Biology Flashcards
The genetic code is said to be degenerate because there are 64 different codons, but translation produces only 20 unique amino acids. The degeneracy of the genetic code is due to which mechanism?
A) exclusion of protein coding regions from mature mRNA
B) errors during tRNA charging
C) ambiguity of the tRNA for the amino acid
D) nontraditional base pairing of the anticodon with the third base of the codon
D) nontraditional base pairing of the anticodon with the third base of the codon
Which statement most accurately describes the role of T tubules in skeletal muscle cells?
A) t tubules bind actylcholine at the neuromuscular junction to generate a depolarizing stimulus
B) depolarizing current reaches the sarcoplasmic reticulum by traveling down t tubules
C) muscle contraction is driven by the sliding of t tubules across one another in the sarcomere
D) t tubules sequester Ca2+ out of the cytosol to prevent prolonged muscle contraction
B) depolarizing current reaches the sarcoplasmic reticulum by traveling down t tubules
For a skeletal muslle cell to contract, Ca2+ must be released into the cytosol from the sarcoplasmic reticulum. Ca2+ release is induced when a depolarizing current (action potential) runs along the sarcolemma and travels down the t tubules. This current causes the nearby sarcoplasmic reticulum to open its Ca2+ channels, allowing Ca2+ ions to flow into the cytosol and induce the sarcomeric actin-mypsin interactions required for muscle contraction
If a viral antigen were to bind to the receptors on the surface of a B lymphocyte, which of the following immune responses would not occur?
A) division of the B lymphocyte into cells that differentiate to secrete antibodies
B) interaction of the B lymphocyte with other immune cells that stimulate B lymphocyte proliferation
C) secretion of toxins by the B lymphocyte that destroy nearby virus-infected cells
D) proliferation of cells that can recognize the antigen more rapidly in the event of future infection
C) secretion of toxins by the B lymphocyte that destroy nearby virus-infected cells
Activation of B lymphocytes by helper T cells:
1) pathogen binds to B lymphocyte receptor, is endoxytized, and presented on MHC II
B) helper T cell binds foreign antigen and releases cytokines that activate the B lymphocyte
C) activated B lymphocyte divides into many clones that differentiate into plasma cells or memory cells
Natural killer and cytotoxic t tells, not B lymphocytes, respond to antigens by releasing toxins that induce apoptosis in nearby infected cells
E. coli K-12, a normal bacterial strain of the human microbiota, is able to cause disease by inducing enterocyte lesions after it is grown in media with EHEC bacteria that contain the F factor plasmid. What process most likely granted virulence to E. coli K-12?
A) Transformation
B) Transduction
C) conjugation
D) transfection
C) conjugation
conjugation = transfer of genetic information from one bacterial cell to another via direct contact. The donor cell contains the F (fertility) factor plasmid, a circular piece of DNA containing genes that direct the formation of the sex pilus. During conjugation, the sex pilus from the donor cell attaches to a recipient cell (one that does not contain F factor) and facilitates the transfer of a single strand of the F factor plasmid DNA to the recipient cell.
According to this question, E. coli K-12 is a nonvirulent bacterial strain. Nonetheless, co-culturing E. coli K-12 with EHEC bactera that contain F factor resulted in E. coli K-12 acquiring virulence. E. coli K-12 virulence most likely resulted from the direct transfer of LEE genes through conjugation.
transformation
the cellular uptake of foreign DNA directly from the environment
transduction
involves the DNA transfer from one bacterial cell to another by a bacteriophage ( a virus that infects bacteria). During assembly of bacteriophages inside an infected cell, bacterial DNA can become trapped within the capsid of newly created bacteriophages. Subsequent infection of other cells with these new bacteriophages results in the transfer of bacterial DNA into a new host
transfection
the process by which genetic material, usually in the form of a plasmid, is introduced into eukaryotic cells
EHEC is classified as a bacillus bacterium. Given this information, this type of classification is most likely based on the bacterium’s
morphology
bacilli = rod cocci = sphere spirilli = spiral
What is the size of the pSKII plasmid after it is digested by EcoRI and XhoI and the clndk gene is inserted?
