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In animals, an important function of enzymes is to help digest food. Digestive enzymes speed up reactions that break down large molecules of carbohydrates, proteins, and fats into smaller molecules the body can use. Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide the energy and nutrients they need to survive.
What is the most important function of enzymes in animals?
[ "carry oxygen", "help digest food", "transport messages", "excrete waste" ]
1
801
After coming apart from the crystal, the individual ions are then surrounded by solvent particles in a process called solvation . Note that the individual Na + ions are surrounded by water molecules with the oxygen atom oriented near the positive ion. Likewise, the chloride ions are surrounded by water molecules with the opposite orientation. Hydration is the process of solute particles being surrounded by water molecules arranged in a specific manner. Hydration helps to stabilize aqueous solutions by preventing the positive and negative ions from coming back together and forming a precipitate.
After coming apart from the crystal, the individual ions are then surrounded by solvent particles in a process called what?
[ "solvation", "hydrolysis", "osmosis", "ionization" ]
0
802
Multiple Voltage Sources There are two voltage sources when a battery charger is used. Voltage sources connected in series are relatively simple. When voltage sources are in series, their internal resistances add and their emfs add algebraically. (See Figure 21.15. ) Series connections of voltage sources are common—for example, in flashlights, toys, and other appliances. Usually, the cells are in series in order to produce a larger total emf. But if the cells oppose one another, such as when one is put into an appliance backward, the total emf is less, since it is the algebraic sum of the individual emfs. A battery is a multiple connection of voltaic cells, as shown in Figure 21.16. The disadvantage of series connections of cells is that their internal resistances add. One of the authors once owned a 1957 MGA that had two 6-V batteries in series, rather than a single 12-V battery. This arrangement produced a large internal resistance that caused him many problems in starting the engine.
A battery is a multiple connection of what kind of cells?
[ "cabri cells", "localweather cells", "voltaic cells", "organic cells" ]
2
803
Autosomal Dominant Only one mutated allele is needed for a person to be affected by an autosomal dominant disorder . Each affected person usually has one affected parent. There is a 50% chance that a child will inherit the mutated gene. Huntingtons disease, Achondroplasia, Neurofibromatosis 1, Marfan Syndrome, Hereditary nonpolyposis colorectal cancer.
What is needed for a person to be affected by an autosomal dominant disorder?
[ "extra alleles", "one isolated allele", "one less chromosome", "one mutated allele" ]
3
804
Scientists discovered another way to tell the approximate age of seafloor rocks. The rocks at the mid-ocean ridge crest are nearly sediment free. The crust is also very thin there. With distance from the ridge crest, the sediments and crust get thicker. This also supports the idea that the youngest rocks are on the ridge axis, and that the rocks get older with distance away from the ridge ( Figure below ). This is because the crust is new at the ridge, and so it is thin and has no sediment. The crust gets older away from the ridge crest. It has cooled and has more sediment.
The rocks athe mid-ocean ridge are nearly free of what?
[ "sediment", "metals", "minerals", "scratches" ]
0
805
A pulley is a simple machine that consists of a rope and grooved wheel. Single pulleys may be fixed or moveable. Single and moveable pulleys may be combined in a compound pulley. The ideal mechanical advantage of a pulley or compound pulley is always equal to or greater than 1. Fixed pulleys and some compound pulleys also change the direction of the input force.
What do we call a simple machine that consists of a rope and grooved wheel?
[ "pedal", "pulley", "axle", "lever" ]
1
806
Antioxidants are important for the health of a cell. An antioxidant is a molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent, producing free radicals in the process. These free radicals initiate a chain reaction in the cell that can cause cell damage, or can lead to cell death. Antioxidants prevent these chain reactions from even initiating.
What do you call health-promoting molecules that inhibit the oxidation of other molecules?
[ "neurotransmitters", "antioxidants", "hormones", "nutrients" ]
1
807
In a correctly balanced equation, all coefficients must be whole numbers. However, the use of fractions can be helpful as a way of finding the correct coefficients. If all atoms in an equation are balanced but some have fractional coefficients, multiply all coefficients in the entire equation (including those not explicitly written!) by the lowest common denominator to get the final balanced equation.
In a correctly balanced equation, all coefficients must be what kind of numbers?
[ "negative", "prime", "whole", "fractional" ]
2
808
Some nonmetals, such as bromine, have an outer energy level that is almost full. They "want" to gain electrons so they will have a full outer energy level. As a result, these nonmetals are very reactive. Because they only accept electrons and do not give them up, they do not conduct electricity.
Highly reactive nonmetals, which only accept electrons and do not give them up, make poor what?
[ "electricity conductors", "alloys", "insulators", "electromagnets" ]
0
809
As scientists learned more about heredity - the passing of traits from parents to offspring - over the next few decades, they were able to describe Mendel’s ideas about inheritance in terms of genes. In this way, the field of genetics was born. At the link that follows, you can watch an animation of Mendel explaining his laws of inheritance in genetic terms. http://www. dnalc. org/view/16182-Animation-4-Some-genes-are-dominant-. html.
What is the passing of traits from parents to offspring called?
[ "cell division", "mutation", "heredity", "variability" ]
2
810
The most important source of electromagnetic waves on Earth is the sun. Many other sources of electromagnetic waves depend on technology.
What is the most important source of electromagnetic waves on earth?
[ "the ocean", "the moon", "clouds", "the sun" ]
3
811
Greenhouse gases trap heat in the troposphere. Some greenhouse gases can trap more heat than others.
Which part of the atmosphere do greenhouse gasses trap heat in?
[ "stratosphere", "thermosphere", "troposphere", "lithosphere" ]
2
812
Eutherians are the most widespread of the mammals, occurring throughout the world. There are 18 to 20 orders of placental mammals. Some examples are Insectivora, the insect eaters; Edentata, the toothless anteaters; Rodentia, the rodents; Cetacea, the aquatic mammals including whales; Carnivora, carnivorous mammals including dogs, cats, and bears; and Primates, which includes humans. Eutherian mammals are sometimes called placental mammals because all species possess a complex placenta that connects a fetus to the mother, allowing for gas, fluid, and nutrient exchange. While other mammals possess a less complex placenta or briefly have a placenta, all eutherians possess a complex placenta during gestation.
