rea online practice biology (20)

8/8/2019 REA Online Practice Biology (20)

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AP Biology Practice Test

1. Hydrolysis of lipid molecules yields:A. amino acids and waterB. amino acids and glucoseC. fatty acids and glycerolD. glucose and glycerol

E. glycerol and water

2. The majority of ATP molecules derived from nutrient metabolism are generated by (the):

A. anaerobic fermentation and glycolysisB. fermentation and electron transport chainC. glycolysis and substrate phosphorylationD. Krebs cycle and electron transport chainE. substrate phosphorylation

3. The Mendelian law that describes the behavior of two or more gene pairsis the law of:

A. codominanceB. dominanceC. independent assortmentD. segregation of genesE. recombination

4. The largest number of known species is represented by the phylum:A. ArthropodaB. AnnelidaC. EchinodermataD. PlatyhelminthesE. Porifera

5. Graded variations in a species trait over a geographic distribution is a(n):

A. clineB. genusC. inbreedingD. mutationE. polymorphism

6. A person receives the results of a hematocrit during a series of blood tests. A hematocrit is the:

A. abundance of white blood cells in bloodB. concentration of sugar in the blood

C. level of circulating antibodiesD. percentage of blood cellular material by volumeE. typing of the blood by the ABO scheme

7. An insect is captured and studied in a laboratory. This insect has a pair of short, rigid wings, and a pair of thin veined wings. It also has chewing mouthparts. The insect will most likely be classified as a member of which of thefollowing orders?

A. DipteraB. HemipteraC. HomopteraD. LepidopteraE. Orthoptera

8. summationA. a short, individual contraction and relaxation


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B. a sustained maximal responseC. an accumulation of an abundance of lactic acidD. the merging of separate responses into a powerful outputE. tonic activity, as occurring in muscle tone

9. tetanusA. a short, individual contraction and relaxation

B. a sustained maximal responseC. an accumulation of an abundance of lactic acidD. the merging of separate responses into a powerful outputE. tonic activity, as occurring in muscle tone

Questions 10 - 13 refer to the organelles of a cell and their function(s).10. centriole

A. site of mRNA translationB. contains a circular arrangement of 18 microtubules that surround

2 microtubulesC. contains a circular arrangement of 27 microtubulesD. site of rRNA synthesis

E. contains a circular arrangement of nine microtubules surroundingtwo microtubules

11. ciliumA. site of mRNA translationB. contains a circular arrangement of 18 microtubules that surround

2 microtubulesC. contains a circular arrangement of 27 microtubulesD. site of rRNA synthesisE. contains a circular arrangement of nine microtubules surrounding

two microtubules

12. nucleolus

A. site of mRNA translationB. contains a circular arrangement of 18 microtubules that surround


two microtubules

13. ribosomeA. site of mRNA translationB. contains a circular arrangement of 18 microtubules that surround


two microtubules

14. The intracellular environment is best described as:A. hypertonicB. hypotonicC. isotonicD. osmoticE. permeable

15. The extracellular environment will:

A. gain waterB. gain soluteC. lose water


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D. lose soluteE. remain unchanged

16.

Over time a cell with 10% solute and 90% water cell will:A. become more hypertonic intracellularly

B. enlarge and experience lysisC. experience crenationD. lose motilityE. lose solute

Questions 17 - 18 refer to the genetic grid below.

AB Ab aB abAb 1 2 3 4ab 5 6 7 8

17. In the genetic cross, what is the percentage of genetic recombinations t

hat are heterozygous for both loci?A. 0B. 25C. 50D. 75E. 100

18. A genotype that is not produced among offspring from this cross:A. AABbB. AAbbC. AaBbD. AabbE. aaBB

Essay

19. Describe the different types of mutations and the process of translation. Include a discussion of how point mutations affect proper protein synthesis at thelevel of translation.

20. Describe how each of the following animal and plant cells perform its uniquefunction by specialized structural traits.

Animal = erythrocyte, neuron, muscle fiber.

Plant = epidermal cell, tracheids, parenchyma cells.