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3.841 base pairs
Figure 1 shows that prior to the insertion of cldnk, the pSKII plasmid contained 2,958 base pairs. Figure 2 shows that the distance between the EcoRI and XhoI restriction sites is 17 + 15 = 32 base pairs; these bases will be removed by the digest.
The passage states that the cldnk gene produces a processed transcript that is 915 base pairs long, so insertion of cldnk cDNA increases the plasmid size by 915 base pairs.
Therefore, the final size can be calculated as 2,958 - 32 + 915 = 3,841
What observation could have led researchers to conclude that cldnk is most likely expressed in oligodendrocytes?
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A) a probe made of cldnk mRNA hybridized to RNA in cells that express Sox10
B) An RNA probe that was complementary to cldnk mRNA hybridized in cells that express plp1a
C) a cldnk cDNA probe obtained from oligodendrocytes bound to a microarray with higher affinity than the same probe obtained from other cells
D) a cDNA probe corresponding to cldnk hybrdiized to the nuclei of oligodendrocytes but not the cytosol
B) An RNA probe that was complementary to cldnk mRNA hybridized in cells that express plp1a
If cldnk is found in the same cells in plp1a, then cldnk must be expressed in oligodendrocytes
Which experiment could confirm that the cldnk gene product is required for myelination?
A) compare myelin formation in wild-type zebrafish to formation in zebrafish that overexpress cloned cldnk
B) overexpress cldnk in zebrafish cells other than oligodendrocytes and observe whether those cells produce myelin
C) compare myeline formation in wild-type zebrafish to that in zebrafish with cldnk knocked out
D) overexpress a form of cldnk that inhibits the wild-type gene in cells other than oligodendrocytes and observe whether myelin forms
C) compare myeline formation in wild-type zebrafish to that in zebrafish with cldnk knocked out
Knockout organisms have one or more genes that have been made inactive. The biological function of a gene can be inferred by knocking it out and observing the differences between wild-type organisms and knockout organisms.
If cldnk is required for wild-type myelination of oligodendrocytes, then knocking the gene out should result in impaired or abnormal myelination. Therefore, comparing myelination of oligodendrocytes in wild-type zebrafish to myelination in cldnk knockout zebrafish would show whether cldnk is required for proper myelin formation
How would expression of cloned cldnk differ from expression of the endogenous cldnk gene?
A) expression of the cloned gene does not involve splicing whereas expression of the endogenous gene does
B) the cloned gene is expressed at lower levels than the endogenous gene
C) the cloned gene produces a protein with a different sequence than the endogenous gene
D) expression of the cloned gene produces a mature mRNA molecule with a different coding region thatn expression of the endogenous gene
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A) expression of the cloned gene does not involve splicing whereas expression of the endogenous gene does
Genes within a eukaryotic chromosome typically consist of exons and introns, both of which are transcribed by RNA polymerase to form pre-mRNA. After transcription, pre-mRNA matures through several processing, including 5’ capping by 7-mehtylguanosine, 3’ polyadenylation, and splicing, to remove introns.
Complementary DNA (cDNA) is derived from mature mRNA through reverse transcription. Because the mature mRNA has already been spliced (introns were removed), the cDNA will not contain any introns. The cDNA can be cloned into expression vectors such as plasmids, which can be introduced into embyronic cells and integrated into the genome. These cloned genes can then be expressed in the organism. However, because the cloned gene does not contain any introns, its expression will not include splicing.
Which of the following conclusions is best supported by the results presented in Figure 1?
A) MAGE mRNAs are all composed of the same number of nucleotides
B) MAGE protein classes targeted by immune cells may differ depending on the cancer cell type
C) MAGE-A6 exhibits the highest level of expression in cancer cells
D) MAGE proteins are more active in breast cancer cells than in melanoma cells
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B) MAGE protein classes targeted by immune cells may differ depending on the cancer cell type
(some are expressed and some aren’t)
Which steps of the viral life cycle would most likely occur in lytic phages?