How are the fetuses of eutherian mammals connected to their mothers during gestation?
[ "Movement Placenta", "visual placenta", "altered placenta", "complex placenta" ]
3
813
Vivipary refers to the development and nourishment of an embryo within the mother’s body. Birth may be followed by a period of parental care of the offspring. This reproductive strategy occurs in almost all mammals.
Vivipary refers to the development and nourishment of a what?
[ "nucleus", "egg", "embryo", "seed" ]
2
814
Red blood cells (RBCs) are flattened, disk-shaped cells that carry oxygen. They are the most common blood cell in the blood. There are about 4 to 6 million RBCs per cubic millimeter of blood. Each RBC has about 200 million molecules of hemoglobin. Hemoglobin is the protein that carries oxygen. Hemoglobin also gives the red blood cells their red color.
What are the flattened, disk-shaped cells in blood that carry oxygen?
[ "white blood cells", "platlets", "plasma", "red blood cells" ]
3
815
matter in the universe that does not emit light.
What is matter in the universe that does not emit light called?
[ "hidden matter", "black matter", "dark matter", "cold matter" ]
2
816
Air includes many tiny particles. The particulates may consist of dust, soil, salt, smoke, or ash. Some particulates pollute the air and may make it unhealthy to breathe. But having particles in the air is very important. Tiny particles are needed for water vapor to condense on. Without particles, water vapor could not condense. Then clouds could not form, and Earth would have no rain.
Without particles, water vapor could not do what?
[ "evaporate", "dissipate", "condense", "dilute" ]
2
817
Sounds are produced when muscles in what organ are tensed, stretching the cords so they vibrate?
[ "throat", "diaphragm", "larnyx", "thorax" ]
2
818
Most energy is lost to the environment as heat.
What is most energy that is lost to the environment lost as?
[ "precipitation", "vapor", "heat", "gravity" ]
2
819
What is produced by the plant cell during photosynthesis? The products of photosynthesis are glucose and oxygen. This means they are produced at the end of photosynthesis. Glucose , the food of plants, can be used to store energy in the form of large carbohydrate molecules. Glucose is a simple sugar molecule which can be combined with other glucose molecules to form large carbohydrates, such as starch. Oxygen is a waste product of photosynthesis. It is released into the atmosphere through the stomata. As you know, animals need oxygen to live. Without photosynthetic organisms like plants, there would not be enough oxygen in the atmosphere for animals to survive.
What is the resultant waste product of photosynthesis?
[ "argon", "sulfur", "carbon", "oxygen" ]
3
820
Velocity is a measure of both speed and direction. It is a vector that can be represented by an arrow. Velocity changes with a change in speed, a change in direction, or both.
What is the term for a measure of both speed and direction?
[ "intensity", "acceleration", "velocity", "momentum" ]
2
821
A stream is a body of freshwater that flows downhill in a channel. The channel of a stream has a bottom, or bed, and sides called banks. Any size body of flowing water can be called a stream. Usually, though, a large stream is called a river .
What is a body of freshwater that flows downhill in a channel?
[ "a creek", "a river", "an eddy", "a stream" ]
3
822
What form of reproduction creates offspring that are genetically identical to the parent?
[ "asexual", "primitive", "sexual", "microscopic" ]
0
823
Earth and many other bodies—including asteroids, comets, and the other planets—move around the sun in curved paths called orbits. Generally, the orbits are elliptical, or oval, in shape. You can see the shape of Earth’s orbit in the Figure below . Because of the sun’s relatively strong gravity, Earth and the other bodies constantly fall toward the sun, but they stay far enough away from the sun because of their forward velocity to fall around the sun instead of into it. As a result, they keep orbiting the sun and never crash to its surface. The motion of Earth and the other bodies around the sun is called orbital motion . Orbital motion occurs whenever an object is moving forward and at the same time is pulled by gravity toward another object. You can explore orbital motion and gravity in depth with the animation at this URL:.
Asteroids, comets, and planets move around the sun in curved paths called what?
[ "curves", "ellipticals", "orbits", "satellites" ]
2
824
Primary Motor Cortex The primary motor cortex is located in the precentral gyrus of the frontal lobe. A neurosurgeon, Walter Penfield, described much of the basic understanding of the primary motor cortex by electrically stimulating the surface of the cerebrum. Penfield would probe the surface of the cortex while the patient was only under local anesthesia so that he could observe responses to the stimulation. This led to the belief that the precentral gyrus directly stimulated muscle movement. We now know that the primary motor cortex receives input from several areas that aid in planning movement, and its principle output stimulates spinal cord neurons to stimulate skeletal muscle contraction. The primary motor cortex is arranged in a similar fashion to the primary somatosensory cortex, in that it has a topographical map of the body, creating a motor homunculus (see Figure 14.23). The neurons responsible for musculature in the feet and lower legs are in the medial wall of the precentral gyrus, with the thighs, trunk, and shoulder at the crest of the longitudinal fissure. The hand and face are in the lateral face of the gyrus. Also, the relative space allotted for the different regions is exaggerated in muscles that have greater enervation. The greatest amount of cortical space is given to muscles that perform fine, agile movements, such as the muscles of the fingers and the lower face. The “power muscles” that perform coarser movements, such as the buttock and back muscles, occupy much less space on the motor cortex.
The primary motor cortex is located in which lobe of the brain?
[ "Temporal lobe", "Occipital", "Parietal", "frontal" ]
3
825
The beginning of what season experiences the shortest period of daylight hours?
[ "autumn", "summer", "spring", "winter" ]
3
826
The sex of developing crocodilians is determined by the temperature of the eggs during incubation.
The sex of developing crocodilians is determined by what during incubation?
[ "the temperature of the eggs", "the size of the eggs", "the color of the eggs", "the location of the eggs" ]
0
827
The two main types of star clusters are open clusters and globular clusters.
What are the two main types of star clusters?
