AP Biology Exam 2023 with complete solution

Resting membrane potential depends on which of the following(s)? I. Active transport II. Selective permeability III. Differential distribution of ions across the anxonal membrane All three. The resting potential depends on active transport (the Na+K+ATPase pump) and the selective permeability of the axon membrane to K+ than to Na+, which leads to a differential distribution of ions across the axonal membrane Mitosis The division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell Stages of mitosis Interphase (G1),S=DNA replication, Late interphase (G3), Prophase, Metaphase, Anaphase,Telophase, Cytokensis Interphase (Mitosis) G1 (1st growth) 1 centriol Choromotids Cells spend most of life in this phase Late Interphase (mitosis) G2 (2nd growth) 2 centriols Sister chromatids Cells spend most of life in this phase Prophase (mitosis) Spindle fibers form Nuclear envelope breaks down Metaphase (mitosis) Chromosomes line up in center along the metaphase plate Spindle fibers are attached Anaphase (mitosis) Spindle fibers begin to shorten, pulling chromotids appart. Telophase (mitosis) Cleavage furrow forms Chromotids pull to opppsote ends Nuclear envelope begins to form Cytokenesis Cytoplasm divides and cells membrane pinched into 2 separate cells Exact copies of cell we began with Meiosis The process by which a single parent diploid cell (Botb homologous chromosomes) divides to produce four daughter haploid cells (One homologous chromosome of the pair). Meiosis is the type of cell division by which germ cells (eggs and sleek) are produced. The Krebs cycle in humans releases a. carbon dioxide b. pyruvate c. glucose d. lactic acid A. The Krebs cycle releases carbon dioxide as the carbon molecules are broken down and electron carriers are generated. Glucose is at the start of glycolysis and pyruvate is at the end of glycolysis. Lactic acid is generated through fermentation. What is the movement of molecules across a membrane from a region of lower concentration to a region of higher concentration-against the concentration gradient; requires cellular energy to achieve this movement Active transport A property of cellular membranes that only allows certain molecules to enter or exit the cell; can occur actively or passively Selective permeability The breakdown of glucose by enzymes, releasing energy and pyruvic acid Glycolysis Fermentation Process by which cells release energy in the absence of oxygen lactic acid fermentation creates ATP, which is a molecular both animal and bacteria need for energy, when there is no oxygen present. This process breaks down glucose into two lactate molecules. Then lactate and hydrogen form lactic acid. Lactic acid fermentation provides an alternative way to generate energy when normal cellular respiration is not possible. A heterotroph a. obtains its energy from sunlight, harnessed by pigments b. obtains its energy from catabolizing organicmolecules c. makes organic molecules from CO2 d. obtains its energy by consuming exclusively autotrophs B. A heterotraph obtains its energy from organic molecules. An autotroph obtains energy from sunlight utilizing pigments such as chlorophyll and uses CO2 and water to make organic molecules. Heterotrophs can obtain their energy from ingesting autotrophs, but they can also consume other heterotrophs. Regarding meiosis and mitosis, one difference between the two forms of cellular reproduction is that in meiosis a. there is one round of cell division, whereas in mitosis there are two rounds of cell division b. separation of sister chromatids occurs during the second division, whereas in mitosis separation of sister chromatids occurring during the first division c. chromonsomes are replicated during interphase, whereas in mitosis chromosomes are replicated during the first phase of mitosis d. spindle fibers form during interphase, whereas in mitosis the spindle fibers form during prophase B. In meiosis, the sister chromatids separate during the second metaphase of meiosis (Meiosis II), whereas the sister chromatids separate during metaphase of mitosis. A feature of amino acids that is NOT found in carbohydrates is the presence of a. carbon atoms b. oxygen atoms c. nitrogen atoms d. hydrogen atoms C. Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen, so eliminate A, B & D. Don't forget to associate amino acids with nitrogen because of the amino group (NH2) Which of the following is NOT a characteristic of prokaryotic cells? a. circular double-stranded DNA b. membrane-bound cellular organelles c. plasma membrane consisting of lipids and proteins d. ribosomes that synthesize polypeptides B. Unlike eukaryotes, prokaryotes (which include bacteria) do not contain membrane-bound organelles. Bacteria contain circular double-stranded DNA, ribosomes, and a cell wall, so A & D are incorrect. Also eliminate C because bacterial cell membranes are made up of a bilipid layer with proteins interspersed. Which of the following best explains why a population is described as the evolutionary unit? a. Genetic changes can occur only at the population level. b. The gene pool in a population remains fixed over time. c. Natural selection affects individuals, not populations. d. Individuals cannot evolve, but populations can. D. Populations can be described as the evolutionary unit because changes in the genetic makeup of populations can be measured over time. Eliminate A, as genetic changes occur only at the individual level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in population. However, this statement does not explain why the population is the evolving unit, so B is incorrect. C is true but does not answer the question. The endocrine system maintains homeostasis using many feedback mechanisms. Which of the following is an example of positive feedback? a. Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk production. b. An enzyme is allosterically inhibited by the product of the reaction it catalyzes. c. When ATP is abundant, the rate of glycolysis decreases. d. When blood sugar levels decrease to normal after a meal, insulin is no longer secreted. A. Positive feedback occurs when a stimulus causes an increased response. B,C,D are examples of negative feedback. A scientist carries out a cross between two guinea pigs, both of which have black coats. Black hair coat is dominant over white hair coat. Three quarters of the offspring have black coats, and one quarter have white coats. The genotypes of the parents were most likely a. bb bb b. Bb Bb c. BB bb d. BB Bb B. In order to determine the genotype of the parents, use the ratio of the offspring given in the question and work backward. The ratio of black-haired to white-haired guinea pigs is 3:1. In order to get a white-haired offspring, each parent must have been able to contribute a b allele. However, since the parents were both black in color, they must have each been Bb. A large island is devastated by a volcanic eruption. Most of the horses die expect for the heaviest males and heaviest females of the group. They survive, reproduce, and perpetuate the population. If weight is a highly heritable trait, which graph represents the change in population before and after the eruption? a. A higher mean weight compared with their parents b. A lower mean weight compared with their parents c. The same mean weight as members of the original population. d. A higher mean weight compared with members of the original population. D. The mean weight of the offspring in the next generation will be heavier than the mean weight of the original population because all the lighter horses n the original population died off. The normal distribution for weight will therefore shift to the heavier end (to the right of graph). You can therefore eliminate C because the mean weight should increase. The mean weight of the offspring could be heavier and lighter than their parents, so you can also eliminate A and B. All of the following play a role in early embryogenesis EXCEPT a. apoptosis b. regulatory factors c. operons d. differentiation C. Apoptosis (programmed cell death), hox and homeotic genes (genes that control differentiation). and differentiation itself play a role in morphogenesis. Operons are sets of multiple genes regulated by a single regulatory unit in bacteria. During the period when life is believed to have begun, the atmosphere on primitive Earth contained abundant amounts of all the following gases EXCEPT a. oxygen b. hydrogen c. ammonia d. methane A. The primitive atmosphere lacked oxygen (O2). It comtained methane (CH4), ammonia (NH3), and hydrogen (H2). The digestive system in humans can be divided into two parts: the alimentary canal and the accessory organs. The canal comprised of the esophagus, stomach, and intestines is where the food actually passes during its transition into waste. The accessory organs are any organs that aid in the digestion by supplying the organs in the alimentary canal with digestive hormones and enzymes. The small intestine is the main site of absorption. It can accomplish it so efficiently because of villi and microvilli that sculpt the membrane into hair-like projections. They likely aid in re-absorption by. a. Increasing the surface area of the small intestine b. Decreasing the surface area of the small intestine c. Making the small intestine more hydrophilic d. Making the small intestine more hydrophobic A. Villi and microvilli are fingerlike projections present in the small intestine which dramatically increase the surface area available for nutrient absorption. The digestive system in humans can be divided into two parts: the alimentary canal and the accessory organs. The canal comprised of the esophagus, stomach, and intestines is where the food actually passes during its transition into waste. The accessory organs are any organs that aid in the digestion by supplying the organs in the alimentary canal with digestive hormones and enzymes. The pancreas is a major accessory organ in the digestive system. Which of the following would destroy the function of the digestive products produced by the pancreas? a. A decrease in absorption rates within the alimentary canal b. Removing the excess water from the food waste c. Increased acidity due to the inability to neutralize stomach acid d. An increase in peristalisis and subsequent diarrhea C. The pancreas produces digestive enzymes, and enzymes are sensitive to pH. The inability to neutralize stomach acid would disrupt the function of the enzyme would be intact. Removal of water should not greatly affect enzyme functions. The digestive