Datasets:

bigbio
/

biology_how_why_corpus

id stringlengths 1 4	question_id stringlengths 1 4	document_id stringlengths 3 10	question stringlengths 18 194	type stringclasses 2 values	choices list	answer sequence
0	1	1_8_6	How does the second law of thermodynamics apply to spontaneity?	how	[]	[ "The second law of thermodynamics states that spontaneous processes, those requiring no outside input of energy, increase the entropy (disorder) of the universe." ]
2	3	1_10_1_3	How does carbon dioxide get into a plant?	how	[]	[ "The Calvin cycle is named for Melvin Calvin, who, along with his colleagues, began to elucidate its steps in the late 1940s. The cycle begins by incorporating CO2 from the air into organic molecules already present in the chloroplast. This initial incorporation of carbon into organic compounds is known as carbon f...
4	5	1_10_3	How does carbon dioxide get into a plant?	how	[]	[ "Phase 1: Carbon fixation. The Calvin cycle incorporates each CO2 molecule, one at a time, by attaching it to a five-carbon sugar named ribulose bisphosphate (abbreviated RuBP). The enzyme that catalyzes this first step is RuBP carboxylase, or rubisco. (This is the most abundant protein in chloroplasts and is also ...
6	7	1_10_1_1	How does carbon dioxide get into a plant?	how	[]	[ "Carbon dioxide enters the leaf, and oxygen exits, by way of microscopic pores called stomata (singular, stoma; from the Greek, meaning \"mouth\")." ]
8	9	1_10_4	How does carbon dioxide get into a plant?	how	[]	[ "The CO2 required for photosynthesis enters a leaf via stomata, the pores on the leaf surface (see Figure 10.4)." ]
10	11	1_35_3_2_2	How does carbon dioxide get into a plant?	how	[]	[ "Mesophyll consists mainly of parenchyma cells specialized for photosynthesis. The mesophylls of many eudicots have two distinct layers: palisade mesophyll and spongy mesophyll. Palisade mesophyll consists of one or more layers of elongated parenchyma cells on the upper part of the leaf. Spongy mesophyll is below t...
12	13	1_36_4	How does carbon dioxide get into a plant?	how	[]	[ "The large surface area enhances light absorption for photosynthesis. The high surface-to-volume ratio aids in CO2 absorption during photosynthesis as well as in the release of O2, a by-product of photosynthesis. Upon diffusing through the stomata, CO2 enters a honeycomb of air spaces formed by the spongy mesophyll...
14	15	1_11_3_2	How does a phosphorylation cascade affect a signal?	how	[]	[ "Figure 11.10 A phosphorylation cascade. In a phosphorylation cascade, a series of different molecules in a pathway are phosphorylated in turn, each molecule adding a phosphate group to the next one in line. In this example, phosphorylation activates each molecule, and dephosphorylation returns it to its inactive f...
16	17	1_11_3_2	How does a phosphorylation cascade affect a signal?	how	[]	[ "Equally important in the phosphorylation cascade are the protein phosphatases, enzymes that can rapidly remove phosphate groups from proteins, a process called dephosphorylation. By dephosphorylating and thus inactivating protein kinases, phosphatases provide the mechanism for turning off the signal transduction p...
18	19	1_11_6	How does a phosphorylation cascade affect a signal?	how	[]	[ "11.3 Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell (pp. 214-219) At each step in a signal transduction pathway, the signal is transduced into a different form, which commonly involves a shape change in a protein. Many signal transduction pathways incl...
20	21	1_17_4_2_3	How does a release factor differ from tRNA?	how	[]	[ "A release factor, a protein shaped like an aminoacyl tRNA, binds directly to the stop codon in the A site. The release factor causes the addition of a water molecule instead of an amino acid to the polypeptide chain. (There are plenty of water molecules available in the aqueous cellular environment. ) This reactio...
22	23	1_5_5_4	How does a release factor differ from tRNA?	how	[]	[ "Consider, for example, the type of RNA called transfer RNA (tRNA), which brings amino acids to the ribosome during the synthesis of a polypeptide. A tRNA molecule is about 80 nucleotides in length. Its functional shape results from base pairing between nucleotides where complementary stretches of the molecule run ...