[ "open and elliptical", "open and supergiant", "open and globular", "closed and spherical" ]
2
828
Many species of flowering plants have coevolved with specific what?
[ "climates", "predators", "pollinators", "spores" ]
2
829
Most waves strike the shore at an angle. This creates longshore currents, which are described in the concept "Surface Ocean Currents. ".
Do most waves strike the shore head on or at an angle?
[ "at an angle", "head on", "side on", "at a distance" ]
0
830
What ingredient has been used in brewing, winemaking and baking for thousands of years?
[ "flour", "oils", "fruit", "yeast" ]
3
831
Figure 8.18 Tibia and Fibula The tibia is the larger, weight-bearing bone located on the medial side of the leg. The fibula is the slender bone of the lateral side of the leg and does not bear weight.
The tibia is the larger, weight-bearing bone located on the medial side of the leg. the fibula is the slender bone of the lateral side of the leg and does not do what?
[ "bear weight", "drive weight", "resist weight", "support weight" ]
0
832
The scales of reptiles prevent them from absorbing oxygen through their skin, as amphibians can. Instead, reptiles breathe air only through their lungs. However, their lungs are more efficient than the lungs of amphibians, with more surface area for gas exchange. This is another important reptile adaptation for life on land.
What are reptiles unable to absorb through their skin because of scales?
[ "food", "oxygen", "carbon", "water" ]
1
833
Regardless of the type of organism, all living cells share certain basic structures. For example, all cells are enclosed by a membrane. The cell membrane separates the cell from its environment. It also controls what enters or leaves the cell.
All types of cells are enclosed by what?
[ "cell wall", "membrane", "substrate", "stoma" ]
1
834
Metalloids are the smallest class of elements, containing just six members: boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Metalloids have some properties of metals (elements that can conduct electricity) and some properties of nonmetals (elements that cannot conduct electricity). For example, most metalloids can conduct electricity, but not as well as metals. Metalloids also tend to be shiny like metals, but brittle like nonmetals. Chemically, metalloids may behave like metals or nonmetals, depending on their number of valence electrons. You can learn more about specific metalloids by clicking on the element symbols in the periodic table at this URL: http://www. chemicool. com/ .
What causes symptoms associated with sickle-cell disease?
[ "transgene effects", "pleiotropic effects", "spontaneous mutation", "genetic drift" ]
1
835
Some fungi cause disease when they become human parasites. Two examples are fungi in the genera Candida and Trichophyton.
Candida and trichophyton are examples of disease-causing types of what organisms, which become parasitic?
[ "yeast", "bacteria", "fungi", "viruses" ]
2
836
Animals can detect environmental stimuli, such as light, sound, and touch. Stimuli are detected by sensory nerve cells. The information is transmitted and processed by the nervous system. The nervous system, in turn, may direct the body to respond.
What type of cells detect stimuli?
[ "expressive nerve cells", "sensory nerve cells", "grid nerve cells", "muscle cells" ]
1
837
What 3 things do animals need to live and survive?
[ "sex, water, and sleep", "air, water, and food", "water, food, and an ecosystem", "air, water, and socialization" ]
1
838
The cultivated forms of wheat, cotton, and tobacco plants are all allopolyploids. Although polyploidy occurs occasionally in animals, it takes place most commonly in plants. (Animals with any of the types of chromosomal aberrations described here are unlikely to survive and produce normal offspring. ) Scientists have discovered more than half of all plant species studied relate back to a species evolved through polyploidy. With such a high rate of polyploidy in plants, some scientists hypothesize that this mechanism takes place more as an adaptation than as an error.
The cultivated forms of wheat, cotton, and tobacco plants are all what?
[ "allopolyploids", "pores", "sporozoans", "bales" ]
0
839
Hydrogen is an example of an element that has isotopes. Three isotopes of hydrogen are modeled in the Figure below . Most hydrogen atoms have just one proton and one electron and lack a neutron. These atoms are just called hydrogen. Some hydrogen atoms have one neutron as well. These atoms are the isotope named deuterium. Other hydrogen atoms have two neutrons. These atoms are the isotope named tritium. For animated versions of these hydrogen isotopes, go to this URL: http://www. s-cool. co. uk/a-level/physics/atomic-structure/revise-it/isotopes .
A hydrogen atom with one neutron is called what?
[ "covalent", "ionic", "magnesium", "deuterium" ]
3
840
Ionic compounds form crystals instead of molecules. Ionic bonds are strong and the crystals are rigid. As a result, ionic compounds are brittle solids with high melting and boiling points. In the liquid state or dissolved in water, ionic compounds are good conductors of electricity.
What compounds form crystals instead of molecules?
[ "ionic compounds", "magnetic compounds", "soluble compounds", "metallic compounds" ]
0
841
One of the most important series of endothermic reactions is photosynthesis. In photosynthesis, plants make the simple sugar glucose (C 6 H 12 O 6 ) from carbon dioxide (CO 2 ) and water (H 2 O). They also release oxygen (O 2 ) in the process. The reactions of photosynthesis are summed up by this chemical equation:.
What is the process by which plants make the simple sugar glucose from carbon dioxide and water is called?
[ "glycolysis", "metamorphosis", "osmosis", "photosynthesis" ]
3
842
Bone: Christopher Auyeung; Tonsils: User:Klem/Wikimedia Commons; Spleen: Henry Gray; Thymus: User:LearnAnatomy/Wikipedia. Each lymph organ has a different job in the immune system . Bone: CC-BY-NC-SA 3.0; Tonsils and Thymus: CC-BY 3.0; Spleen: Public Domain.
The three units of kpa, atm or mmhg commonly measure what?