Answer Key1 C2 D3 C4 A5 A6 D7 E8 D9 B10 C

11 B12 D13 A


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14 A15 C16 B17 B18 E

Answer Explanations

Question 1: Hydrolysis is a type of chemical digestion. Amino acids are the digested building blocks of proteins. Glucose is a subunit of carbohydrates. Watermolecules are required to split chemical bonds in hydrolysis but are not produced in the process.

Question 2: Only a small fraction of ATP molecules is produced from anaerobic process of fermentation or glycolysis. Once pyruvic acid is formed, its entry into the aerobic Krebs cycle unleashes most of the original glucose molecule's energy. Krebs cycle reactions yield high energy electrons (oxidation) that are thenshuttled down a series of transport acceptors located in the inner mitochondrialmembrane until they finally combine with oxygen and H+ to form water. During el

ectron transport, a proton gradient is generated across the inner mitochondrialmembrane. The collapse of this proton gradient provides energy for the production of ATP molecules from ADP molecules and inorganic phosphates.

Question 3: The law of independent assortment states that if two genes are on different chromosomes, then, during meiosis, they may end up in the same gamete,or they may not.

Question 4: There are more arthropod species than species of any other phylum.Arthropods include such well-known groups as arachnids, crustaceans, and insects. Annelids are segmented worms; echinoderms include sea urchins and sea anemones; poriferans are sponges; phylum Platyhelminthes represents the flatworms.

Question 5: This is a strict definition of cline. For example, north-south clines in average body size are found in many birds and mammals. These species are larger in the colder climate and smaller in the warmer climate. Genus is a taxonomy unit and mutations are a source of genetic variation. Inbreeding refers to the matings of closely related individuals, which increases the percentage of homozygosity within a population. Two or more morphologically distinct forms in a population constitute polymorphism.

Question 6: Hematocrit is the percentage of blood cells in blood by volume. Formales this value is normally 47 + 5; for females, it is 42 +5. Thirty-two percent is abnormally low, indicating anemia - a diminished capacity of the blood carry oxygen.

Question 7: The traits that are mentioned in question 70 are those of Orthopterans. Members of this order include grasshoppers and cockroaches. Dipterans, suchas houseflies, have one pair of wings and sucking mouthparts. Hemipterans, thetrue bugs, have one pair of wings that are thicker proximally and membranous distally, and a pair of wings that are totally membranous. Homopterans have eitherno wings, or two pairs of arched wings. Lepidopterans, such as butterflies, havetwo pairs of scale-covered wings and sucking mouthparts.

Question 9: As a skeletal muscle receives separate, well-spaced stimuli of sufficient intensity, it will twitch to each stimulus. Each twitch is marked by contraction and relaxation of a muscle. As the rate of stimulation increases, the muscle does not have sufficient time to totally relax between contractions. The mu

scle then contracts from an already partially contracted position, producing greater force than that produced by a normal twitch. Rapid signals from the nervoussystem causes this to occur quite often; each time, the muscle is more contract


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ed prior to the next signal and subsequent contraction. In this way, the contractions summate to produce a greater muscular force than the force of a single simple twitch. At some point, the neural impulses arrive at so rapid a rate, that the muscle has absolutely no time to relax between impulses. It is at this pointthat the muscle has reached a state of tetanus. Overwhelming a muscle with demands beyond its ability to receive new nutrients and oxygen yields accumulatio n of lactic acid, the source of muscle fatigue. Muscles, when not producing movemen

t, still remain somewhat taut or maintain muscle tone (tonus).

Question 14: Since the extracellular environment has a 95% concentration of water, the extracellular environment has a greater concentration of water than theintracellular environment does. Therefore, water will flow into the cell due toosmosis. Terms of "tonicity" refer to the solute concentration in water. The inside cell setting has a higher, hyper, solute concentration. Its solute concentration is not less, hypo, or equal, iso, to the extracellular environment.

Question 15: As explained in solution 108, water will flow into the cell. Therefore, the extracellular environment will lose water.