24	25	1_17_4_1	How does a release factor differ from tRNA?	how	[]	[ "As a molecule of mRNA is moved through a ribosome, codons are translated into amino acids, one by one. The interpreters are tRNA molecules, each type with a specific anticodon at one end and a corresponding amino acid at the other end. A tRNA adds its amino acid cargo to a growing polypeptide chain when the antico...
26	27	1_17_4_1_1	How does a release factor differ from tRNA?	how	[]	[ "A tRNA molecule consists of a single RNA strand that is only about 80 nucleotides long (compared to hundreds of nucleotides for most mRNA molecules). Because of the presence of complementary stretches of nucleotide bases that can hydrogen-bond to each other, this single strand can fold back upon itself and form a ...
28	29	1_17_4_2_3	How does release factor release a polypeptide from the ribosome?	how	[]	[ "A release factor, a protein shaped like an aminoacyl tRNA, binds directly to the stop codon in the A site. The release factor causes the addition of a water molecule instead of an amino acid to the polypeptide chain. (There are plenty of water molecules available in the aqueous cellular environment. ) This reactio...
30	31	1_27_2_2	How does recombination occur in bacteria?	how	[]	[ "Although new mutations are a major source of variation in prokaryotic populations, additional diversity arises from genetic recombination, the combining of DNA from two sources. In eukaryotes, the sexual processes of meiosis and fertilization combine DNA from two individuals in a single zygote. But meiosis and fer...
32	33	1_27_2_2_1	How does recombination occur in bacteria?	how	[]	[ "In transformation, the genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings. For example, a harmless strain of Streptococcus pneumoniae can be transformed into pneumonia-causing cells if the cells are placed in a medium containing DNA from a pathogeni...
34	35	1_27_2_2_2	How does recombination occur in bacteria?	how	[]	[ "Figure 27.12 Bacterial. The E. coli donor cell (left) extends a pilus that attaches to a recipient cell, a key first step in the transfer of DNA. The pilus is a flexible tube of protein subunits (TEM). In a process called conjugation, DNA is transferred between two prokaryotic cells (usually of the same species) t...
36	37	1_43_2	How is a lymphocyte activated?	how	[]	[ "Vertebrates are unique in having adaptive immunity in addition to innate immunity. The adaptive response relies on T cells and B cells, which are types of white blood cells called lymphocytes. Like all blood cells, lymphocytes originate from stem cells in the bone marrow. Some lymphocytes migrate from the bone mar...
38	39	1_43_2_3	How is a lymphocyte activated?	how	[]	[ "Receptor diversity and self-tolerance arise as a lymphocyte matures. Proliferation of cells and the formation of immunological memory occur later, after a mature lymphocyte encounters and binds to a specific antigen." ]
40	41	1_43_2_3_3	How is a lymphocyte activated?	how	[]	[ "To begin with, an antigen is presented to a steady stream of lymphocytes in the lymph nodes (see Figure 43.7) until a match is made. A successful match then triggers changes in cell number and activity for the lymphocyte to which an antigen has bound. The binding of an antigen receptor to an epitope initiates even...
42	43	1_43_5	How is a lymphocyte activated?	how	[]	[ "43.2 In adaptive immunity, receptors provide pathogen-specific recognition (pp. 935-940) Adaptive immunity relies on lymphocytes that arise from stem cells in the bone marrow and complete their maturation in the bone marrow (B cells) or in the thymus (T cells). Lymphocytes have cell-surface antigen receptors for f...
44	45	1_43_5	How is a lymphocyte activated?	how	[]	[ "43.3 Adaptive immunity defends against infection of body fluids and body cells (pp. 940-946) Helper T cells interact with antigen fragments displayed by class II MHC molecules on the surface of dendritic cells, macrophages, and B cells (antigen-presenting cells). Activated helper T cells secrete cytokines that sti...
46	47	1_8_2_3_2	How do cells avoid coming to equilibrium?	how	[]	[ "Like most systems, a living cell is not in equilibrium. The constant flow of materials in and out of the cell keeps the metabolic pathways from ever reaching equilibrium, and the cell continues to do work throughout its life. This principle is illustrated by the open (and more realistic) hydroelectric system in Fi...