[ "energy", "resistance", "pressure", "weight" ]
2
843
Summary The behavior of ideal gases is explained by the kinetic molecular theory of gases. Molecular motion, which leads to collisions between molecules and the container walls, explains pressure, and the large intermolecular distances in gases explain their high compressibility. Although all gases have the same average kinetic energy at a given temperature, they do not all possess the same root mean square (rms) speed (vrms). The actual values of speed and kinetic energy are not the same for all particles of a gas but are given by a Boltzmann distribution, in which some molecules have higher or lower speeds (and kinetic energies) than average. Diffusion is the gradual mixing of gases to form a sample of uniform composition even in the absence of mechanical agitation. In contrast,effusion is the escape of a gas from a container through a tiny opening into an evacuated space. The rate of effusion of a gas is inversely proportional to the square root of its molar mass (Graham’s law), a relationship that closely approximates the rate of diffusion. As a result, light gases tend to diffuse and effuse much more rapidly than heavier gases. The mean free path of a molecule is the average distance it travels between collisions.
The behavior of ideal gases is explained by what theory of gases?
[ "Charles's Law", "kinetic theory", "kinetic molecular theory", "molecular theory" ]
2
844
Protists get food through ingestion, absorption, or photosynthesis.
Besides ingesting and photosynthesis how can protists get their food?
[ "absorption", "osmosis", "digestion", "accumulation" ]
0
845
the pterophytes, from which modern ferns are derived. The life cycle of bryophytes and pterophytes is characterized by the alternation of generations. The completion of the life cycle requires water, as the male gametes must swim to the female gametes. The male gametophyte releases sperm, which must swim—propelled by their flagella—to reach and fertilize the female gamete or egg. After fertilization, the zygote matures and grows into a sporophyte, which in turn will form sporangia, or "spore vessels,” in which mother cells undergo meiosis and produce haploid spores. The release of spores in a suitable environment will lead to germination and a new generation of gametophytes.
The male gametophyte releases what, which swim - propelled by their flagella - to reach and fertilize the female gamete or egg?
[ "dna", "tadpoles", "cytoplasm", "sperm" ]
3
846
In a car, the moving piston rotates a crankshaft, which turns a driveshaft. The turning driveshaft causes the wheels of the car to turn.
What causes the wheels of the car to turn?
[ "turning driveshaft", "once driveshaft", "Gear Shift", "Wheel Line" ]
0
847
Technology is sometimes referred to as applied science, but it has a different goal than science. The goal of science is to increase knowledge. The goal of technology is to use knowledge for practical purposes.
While the goal of science is to increase knowledge, the goal of what is to use knowledge for practical purposes?
[ "technology", "industry", "invention", "advancement" ]
0
848
Aqueous solutions can be classified as polar or nonpolar depending on how well they conduct electricity.
What are the two terms that designate how well aqueous solutions conduct electricity?
[ "secular and nonpolar", "filter and nonpolar", "polar and nonpolar", "hot and nonpolar" ]
2
849
The octet rule is the concept that atoms tend to have eight electrons in their valence electron shell.
The concept that atoms tend to have eight electrons in their valence electron shell is called what?
[ "diagonal rule", "coupling rule", "string rule", "octet rule" ]
3
850
stresses that push toward each other, which causes a decrease in the space a rock takes up.
What separates one river system's basin from another river system's basin?
[ "a divert", "a sink", "a divide", "a bend" ]
2
851
Immunological Memory The adaptive immune system possesses a memory component that allows for an efficient and dramatic response upon reinvasion of the same pathogen. Memory is handled by the adaptive immune system with little reliance on cues from the innate response. During the adaptive immune response to a pathogen that has not been encountered before, called a primary response, plasma cells secreting antibodies and differentiated T cells increase, then plateau over time. As B and T cells mature into effector cells, a subset of the naïve populations differentiates into B and T memory cells with the same antigen specificities, as illustrated in Figure 42.16. A memory cell is an antigen-specific B or T lymphocyte that does not differentiate into effector cells during the primary immune response, but that can immediately become effector cells upon re-exposure to the same pathogen. During the primary immune response, memory cells do not respond to antigens and do not contribute to host defenses. As the infection is cleared and pathogenic stimuli subside, the effectors are no longer needed, and they undergo apoptosis. In contrast, the memory cells persist in the circulation.
What system possesses a memory component that allows for an efficient and dramatic response upon reinvasion of the same pathogen?
[ "societal immune system", "suggestive immune system", "incorporate immune system", "adaptive immune system" ]
3
852
Examples of innate behavior include honeybees doing the waggle dance or spiders spinning a web.
Honeybees doing the waggle dance or spiders spinning a web are examples of what type of behavior?
[ "genuine", "learned", "intuitive", "innate" ]
3
853
Skin Sweat glands remove water, salts, and other wastes. Integumentary system.
What glands remove water, salts and other wastes from skin?
[ "sweat glands", "push glands", "sex glands", "water glands" ]
0
854
The branchial arches , a series of arches that support the gills of aquatic amphibians and fishes. They lie close to the body's surface.
A series of arches that support the gills of aquatic amphibians and fish are known as what?
[ "scythian arches", "aquatic arches", "cochlear arches", "branchial arches" ]
3
855
Blood Pressure Regulation Cardiac output is the volume of blood pumped by the heart in one minute. It is calculated by multiplying the number of heart contractions that occur per minute (heart rate) times the stroke volume (the volume of blood pumped into the aorta per contraction of the left ventricle). Therefore, cardiac output can be increased by increasing heart rate, as when exercising. However, cardiac output can also be increased by increasing stroke volume, such as if the heart contracts with greater strength. Stroke volume can also be increased by speeding blood circulation through the body so that more blood enters the heart between contractions. During heavy exertion, the blood vessels relax and increase in diameter, offsetting the increased heart rate and ensuring adequate oxygenated blood gets to the muscles. Stress triggers a decrease in the diameter of the blood vessels, consequently increasing blood pressure. These changes can also be caused by nerve signals or hormones, and even standing up or lying down can have a great effect on blood pressure.
What term, calculated by multiplying heart contractions by stroke volume, means the volume of blood pumped by the heart in one minute?
[ "respiratory output", "blood output", "cardiac output", "liver output" ]
2
856
Birds are thought to have evolved from a group of bipedal dinosaurs called theropods . The ancestor of birds was probably similar to the theropod called Deinonychus, which is represented by the sketch in Figure below . Fossils of Deinonychus were first identified in the 1960s. This was an extremely important discovery. It finally convinced most scientists that birds had descended from dinosaurs, which had been debated for almost a century.
