. In saponification, the triester is hydrolyzed to a triol (glycerol) and 3 fatty acid salts.

In a human liver cell, approximately how many glucose molecules would be required to synthesize a 750-amino acid protein?

100 A. To synthesize a 750-amino acid protein would require 2999 ATP molecules (4 ATP per amino acid, minus 1), or approximately 3000. A human liver cell typically undergoes aerobic respiration (glycolysis, PDC, Krebs cycle, electron transport, oxidative phosphorylation) and produces 30 ATP per glucose molecule. Thus, approximately 3000/30 = 100 glucose molecules would be required for this synthesis.

Each polymerase needs a free ______ so polymerization can occur

3- OH group

ATP required for amino acid synthesis

4 ATP/amino acid minus 1

Huckel's Rule

4n + 2

DNA/RNA polymerization occurs in which direction

5 to 3

cDNA (complementary DNA) is often reverse transcribed from mature (processed) eukaryotic mRNA in order to create DNA without introns. The enzyme reverse transcriptase is used to create the initial complementary DNA strand, and requires a short sequence of DNA to act as primer. Which of the following sequences would make a good primer? A. Any random sequence of DNA could be used, as long as it has a free 3' end for reverse transcriptase to act on. B. Any random sequence of DNA could be used, as long as it has a free 5' end for reverse transcriptase to act on. C. UUUUUUUU D. TTTTTTTTT

TTTTTTTTTTT D. Since DNA and RNA polymerization always take place in a 5' to 3' direction, each polymerase needs a free 3'-OH group so polymerization can occur (B is wrong). Although a random DNA sequence might coincidentally match the mRNA somewhere in its sequence and bind there, a poly-T sequence would be guaranteed to pair with the 3' poly-A tail of the mRNA, maing D a better answer than A. Uracil (U) is a component of RNA, not DNA (C is wrong).

Individuals with immune deficiencies are found to be more susceptible to cancer than are healthy individuals. Which of the following reasons is the most likely explanation? A. The lymph vessels contain tumor cells. B. These individuals produce an abundant amount of lymphocytes in their bone marrow. C. The immune system is compromised and cannot eliminate cancerous cells D. The lymphocytes are no longer able to make antigens.

The immune system is compromised and cannot eliminate cancerous cells. C. The job of the immune system is to remove any foreign substances (pathogens, toxins, etc.) from the body to prevent possible harm to the body. It also patrols the body for normal cells displaying abnormal functions (i.e., cancer cells) and eliminates them. If the immune system is deficient, it cannot do this very effectively (C is correct). Immune-deficient individuals would produce fewer lymphocytes than normal individuals, not more (B is wrong), and lymphocytes do not make antigens, they fight antigens (D is wrong). While choice A may be true, it is not the reason these individuals are more susceptible to cancer, but rather the outcome of being more susceptible to cancer (eliminating A).

If benzaldehyde and 2-methylcyclohexanone are placed together in the presence of an acid, and a mixed aldol condensation takes place, which one will serve as the nucleophile?

The ketone to give two different products. B. The aldehyde cannot act as the nucleophile since it has no α-hydrogens. Two different products form because a stereocenter is formed in the reaction. This comes from addition of the nucleophile to the "top face" and "bottom face" of the benzaldehyde.

Outcome of being more susceptible to cancer

The lymph vessels contain tumor cells.

All of the following tissues are part of the immune response EXCEPT the: A. thymus. B. spleen. C. lymph nodes. D. pancreas.

The thymus is the site of T-cell maturation (A can be eliminated), the spleen is the site of B-cell maturation and also filters antigens from blood (B is wrong), and lymph nodes are sites of both B- and T-cell proliferation (C can be eliminated). The pancreas produces digestive enzymes, bicarbonate, and hormones but is not involved in the immune response (choice D is not true and thus the correct answer choice).

Why is there a latent period in the production of antibodies during the primary response?

Time is required for B lymphocytes to proliferate. B. The passage describes the latent period as the time required for the lymphocytes to begin to divide and differentiate into plasma and memory cells (B is correct). The pathogen need not proliferate for an immune response to be mounted; it only needs to be present (A is wrong). Antibodies are produced by B lymphocytes, not T lymphocytes (C is wrong), and an antigen does not infect the B cells, it must only bind to them (D is wrong).