system in humans can be divided into two parts: the alimentary canal and the accessory organs. The canal comprised of the esophagus, stomach, and intestines is where the food actually passes during its transition into waste. The accessory organs are any organs that aid in the digestion by supplying the organs in the alimentary canal with digestive hormones and enzymes. In animal cells, which of the following represents the most likely pathway that a secreted protein takes as it is synthesized in a cell? a. Plasma membrane-Golgi apparatus-ribosome-secretory vesicle-rough ER b. Ribosome-Golgi apparatus-rough ED-secretory vesicle-plasma membrane c. Plasma membrane-Golgi apparatus-ribosome-rough ER-secretory vesicle d. Ribosome-rough ER-Golgi apparatus-secretory vesicle-plasma membrane D. Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with ribosome. So eliminate A and C. The polypeptide then moves through the rough ER to the Golgi apparatus, where it is modified and packaged into a veschile. The vesicle then floats to the plasma membrane and is secreted. All of the following statements are correct regarding alleles EXCEPT a. Alleles are alternative forms of the same gene b. Alleles are found on corresponding loci of homologous chromosomes C. A gene can have more than two alleles D. An individual with two identical alleles is said to be heterzygous with respect to the gene D. Choice D is false because an individual with two identical alleles is said to be hemozygous, not heterzygous, with respect to that gene. Alleles are different forms of the same gene found on corresponding positions of homologous chromosomes, so A and B are incorrect. More than two alleles can exist for a gene, but a person can have only two alleles for each trait. Surface area to volume ratio The amount of surface covering an object (or a cell) compared to the volume contained within; as surface to volume ratio decreases in cells, division becomes necessary Cell Division The process of creating two new cells Mitosis When the nucleus itself divides into two new nuclei Cytokinesis When the rest of the cell divides to form two new daughter cells Chromatin When the DNA inside the nucleus appears as disorganized, long strands Chromosomes When the DNA coils tightly, shortens and thickens prior to mitosis DNA molecule Another name for a chromosome; contains the genes Replication The process of chromosomes making exact duplicates Sister chromatids The two sides of the "X" formed by replicated chromosomes Centromere Acentral protein bundle that connects sister chromatids Autosomes All chromosomes except for the sex chromosomes Genes Codes within DNA that specify a particular trait Alleles Two alternate forms of each gene (such as blue eyes or brown eyes) Somatic cells All of the body cells Gametes Sperm and egg cells, also referred to as sex cells Diploid number The total number of chromosomes in normal body cells; two matching homologs of each kind Cell cycle The entire life cycle of the parent cell Interphase The cell is carrying out its normal everyday cell activities as well as preparing for the Mitotic phase G1 and G2 phases Gap phases; G1 is mostly growth and development G2 occurs after replication of chromosomes and involves replication of additional organelles and membranes in preparation for cell division S phase Synthesis of new DNA; also called replication Prophase The first phase of mitosis characterized by a disappearance of the nuclear membrane and nucleolus Spindle basket This structure will assist in pulling apart the doubled chromosomes Metaphase The second phase of mitosis where all of the doubled chromosomes move to the center of the cell, called the equator Anaphase The third phase of mitosis where the spindle fiber shorten from the poles, pulling the doubled chromosomes apart from each other, toward the poles of the cell Telophase The final phase of mitosis characterized by the separated chromosomes reaching the poles of the cell. The nuclear membrane and nucleolus begins to reappear around each set of chromosomes Cell plate A structure which eventually forms a cell wall that begins to grow out from the center and merely separates the two daughter cells Microtubule Organizing center which performs the job of the centriole in plants Genetic recombinations Different ways chromosomes can provide variation in the species depending on which chromosomes are inherited and whether or not crossing over occurs Sex chromosomes In humans, XY designates a male; XX designates a female Crossing over Each chromatid may exchange a part of itself with its homolog as it crosses over the other during late prophase I or early metaphase I of meiosis Homologous pairs Matching chromosomes that each came from either the father or the mother; homologs code for different versions of the same genes Meiosis The division of a nucleus that results in four nuclei with one half the original number of chromosomes; used to produce gametes Haploid number One half the total number of chromosomes in a normal body cell; one of each kind of homolog Oogenesis Meiosis that produces eggs (ova) Ovum An egg resulting from oogenesis Spermatogenesis Meiosis that produces sperm Nondisjunction Mutations Improper separation of sister chromatids may result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (monosomy) Karyotype