48	49	1_17_1_2	How does an mRNA strand compare to its coding strand?	how	[]	[ "Transcription is the synthesis of RNA using information in the DNA. The two nucleic acids are written in different forms of the same language, and the information is simply transcribed, or \"rewritten,\" from DNA to RNA. Just as a DNA strand provides a template for making a new complementary strand during DNA repl...
50	51	1_17_1_3_1	How does an mRNA strand compare to its coding strand?	how	[]	[ "The series of words in a gene is transcribed into a complementary series of nonoverlapping, three-nucleotide words in mRNA, which is then translated into a chain of amino acids (Figure 17.4). During transcription, the gene determines the sequence of nucleotide bases along the length of the RNA molecule that is bei...
52	53	1_17_1_3_1	How does an mRNA strand compare to its coding strand?	how	[]	[ "In the example in Figure 17.4, the nucleotide triplet ACC along the DNA (written as 3'-ACC-5') provides a template for 5'-UGG-3' in the mRNA molecule. The mRNA nucleotide triplets are called codons, and they are customarily written in the 5' → 3' direction. In our example, UGG is the codon for the amino acid ...
54	55	1_25_1_4	How does the structure of a ribosome's active site support the RNA world hypothesis?	how	[]	[ "In a particular environment, RNA molecules with certain base sequences are more stable and replicate faster and with fewer errors than other sequences. The RNA molecule whose sequence is best suited to the surrounding environment and has the greatest ability to replicate itself will leave the most descendant molec...
56	57	1_8_2_2	How are free energy and a system's likelihood to change related?	how	[]	[ "Unstable systems (top) are rich in free energy, G. They have a tendency to change spontaneously to a more stable state (bottom), and it is possible to harness this \"downhill\" change to perform work. We can think of free energy as a measure of a system's instability: its tendency to change to a more stable state....
58	59	1_12_3_3	How do malignant tumor cells spread?	how	[]	[ "Figure 12.20 The growth and metastasis of a malignant breast tumor. The cells of malignant (cancerous) tumors grow in an uncontrolled way and can spread to neighboring tissues and, via lymph and blood vessels, to other parts of the body. The spread of cancer cells beyond their original site is called metastasis. T...
60	61	1_12_4	How do malignant tumor cells spread?	how	[]	[ "Cancer cells elude normal cell cycle regulation and divide out of control, forming tumors. Malignant tumors invade surrounding tissues and can undergo metastasis, exporting cancer cells to other parts of the body, where they may form secondary tumors." ]
62	63	1_18_5_3	How do malignant tumor cells spread?	how	[]	[ "The model of a multistep path to cancer is well supported by studies of one of the best-understood types of human cancer, colorectal cancer. About 135,000 new cases of colorectal cancer are diagnosed each year in the United States, and the disease causes 60,000 deaths each year. Like most cancers, colorectal cance...
64	65	1_14_1_1	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "Around 1857, Mendel began breeding garden peas in the abbey garden to study inheritance. Although the question of heredity had long been a focus of curiosity at the monastery, Mendel's fresh approach allowed him to deduce principles that had remained elusive to others. One reason Mendel probably chose to work with...
66	67	1_14_1_1	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "In nature, pea plants usually self-fertilize: Pollen grains from the stamens land on the carpel of the same flower, and sperm released from the pollen grains fertilize eggs present in the carpel. To achieve cross-pollination (fertilization between different plants), Mendel removed the immature stamens of a plant b...
68	69	1_14_1_1	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "Mendel chose to track only those characters that occurred in two distinct, alternative forms. For example, his plants had either purple flowers or white flowers; there were no colors intermediate between these two varieties. Had Mendel focused instead on characters that varied in a continuum among individuals: see...
70	71	1_14_1_1	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "In a typical breeding experiment, Mendel cross-pollinated two contrasting, true-breeding pea varieties: for example, purple-flowered plants and white-flowered plants (see Figure 14.2). This mating, or crossing, of two true-breeding varieties is called hybridization. The true-breeding parents are referred to as the...
72	73	1_14_1_2	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "If the blending model of inheritance were correct, the F1 hybrids from a cross between purple-flowered and white-flowered pea plants would have pale purple flowers, a trait intermediate between those of the P generation. Notice in Figure 14.2 that the experiment produced a very different result: All the F1 offspri...