If yeast cells were cultured under aerobic conditions would there be a greater number of cells than under anaerobic respiration?

Yes, because the cells have more ATP available to them for reproduction.

Transformation of a normal cell to a cancerous cell may begin with any of the following EXCEPT: A. a series of mutations. B. conversion of a proto-oncogene to an oncogene. C. infection of a cell with a virus that changes the nuclear genome. D. a delay in prophase of mitotic division.

a delay in prophase of mitotic division. D. The passage states that mutation of genes and conversion of proto-oncogenes into oncogenes are two of the main causes of cancer (A and B are true and thus eliminated). Viruses that change (mutate) the nuclear genome could therefore also cause cancer (C is eliminated). A delay in mitotic division would not change the DNA in any way and would not induce cancer (D is false and the correct answer choice here).

If labeled ethyl propanoate, CH3CH2CO18OCH2CH3 is hydrolyzed in aqueous NaOH, the 18O label would be found exclusively in the:

ethanol product. According to the addition-elimination mechanism, the 18O label would end up in the ethanol:

B lymphocytes are involved in a process called: A. humoral immunity. Correct Answer B. cell-mediated immunity. C. passive immunity. D. the complement system.

humoral immunity. A. Humoral immunity refers to immunity through fluid; in this case, the blood. This is where B cells have their effect: They release antibody into the bloodstream (A is true). Cell-mediated immunity is the process that cytotoxic T cells are involved in (B is wrong). Passive immunity refers to an injection of antibodies which can act as a temporary supply and help fight off a disease until a person's own immune system can start producing antibodies (C is wrong). The complement system is a system of proteins and enzymes which, when activated, can cause cell lysis (D is wrong).

Saponification is the process by which triglycerides are

hydrolyzed under basic conditions

Decreasing collagen content in bones

results in weaker bones and the amount of collagen is not dependent on calcium or its regulatory hormones

Which of the following reagents would lead to the conversion of esters into alcohols? A. CrO3 B. H2SO4 C. PCl3 D. 1) BH3 2) H2O2/KOH

H2SO4 B. Of the choices given, only strong acid would convert an ester into an alcohol.

After implantation of a fertilized ovum, which of the following prevents menstruation?

Human chorionic gonadotropin C. Human chorionic gonadotropin prolongs the life of the corpus luteum, the post-ovulatory structure which secretes progesterone. HCG is only secreted by a fertilized ovum. The function of progesterone is to maintain the uterine lining thereby preventing menstruation (C is correct). Oxytocin (choice A) causes uterine contractions during pregnancy, luteinizing hormone (choice B) causes ovulation, and gonadotropin-releasing hormone (choice D) stimulates the release of FSH and LH from the anterior pituitary.

In the alkaline hydrolysis of triglycerides, the molecule that acts as the nucleophile is the:

Hydroxide ion In this reaction, hydroxide (the nucleophile) attacks the electrophilic ester.

If a person is hyperventilating, the blood has:

A. increased saturation of hemoglobin with O2. B. a higher level of CO2. C. a higher pH level. Correct Answer D. an increase in carbonic acid. C. A person who is hyperventilating is breathing more deeply and more rapidly. This would blow off more CO2 from the system (B is wrong). If CO2 levels are reduced, then levels of carbonic acid are also reduced (D is wrong), and the pH would rise (C is correct). Note that hemoglobin saturation would remain essentially unchanged. During normal respiration, Hb is nearly 100% saturated (98%), and it is difficult to increase that number without breathing pure oxygen (A is wrong).

Excess calcitonin in the blood would most likely result in which of the following abnormalities?

Abnormally dense bones B. Calcitonin reduces blood calcium levels through three processes: decreasing calcium reabsorption by the kidney, decreasing calcium absorption by the small intestine, and activating osteoblasts, which store calcium as bone. This last function increases bone density (A is wrong, and B is correct). Osteoclasts degrade bone and are stimulated by parathyroid hormone, not calcitonin (C is wrong). Decreasing the collagen content in bones would also result in weaker bones (D is wrong), and in any case, the amount of collagen is not dependent on calcium or its regulatory hormones.