A photograph of an individual's chromosomes Amniocentesis When a long needle withdraws fluid around fetus; some of the embryo's cells that have sloughed off into the fluid will be collected and examined Chorionic Villi Testing Scraping a few cells from villi of the placenta which connect fetus to mother in the uterus Ultrasound Images formed by sound waves can be converted into pictures of the uterus to determine gross structural abnormalities of the fetus; this is a safe and non-invasive procedure Laws of Probability If A and B are mutually exclusive, then: P (A or B) = P (A) + P (B) If A and B are independent, then: P (A and B) = P (A) × P (B) Hardy-Weinberg Equations p2 + 2pq + q2 = 1 p = frequency of the dominant allele in a population p + q = 1 q = frequency of the recessive allele in a population Mode Value that occurs most frequently in a data set Median Middle value that separates the greater and lesser halves of a data set Median Middle value that separates the greater and lesser halves of a data set Range Value obtained by subtracting the smallest observation (sample minimum) from the greatest (sample maximum) Insulin is a protein hormone that is secreted in response to elevated blood glucose levels. When insulin binds to its receptors on liver cells, the activated receptors stimulate phosphorylation cascades that cause the translocation of glucose transporters to the plasma membrane. Based on the information provided, which of the following best describes the role of insulin in this liver cell signal transduction pathway? (A) It acts as a ligand. (B) It acts as a receptor. (C) It acts as a secondary messenger. (D) It acts as a protein kinase A. Cells communicate over short distances by using local regulators that target cells in the vicinity of the signal-emitting cell — a. Signals released by one cell type can travel long distances to target cells of another cell type. Humans have a diploid number ("2n" ) of 46. Which of the following statements best predicts the consequence if meiosis did not occur during gametogenesis? (A) The gametes would get larger from one generation to the next. (B) The chromosome number would double with each generation. (C) The chromosome number would be halved with each generation. (D) The chromosome number would triple with each generation. B. Meiosis is a process that ensures the formation of haploid gamete cells in sexually reproducing diploid organisms— a. Meiosis results in daughter cells with half the number of chromosomes of the parent cell. b. Meiosis involves two rounds of a sequential series of steps (meiosis I and meiosis II). Mutations in the MYO6 and POU4F3 genes have been associated with a form of hereditary hearing loss in humans. Researchers studying the genes have proposed that POU4F3 encodes a transcription factor that influences the regulation of MYO6. Which of the following questions will best help guide the researchers toward a direct test of their proposal? (A) Have mutations in other genes also been associated with hearing loss? (B) In what types of cells are the mutant forms of the POU4F3 gene expressed? (C) Are mutations in the MYO6 and POU4F3 genes also found in mice? (D) Do mutations in the POU4F3 gene affect MYO6 mRNA levels in cells? D. Promoters are DNA sequences upstream of the transcription start site where RNA polymerase and transcription factors bind to initiate transcription. Negative regulatory molecules inhibit gene expression by binding to DNA and blocking transcription. The human TPM1 gene encodes members of the tropomyosin family of cytoskeletal proteins. Which of the following best explains how different proteins can be made in different cell types from the one TPM1 gene? (A) Different introns are selectively converted to exons. (B) Different exons are retained or spliced out of the primary transcript. (C) The GTP cap is selectively added to and activates different exons. (D) Different portions of the primary transcript remain bound to the template DNA. B. The sequence of the RNA bases, together with the structure of the RNA molecule, determines RNA function— a. mRNA molecules carry information from DNA to the ribosome. b. Distinct tRNA molecules bind specific amino acids and have anti-codon sequences that base pair with the mRNA. tRNA is recruited to the ribosome during translation to generate the primary peptide sequence based on the mRNA sequence. c. rRNA molecules are functional building blocks of ribosomes. Genetic information flows from a sequence of nucleotides in DNA to a sequence of bases in an mRNA molecule to a sequence of amino acids in a protein. RNA polymerases use a single template strand of DNA to direct the inclusion of bases in the newly formed RNA molecule. This process is known as transcription. The DNA strand acting as the template strand is also referred to as the noncoding strand, minus strand, or antisense strand. Selection of which DNA strand serves as the template strand depends on the gene being transcribed. The enzyme RNA polymerase synthesizes mRNA molecules in the 5' to 3' direction by reading the template DNA strand in the 3' to 5' direction. In eukaryotic cells the mRNA transcript undergoes a series of enzyme-regulated modifications— a. Addition of a poly-A tail. b. Addition of