I. injection of viral genetic material into the bacterial host
II. integration of viral DNA into the bacterial genome
III. Degradation of the host genome
I and III only
Lytic life cycle steps
- Attachment: the bacteriophage contacts the bacterial cell wall and attaches to the host bacterium using its tail fibers
- Viral genome entry: the phage uses its tail sheath to inject its genome into the cytoplasm of the bacterial host
- Host genome degredation: viral enzymes degrade the host genome into its nucleotide components to provide the building blocks for replication of the viral genome
- Synthesis : Loss of the bacterial (ie host) chromosome ends the synthesis of host molecules, now under the control of the viral genome. As a result, the host machinery (eg ribosomes) begins to synthesize the components needed for new viral progeny, which then assemble inside the host cell
- Release: many newly assembled viral progeny (virions) are released as the bacterium disintegrates (lysis) due to the action of lysozymes on the host cell wall
The scientists hypothesize that genetic leakage has occurred in some of the studied yeast lineages over time. Which of the following best supports this hypothesis?
A) hybrid indivodials express certain phenotypes that differ from those expressed in the parental species
B) hybrid individuals exhibit reproductive isolation with some other Saccharomyces species
C) hybrid individuals can produce some viable offspring when mated with their parental species
D) hybrid individuals frequently pass genetic information to clones of themselves via asexual reproduction
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C) hybrid individuals can produce some viable offspring when mated with their parental species
Genetic leakage: initially, inbreeding of two different parental species occurs, hybrid offspring contains genes from both species 1 and 2.
Over time, inbreeding of hybrid and parental species occurs. This leads to viable offspring which contains mostly parental species 1 genes and some parental species 2 genes
Gene flow will occur from hybrid species and parental species because hybrid genes continue to be transferred to the parental species
Compared to crpssing Sp1 individuals with other Sp1 individuals, crossing Sp1 individuals with Sp4 individuals (Table 1) resulted in:
(how many more/fewer spores)
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Approximately 1/2 fewer viable spores
62% vs 29%
The researchers hypothesize that the ability of marine teleost kidneys to filter salts is independent of the presence of a glomuerulus. Bassed on the passage, this hypothesis would best be supported if the researchers discovered:
A) higher urinary concentrations of Mg2+ and SO4 2- in the eel than in the goosefish
B) higher urinary concentrations of Cl- and Na+ in the eel than in the goosefish
C) equally high urinary concentrations of Mg2+ and So4 2- in the eel and the goosefish
D) equally high urinary concentrations of Cl- and Na+ in the eel and the goosefish
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C) equally high urinary concentrations of Mg2+ and So4 2- in the eel and the goosefish
In the passage, the passage states that scientists concluded that osmoregulation in marine teleosts involves:
- seawater ingestion
- retrieval / absorption of salt and water from intestines
- excretion of divalent ions primarily through the urine and monovalent ions through the gills
To confirm that the glomerulus does not affect filtration of salts, scientists would have to find similar concentrations of the relevant salts in the urine of both glomeruluar and aglomerular fish. Because divalent ions (mg2+ and sor 2-) are primarily excreted in the urine and monovalent ions (Na+ and Cl-) are primarily excreted through the gills of marine teleosts, researchers would have to find equally high urinary concentrations of the divalent ions in the glomerular eel and the aglomerular goosefish .
Which of the following would most likely cause an embryo to implant in a location other than the uterine lining?
A) reduced number of fallopian cilia
B) surge in lutenizing hormone prior to ovulation
C) incomplete gastrulation
D) rupture of follcile from the ovary
A) reduced number of fallopian cilia
Typically, fallopian cilia help propel the fertilized oocyte toward the uterus for implantation. However, with a reduced number for fallopian cilia, improper implantation of the fertilized egg can occur outside the uterus
A mutant mouse is found to exhibit normal musculoskeletal function following the administration of anti-nAchR antibodies. Compared to a wild-type mouse, this mutant mouse is most likely to show which of the following changes at the neuromuscular junction?