Hormones are chemically diverse. Epinephrine is an example of a hormone derived from: A. a lipid. B. an amino acid. C. a steroid. D. a carbohydrate.

Amino Acid Hormones are either proteins or steroids, not carbohydrates (D is wrong). Steroids are a specific form of lipid derived from cholesterol, and epinephrine, as shown in the figure, is clearly derived from an amino acid (A and C are wrong, and B is correct)

Receptors are needed by ____ and ______ to recognize antigens

B and T cells

Lysine is an amino acid with a basic side chain. Its isoelectric point would be closest to: A. 6. B. 7. C. 8. D. 12

C.-8 Having a basic side chain increases an amino acid's pI value.

Based on the information in the passage, which of the following is the most likely product of the reaction between propanal and 2-propanone, in the presence of base?

D. This is the product of an aldol reaction resulting from the attack of the enolate of 2-propanone on propanal. In an aldol condensation the α-carbon of the nucleophile will make a new bond to the carbonyl carbon of the electrophile, so the product is always a β-hydroxy carbonyl compound. Neither answer choice B nor C is a viable answer since they are both γ-hydroxy carbonyl compounds. While answer choice A is a β-hydroxy aldehyde, the electrophile in this case contains 4 carbons instead of 3, and is therefore incorrect.

All of the following are true of eukaryotic mRNA EXCEPT that: A. transcription occurs in the 5' 3' direction. B. the 5' end is usually capped. C. the mRNA is smaller than the initial transcript. D. it is polycistronic.

D. Transcription always occurs in the 5' to 3' direction, and eukaryotic mRNA is usually capped before translation (A and B are true and therefore eliminated). Eukaryotic mRNA is smaller than the original RNA transcript due to the fact that the introns must be removed and the exons spliced together (C is true and eliminated). However, eukaryotic mRNA is monocistronic, meaning that only a single type of protein can be translated from a given mRNA. Polycistronic mRNA is a feature of prokaryotes, which must be more efficient with the limited amount of DNA they have to work with and can translate several different proteins from the same mRNA.

How calcitonin reduces blood calcium levels

Decreases calcium reabsorption by kidney, small intestine and activates osteoblasts

If an individual is reinfected with the same virus the immune system will: A. elicit a slow immune response. B. require a greater amount of the virus than the first response. C. destroy the pathogen before it has time to cause disease. D. reject the pathogen before it has a chance to proliferate in the body.

Destroy the pathogen before it has time to cause disease C. The passage states that the response to a second infection with the same antigen is much more rapid than the primary response and also requires much less antigen (A and B are wrong). Furthermore, the pathogen is not rejected by the body; it is destroyed by the body (D is wrong, and C is correct).

Function of organs: Kidney

Filter blood, maintains blood pressure, regulated body water balance, electrolyte balance, and pH

Function of organs: Spleen

Filters blood, removes old red blood cells, provides a site for B cells to mature and stores blood

If a primary immune response confers immunity, why do individuals get the common cold more than once?

Individuals are not exposed to the same virus. All viruses (and other pathogens) will trigger the production of both B and T lymphocytes (A is wrong). The common cold virus does not have receptors, but receptors are not needed by the virus. Receptors are needed by B and T cells to recognize antigens (B is true, but irrelevant, thus eliminated). The number of viruses circulating in the body has nothing to do with whether a disease can cause immunity or not (D is wrong). There are many different viruses that can cause the symptoms we associate with the common cold: runny nose, sore throat, etc. Exposure to one of these viruses will cause the disease and confer immunity to that particular virus, but not to the hundreds of other viruses capable of causing the common cold (C is correct).

Given its many effects, epinephrine probably acts antagonistically on plasma glucose levels to which of the following hormones? A. Thyroxine B. Glucagon C. Calcitonin D. Insulin

Insulin D. Calcitonin does not affect blood glucose levels (C is wrong). Thyroxine and glucagon can both increase plasma glucose levels, thus they act in concert with epinephrine (A and B are wrong). Insulin lowers plasma glucose levels, acting in an opposite manner to epinephrine (D is correct).

