Semester 2 - AP Bio
The data in Figures 1 through 4 below, were collected during a study of the growth of plant seedlings. The concentration of all gibberellins 65 days after planting is approximately
20 ng/gram
Most tomatoes contain 12 chromosomes in gametophytes. How many chromosomes are in the sporophytes?
24
If two carrier parents produce offspring, what is the probability that the offspring will be affected by a recessive disorder? Choose the answer that is not correct.
25 (last choice)
In eukaryotic cells what macromolecule controls checkpoints in the cell cycle?
proteins
At the conclusion of cytokinesis in a somatic cell, the result is
two diploid (2n) daughter cells
If four diploid cells undergo meiosis, how many diploid daughter cells will be produced?
0
A human kidney filters about 200 liters of blood each day. Approximately two liters of liquid and nutrient waste are excreted as urine. The remaining fluid and dissolved substances are reabsorbed and continue to circulate throughout the body. Antidiuretic hormone (ADH) is secreted in response to reduced plasma volume. ADH targets the collecting ducts in the kidney, stimulating the insertion of aquaporins into their plasma membranes and an increased reabsorption of water. If ADH secretion is inhibited, which of the following would initially result?
1
Depolarization is found between which points?
1 and 2
An allele on the X chromosome is responsible for the recessive trait of red-green color blindness in humans. The daughter of a woman who is color-blind has hormal vision, and marries a man who is color blind. This couple has a son, what is the probability that the son will be color blond?
1/2
The data in Figures 1 through 4 below, were collected during a study of the growth of plant seedlings. When the concentration of GAl is highest, the average height of the control seedlings is approximately
10 cm
A cell in the G1 phase has two homologous pairs of chromosomes. It undergoes a mitotic division, followed by meiosis. At the end of meiosis 2, what is the sum of all the products of these divisions in all cells?
16 chromosomes, 16 chromatids, 8 cells, 4 times as many alleles.
What is the genotypic ratio from heterozygous parents in the F1 generation?
1:2:1
At which point do the Na+ gates close?
2
Assume Mendel's ratios are true. A scientist discovers that there is only one gene for eye-color in a particular species of fish. The two alleles for it are R and H. A red-eyed fish (RR) is mated with a white-eye fish (HH). All fish in the F1 generation have pink eyes. The F1 offspring are mated together. What is the expected ratio of eye color in F2? (adapted from University of Toronto National Biology Competition 2011)
25% RR (red), 50% RH (pink), 25% HH (white)
A trisomic cell has
2n+1
Glutamate is a general excitatory postsynaptic neurotransmitter. It is active in all parts of the brain and is especially active in regions associated with cognition and memory. Ketamine blocks glutamate receptors in postsynaptic cells. Using the image, above, which number represents the postsynaptic cell?
3
Hemophilia is a sex-linked recessive condition. A genetic counselor is looking at pedigree charts for a human male and human female to determine the probability that a male offspring might have hemophilia. In the parental generation, the individuals marked with "?" have unknown phenotypes. If the F1 female's father did NOT have hemophilia, what is the probability that her male child (F2) will have hemophilia?
50%
In the following human pedigree, squares represent males, circles represent females, and shade symbols indicate individuals affected with a disorder. One of the affected males from the third generation has a child with a female who is a carrier. For the pedigree shown above, which of the following best expresses the probability that the couple's first son will be affected with the disorder?
50%
Assume these genes are homologous but only one homologue is shown. Which genes are most likely to be segregated during crossing over?
9 & 8
In the F2 generation what is the ratio for a dihybrid cross of two unlinked traits?
9:3:3:1
Touching a very hot surface causes an involuntary reflexive response which draws the body part away from the hot surface. What is the correct pathway of this stimulus & response?