A) decreased ACh degradation within the synapse
B) reduced expression of nAchR by skeletal muscle fibers
C) decreased reuptake of Ach degredation byproducts into the presynaptic neuron
D) Reduced release of Ach from the presynaptic vesicles
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A) decreased ACh degradation within the synapse
Based on the passage, anti-nAchR antibodies bind nAchR reversibly to block the interaction between Ach and nAchR, resulting in muscle weakness. Accordingly, administration of these antibodies in a wild-type mouse would temporarily prevent binding of Ach to its receptor. However, if a mutant mouse were to exhibit normal muscle contraction despite being treated with anti-nAChR antibodies, the most likely reason in this scenario is that ACh degredation within the mutant ‘s synapse would be decreased compared to the wild-type.
If ACH degredation is decreased, more ACh molecules will remain in the synapse for a longer time period and be able to bind nAChRs after these are no longer bound to anti-nAChR antibodies. This would result in muscle contraction that is delayed but still normal
ACh degradation within the neuromuscular junction is one process by which muscle fiber contraction is terminated. However, decreased Ach degredation would allow more Ach to remain in the synapse, and prolong stimulaiton of nAchR and subsequent muscle contraction
To interpret the results of Experiement 2, researchers must assume that:
I. muscle samples were of uniform weight and size
II. no intermolecular interactions occurred between Ach and anti-AChR antibodies in INfusion C
III. co-infusion of ACH and anti-AChR antibodies was performed following ACH infusion
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I and II only
These are both examples of possible confounding variables
To further study anti-nAChr antibody function, the researchers wanted to replicate the experiments described in the passage in other mammalian animal models, but their research proposal was rejected by other scientists. Why was the proposal rejected?
A) because resting muscle tension cannot be used as a control for post-infusion tension
B) because the electrolyte-rich baths were infused with inconsistent amounts of ACh
C) because skeletal muscles in the body would not be exposed to autoimmune antibodies
D) because animal models cannot be used to study human diseases
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B) because the electrolyte-rich baths were infused with inconsistent amounts of ACh
*multiply mL of ACH by 2.5 mg/Ml concentration
A subset of aggressive cancers has a relatively high growth rate, leading to the formation of large tumours. An effective drug against fast-growing tumours would most likely not target which stage of the cell cycle?
G0
A student adds 5 bacterial cells to a test tube containing fresh medium and incubates it for 3 hours at 37C. The bacterial population shows an initial lag phase of 20 minutes followed thereafter by a growth phase with a doubling time of 40 minutes. Given this, what is the approximate number of bacterial cells present at the end of the incubation period?
80 cells
- calculate the amount of time in which the bacterial population was in log phase: 180 min incubation time - 0 min lag phase = 160 min log phase
- Find the number of generations in the log phase period:
160 min log phase / 40 min generation time = 4 generations - Multiple the original number of bacterial cells by 2^n to get the final population size:
5 bacterial cells x 2^4 = 80 cells
Which of the following cell-cell junctions would help skin cells withstand mechanical stress by directly anchoring the intermediate filaments of adjacent cells?
I. Desmosomes
II. Gap junctions
III. Tight junctions
I. Desmosomes only
Hormones secreted by the adrenal medulla most likely influence energy metabolism by:
A) inhibiting proteins that mediate glycogen synthesis
B) activating their cytosolic receptors in target cells
C) reducing the activity of enzymes that catalyze fat hydrolysis
D) increasing the activity of proteins that inhibit gluconeogenesis
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A) inhibiting proteins that mediate glycogen synthesis
Hormones secreted by the adrenal gland regulate energy metabolism as follows:
Glucocorticoids (eg cortisol) released by the adrenal cortex act on the liver to stimualte the synthesis of glucose from other molecules (ie gluconeogenesis) and the breakdown of fats into fatty acids (ie lipolysis). Both glucose and free fatty acids are forms of cellular energy that can be readily utilized.