74	75	1_14_1_3	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "Mendel derived the law of segregation from experiments in which he followed only a single character, such as flower color. All the F1 progeny produced in his crosses of true-breeding parents were monohybrids, meaning that they were heterozygous for the one particular character being followed in the cross. We refer...
76	77	1_14_3	Since DNA had not yet been discovered, how was Mendel able to determine how traits are passed from parents to offspring?	how	[]	[ "For the work that led to his two laws of inheritance, Mendel chose pea plant characters that turn out to have a relatively simple genetic basis: Each character is determined by one gene, for which there are only two alleles, one completely dominant and the other completely recessive." ]
78	79	1_8_2_2	How does equilibrium describe a state of maximum stability?	how	[]	[ "Another term that describes a state of maximum stability is equilibrium, which you learned about in Chapter 2 in connection with chemical reactions. There is an important relationship between free energy and equilibrium, including chemical equilibrium. Recall that most chemical reactions are reversible and proceed...
80	81	1_22_2_1_2	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Darwin realized that explaining such adaptations was essential to understanding evolution. As we'll explore further, his explanation of how adaptations arise centered on natural selection, a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other ind...
82	83	1_22_2_2_2	How does natural selection act on a sexually-reproducing population?	how	[]	[ "An organism's heritable traits can influence not only its own performance, but also how well its offspring cope with environmental challenges. For example, an organism might have a trait that gives its offspring an advantage in escaping predators, obtaining food, or tolerating physical conditions. When such advant...
84	85	1_22_2_2_3	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Let's now recap the main ideas of natural selection: Natural selection is a process in which individuals that have certain heritable traits survive and reproduce at a higher rate than other individuals because of those traits." ]
86	87	1_22_2_2_3	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Over time, natural selection can increase the match between organisms and their environment (Figure 22.12). If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species. One subtle but important poin...
88	89	1_22_4	How does natural selection act on a sexually-reproducing population?	how	[]	[ "22.1 The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species (pp. 453-455) Darwin proposed that life's diversity arose from ancestral species through natural selection, a departure from prevailing views. In contrast to catastrophism (the principle that events in the p...
90	91	1_23	How does natural selection act on a sexually-reproducing population?	how	[]	[ "23.4 Natural selection is the only mechanism that consistently causes adaptive evolution" ]
92	93	1_23_0_0	How does natural selection act on a sexually-reproducing population?	how	[]	[ "One common misconception about evolution is that individual organisms evolve. It is true that natural selection acts on individuals: Each organism's traits affect its survival and reproductive success compared with other individuals. But the evolutionary impact of natural selection is only apparent in the changes ...
94	95	1_23_3	How does natural selection act on a sexually-reproducing population?	how	[]	[ "The three mechanisms that alter allele frequencies directly and cause most evolutionary change are natural selection, genetic drift, and gene flow (violations of conditions 3-5)." ]
96	97	1_23_3_1	How does natural selection act on a sexually-reproducing population?	how	[]	[ "As you read in Chapter 22, Darwin's concept of natural selection is based on differential success in survival and reproduction: Individuals in a population exhibit variations in their heritable traits, and those with traits that are better suited to their environment tend to produce more offspring than those with ...
98	99	1_23_4	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Evolution by natural selection is a blend of chance and \"sorting\": chance in the creation of new genetic variations (as in mutation) and sorting as natural selection favors some alleles over others. Because of this favoring process, the outcome of natural selection is not random. Instead, natural selection consi...
100	101	1_23_4_1_2	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Natural selection can alter the frequency distribution of heritable traits in three ways, depending on which phenotypes in a population are favored. These three modes of selection are called directional selection, disruptive selection, and stabilizing selection. Figure 23.13 Modes of selection. These cases describ...
102	103	1_23_4_5	How does natural selection act on a sexually-reproducing population?	how	[]	[ "Though natural selection leads to adaptation, nature abounds with examples of organisms that are less than ideally \"engineered\" for their lifestyles. There are several reasons why. Selection can act only on existing variations. Natural selection favors only the fittest phenotypes among those currently in the pop...