Question 16: Osmosis is the movement of water from an area of a higher level ofconcentration to one of lower concentration through a semipermeable membrane. Water concentration is higher outside, 95%, and lower inside. The semipermeable membrane allows it to flow in.

Question 18: Only cells 3 and 5 (1/4 of total) show genetic recombinations heterozygous for both gene pairs. Of all the genotypes listed in problem 112, only aaBB does not appear in the Punnett square, and therefore is not a possible genotype for the offspring.

Question 19: A mutation is a change in the base sequence of a gene which leadsto the formation of a new allele. Mutations can be classified into point mutations, chromosomal mutations, and genomic mutations.

Point mutations affect small regions of a chromosome. Substitution is a point mutation in which nucleotides are replaced by different ones. Substitution can occur spontaneously through the mispairing of bases during DNA replication. Deletion causes a gene to have several bases less than normal while addition gives theopposite result.

Chromosomal mutations affect larger regions of a chromosome and are usually initiated by a breakage in the DNA backbone. Translocation is the interchange of chromosome segments between two nonhomologous chromosomes. It is different from crossing-over, a normal genetic process that gives rise to variation. Crossing-overinvolves two homologous chromosomes. Deletion results in a karyotype that has lost a segment or segments of chromosome. A segment of chromosome without a centromere does not attach to any chromosome, it does not move with the spindle fiberduring cell division, and is not incorporated into either daughter cell. A karyotype has a chromosome longer than normal because of a duplicate segment at itsend. When a broken segment reattaches to its original position in a reversed order, a change in genetic order results without loss or gain of total gene count.This is called inversion. Translocation and inversion cause new groupings of genes. The favorable groupings are conserved by natural selection while the unfavorable ones are selected out.

Genomic mutations involve changes in the number of chromosomes present in the karyotype. This abnormality results from nondisjunction, a process in which homologous chromosomes fail to separate and move to opposite poles during cell divisio

n. This results in one daughter cell receiving an extra chromosome while the other daughter cell receives one less. Trisomy is a condition where three chromosomes of one type are present in the nucleus. For example, Down's Syndrome is also


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called Trisomy 21 because of the presence of three chromosome #21 in the nucleusof the affected individual.

Messenger RNA (mRNA) is synthesized in the nucleus by the process of transcription from a DNA template. mRNA is transported to the cytoplasm for translation. Ribosomes convert the nucleotide sequence of mRNA into the amino acid sequence ofthe polypeptide chain. Ribosomes consist of two subunits. The smaller subunit is

responsible for binding the mRNA, and the larger subunit contains the enzymes that catalyze the formation of peptide bonds. An mRNA molecule associated with several ribosomes is called a polysome, which allows protein to be synthesized before mRNA becomes degraded. Protein synthesis is invariably started at AUG, the start codon. mRNA is translated from the 5' end to the 3' end and polypeptides are synthesized from the left amino end to the right carboxyl end. Specific aminoacids are brought to the mRNA ribosome complex by tRNA which has an anticodon complementary to the triplet codon of the mRNA. Three nucleotides of the mRNA sequence are read at a time. The translocation of a ribosome along the mRNA, three nucleotides to the right, is an energy requiring process. During protein synthesis, adjacent amino acids are linked together by peptide bonds formed through dehydration. Once a stop codon is encountered, protein synthesis stops and the compl

ex of mRNA, ribosome, and nascent polypeptide chain dissociates. There are threestop codons among the 64 triplet codes and these stop codons have no tRNA anticodon complementary to them. Some nascent polypeptides have to be modified beforethey become useful.

A single base substitution changes a codon to another of the 64 possible geneticcodes. Substitution at the third base of a codon may not cause any effect because some amino acids are coded by multiple codons which differ from each other atthe third base position, e.g., both UUA and UUG code for leucine. However, theresults of an amino acid substitution can be serious. The degree of seriousnessincreases when the exchanged amino acid belongs to a different charge group, such as a nonpolar amino acid being substituted by a polar one, etc. Also, amino acid substitution at the functional site of a protein, such as the active site of

an enzyme, has a more serious effect than at other locations. Sometimes, base substitution changes a coding codon to a stop codon, and this leads to premature termination of protein synthesis. The effect is deleterious if this extra stop codon is close to the start codon.