<p> sensory neurons send the impulse to interneurons which send an impulse to motor neurons which flex a muscle</p>
Alcohol is a neurotoxin. Alcohol abuse can cause neurological health problems because it opens K+ channels and mimics GABA. GABA has an inhibitory effect on neuronal axons. How will large quantities of alcohol affect action potential of neurons?
<p> the presynaptic neuron will fail to meet the threshold and therefore will not transfer information efficiently</p>
According to this Genetic Map, which genes are most likely to segregate during crossing over?
A & D
The diagram above shows a developing worm embryo at the four-cell stage. Experiments have shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from one another early during the four-cell stage, no intestine will form. Other experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the following is the most plausible explanation for these findings?
A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.
Which of the following cells has the same amount of DNA as a cell that is undergoing metaphase of meiosis I? (All cells come from the same individual, and all cells have no genetic abnormalities.)
A cell that is at metaphase of mitosis.
The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase?
A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.
The graph above shows changes in glucagon and insulin secretions at different concentrations of blood glucose. Which of the following feedback mechanisms is best supported by the data?
A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released.
Mendel set up his experiments so that there were no hidden traits in the parental generation. Which set represents Mendel's approach?
AAbb x aaBB
Which image shows homologous chromosomes?
ABCDE ABCDE
Using the pedigree below, what is the genotype of female 5 in the third generation?
Aa
The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system?
After a meal, blood glucose levels become elevated, stimulating betacells of the pancreas to release insulin into the blood. Excess glucoseis then converted to glycogen in the liver, reducing blood glucose levels.
A pheromone is a chemical factor that triggers responses in organisms of the same species. One type of pheromone, aggregation pheromones, cause many of a species to swarm a location. Aggregation pheromones are used in defense against predators, mate selection, and overcoming a host's resistance. Which of the following is another example of possible pheromone use?
An ant leaves a chemical trail to lead other ants to food
The vertebrate forelimb initially develops in the embryo as a solid mass of tissue. As development progresses, the solid mass near the end of the forelimb is remodeled into individual digits. Which of the following best explains the role of apoptosis in remodeling of the forelimb?
Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells.
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?
As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
Between which points are the Na+ and K+ gated channels open?
At no point are both gated channels open
In the pedigree above, circles represent females, squares represent males, and shaded figures represent individuals expressing a specific trait. The expression of this trait is most likely due to which of the following?
Autosomal recessive inheritance
Which letter represents the structure that acts as an insulator and what is the name of that structure?
B, myelin sheath
Assume complete dominance for hair color and hair length in a particular species. Black hair (B) is dominant over white hair (b). Long hair (H) is dominant over short hair (h). Which parental genotypes would produce only 2 distinct offspring phenotypes.
BBHh x BBHh
Mitosis only happens after what criteria is met?
DNA replication
Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane. To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus. Previous experiments indicate that CDK5 is active only when attached to a protein called p35. Which of the following predicts how p35 might play a role in regulating neuron function?
Degradation of p35 results in increased synaptic activity.
Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane. To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus. Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system?
Different neurons in the same neural network can release different amounts of neurotransmitter.
Identify the correct statement about cytokinesis in plants
Division begins with the formation of a line of fused vesicles within which the cell walls of the daughter cells form known as the cell plate
The process depicted in the image above is best summarized by which of the following descriptions?
During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.
Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening?
Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits.
Following S phase, which checkpoint will a cell encounter first?
G2 checkpoint
A student in a biology class crossed a male Drosophila melanogaster having a gray body and long wings with a female D. melanogaster having a black body and apterous wings. The following distribution of traits was observed in the offspring Which of the following is supported by the data?
Genes for the two traits are located close together on the same chromosome, and crossing over occurred between the two gene loci.
Huntington's disease is caused by an abnormal dominant allele for the Huntington gene. The disease is fatal and heritable. What is/are the genotype(s) of people with Huntington's disease?