104	105	1_23_5	How does natural selection act on a sexually-reproducing population?	how	[]	[ "23.4 Natural selection is the only mechanism that consistently causes adaptive evolution (pp. 480-485) One organism has greater relative fitness than a second organism if it leaves more fertile descendants than the second organism. The modes of natural selection differ in how selection acts on phenotype (the white...
106	107	1_9_6_3	How does phosphofructokinase play a role in regulating glycolysis?	how	[]	[ "Allosteric enzymes at certain points in the respiratory pathway respond to inhibitors and activators that help set the pace of glycolysis and the citric acid cycle. Phosphofructokinase, which catalyzes an early step in glycolysis (see Figure 9.9), is one such enzyme. It is stimulated by AMP (derived from ADP) but ...
108	109	1_9_6_3	How does phosphofructokinase play a role in regulating glycolysis?	how	[]	[ "As shown in Figure 9.20, one important switch is phosphofructokinase, the enzyme that catalyzes step 3 of glycolysis (see Figure 9.9). That is the first step that commits the substrate irreversibly to the glycolytic pathway. By controlling the rate of this step, the cell can speed up or slow down the entire catabo...
110	111	1_14_4_2_3	How does the gene for sickle cell anemia show heterozygote advantage?	how	[]	[ "About one out of ten African-Americans have sickle-cell trait, an unusually high frequency of heterozygotes for an allele with severe detrimental effects in homozygotes. Why haven't evolutionary processes resulted in the disappearance of this allele among this population? One explanation is that having a single co...
112	113	1_18_1	How can a bacterial cell regulate which genes get expressed?	how	[]	[ "Second, cells can adjust the production level of certain enzymes; that is, they can regulate the expression of the genes encoding the enzymes. If, in our example, the environment provides all the tryptophan the cell needs, the cell stops making the enzymes that catalyze the synthesis of tryptophan (Figure 18.2b). ...
114	115	1_18_1_1	How can a bacterial cell regulate which genes get expressed?	how	[]	[ "E. coli synthesizes the amino acid tryptophan from a precursor molecule in the multistep pathway shown in Figure 18.2. Each reaction in the pathway is catalyzed by a specific enzyme, and the five genes that code for the subunits of these enzymes are clustered together on the bacterial chromosome. A single promoter...
116	117	1_18_1_1	How can a bacterial cell regulate which genes get expressed?	how	[]	[ "A key advantage of grouping genes of related function into one transcription unit is that a single \"on-off switch\" can control the whole cluster of functionally related genes; in other words, these genes are coordinately controlled. When an E. coli cell must make tryptophan for itself because the nutrient medium...
118	119	1_10_4_3	How can CAM plants take carbon dioxide in at night when photosynthesis requires light?	how	[]	[ "A second photosynthetic adaptation to arid conditions has evolved in many succulent (water-storing) plants, numerous cacti, pineapples, and representatives of several other plant families. These plants open their stomata during the night and close them during the day, just the reverse of how other plants behave. C...
120	121	1_10_5	How can CAM plants take carbon dioxide in at night when photosynthesis requires light?	how	[]	[ "CAM plants open their stomata at night, incorporating CO2 into organic acids, which are stored in mesophyll cells. During the day, the stomata close, and the CO2 is released from the organic acids for use in the Calvin cycle." ]
122	123	1_13_4_1_2	How does crossover provide more variation for natural selection to act on?	how	[]	[ "Figure 13.11 The results of crossing over during meiosis. As a consequence of the independent assortment of chromosomes during meiosis, each of us produces a collection of gametes differing greatly in their combinations of the chromosomes we inherited from our two parents. Figure 13.10 suggests that each chromosom...
124	125	1_23_1_2_4	How does crossover provide more variation for natural selection to act on?	how	[]	[ "During meiosis, homologous chromosomes, one inherited from each parent, trade some of their alleles by crossing over. These homologous chromosomes and the alleles they carry are then distributed at random into gametes." ]
126	127	1_13_4_1_2	How does crossover provide more variation for natural selection to act on?	how	[]	[ "The important point for now is that crossing over, by combining DNA inherited from two parents into a single chromosome, is an important source of genetic variation in sexual life cycles." ]
128	129	1_13_5	How does crossover provide more variation for natural selection to act on?	how	[]	[ "Crossing over involves breakage and rejoining of the DNA of nonsister chromatids in a homologous pair, resulting in recombinant chromatids that will become recombinant chromosomes." ]
130	131	1_15_3_2_2	How does crossover provide more variation for natural selection to act on?	how	[]	[ "Subsequent experiments demonstrated that this process, now called crossing over, accounts for the recombination of linked genes. In crossing over, which occurs while replicated homologous chromosomes are paired during prophase of meiosis I, a set of proteins orchestrates an exchange of corresponding segments of on...