Deletion or addition of a three base multiple results in the deletion or insertion of amino acids. The significance depends on the location of the deletion or insertion. If it happens on a region such that the functional site of a protein is malformed, this mutation can be deleterious. Deletion or addition of bases notat a multiple of three causes a reading-frame shift, where the order in which the mRNA is read is shifted according to the number of amino acids. Starting fromthe site of mutation, the mRNA is translated into a different polypeptide chain. Proteins formed this way cannot carry out their normal functions. This type ofmutation is usually deleterious as well.

Question 20: Erythrocytes synthesize, store, and transport hemoglobins. Hemoglobin binds O2 and CO2. Its affinities for these gases depend on the pH of the medium modulated by CO2 concentration. Mature erythrocytes are enucleated in highervertebrates and are biconcave disk- shaped. These special structures give the erythrocyte a larger surface area to accommodate hemoglobin and the diffusion of gases across its membrane. Hemoglobin embedded in the stroma of an erythrocyte isadvantageous in that no free floating hemoglobin is present to disturb the osmotic relationship between blood and tissue fluid.

Neurons are capable of conducting and transmitting electric impulses rapidly. Th

ey consist of a cell body containing the nucleus and other organelles, extensively branched dendrites, and a long, single axon which may branch at its terminalend. Dendrites receive and direct impulses to the cell body. Axons transmit impu


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lses away from the cell body. The capability of forming synapsis with other neurons and target organs allows neurons to form long conducting pathways to variousparts of the body. Axons in the central nervous system are wrapped in glial cells while those outside the central nervous system are enveloped in Schwann cells. These two kinds of cells form myelin sheaths that speed up the conduction of impulses in the axon.

Muscles in our body can be differentiated into skeletal muscles, smooth muscles,and cardiac muscles. Skeletal muscle fiber is cylindrical, coenocytic (with many nuclei) with a striated appearance. Bundles of skeletal muscle fibers attach to bone and are responsible for rapid action under the control of the voluntary nervous system. Smooth muscle fibers are nonstriated, thin, and elongated cells,and they form a sheet of muscle tissue which serves as the walls of the visceraand blood vessels. Cardiac muscle fibers are striated, their activity similar tosmooth muscle. Muscle fiber is composed of a sheath enclosing numerous myofibrils. The contractile materials of the myofibril are thin actin and thick myosin filaments. A special structure called a crossbridge is formed when the globular heads of myosin filament are in contact with the actin molecule of the thin filament. This crossbridge is responsible for the sliding together of the thick and t

hin filaments which produce muscle contraction.

Epidermal cells are relatively flat with a thicker outer cell wall. These irregularly shaped cells interlock to form the surface tissue of stem, roots, and leafwith no intercellular spaces for the prevention of water loss. Some epidermal cells are specialized to perform different functions. For example, guard cells are sausage-shaped epidermal cells that regulate the size of stomata. Epidermal cells of root tissue are devoid of cuticle and have hairlike processes to facilitate water absorption.

Tracheids and vessel cells are the two main elements of the xylem of plant's vascular tissue. Tracheids are elongated, tapering cells with pits on their cell walls. These pits are particularly numerous at the tapering ends and the verticall

y linked pattern of the tracheids form an upward transport system for water anddissolved substances. Tracheids have liquefied secondary cell walls which serveas a supportive structure for the plant.

Parenchyma cells are relatively unspecialized vegetative cells found in roots, stems, and leaves. They have a thin primary cell wall and usually lack a secondary cell wall. They are capable of cell division.

Parenchyma cells in leaves contain a high density of chloroplasts and are photosynthetic. Those located in stem and root serve to store nutrients and water. Turgid parenchyma cells help to give shape and support to the plant. Their large vacuoles take in water and push against the cell wall to maintain turgidity.

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