Norepinephrine and epinephrine are released by the adrenal medulla to modulate the metabolism of glycogen, the storage form of glucose. In addition, both hormones promote the breakdown of glycogen into glucose monomers in a process known as glycogenolysis. By inhibiting the enzymes that mediate glycogen synthesis, norepinephrine and epinephrine also inhibit glycogenesis
A woman with low serum due to partial adrenal dysfunction is treated with high doses of a synthetic cortisol analogue. According to figure 2, treatment with a cortisol analogue will most likely cause this patient’s serum level of endogenous cortisol to:
(increase or decrease)
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decrease only
Figure 2 shows the negative feedback pathway that influences the synthesis and secretion of cortisol (and that cortisol decreases)
synthetic cortisol analogues have a molecular structure that resembles that of endogenous cortisol. therefore, the analogue will be able to mimic the effect of cortisol by binding hypothalamic and pituitary cortisol receptors. This interaction will increase negative feedback and reduce the synthesis and secretion of natural cortisol by the adrenal glands.
Therefore, after treatment with a synthetic cortisol analogue, the patient’s serum level of endogenous cortisol would decrease due to the increase in negative feedback on the hypothalamus and pituitary gland by the cortisol analogue.
Cirrhosis of the liver is characterized by hepatic cell death, tissue scarring, and altered liver function. All of the following would be disrupted by cirrhosis of the liver except:
A) production of ketone bodies
B) metabolism of most drugs
C) oncotic pressure within capillaries
D) secretion of digestive proteolytic enzymes
D) secretion of digestive proteolytic enzymes
Function of liver cells
- Regulation of blood glucose via glycogenesis, glycogenolysis, and gluconeogenesis
- Storage of glycogen, minerals (iron) and vitamins
- Synthesis of macromolecules such as plasma proteins (clotting factors & albumin), fats, ketone bodies, and cholesterol
- Production and secretion of bile
- Breakdown / detoxification of numerous drugs and metabolic waste products (bilirubin, ammonia)
T. brucei cells and higher eukaryotes are similar in that they both undergo:
I. Interphase
II. Prophase
III. Cytokinesis
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I and III only
Passage states that T. brucei cells were arrested in S phase. Because S phase is a part of interphase, T. brucei cells undergo interphase.
In addition, Figure 1 shows that in M phase, T. brucei cells undergo cytokinesis longitudinally, along the longest axis
During prophase, the first phase of mitosis, chromatin condensesinto distinct chromosomes and the nuclear envelop disintegrates. However, according to the passge the chromatin in T. brucei does not condense, and the nuclear envelope remains intact throughout mitosis
The number of each type of sex chromosome in a group of 5 male and 5 female rabbits is shown. In the combined population of 15X and 5 Y chromosomes, which of the following types of allele, if any, would be most susceptible to compelte loss from the population due to random chance alone?
A) Y-linked allele
B) X-linked allele
C) either an X or a Y linked
D) only an autosomal allele would be subject to complete loss by random chance alone
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A) Y-linked allele
Y chromosome alleles present at lowest numbers; more susceptible to complete loss by random chance (genetic drift)
Based on the passage, the cells that directly stimulate OPCs to differentiate are cells that promote:
A) calcium transfer from bone tissue into the bloodstream
B) calcium transfer from the bloodstream into bone tissue
C) acid production in bone tissue
D) proteolytic enzyme production in bone tissue
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B) calcium transfer from the bloodstream into bone tissue
The passage states that RANKL is a ligand expressed by osteoblasts that binds RANK, a transmembrane receptor expressed by OPCs. The binding of RANKL on osteoblasts to RANK on OPCs induces downstream signaling pathways that lead to the differentiation of OPCs into mature osteoclasts. Accordingly, osteoblasts, which promote the absorption of calcium from blood to bone tissue, directly stimulate OPCs to differentiate
A student isolates the cellular components of OPCs in wild-type mice and mutant mice exhibiting a single base substitution that cases reduced osteoclast activity. Western blot analysis is then performed to test for NF-kb and c-FOS expression in the cytoplasm and nucleus of OPCs isolated from these mice. The results of this analysis are shown:
Based on the passage, which statement best explains these results?