132	133	1_43_3_1	How do cytotoxic T lymphocytes kill viral cells?	how	[]	[ "Activated helper T cells also help stimulate cytotoxic T cells, as we'll discuss next." ]
134	135	1_43_3_2	How do cytotoxic T lymphocytes kill viral cells?	how	[]	[ "In the cell-mediated immune response, cytotoxic T cells are the effector cells. The term cytotoxic refers to their use of toxic gene products to kill infected cells. To become active, they require signaling molecules from helper T cells as well as interaction with a cell that presents an antigen. Once activated, c...
136	137	1_43_5	How do cytotoxic T lymphocytes kill viral cells?	how	[]	[ "43.3 Adaptive immunity defends against infection of body fluids and body cells (pp. 940-946) Helper T cells interact with antigen fragments displayed by class II MHC molecules on the surface of dendritic cells, macrophages, and B cells (antigen-presenting cells). Activated helper T cells secrete cytokines that sti...
138	139	1_45_3_1	How does the hypothalamus affect the anterior pituitary?	how	[]	[ "In vertebrates, the hypothalamus plays a central role in integrating the endocrine and nervous systems. One of several endocrine glands located in the brain (Figure 45.14), the hypothalamus receives information from nerves throughout the body, including the brain. In response, the hypothalamus initiates endocrine ...
140	141	1_45_3_1	How does the hypothalamus affect the anterior pituitary?	how	[]	[ "In contrast, the anterior pituitary is an endocrine gland that synthesizes and secretes hormones in response to signals from the hypothalamus. Many anterior pituitary hormones act as tropic hormones, meaning that they regulate the function of other endocrine cells or glands." ]
142	143	1_45_3_1_2	How does the hypothalamus affect the anterior pituitary?	how	[]	[ "Endocrine signals generated by the hypothalamus regulate hormone secretion by the anterior pituitary (Figure 45.16). Each hypothalamic hormone is either a releasing hormone or an inhibiting hormone, reflecting its role in promoting or inhibiting release of one or more specific hormones by the anterior pituitary. P...
144	145	1_8_3_2	How can an endergonic cellular process be made exergonic?	how	[]	[ "In this example, the exergonic process of ATP hydrolysis is used to drive an endergonic process: the cellular synthesis of the amino acid glutamine from glutamic acid and ammonia. For example, with the help of specific enzymes, the cell is able to use the energy released by ATP hydrolysis directly to drive chemica...
146	147	1_8_6	How can an endergonic cellular process be made exergonic?	how	[]	[ "ATP is the cell's energy shuttle. Hydrolysis of its terminal phosphate yields ADP and phosphate and releases free energy. Through energy coupling, the exergonic process of ATP hydrolysis drives endergonic reactions by transfer of a phosphate group to specific reactants, forming a phosphorylated intermediate that i...
148	149	1_8_3_3	How is ATP regeneration an anabolic process?	how	[]	[ "An organism at work uses ATP continuously, but ATP is a renewable resource that can be regenerated by the addition of phosphate to ADP (Figure 8.11). The free energy required to phosphorylate ADP comes from exergonic breakdown reactions (catabolism) in the cell. This shuttling of inorganic phosphate and energy is ...
150	151	1_8_3_3	How is ATP regeneration an anabolic process?	how	[]	[ "Because both directions of a reversible process cannot be downhill, the regeneration of ATP from ADP and Ⓟi is necessarily endergonic: ADP + Ⓟi → ATP + H2O ΔG = +7.3 kcal/mol (+30.5 kJ/mol) (standard conditions) Since ATP formation from ADP and Ⓟi is not spontaneous, free energy must b...