Birds are thought to have evolved from a group of bipedal dinosaurs called what?
[ "pteradactyls", "therapods", "staurikosaurus", "sporozoans" ]
1
857
Elements in different groups are lumped together in one of three classes, depending on their properties. The classes are metals, nonmetals, and metalloids. Knowing the class of an element lets you predict many of its properties. The video at the URL below is a good introduction to the classes.
What is the third class of elements after metals and nonmetals?
[ "halogens", "noble gases", "metalloids", "synthetics" ]
2
858
Each of the thousands of naturally occurring proteins has its own characteristic amino acid composition and sequence that result in a unique three-dimensional shape. Since the 1950s, scientists have determined the amino acid sequences and three-dimensional conformation of numerous proteins and thus obtained important clues on how each protein performs its specific function in the body. Proteins are compounds of high molar mass consisting largely or entirely of chains of amino acids. Because of their great complexity, protein molecules cannot be classified on the basis of specific structural similarities, as carbohydrates and lipids are categorized. The two major structural classifications of proteins are based on far more general qualities: whether the protein is (1) fiberlike and insoluble or (2) globular and soluble. Some proteins, such as those that compose hair, skin, muscles, and connective tissue, are fiberlike. These fibrous proteins are insoluble in water and usually serve structural, connective, and protective functions. Examples of fibrous proteins are keratins, collagens, myosins, and elastins. Hair and the outer layer of skin are composed of keratin. Connective tissues contain collagen. Myosins are muscle proteins and are capable of contraction and extension. Elastins are found in ligaments and the elastic tissue of artery walls. Globular proteins, the other major class, are soluble in aqueous media. In these proteins, the chains are folded so that the molecule as a whole is roughly spherical. Familiar examples include egg albumin from egg whites and serum albumin in blood. Serum albumin plays a major role in transporting fatty acids and maintaining a proper balance of osmotic pressures in the body. Hemoglobin and myoglobin, which are important for binding oxygen, are also globular proteins.
Proteins are categorized according to shape and what property, which correlates with it?
[ "size", "solubility", "salinity", "viscosity" ]
1
859
In Glacier National Park ( Figure below ), many glaciers have become ice sheets. In 1850, the park had 150 glaciers. There are only about 25 today. The reason that there is so much melting is that summer temperatures have risen. Scientists estimate that the park will have no active glaciers as early as 2020.
Melting ice is drastically impacting the number of what at glacier national park?
[ "icebergs", "gaisers", "trees", "active glaciers" ]
3
860
The Carbon Cycle Carbon is the fourth most abundant element in living organisms. Carbon is present in all organic molecules, and its role in the structure of macromolecules is of primary importance to living organisms. Carbon compounds contain energy, and many of these compounds from plants and algae have remained stored as fossilized carbon, which humans use as fuel. Since the 1800s, the use of fossil fuels has accelerated. As global demand for Earth’s limited fossil fuel supplies has risen since the beginning of the Industrial Revolution, the amount of carbon dioxide in our atmosphere has increased as the fuels are burned. This increase in carbon dioxide has been associated with climate change and is a major environmental concern worldwide.
What element is present in all organic molecules?
[ "sodium", "oxygen", "carbon", "hydrogen" ]
2
861
A sample of matter that has the same physical and chemical properties throughout is called a substance. Sometimes the phrase pure substance is used, but the word pure isn’t needed. The definition of the term substance is an example of how chemistry has a specific definition for a word that is used in everyday language with a different, vaguer definition. Here, we will use the term substance with its strict chemical definition. Chemistry recognizes two different types of substances: elements and compounds. An element is the simplest type of chemical substance; it cannot be broken down into simpler chemical substances by ordinary chemical means. There are about 115 elements known to science, of which 80 are stable. (The other elements are radioactive, a condition we will consider in Chapter 15 "Nuclear Chemistry". ) Each element has its own unique set of physical and chemical properties. Examples of elements include iron, carbon, and gold.
A sample of matter that has the same physical and chemical properties throughout itself is known as what?
[ "antimatter", "molecule", "essence", "substance" ]
3
862
Hepatitis B is inflammation of the liver caused by infection with the hepatitis B virus. In many people, the immune system quickly eliminates the virus from the body. However, in a small percentage of people, the virus remains in the body and continues to cause illness. It may eventually damage the liver and increase the risk of liver cancer, which is usually fatal.
Hepatitis b is inflammation of which organ?
[ "the colon", "the liver", "the brain", "the kidney" ]
1
863
The strength of bases is measured on the pH scale. A pH value greater than 7 indicates a base, and the higher the number is, the stronger the base.
If a substance has a ph value greater than 7, what does it indicate?
[ "neutral", "volatile", "base", "acidic" ]
2
864
The percent yield is determined by calculating the ratio of actual yield/theoretical yield.
The percent yield is determined by calculating the ratio of actual yield by what?
[ "predicted return", "past balance", "theoretical yield", "actual loss" ]
2
865
Volcanoes are located along convergent and divergent plate boundaries. They can be found in the middle of plates at hot spots.
What are located along convergent and divergent plate boundaries?
[ "dunes", "mezas", "volcanoes", "megaliths" ]
2
866
33.19. The large structure with a central nucleus is the cell body of the neuron. Projections from the cell body are either dendrites specialized in receiving input or a single axon specialized in transmitting impulses. Some glial cells are also shown. Astrocytes regulate the chemical environment of the nerve cell, and oligodendrocytes insulate the axon so the electrical nerve impulse is transferred more efficiently. Other glial cells that are not shown support the nutritional and waste requirements of the neuron. Some of the glial cells are phagocytic and remove debris or damaged cells from the tissue. A nerve consists of neurons and glial cells.
What part of the neuron is a large structure with a central nucleus?