Which one of the following mutations would be most likely to convert a proto-oncogene into an oncogene? A. Silent mutation B. Missense mutation C. Nonsense mutation D. Deletion mutation

Missense mutation In order for the mutation to have the described effect, it must modify the protein without completely eliminating it or destroying its effect. A missense mutation converts a codon for one amino acid into a codon for a new amino acid, resulting in a small change within the protein's primary sequence, and an alteration (but usually not a total elimination) of the protein's function. A silent mutation converts a codon for an amino acid into a new codon for the same amino acid and has no effect on the protein product (A is wrong). A nonsense mutation creates a stop codon out of an amino acid codon, resulting in truncation of the protein and (usually) a loss of its function (C is eliminated). A deletion mutation eliminates one or more base pairs, altering the reading frame and drastically changing the amino acid sequence of the protein (and therefore eliminating its function, D is wrong).

An extraction is a purification technique involving the separation of compounds based on which of the following physical properties?

Solubility C. In an extraction, the chemist exploits the differential solubility of compounds to effect their separation.

Diabetes insipidus is a condition in which an individual fails to produce antidiuretic hormone. If a person suffering from diabetes insipidus were to consume large amounts of a sugar-containing beverage, which of the following would most likely be observed after one hour?

Production of dilute urine B. An individual who cannot make ADH will be unable to reabsorb water from the collecting duct of the nephron, resulting in urine that is very dilute (B is correct, and A is wrong). Since diabetes insipidus is strictly a disorder involving ADH production, no effect would be seen on plasma glucose levels (very low after one hour) or urine glucose levels (always zero, C and D are wrong).

Normal cells of a tissue use molecules on the surface to recognize one another and stick together. These molecules are on the surface of the plasma membrane. These molecules are best described as: A. proteins. B. hormones. C. filaments of cytoskeleton. D. lipids.

Proteins Protein receptors are often used by cells to recognize similar cells (A is true). Hormones and cytoskeleton filaments are not found on the surface of cells (B and C are wrong), and lipids are common to all cell membranes and would not be helpful in identifying cells as part of a group (D is wrong).

The primary enzyme that is involved in transcription is called: A. DNA polymerase. B. DNA ligase. C. RNA polymerase. Correct Answer D. primase.

RNA Polymerase C. Transcription is the creation of a strand of RNA by reading a DNA template. Enzymes which do this are called RNA polymerases (choice C). DNA polymerase creates a strand of DNA by reading a DNA template (A is wrong), DNA ligase connects (ligates) two pieces of DNA (B is wrong), and primase is the RNA polymerase that puts a primer on DNA during replication (D is wrong).

According to the information in the passage, all post-transcriptional processing occurs during which of the following steps? A. DNA -> RNA transcript B. RNA transcript-> processed mRNA C. mRNA -> processed mRNA D. processed mRNA -> protein

RNA transcript processed mRNA B. The passage states that post-transcriptional modification also involves the addition of a 5' cap and a 3' poly-A tail, implying that intron excision is included in the definition of post-transcriptional modification. Therefore, B is the only correct choice, because it incorporates all the steps in post-transcriptional modification: exon splicing, 5' capping, and 3' tailing. Choice A is wrong since this only creates a transcript; it does not modify it. Choice C is wrong since it does not include exon splicing, and D is wrong since it occurs after modification.

Calcitonin

Reduces blood calcium levels

Function of organs: Liver

Regulated gluconeogensis, urea production, and drug detoxification

Function of organs: Small intestine

Site of digestion and absorption of food molecules

If a single base pair mutation creates an oncogene from a proto-oncogene, this could possibly create all of the following outcomes EXCEPT: A. a protein that is more active. B. a protein that is more resistant to degradation than a normal protein. C. a tumor that metastasizes in the body. D. a tissue that undergoes the normal rounds of interphase

a tissue that undergoes the normal rounds of interphase. D. A single base pair mutation in a gene could result in the replacement of an amino acid in the final protein produced from that gene with a new amino acid. This new protein could be more active or more resistant to degradation than the original protein (A and B are true and therefore eliminated). The passage states that cancer (a metastasizing tumor) is the result of an activated oncogene (C is true and eliminated) and also that cancer cells lack the normal controls on cell growth and divide continuously (D is false and the correct answer choice here).