152	153	1_9_1_1	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "Although carbohydrates, fats, and proteins can all be processed and consumed as fuel, it is helpful to learn the steps of cellular respiration by tracking the degradation of the sugar glucose (C6H12O6): C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat) Glucose is the fuel that cells most often use; we will...
154	155	1_9_1_2	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "How do the catabolic pathways that decompose glucose and other organic fuels yield energy? The answer is based on the transfer of electrons during the chemical reactions. The relocation of electrons releases energy stored in organic molecules, and this energy ultimately is used to synthesize ATP." ]
156	157	1_9_1_2_2	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "But the energy-yielding redox process of greatest interest to biologists is respiration: the oxidation of glucose and other molecules in food. Examine again the summary equation for cellular respiration, but this time think of it as a redox process: As in the combustion of methane or gasoline, the fuel (glucose) i...
158	159	1_9_1_2_3	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "Electrons lose very little of their potential energy when they are transferred from glucose to NAD+. Each NADH molecule formed during respiration represents stored energy that can be tapped to make ATP when the electrons complete their \"fall\" down an energy gradient from NADH to oxygen. Figure 9.5 An introductio...
160	161	1_9_1_3	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "The harvesting of energy from glucose by cellular respiration is a cumulative function of three metabolic stages: Biochemists usually reserve the term cellular respiration for stages 2 and 3. We include glycolysis, however, because most respiring cells deriving energy from glucose use glycolysis to produce the sta...
162	163	1_9_1_3	How is the change in free energy that occurs during glucose oxidation used in the cell?	how	[]	[ "Some of the steps of glycolysis and the citric acid cycle are redox reactions in which dehydrogenases transfer electrons from substrates to NAD+, forming NADH. In the third stage of respiration, the electron transport chain accepts electrons from the breakdown products of the first two stages (most often via NADH)...
164	165	1_8_1_3_2	How does the highly-ordered structure of an organism not contradict the second law of thermodynamics?	how	[]	[ "We can now state the second law of thermodynamics: Every energy transfer or transformation increases the entropy of the universe. Although order can increase locally, there is an unstoppable trend toward randomization of the universe as a whole." ]
166	167	1_8_1_3_3	How does the highly-ordered structure of an organism not contradict the second law of thermodynamics?	how	[]	[ "During the early history of life, complex organisms evolved from simpler ancestors. For example, we can trace the ancestry of the plant kingdom from much simpler organisms called green algae to more complex flowering plants. However, this increase in organization over time in no way violates the second law. The en...
168	169	1_4_2_2	How do the carbon atoms of an organic molecule contribute to its shape?	how	[]	[ "Carbon chains form the skeletons of most organic molecules. The skeletons vary in length and may be straight, branched, or arranged in closed rings (Figure 4.5). Some carbon skeletons have double bonds, which vary in number and location. Such variation in carbon skeletons is one important source of the molecular c...
170	171	1_8_2_3_2	How can one disrupt a system in equilibrium?	how	[]	[ "Like most systems, a living cell is not in equilibrium. The constant flow of materials in and out of the cell keeps the metabolic pathways from ever reaching equilibrium, and the cell continues to do work throughout its life." ]
172	173	1_8_2_3_2	How can one disrupt a system in equilibrium?	how	[]	[ "Some of the reversible reactions of respiration are constantly \"pulled\" in one direction: that is, they are kept out of equilibrium. The key to maintaining this lack of equilibrium is that the product of a reaction does not accumulate but instead becomes a reactant in the next step; finally, waste products are e...
174	175	1_18_0_0	How are genes expressed?	how	[]	[ "Figure 18.1 What regulates the precise pattern of gene expression in the developing wing of a fly embryo? An adult fruit fly, for example, develops from a single fertilized egg, passing through a wormlike stage called a larva. At every stage, gene expression is carefully regulated, ensuring that the right genes ar...
176	177	1_18_2	How are genes expressed?	how	[]	[ "All organisms, whether prokaryotes or eukaryotes, must regulate which genes are expressed at any given time. Both unicellular organisms and the cells of multicellular organisms must continually turn genes on and off in response to signals from their external and internal environments. Regulation of gene expression...