HH Hh
From this list identify all examples of second messengersI. cAMPII. K+III. ATPIV. adenylate cyclaseV. Ca2+
I and V only
Meiosis occurs in: I. germ cells II. somatic cells III. autosomes IV. cardiac cells
I only
Which statements are true regarding Down syndrome? I. usually caused by nondisjunction during anaphase II II. usually caused by nondisjunction during anaphase I III. usually caused by nondisjunction in the oocyte IV. usually caused by nondisjunction in the sperm V. trisomy of chromosome 21 causes some genes to be expressed in excess VI. can be reversed with gene therapy
II, III , V only
Which of the following disorders is (are) caused by nondisjunction? I. Color-blindness II. Turner syndrome III. Down syndrome IV. Klinefelter syndrome
II, III, IV only
I. ligand-gated ion channels would remain open II. ligand-gated ion channels would remain closed III. the signaling cascade would slow or stop IV. cellular responses would cease or stop V. cellular activity would increase dramatically
II, III, and IV only
What is unique about how chromosomes line up during metaphase II as compared to metaphase in mitosis?
In metaphase II, sister chromatids undergo crossing over.
Which statement is false?
In signal transduction, a receptor on the outside of the cell membranebinds to a ligand; the receptor changes shape and transports the ligandinto the cell.
Table I shows the results of breeding experiments to examine the inheritance of flower color (purple versus white) and pod shape (inflated versus constricted). For the crosses recorded in Table I, true-breeding parents were crossed to produce F 1 offspring, which were then test-crossed to homozygous recessive individuals. Table II shows the results of computer-simulated crosses to model the inheritance of leaf shape (broad versus narrow) and flower color (purple versus white). Based on the data in Table I, which of the following best explains why there are no individuals with constricted pods in the F1 generation?
Inflated pod shape is dominant to constricted pod shape.
Which of the following is true of mitosis?
It maintains the same chromosome number in the daughter cells as in the parent cell.
Which of the following is false about a hormone that is a local regulator?
It reaches all the cells of the body.
Which statement is true regarding Mendelian genetics?
Mendelian genetics did not consider the existence and expression ofnon-nuclear genes
Gregor Mendel's pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome?
Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.
What is the name of the phase when chromosomes cross over?
Prophase I
Table I shows the results of breeding experiments to examine the inheritance of flower color (purple versus white) and pod shape (inflated versus constricted). For the crosses recorded in Table I, true-breeding parents were crossed to produce F 1 offspring, which were then test-crossed to homozygous recessive individuals. Table II shows the results of computer-simulated crosses to model the inheritance of leaf shape (broad versus narrow) and flower color (purple versus white). In Table II, the F1 offspring of the cross between broad-leaved, white-flowered plants with narrow-leaved, purple-flowered plants have a phenotype that differs from that of either parent. However, many testcross offspring have the same phenotype as one of the two plants in the parental cross, but relatively few testcross offspring have the same phenotype as the F1 offspring. Which of the following best explains this observation?
Recombination between the leaf-shape and flower-color genes resulted in chromosomes carrying a dominant allele of both genes.
In a particular species of pea flowers the red allele R is dominant to the yellow allele r. 292 seeds were produced from the initial plants. All 292 seeds were planted and matured into 174 plants with red flowers and 118 plants with yellow flowers. Assume the red-flower parent is heterozygous and the yellow flower is homozygous recessive, what are the expected ratios?
Red Flowers - 146 Yellow Flowers - 146
Which of the following occurs in both meiosis and mitosis?
Separation of sister chromatids
A child is born with blood type A. Her mother is blood type B. If the father has blood type AB, which of the following statements is correct about the mother?
She contributes an i allele, which is recessive to the father IA allele.
Most cells that have become transformed in cancer cells have which of the following characteristics when compared to normal, healthy cells?
Shorter cell cycle
Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?
Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.
Which of the following occurs during mitosis but not during meiosis I?
The chromatids of each chromosome are separated
In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a color-blind son, which of the following must be true?
The mother carries the allele for color blindness.