A) Mutant mice have a mutation that disables the ability of Nf-kB to localize the nucleus
B) mutant mice have a mutation that prevents c-FOS from interacting with Nf-kB
C) Mutant mice have a mutation in the DNA binding region of NF-kB
D) Mutant mice have a mutation that prevents the transcription of c-Fos in osteoclast progenitor cells
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A) Mutant mice have a mutation that disables the ability of Nf-kB to localize the nucleus
Western blot shows that compared to WT mice, MT mice lack nuclear expression of NF-kB and exhibit reduced c-Fos expression. Because Nf-kB requires an intact nuclear localization sequence to enter the nucleus and increase c-Fos expression, a mutation in the NF-kB nuclear localization sequence of MT mice best explains these results
Sustained excess nutrient intake can result in resistance of target cells to insulin. Compared to normal patterns after a meal, which of the following best describes an effect of insulin resistance?
A) Liver cells form glycogen at a higher rate
B) liver cells secrete glucagon at a lower rate
C) liver cells produce glucose at a higher rate
D) kidney cells secrete glucose at a lower rate
C) liver cells produce glucose at a higher rate
In patients with insulin resistance, the liver will increase production of glucose and decrease production of glycogen after a meal. The liver normally decreases production of glucose and increases production of glycogen after a meal
When present in exocrine gland cells, specific chloride channels reabsorb chloride ions from fluids in the exocrine gland lumen. Individuals with cystic fibrosis, an inherited disorder involving mucus buildup in certain tissues, exhibit decreased function of these chloride channels. An individual with cystic fibrosis in a hot environment is most likely to demonstrate:
A) high plasma chloride ion levels
B) low osmolarity of fluid in sweat gland lumens
C) high chloride ion concentrations in secreted sweat
D) low numbers of chloride channels in exocrine glands
C) high chloride ion concentrations in secreted sweat
Few chloride ions will be reabsorbed by the dysfunctional chloride channels in sweat gland cells
A certain eukarytoic species is triploid and has 24 total chromosomes. A feature of this species is:
A) an inability of some chromosomes to form homologous pairs during meiosis
B) high fitness relative to diploid eukaryotic species
C) production of viable gametes with low genetic diversity
D) somatic cells with 12 chromosome pairs
A) an inability of some chromosomes to form homologous pairs during meiosis
24 chromomes , 8 groups containing 3 chromosomes each
As such, 16 of the 24 chromosomes can form homologous fairs during meiosis, 8 pairs, but the remaining 8 chromosomes exist in unpaired form
Which of the following molecules is most likely found within the cell membranes of intestinal epithelial cells?
A) Peptidoglycan
B) Cholesterol
C) cytoskeletal filaments
D) cellulose
B) Cholesterol
cholesterol mitigates the fluid mosaic model
A certain eukaryotic organism has multiple, distinct genes with highly similar sequences that are expressed at different times in the organism’s life cycle. These genes could have arisen by:
A) alternative splicing
B) conjugation
C) gene duplication
D) transformation
C) gene duplication
mutations, similar but not identical sequences. These differences allow the gene to carry out distinct roles at various times in an organism’s life cycle
Not alternative splicing, as this produces multiple protein products by producing distinct mRNA molecules from the same gene / same segment of DNA. In contrast, the question asks about distinct genes / distinct segments of DNA with similar sequences
Bacteria are removed from lymph and blood in the
lymph nodes and spleen, respectively
A patient found to have abnormally low number of helper T cells in her blood contracts a bacterial infection. During the infection, which of the following is most likely not affected by the patient’s low count of helper T cells?