To undergo condensation, you need

alpha hydrogens

Each of the following could interrupt the normal functioning of epinephrine EXCEPT: A. a target cell which lacks receptors. B. receptors that do not work properly. C. epinephrine that is not secreted into the bloodstream. D. an enzyme which binds to epinephrine in the cytoplasm of the target cell.

an enzyme which binds to epinephrine in the cytoplasm of the target cell. Since hormones are carried through the bloodstream and encounter all tissues and organs, the only way they can be specific for a particular tissue or organ is if the cells of that tissue have receptors for the hormone. Thus, missing or malfunctioning receptors can disrupt function of the hormone (A and B are true and therefore eliminated), and if the hormone is not carried through the body by the blood, its function will also be impaired (C is true and eliminated). Since epinephrine is a peptide hormone, it cannot cross the cell membrane and must bind to a receptor on the cell surface, activating a second messenger system. It would never be found in the cytoplasm of the target cell (D is false and therefore the correct choice here).

Lymphocytes do not make _______ they fight ________

antigens

Aldol condensation, product is always a

beta hydroxy carbonyl compound q

An increase in epinephrine in the blood will produce all of the following physiological changes EXCEPT: A. an increase in the blood supply to skeletal muscles. B. constriction of blood vessels in the skin and kidneys. C. an increase in heart rate. D. contraction of smooth muscles.

contraction of smooth muscles. D. Epinephrine augments the fright, flight, or fight response of the sympathetic nervous system. This increases blood flow to the skeletal muscles and reduces flow to the visceral organs (A and B are true and therefore eliminated) and increases the heart rate (C is true and eliminated). Contraction of smooth muscle is caused by activation of the parasympathetic nervous system (D is false and therefore the correct choice here).

Osteoclasts

degrade bone and are stimulated by parathyroid hormone

Sympathomimetic drugs are often used to treat asthma. This is because these drugs:

dilate the bronchioles, allowing increasing gas flow to the lungs. B. Sympathomimetic drugs are drugs which can mimic the effects of the sympathetic nervous system. One of the effects of the sympathetic system is to dilate the bronchiole tubes thereby increasing gas flow to the lungs and oxygen delivery to the blood (B is correct, and C is wrong). The pulmonary arteries carry oxygen-poor blood to the lungs for oxygenation, so dilating them would not increase oxygen delivery to the lungs (A is wrong). Constricting the pulmonary arteries might ultimately decrease oxygen delivery to the body, but this would not help treat asthma (D is wrong).

A gene has 900 base pairs, and the protein translated from this gene has 210 amino acids. This is mostly likely due to the fact that: A. exons have been removed from the RNA transcript. B. the stop codon in mRNA is found at the 210th base pair. C. the DNA molecule was not synthesized with the appropriate enzymes. D. introns have been removed in the formation of the mRNA.

introns have been removed in the formation of the mRNA. D. Exons are not removed from the transcript; they are ligated together to form the mature mRNA (A is wrong). A stop codon at the 210th base pair would result in a protein only 70 amino acids long (3 nucleotides = 1 amino acid), so B is wrong. There is only one enzyme which can synthesize DNA (DNA polymerase) and in any case, if the DNA molecule was synthesized incorrectly, it would be highly unlikely that any protein could be made from that gene at all (C is wrong). Choice D is correct: In the formation of mature mRNA, introns are removed and exons are ligated together. To make a protein of 210 amino acids, exons amounting to 210 × 3 = 630 base pairs must have been ligated together, along with 3 base pairs for a stop codon (633bp total); introns amounting to 900 - 633 = 267 base pairs were spliced out.

The sodium salt of benzoic acid is: A. a carboxylic acid. B. ionic. C. an anhydride. D. antiaromatic.

ionic. B. It is a salt and therefore ionic.

repolarization

is a return to rest potential

Hyperpolarization

is defined as the membrane potential moving away from rest potential in the negative direction

Depolarization

is movement of the membrane potential away from rest in the positive direction

In digestion, the enzyme responsible for the hydrolysis of triglycerides is: A. pancreatic amylase. B. pancreatic lipase. C. salivary amylase. D. bile.

pancreatic lipase. B. The pancreas produces many different enzymes for the digestion of macromolecules. Lipases digest lipids (fats), making B the answer. Amylase digests starch, regardless of whether it comes from the salivary glands or the pancreas (A and C are wrong), and bile emulsifies fats, preparing them for digestion by the lipases (D is wrong).