178	179	1_18_2_3_2	How are genes expressed?	how	[]	[ "The specific transcription factors made in a cell determine which genes are expressed. In this example, the genes for albumin and crystallin are shown at the top, each with an enhancer made up of three different control elements. Although the enhancers for the two genes share one control element (gray), each enhan...
180	181	1_18_2_3_3	How are genes expressed?	how	[]	[ "How does the eukaryotic cell deal with genes of related function that need to be turned on or off at the same time? Earlier in this chapter, you learned that in bacteria, such coordinately controlled genes are often clustered into an operon, which is regulated by a single promoter and transcribed into a single mRN...
182	183	1_21_3_2	How are genes expressed?	how	[]	[ "What genetic attributes allow humans (and other vertebrates) to get by with no more genes than nematodes? An important factor is that vertebrate genomes \"get more bang for the buck\" from their coding sequences because of extensive alternative splicing of RNA transcripts. Recall that this process generates more t...
184	185	1_17_6_2	How are genes expressed?	how	[]	[ "Thus, we arrive at the following definition: A gene is a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule. When considering phenotypes, however, it is often useful to start by focusing on genes that code for polypeptides. In this chapter, you...
186	187	1_17_0_0	How are genes expressed?	how	[]	[ "Gene expression is the process by which DNA directs the synthesis of proteins (or, in some cases, just RNAs). The expression of genes that code for proteins includes two stages: transcription and translation." ]
188	189	1_17_1_2	How are genes expressed?	how	[]	[ "Genes are typically hundreds or thousands of nucleotides long, each gene having a specific sequence of nucleotides. Each polypeptide of a protein also has monomers arranged in a particular linear order (the protein's primary structure), but its monomers are amino acids. Thus, nucleic acids and proteins contain inf...
190	191	1_17_1_3_1	How are genes expressed?	how	[]	[ "Experiments have verified that the flow of information from gene to protein is based on a triplet code: The genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, three-nucleotide words. The series of words in a gene is transcribed into a complementary series of nonoverl...
192	193	1_12_1_2	How are sister chromatids connected to each other?	how	[]	[ "Each duplicated chromosome has two sister chromatids, which are joined copies of the original chromosome (Figure 12.4). The two chromatids, each containing an identical DNA molecule, are initially attached all along their lengths by protein complexes called cohesins; this attachment is known as sister chromatid co...
194	195	1_12_4	How are sister chromatids connected to each other?	how	[]	[ "In preparation for cell division, chromosomes are duplicated, each one then consisting of two identical sister chromatids joined along their lengths by sister chromatid cohesion and held most tightly together at a constricted region at the centromeres of the chromatids." ]
196	197	1_13_3_2	How are sister chromatids connected to each other?	how	[]	[ "How do sister chromatids stay together through meiosis I but separate from each other in meiosis II and mitosis? Sister chromatids are attached along their lengths by protein complexes called cohesins." ]
198	199	1_17_2_1	How does RNA polymerase know when to stop transcription?	how	[]	[ "Unlike DNA polymerases, however, RNA polymerases are able to start a chain from scratch; they don't need a primer. Specific sequences of nucleotides along the DNA mark where transcription of a gene begins and ends. The DNA sequence where RNA polymerase attaches and initiates transcription is known as the promoter;...

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Dataset Card for BiologyHowWhyCorpus

This dataset consists of 185 "how" and 193 "why" biology questions authored by a domain expert, with one or more gold answer passages identified in an undergraduate textbook. The expert was not constrained in any way during the annotation process, so gold answers might be smaller than a paragraph or span multiple paragraphs. This dataset was used for the question-answering system described in the paper “Discourse Complements Lexical Semantics for Non-factoid Answer Reranking” (ACL 2014).

Citation Information

@inproceedings{jansen-etal-2014-discourse,
    title = "Discourse Complements Lexical Semantics for Non-factoid Answer Reranking",
    author = "Jansen, Peter  and
      Surdeanu, Mihai  and
      Clark, Peter",
    booktitle = "Proceedings of the 52nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)",
    month = jun,
    year = "2014",
    address = "Baltimore, Maryland",
    publisher = "Association for Computational Linguistics",
    url = "https://aclanthology.org/P14-1092",
    doi = "10.3115/v1/P14-1092",
    pages = "977--986",
}