A) Expression of MHC proteins that present bacterial antigens on the membrane of infected host cells
B) proliferation of B lymphocytes in response to the bacterial infection
C) levels of circulating antibodies against the invading bacterium
D) Activation of apoptosis-inducing cytotoxic T cells
A) Expression of MHC proteins that present bacterial antigens on the membrane of infected host cells
Helper T cell function for B lymphocyte
Promotes B lymphocyte activation and proliferation
-induces differentiation of B lymphocytes in antibody secreting plasma cells and memory cells
helper t cell function –> cytotoxic t cell
promotes cytotoxic t cell activation and proliferation
helper t cell function –> macrophage
enhances activity of macrophage
helper t cell function –> other immune cells
attracts other immune cells to site of infection
Cells of the innate immune system and cells of the adaptive immune system differ in that only the latter:
A) mount an immediate response against pathogens
B) are produced by bone marrow
C) bind only one type of antigen
D) express antigen-presenting proteins on their cell surface
C) bind only one type of antigen
specific immunity
Compared to the axons investigated by Biologist 2, the axons studied by Biologist 1 most likely had:
A) faster decay of the propagating electrical signal
B) axonal membranes that were more exposed to the extracellular space
C) slower rates of action potential conduction
D) voltage-gated ion channels clustered only at specific locations
D) voltage-gated ion channels clustered only at specific locations
According to the passage, Biologist 1 studied brain tissue with neurons containing primarily myelinated axons, whereas Biologist 2 studied unmyelinted axons. Therefore, the myelinated axons investigated by Biologist 1 would contain voltage-gated ion channels clustered at the nodes of Ranvier. However, the unmyelinated axons investigated by Biologist 2 would contain voltage-gated ion channels that are more evenly distributed across the entire axon.
Which of the following synaptic events would likely contribute most directly to the generation of an action potential in a postsynaptic neuron?
A) the presynaptic neuron releases large quantities of GABA
B) postsynaptic neurotransmitter-gated Na+ and Ca2+ channels open
C) Neurotransmitter reuptake into the presynaptic cell and surrounding glia is increased
D) Neurotransmitter binding activates G protein coupled receptors on the postsynaptic membrane
B) postsynaptic neurotransmitter-gated Na+ and Ca2+ channels open
Which of the following cellular processes would most likely lead to increased genetic variation in a population of organisms?
A) DNA replication during S phase of the cell cycle
B) synapsis involving two homologous chromosomes
C) alternative splicing of gene transcripts
D) cell division via mitosis
B) synapsis involving two homologous chromosomes
This is crossing over
One function of endothelial cells is to:
A) contract to release blood pressure
B) line the inside of the GI tract
C) bind sites of vascular damage to form clots
D) line the inside of blood vessels
D) line the inside of blood vessels
Endothelium is the one-cell-thick layer of specialized epithelial cells that line the interior of the cardiovascular system, which includes the heart, arteries, capillaries, and veins
how to differentiate thymine and cytosine
thymine has a methyl group attached to the carbon in the 5th position
how to differentiate guanine and adenine
guanine has a carbonyl group at the 6th position
Human cardiac muscle differs from skeletal muscle because it:
A) apears striated
B) requires acetylcholine to contract
C) contains intercalated discs
D) contains cells with multiple nuclei
C) contains intercalated discs
Skeletal muscle appearance
bunched fibers
- striated (has sarcomeres)
- multinucleated
skeletal muscle location and function
- attached to bone via tendons & leverages bones to generate movement
- aids circulation by squeezing vessels
- heat production (shivering)
skeletal muscle gap junctions
not present, cells are electrically isolated
skeletal muscle control
voluntary, somatic nervous system (ACh)
cardiac muscle appearance
- branched fibers
- striated (has sarcomeres)
- 1-2 nuclei
cardiac muscle location and function
makes up heart walls and pumps blood through circulatory system
cardiac muscle gap junctions
present