[ "Eye body", "proteins body", "Environmental", "cell body" ]
3
867
Hydrogen-based fuel cells were and are used to provide electricity for manned space vehicles, partly because their only chemical product is water, which could be used for drinking. However, there has been a recent resurgence in interest in fuel cells because of their potential use in electric cars. Most electric cars run on conventional batteries, which can be very heavy and expensive to replace. It is thought that fuel cells, rather than conventional batteries, might be better sources of electricity for automobiles. Several current barriers to fuel cell use in electric cars include capacity, cost, and overall energy efficiency. The 2008 Honda FCX, the first production model of a vehicle powered with a fuel cell, can hold 4.1 kg (just under 9 lb) of highly pressured H2 gas and has a range of 450 km (280 mi). It costs about $120,000–$140,000 to build, making the vehicle beyond the ability of most people to own. Finally, it always requires more energy to produce elemental hydrogen as a fuel than can be extracted from hydrogen as a fuel. As such, hydrogen is described as an energy carrier (like electricity) rather than an energy source (like oil and gas). This distinction points out a fundamental argument against fuel cells as a “better” power source.
Hydrogen-based fuel cells were and are used to provide what for manned space vehicles?
[ "magnetism", "gravity", "light", "electricity" ]
3
868
Plants that live in extremely dry environments have the opposite problem: how to get and keep water. Plants that are adapted to very dry environments are called xerophytes . Their adaptations may help them increase water intake, decrease water loss, or store water when it's available.
What are plants that are adapted to very dry environments called?
[ "sporozoans", "xerophytes", "succulents", "pores" ]
1
869
Sensory neurons carry nerve impulses from sense organs and internal organs to the central nervous system.
What neurons carry nerve impulses from sense organs and internal organs to the central nervous system?
[ "vascular", "axons", "autonomic", "sensory" ]
3
870
Sebaceous Glands A sebaceous gland is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands are associated with hair follicles. They generate and excrete sebum, a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable. The fatty acids of sebum also have antibacterial properties, and prevent water loss from the skin in low-humidity environments. The secretion of sebum is stimulated by hormones, many of which do not become active until puberty. Thus, sebaceous glands are relatively inactive during childhood.
Associated with hair follicles, what type of oil gland is found all over the body and helps to lubricate and waterproof the skin and hair?
[ "sebaceous gland", "melanin gland", "gametes gland", "sweat gland" ]
0
871
Vision is just one of several human senses. Other human senses include hearing, touch, taste, and smell. Imagine shopping at the fruit market in Figure below . It would stimulate all of these senses. You would hear the noisy bustle of the market. You could feel the smooth skin of the fruit. If you tried a sample, you could smell the fruity aroma and taste its sweet flavor.
The five human senses are taste, touch, vision, hearing and one more. what is it?
[ "smell", "audio", "perception", "fear" ]
0
872
Bones are the main organs of the skeletal system. In adults, the skeleton consists of a whopping 206 bones, many of them in the hands and feet. You can see many of the bones of the human skeleton in Figure below . The skeletal system also includes cartilage and ligaments.
How many bones does an adult skeleton have?
[ "196", "192", "208", "206" ]
3
873
Temperature and precipitation determine what types of plants can grow in an area. Animals and other living things depend on plants. So each climate is associated with certain types of living things. A major type of climate and its living things make up a biome . As you read about the major climate types below, find them on the map above ( Figure above ).
Temperature and precipitation determine the types of what that can grow in an area, in turn affecting the animals that live there?
[ "building", "birds", "roots", "plants" ]
3
874
Heat can be transferred in three ways, through conduction, convection, and radiation. Conduction is the transfer of heat by physical contact. Heat flows form the hotter object to the cooler object. Convection is heat transfer by an intermediate substance (for example air or water). Your oven (often properly called the ‘convection oven’) works by heating up the air and then the air heats up your food. Radiation is the release of heat (and thus the lowering of its internal energy) by releasing electromagnetic waves. The hotter the object the higher the frequency of the light emitted. When you look at a fire the blue flames our hotter than the red flames because blue has a higher frequency than red.
What is the transfer of heat by physical contact?
[ "oxidation", "diffusion", "inhibition", "conduction" ]
3
875
Gel electrophoresis is an analytical technique used to separate DNA fragments by size and charge. Notice in Figure below that the "gels" are rectangular in shape. The gels are made of a gelatin-like material of either agarose or polyacrylamide. An electric field, with a positive charge applied at one end of the gel, and a negative charge at the other end, forces the fragments to migrate through the gel. DNA molecules migrate from negative to positive charges due to the net negative charge of the phosphate groups in the DNA backbone. Longer molecules migrate more slowly through the gel matrix. After the separation is completed, DNA fragments of different lengths can be visualized using a fluorescent dye specific for DNA, such as ethidium bromide. The resulting stained gel shows bands correspond to DNA molecules of different lengths, which also correspond to different molecular weights. Band size is usually determined by comparison to DNA ladders containing DNA fragments of known length. Gel electrophoresis can also be used to separate RNA molecules and proteins.
What analytical technique, using stained gel, can separate dna fragments or rna molecules and proteins?
[ "gel electrophoresis", "microwave electrophoresis", "static electrophoresis", "surface electrophoresis" ]
0
876
Scientific skepticism questions claims based on their scientific verifiability rather than accepting claims based on faith or anecdotes. Scientific skepticism uses critical thinking to analyze such claims and opposes claims which lack scientific evidence.
Questioning claims based on their scientific verifiability rather than accepting claims based on faith or anecdotes is called what?
[ "scientific skepticism", "scientific extreme", "scientific fact", "scientific mimicry" ]
0
877
Like the animals pictured above, all animals have behaviors that help them achieve these basic ends. Behaviors that help animals reproduce or survive increase their fitness. Animals with greater fitness have a better chance of passing their genes to the next generation. If genes control behaviors that increase fitness, the behaviors become more common in the species. In other words, they evolve by natural selection.
Animals with better fitness have a better chance of passing their genes onto the next generation, this process is known as?
[ "fitness selection", "natural evolution", "natural selection", "survival selection" ]
2
878
Fatty acids are carboxylic acids that are the structural components of many lipids. They may be saturated or unsaturated.
What acids are the structural components of many lipids and may be saturated or unsaturated?