The Gram staining in Gram-positive bacteria is due to the presence of:

peptidoglycan D. Gram stain binds to the cell wall in bacteria, which is made up of peptidoglycan (proteins and sugars). Gram positive bacteria have no external membrane, no capsule (an external coat of carbohydrates), and a very thick cell wall, so they stain very darkly with Gram stain (A and B are wrong, and D is correct). Bacteria are prokaryotes and do not have a nucleus or any other organelles (C is wrong).

During a mastectomy, the lymph nodes are often removed in addition to the tumor. This surgical procedure will most likely:

stop the spread of breast cancer to the rest of the body. B. When cancers metastasize, tumor cells leave their original site and enter the blood or lymph vessels to travel to a new part of the body where they can implant and grow. Therefore, removal of nearby lymph nodes during surgery to remove a cancerous tumor is often done to help ensure that the cancer cannot spread (B is correct). Removal of the lymph nodes could render the patient more susceptible to infection and decrease the number of circulating lymphocytes (A and C are wrong). Finally, to remove the oncogenes within the affected tissue, the surgeons would only need to remove the breast tissue since the lymph nodes are not affected (D is wrong).

Osteoblasts

store calcium- increases bone density

If a nucleotide is deleted during the transcription process this event would most likely lead to: A. no change in the protein. B. the destruction of the correct reading frame. C. an mRNA without a cap. D. a DNA gene with the incorrect base pairs.

the destruction of the correct reading frame. B. Deleting a nucleotide during transcription would result in a serious mutation called a frameshift mutation, which would completely destroy the protein's amino acid sequence and structure (B is correct, and A is wrong). It is unlikely that it would cause the mRNA to not be capped (and, in any case, this would be the least of your worries), so C is eliminated. Finally, removing a base from RNA would have no effect on the DNA, as DNA replication does not depend on RNA at all (eliminating D).

An error is made during production of an RNA transcript which results in a change in a single amino acid in the final protein. This error is most likely a result of: A. incorrect translation of the mRNA into protein by the ribosomes. B. the poor editing ability of RNA polymerase. C. a frameshift mutation occurring during transcription. D. incorrect translation of the DNA into RNA by RNA polymerase.

the poor editing ability of RNA polymerase. B. RNA polymerases have no editing function since RNA is a transient molecule and its information is not passed on to offspring (B is correct). The question states that the error is made during production of the RNA, so the change in amino acid sequence reflects the new nucleotide sequence and is not due to incorrect translation of the mRNA (A is wrong). Frameshift mutations are very severe and would result in all of the amino acids from the error on being changed (C is wrong), and DNA is not translated by RNA polymerase, it is transcribed (D is wrong).

In an aldol condensation

the α-carbon of the nucleophile will make a new bond to the carbonyl carbon of the electrophile, so the product is always a β-hydroxy carbonyl compound. Neither answer choice B nor C is a viable answer since they are both γ-hydroxy carbonyl compounds. While answer choice A is a β-hydroxy aldehyde, the electrophile in this case contains 4 carbons instead of 3, and is therefore incorrect.

A cancer-inducing virus was found that incorporates the sequence of a proto-oncogene into its DNA. The gene in the viral genome was transcribed in infected cells at a much higher rate than the same gene in the genome of the host cell. The induction of cancer is most likely due to: A. uncontrolled cell growth resulting from the overexpression of the gene product. B. mutation of the host-cell genome. C. tissue exhibiting contact inhibition. D. removal of oncogenes within the affected tissues.

uncontrolled cell growth resulting from the overexpression of the gene product. A. A proto-oncogene being transcribed at a higher rate than normal could result in uncontrolled cell growth and cancer (A is correct). While mutation of the host-cell genome could cause cancer, this is not occurring in this case. The viral genome is merely being transcribed at a high rate (B is wrong). Contact inhibition is a means by which normal tissues can control their growth and division. A tissue exhibiting contact inhibition is not a cancerous tissue (C is wrong). Removal of oncogenes within the affected tissues would reduce the rate of cancer, not cause cancer (D is wrong).