a GTP cap. c. Excision of introns and splicing and retention of exons. d. Excision of introns and splicing and retention of exons can generate different versions of the resulting mRNA molecule; this is known as alternative splicing. Scientists examined the folded structure of a purified protein resuspended in water and found that amino acids with nonpolar R groups were primarily buried in the middle of the protein, whereas amino acids with polar R groups were primarily on the surface of the protein. Which of the following best explains the location of the amino acids in the folded protein? (A) Polar R groups on the surface of the protein can form ionic bonds with the charged ends of the water molecules. (B) Polar R groups are too bulky to fit in the middle of the protein and are pushed toward the protein's surface. (C) Nonpolar R groups that cannot form hydrogen bonds with water are pushed into the middle of the protein. (D) Nonpolar R groups from different parts of the protein form covalent bonds with each other to maintain the protein's structure. C. Hydrolysis and dehydration synthesis are used to cleave and form covalent bonds between monomers. Structure and function of polymers are derived from the way their monomers are assembled— a. In nucleic acids, biological information is encoded in sequences of nucleotide monomers. Each nucleotide has structural components: a five-carbon sugar (deoxyribose or ribose), a phosphate, and a nitrogen base (adenine, thymine, guanine, cytosine, or uracil). DNA and RNA differ in structure and function. b. In proteins, the specific order of amino acids in a polypeptide (primary structure) determines the overall shape of the protein. Amino acids have directionality, with an amino (NH2) terminus and a carboxyl (COOH) terminus. The R group of an amino acid can be categorized by chemical properties (hydrophobic, hydrophilic, or ionic), and the interactions of these R groups determine structure and function of that region of the protein. c. Complex carbohydrates comprise sugar monomers whose structures determine the properties and functions of the molecules. d. Lipids are nonpolar macromolecules— i. Differences in saturation determine the structure and function of lipids. ii. Phospholipids contain polar regions that interact with other polar molecules, such as water, and with nonpolar regions that are often hydrophobic. The apple maggot fly, Rhagoletis pomonella, is native to North America and originally fed on fruit of the wild hawthorn. Since the mid-1800s, a population of flies has emerged that instead feed on domesticated apples. Apple maggot flies typically mate on or near the fruit of their host plants. Many varieties of apples ripen three to four weeks before the hawthorn fruits do. The different fruit preferences of the two fly populations will most likely have which of the following effects? (A) The flies that eat hawthorn fruit will increase in number, while the flies that eat apples will decrease in number because of the use of insecticides on apple trees. (B) The single fly species will evolve into two distinct species because of the lack of gene flow between the two populations. (C) The ability to survive on a diet of two different fruits will help the flies learn to eat many more types of fruit. (D) The flies that eat hawthorn fruit will lay some of their eggs on the earlierripening apples to minimize competition among the larvae. B. Speciation results in diversity of life forms. Speciation may be sympatric or allopatric. Various prezygotic and postzygotic mechanisms can maintain reproductive isolation and prevent gene flow between populations. It is estimated that oxygen production first evolved in photosynthetic prokaryotes approximately 2.7 billion years ago. The first photosynthetic prokaryotes are presumed to be similar to today's cyanobacteria. Which of the following best supports the claim that photosynthetic prokaryotes were responsible for the oxygen in Earth's atmosphere? (A) The light reactions of photosynthesis split carbon dioxide into carbon and oxygen. (B) The light reactions of photosynthesis split water into hydrogen ions and oxygen. (C) The Calvin cycle splits glucose into carbon, hydrogen, and oxygen. (D) The Calvin cycle splits water into hydrogen ions and oxygen. B. releases energy in glucose to form ATP from ADP and inorganic phosphate, NADH from NAD+, and pyruvate. Pyruvate is transported from the cytosol to the mitochondrion, where further oxidation occurs. In the Krebs cycle, carbon dioxide is released from organic intermediates, ATP is synthesized from ADP and inorganic phosphate, and electrons are transferred to the coenzymes NADH and FADH2. Electrons extracted in glycolysis and Krebs cycle reactions are transferred by NADH and FADH2 to the electron transport chain in the inner mitochondrial membrane. When electrons are transferred between molecules in a sequence of reactions as they pass through the ETC, an electrochemical gradient of protons (hydrogen ions) across the inner mitochondrial membrane is established. Fermentation allows glycolysis to proceed in the absence of oxygen and produces organic molecules, including alcohol and lactic acid, as waste products. The conversion of ATP to ADP releases energy, which is used to power many metabolic processes.