Table I shows the results of breeding experiments to examine the inheritance of flower color (purple versus white) and pod shape (inflated versus constricted). For the crosses recorded in Table I, true-breeding parents were crossed to produce F 1 offspring, which were then test-crossed to homozygous recessive individuals. Table II shows the results of computer-simulated crosses to model the inheritance of leaf shape (broad versus narrow) and flower color (purple versus white). Which of the following provides the best justification for an assumption that might have been used in the computer simulation (Table II)?
The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and white-flowered plants had purple flowers.
Which of the following is the most likely explanation for a high rate of crossing-over between two genes?
The two genes are far apart on the same chromosome.
A series of crosses is performed with fruit flies (Drosophila melanogaster) to examine inheritance of the genes vestigial (vg) and cinnabar (cn). The recessive vg allele causes small malformed wings called vestigial wings. The recessive cn allele causes bright-red eyes called cinnabar eyes. In the first test cross, a female with wild-type wings and eyes is mated with a male with vestigial wings and cinnabar eyes. All the F1 flies are mated with males with vestigial wings and cinnabar eyes. The phenotypes of 500 F2 individuals are shown in the table. Which of the following is the most likely explanation of the results?
The two genes are linked on an autosome
Which statement about mitosis is FALSE?
prophase is when homologous chromosomes pair
Which of the following best describes the cells that result from the process of meiosis in mammals?
They are genetically different from the parent cell.
Which statement about cytokinesis is correct?
To divide cytoplasm between two daughter cells, a cleavage furrow forms in animal cells and a cell plate forms in plant cells.
Platelet-derived growth factor, PDGF, is required in order to induce mitosis in some cells. Connective tissue cells have PDGF receptors in the plasma membrane. What is likely the first thing to happen when PDGF receptors are activated?
a kinase cascade is initiated
The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway? (source: College Board 2012 Practice Test)
a medication enters the target cell and inhibits an enzyme that normallysynthesizes a second messenger.
Which statement is true regarding G-protein coupled receptors?
activate a single G-protein when a hormone binds to the receptor.
A famous article by R.A. Fisher published in 1936 claimed that Mendel's data was wrong and declared that the ratios do not work out according to Mendel's methods. There is still lively debate surrounding Mendel's ratios and Fisher's criticism. (for more information read Daniel Hartl's article in Mud Sticks: On the Alleged Falsification of Mendel's Data in Genetics March 2007 vol. 175 no. 3 975-979 - Full Text (PDF)). Some critics claim Mendel's data was falsified. Others claim the statistical analysis yielded false conclusions. Regardless, these critics are focusing on Mendel's work and his very limited understanding of genetics. Although many of his findings are considered valid and still applied today, what discoveries at the chromosomal level have shown his assumptions to be overly simplistic?
all of the above
After reading about Mendel's experiments you are doubtful about the validity of the results and decide to recreate the experiments yourself. You use pea seeds but are a little short on cash so you can only begin with two seeds both of which are yellow and round.You have quite a green thumb and were able to grow hundreds of seeds for the F1 generation. Data from F1 generation of peas is in the table below. What is the best explanation for this data?
alleles for shape and color were assorted independently
According to the image, this cell is in which stage of mitosis?
anaphase
According to this image, what is the result of these pathways if Caspase 8 or Caspase 9 are activated?
apoptosis
Read and analyze the pedigree chart below, to determine which pattern of inheritance explains inheritance of this trait.
autosomal dominant
According to this pedigree, what pattern of inheritance best explains transmission of this trait?
autosomal recessive
Which types of cells use quorum sensing to communicate with cells in the vicinity?
bacteria
Two genes control the color of coats in Labrador retrievers. The coat color is controlled by the first gene with black coat (B) being dominant to brown coat (b). The expression of color is controlled by the second gene. Expression of color (E) is dominant to not expressing color (e). Several generations of puppies are born as a result of breeding a brown Lab and a yellow Lab. All the puppies are either black or yellow. No brown puppies are ever produced from crossing these two Labs. What are the genotypes of the parent Labs?