[ "fatty acids", "carbonic acids", "ionic acids", "fundamental acids" ]
0
879
Earth's axis is an imaginary line passing through the North and South Poles. Earth's rotation is its spins on its axis. Rotation is what a top does around its spindle. As Earth spins on its axis, it also orbits around the Sun. This is called Earth's revolution . These motions lead to the cycles we see. Day and night, seasons, and the tides are caused by Earth's motions.
Earth's axis is an imaginary line passing through which poles?
[ "north and south", "southwest and south", "west and south", "East and North" ]
0
880
What system does addictive drugs affect?
[ "digestive system", "honor system", "checks and balances", "reward system" ]
3
881
Ionic compounds conduct electricity when dissolved in water.
What happens when ionic compounds are dissolved in water?
[ "magnetize electricity", "deflect electricity", "repel electricity", "conduct electricity" ]
3
882
Development, growth and reproduction Development is all of the changes the body goes through in life. Development includes the process of differentiation, in which unspecialized cells become specialized in structure and function to perform certain tasks in the body. Development also includes the processes of growth and repair, both of which involve cell differentiation. Growth is the increase in body size. Humans, like all multicellular organisms, grow by increasing the number of existing cells, increasing the amount of non-cellular material around cells (such as mineral deposits in bone), and, within very narrow limits, increasing the size of existing cells. Reproduction is the formation of a new organism from parent organisms. In humans, reproduction is carried out by the male and female reproductive systems. Because death will come to all complex organisms, without reproduction, the line of organisms would end.
What is the process in which unspecialized cells become specialized in structure and function to perform certain tasks in the body?
[ "differentiation", "mutation", "transcription", "speciation" ]
0
883
Toxins and poisons are ______ enzyme inhibitos
[ "irreversible", "observable", "cancerous", "reversible" ]
0
884
How many types of basic sensory receptors are there?
[ "five", "four", "six", "five" ]
0
885
A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. Covalent bonds form only between atoms of nonmetals.
What bond is the force of attraction that holds together two atoms that share a pair of valence electrons?
[ "hydrogen", "polar", "metallic", "covalent" ]
3
886
Above the meristem, the rest of the root is covered with a single layer of epidermal cells. These cells may have root hairs that increase the surface area for the absorption of water and minerals from the soil. Beneath the epidermis is ground tissue, which may be filled with stored starch. Bundles of vascular tissues form the center of the root. Waxy layers waterproof the vascular tissues so they don’t leak, making them more efficient at carrying fluids. Secondary meristem is located within and around the vascular tissues. This is where growth in thickness occurs.
Above the meristem, the rest of the root is covered with a single layer of what type of cells, which may have root hairs?
[ "single celled", "dermal", "vegetative", "epidermal" ]
3
887
Nonvascular plants were the first plants to evolve and do not have vascular tissue.
What were the first plants to evolve?
[ "trees", "photoreactive plants", "fungi", "nonvascular plants" ]
3
888
Another important measure of wave size is wavelength. Wavelength is the distance between two corresponding points on adjacent waves (see Figure above ). Wavelength can be measured as the distance between two adjacent crests of a transverse wave or two adjacent compressions of a longitudinal wave. It is usually measured in meters. Wavelength is related to the energy of a wave. Short-wavelength waves have more energy than long-wavelength waves of the same amplitude. You can see examples of waves with shorter and longer wavelengths in Figure below .
What term describes the distance between two corresponding points on adjacent waves?
[ "variation", "frequency", "wavelength", "threshold" ]
2
889
Decomposers break down dead organisms and other organic wastes and release inorganic molecules back to the environment.
What break down dead organisms and other organic waste and release inorganic molecules back to the environment called?
[ "nematodes", "detritivores", "decomposers", "carnivores" ]
2
890
The variety of cell shapes seen in prokaryotes and eukaryotes reflects the functions that each cell has, confirming the structure-function relationship seen throughout biology. Each cell type has evolved a shape that is best related to its function. For example, the neuron in Figure below has long, thin extensions ( axons and dendritres ) that reach out to other nerve cells. The extensions help the neuron pass chemical and electrical messages quickly through the body. The shape of the red blood cells ( erythrocytes ) enable these cells to easily move through capillaries . The spikes on the pollen grain help it stick to a pollinating insect or animal so that it can be transferred to and pollinate another flower. The long whip-like flagella (tails) of the algae Chlamydomonas help it swim in water.
The variety of cell shapes seen in prokaryotes and eukaryotes reflects the functions that each what has?
[ "cell", "organ", "proteins", "life" ]
0
891
Like you, scientists also group together similar organisms. The science of classifying living things is called taxonomy. Scientists classify living things in order to organize and make sense of the incredible diversity of life. Modern scientists base their classifications mainly on molecular similarities. They group together organisms that have similar proteins and DNA. Molecular similarities show that organisms are related. In other words, they are descendants of a common ancestor in the past.
What is the science of classifying living things called?
[ "taxonomy", "botany", "terminology", "methodology" ]
0
892
Although some polypeptides exist as linear chains, most are twisted or folded into more complex secondary structures that form when bonding occurs between amino acids with different properties at different regions of the polypeptide. The most common secondary structure is a spiral called an alpha-helix. If you were to take a length of string and simply twist it into a spiral, it would not hold the shape. Similarly, a strand of amino acids could not maintain a stable spiral shape without the help of hydrogen bonds, which create bridges between different regions of the same strand (see Figure 2.26b). Less commonly, a polypeptide chain can form a beta-pleated sheet, in which hydrogen bonds form bridges between different regions of a single polypeptide that has folded back upon itself, or between two or more adjacent polypeptide chains. The secondary structure of proteins further folds into a compact three-dimensional shape, referred to as the protein’s tertiary structure (see Figure 2.26c). In this configuration, amino acids that had been very distant in the primary chain can be brought quite close via hydrogen bonds or, in proteins containing cysteine, via disulfide bonds. A disulfide bond is a covalent bond between sulfur atoms in a polypeptide. Often, two or more separate polypeptides bond to form an even larger protein with a quaternary structure (see Figure 2.26d). The polypeptide subunits forming a quaternary structure can be identical or different. For instance, hemoglobin, the protein found in red blood cells is composed of four tertiary polypeptides, two of which are called alpha chains and two of which are called beta chains. When they are exposed to extreme heat, acids, bases, and certain other substances, proteins will denature. Denaturation is a change in the structure of a molecule through physical or chemical means. Denatured proteins lose their functional shape and are no longer able to carry out their jobs. An everyday example of protein denaturation is the curdling of milk when acidic lemon juice is added. The contribution of the shape of a protein to its function can hardly be exaggerated. For example, the long, slender shape of protein strands that make up muscle tissue is essential to their ability to contract (shorten) and relax (lengthen). As another example, bones contain long threads of a protein called collagen that acts as scaffolding upon which bone minerals are deposited. These elongated proteins, called fibrous proteins, are strong and durable and typically hydrophobic.