bbEe and BBee
Most receptors are membrane proteins. Which of the following is a true statment about receptors?
bonding with ligand molecules will cause a conformational change in the receptor
Cystic fibrosis is a genetic condition afflicting vertebrates. Individuals with CF have missing or nonfunctional cystic fibrosis transmembrane conductance regulator proteins (CFTR) which are chloride ion channels. If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane?
both chloride ions and water will move out of the cell
Achondroplasia is the common cause of dwarfism and is caused by a mutation on the fibroblast growth factor receptor (FGFR-3) which includes a tyrosine kinase domain. The mutation of FGFR-3 magnifies the inhibitory effect of endochondrial ossification at the epiphyseal plates of the long bones. Which image represents a properly arranged tyrosine kinase dimer?
bottom right
A hormone:
can stimulate the synthesis and secretion of a different hormone.
Which statement is true about meiosis?
centromeres divide at anaphase II
When a hormone binds to its receptor, the receptor ________. This event initiates the transmission of ________ to the inside of the cell
changes shape; information
Prolonged stress such as sitting an exam triggers the release of the hormone cortisol from the adrenal cortex. Cortisol is lipophilic and nearly insoluble in blood. Cortisol travels through the blood attached to carrier proteins. After traveling through the blood, how will cortisol enter the cell membrane?
cortisol will pass through the lipid bilayer of the cell membrane andwill then bind with protein-bound cytoplasmic receptors.
Which of these does NOT create genetic variation in offspring?
crossing over during anaphase II
If chiasmatas fail to form what is the result?
crossing over will not occur
Which of these is a potential cause of unregulated cell division?
excessive cyclin causing over-activation of MPF
Interference with feedback loops regulating thyroid hormones can result in
hyperthyroidism
Cyclin-dependent Protein Kinases (Cdks) control the cell cycle through phosphorylation. What conclusion can be drawn based on the graph, below.
increases in protein kinase activity are followed by increases in division of cells, indicating a relationship
Denaturing BAX would result in
inhibition of apoptosis
Cells spend the majority of their life in _______ stage
interphase
In which direction does information travel along this neuron?
left to right
King crabs have an astonishing 208 chromosomes in somatic cells. The diagram below represents numbers of chromosomes in particular king crab cells. What processes are happening in this diagram?
meiosis and fertilization
Which statement about mitosis is false?
mitosis is a reduction division because it results in haploid daughter cells
Several types of fish that live in very cold water have been found to possess an extra gene which makes the "antifreeze" protein. This protein arose from an extra copy of the pancreatic trypsinogen gene which mutated slightly and began expressing the "antifreeze" gene which prevents formation of ice crystals in tissue and cells. This neofunctionalization (new, extra function on top of the original gene's continued expression) supports which of these conclusions?
mutations are not always bad and often result in improved traits
Birth control pills are generally a combination of synthetic estrogen and progestin hormones. These hormones work together to stop the release of GnRH which then stops release of FSH and LH. Preventing release of LH stops ovulation. What type of feedback loop is utilized by birth control pills?
negative feedback
What type of regulatory mechanism is demonstrated in the graph, above?
negative feedback loop
Quorum sensing uses autoinducers as signaling molecules. Autoinducers are signaling molecules secreted by bacteria to communicate with other bacteria of the same kind. The secreted autoinducers can be small, hydrophobic molecules such as acyl-homoserine lactone, (AHL) or larger peptide-based molecules; each type of molecule has a different mode of action. When AHL enters target bacteria, it binds to transcription factors, which then switch gene expression on or off. The peptide autoinducers stimulate more complicated signaling pathways that include bacterial kinases. The changes in bacteria following exposure to autoinducers can be quite extensive. The pathogenic bacterium Pseudomonas aeruginosa has 616 different genes that respond to autoinducers. Quorum sensing can be an effective form of cell-to-cell communication for unicellular organisms such as bacteria and yeast. Which statement identifies one weakness of quorum sensing.
quorum sensing is density dependent. Small populations will secrete low levels of autoinducers which will cause a slow response leaving the population vulnerable to attack
Precise regulation of specific hormone levels is required for optimal sperm production in mammals, as summarized in the figure above. Anabolic-androgenic steroids (AAS) are synthetic variants of testosterone that are sometimes abused by persons who desire to enhance their athletic performance or alter their physique. Assuming that AAS function in the same way as naturally occurring testosterone, it is most likely that long-term abuse of AAS would
reduce sperm production
If not met, which requirement at G2 could prevent a cell from continuing through the cell cycle?
replication of chromosomes already completed successfully
Which of these is NOT an example of a positive feedback loop?
secretion of insulin
Based on the pedigree chart below, what type of inheritance pattern does this trait display?
sex-linked recessive
The color and length of cat fur is controlled by autosomal genes shown in the table, below. Gene Trait B Black fur b White fur H Short-haired fur h Long-haired fur Offspring are produced from two cats with these genotypes: BbHh & bbHH What trait will ALWAYS be expressed in their offspring?
short hair
Which step in this signal transduction pathway is out of order and what is the correct version? I. reception of signal molecule II. ligand attaches to complementary molecule on receptor III. transduction is initiated IV. cascade activates second messengers V. response either in nucleus or cytoplasm of cell
step 4, should be second messengers activate cascade
Although it is unlikely, this image could show metaphase II of meiosis. What could be changed in this image to more accurately reflect a cell in metaphase II?
the chromosomes should display recombinant chromosomes as a result of crossing over
Lipid soluble hormones such as testosterone enter cells by passing directly through the cell membrane. Once testosterone has entered a target cell what will happen?
the hormone will result in changes to gene expression within the target cell
Many medications interfere with normal signal pathways used by cells to respond to messengers such as hormones. Which answer represents a drug that interferes with a signal transduction pathway?
the medicine denatures a specific enzyme that acts as a second messenger
A tissue culture of vertebrate muscle was provided with a constant excess supply of glucose under anaerobic conditions starting at time zero and the amounts of pyruvic acid and ATP produced were measured. The solid line in the graph above represents the pyruvic acid produced in moles per liter per minute. ATP levels were also found to be highest at points A and C, lowest at B and D. A second culture was set up under the same conditions, except that substance X was added, and the results are indicated by the dotted line. The rate of pyruvic acid formation fluctuates because
the reaction is affected by negative feedback
Chose from the following answers. Which of the following is most similar to a membrane receptor protein that recognizes a chemical signal? (adapted from Pearson Bio 8e (campbell) MCQ)
the substrate-specific active site on an enzyme
Acetylcholine functions as a neurotransmitter at some nerve to muscle cell synapses by causing an action potential in the receiving skeletal muscle cell. The enzyme that breaks down acetylcholine, acetylcholine esterase, is found in the synaptic cleft. What would happen if there is an excess of acetylcholine esterase in synaptic clefts?
transmission of impulses would be impeded or prevented causing muscle paralysis
Hormones, such as testosterone and estrogen, are lipid-soluble signal molecules. These molecules can enter and exit cells by simple diffusion. If these molecules can easily enter and exit all cells, why do only some cells react to the presence of these hormones?
unresponsive cells, known as non-target cells, lack intracellularreceptors that recognize these hormones, which means they cannot triggera genetic response
Which image represents a possible modification made to a membrane receptor protein due to involvement in signal transduction?
very swiggly, to (blue, purple, orange) diagram
Which statement is false?
water-soluble hormones result in changes in gene expression
What would happen if gametes did not go through meiosis before fertilization?
zygotes would contain twice as many chromosomes as necessary