Illustrating how form follows function, long, slender protein strands that make up what tissue are essential for contracting and relaxing?
[ "tendons", "veins", "muscle", "ligaments" ]
2
893
Many lands are marginal for farming. When rainfall is normal or high, the lands can produce. When rainfall is low, no crops grow. Drought makes marginal lands unsuitable for farming. Drought can also make good lands more difficult to farm. These changes will increase as temperatures warm.
What makes marginal lands unsuitable for farming?
[ "flood", "pestilence", "disease", "drought" ]
3
894
In its pure liquid form, water is a poor conductor of electricity. Unlike most substances, water is more dense in its liquid state than its solid state. As a result, water expands when it freezes, and ice floats on water.
What happens to water when it freezes?
[ "it shrinks", "it expands", "changes volume", "changes to gas" ]
1
895
Which of the following statements about the small intestine is false? a. Absorptive cells that line the small intestine have microvilli, small projections that increase surface area and aid in the absorption of food. The inside of the small intestine has many folds, called villi. Microvilli are lined with blood vessels as well as lymphatic vessels. The inside of the small intestine is called the lumen. The human small intestine is over 6m long and is divided into three parts: the duodenum, the jejunum, and the ileum. The “C-shaped,” fixed part of the small intestine is called the duodenum and is shown in Figure 34.11. The duodenum is separated from the stomach by the pyloric sphincter which opens to allow chyme to move from the stomach to the duodenum. In the duodenum, chyme is mixed with pancreatic juices in an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme and acts as a buffer. Pancreatic juices also contain several digestive enzymes. Digestive juices from the pancreas, liver, and gallbladder, as well as from gland cells of the intestinal wall itself, enter the duodenum. Bile is produced in the liver and stored and concentrated in the gallbladder. Bile contains bile salts which emulsify lipids while the pancreas produces enzymes that catabolize starches, disaccharides, proteins, and fats. These digestive juices break down the food particles in the chyme into glucose, triglycerides, and amino acids. Some chemical digestion of food takes place in the duodenum. Absorption of fatty acids also takes place in the duodenum. The second part of the small intestine is called the jejunum, shown in Figure 34.11. Here, hydrolysis of nutrients is continued while most of the carbohydrates and amino acids are absorbed through the intestinal lining. The bulk of chemical digestion and nutrient absorption occurs in the jejunum.
The three parts of the human small intestine is the duodenum, jejunum, and what?
[ "cecum", "appendix", "colon", "ileum" ]
3
896
Buoyancy is the ability of a fluid to exert an upward force on any object placed in it. The upward force is called buoyant force. An object’s weight and the buoyant force acting on it determine whether the object sinks or floats. Less dense objects and fluids float in fluids with greater density.
What is the term for the ability of a fluid to exert an upward force on any object placed in it?
[ "resonance", "buoyancy", "density", "viscosity" ]
1
897
Fuel Cells A fuel cell is a galvanic cell that requires a constant external supply of reactants because the products of the reaction are continuously removed. Unlike a battery, it does not store chemical or electrical energy; a fuel cell allows electrical energy to be extracted directly from a chemical reaction. In principle, this should be a more efficient process than, for example, burning the fuel to drive an internal combustion engine that turns a generator, which is typically less than 40% efficient, and in fact, the efficiency of a fuel cell is generally between 40% and 60%. Unfortunately, significant cost and reliability problems have hindered the wide-scale adoption of fuel cells. In practice, their use has been restricted to applications in which mass may be a significant cost factor, such as US manned space vehicles. These space vehicles use a hydrogen/oxygen fuel cell that requires a continuous input of H2(g) and O2(g), as illustrated in Figure 19.16 "A Hydrogen Fuel Cell Produces Electrical Energy Directly from a Chemical Reaction". The electrode reactions are as follows: Equation 19.93.
A fuel cell is a galvanic cell that requires a constant external supply of what?
[ "reactants", "generators", "electricity", "complexes" ]
0
898
Lichens are not a single organism, but rather an example of a mutualism, in which a fungus (usually a member of the Ascomycota or Basidiomycota phyla) lives in close contact with a photosynthetic organism (a eukaryotic alga or a prokaryotic cyanobacterium) (Figure 24.23). Generally, neither the fungus nor the photosynthetic organism can survive alone outside of the symbiotic relationship. The body of a lichen, referred to as a thallus, is formed of hyphae wrapped around the photosynthetic partner. The photosynthetic organism provides carbon and energy in the form of carbohydrates. Some cyanobacteria fix nitrogen from the atmosphere, contributing nitrogenous compounds to the association. In return, the fungus supplies minerals and protection from dryness and excessive light by encasing the algae in its mycelium. The fungus also attaches the symbiotic organism to the substrate.
Lichens are not a single organism, but rather an example of a what?
[ "fusion", "symbiosis", "mutualism", "homogeneous mixture" ]
2
899
The kinetic theory also states that there is no interaction between individual gas particles. Although we know that there are, in fact, intermolecular interactions in real gases, the kinetic theory assumes that gas particles are so far apart that the individual particles don’t “feel” each other. Thus, we can treat gas particles as tiny bits of matter whose identity isn’t important to certain physical properties.
What theory states that there is no interaction between individual gas particles?
[ "kinetic theory", "vortex theory", "Avoidance theory", "viscosity theory" ]
0