Question 1: All of these play an important role in human respiration EXCEPT

• A decrease in the plasma pH level
• An increase in the amount of CO2 in the blood
• A decrease in the amount of O2 in the blood (Correct answer)
• They all play a role

Correct answer: A decrease in the amount of O2 in the blood

Human respiration is primarily regulated by chemoreceptors that are highly sensitive to changes in blood CO2 levels and pH (which is affected by CO2). An increase in CO2 or a decrease in pH strongly stimulates breathing to expel CO2. While a decrease in blood O2 (hypoxemia) does stimulate respiration, it is a less potent and less sensitive stimulus compared to CO2/pH, only becoming significant when O2 levels drop substantially. Therefore, a decrease in O2 plays a less important role in the *normal* regulation of respiration compared to the other factors listed.

Question 2: Animal cells vary from plant cells in that they have

• Lysosomes
• A cell wall made of cellulose
• Centrioles within centrosomes (Correct answer)
• Large vacuoles that store water

Correct answer: Centrioles within centrosomes

Animal cells differ from plant cells in several key ways. Animal cells possess centrioles, which are involved in cell division and the formation of cilia and flagella, located within centrosomes. Higher plant cells, in contrast, typically lack centrioles. Plant cells have a rigid cell wall made of cellulose and a large central vacuole, which are absent in animal cells, while lysosomes are more prominent in animal cells, though plant vacuoles can perform similar functions.

Question 3: The liver is an important organ that performs all of the functions listed below. EXCEPT

• Detoxifying harmful substances such as alcohol or certain drugs
• Breaking down peptides into amino acids (Correct answer)
• Storage of glycogen to be used as fuel in the body
• Storing amino acids that were absorbed in the capillaries of the small intestine

Correct answer: Breaking down peptides into amino acids

The liver performs numerous vital functions, including detoxification of harmful substances, storage of glycogen, and extensive metabolism of amino acids. However, the primary site for breaking down peptides into individual amino acids is the gastrointestinal tract, specifically in the stomach by pepsin and in the small intestine by pancreatic proteases (like trypsin and chymotrypsin) and brush border peptidases. The liver receives amino acids from the small intestine but does not perform the initial peptide breakdown.

Question 4: A symbiotic relationship is defined as which of the following?

• A cat is no longer startled after hearing the door open multiple times every day
• A tapeworm feeds off of its host's nutrients causing the host to lose large amounts of weight
• Meerkats sound alarm calls to warn other meerkats of predators
• Remora fish eat parasites off of sharks; the sharks stay free of parasites, and the remora fish are protected from predators (Correct answer)

Correct answer: Remora fish eat parasites off of sharks; the sharks stay free of parasites, and the remora fish are protected from predators

A symbiotic relationship describes a close and long-term interaction between two different biological organisms. Option D, where remora fish eat parasites off sharks (benefiting the shark) and are protected from predators (benefiting the remora), is an example of mutualism. Mutualism is a type of symbiosis where both species benefit from the interaction, making it a clear and illustrative example of a symbiotic relationship.

Question 5: Calypso bulbosa, the Calypso Orchid, grows in close proximity to mycorrhizal fungi. The fungus infiltrate the flower's roots and take use of the plant's food supply. Rare minerals, such as phosphates, are concentrated in the roots by the fungi and made readily available to the orchid. This is an example of

• Mutualism (Correct answer)
• Parasitism
• Endosymbiosis
• Commensalism

Correct answer: Mutualism

The relationship between the Calypso Orchid and mycorrhizal fungi is an example of mutualism. The fungi benefit by obtaining food (carbohydrates) from the plant, while the orchid benefits from the fungi's ability to concentrate and make rare minerals, such as phosphates, readily available to its roots. Since both organisms derive a clear benefit from this close interaction, it is classified as mutualism.

Question 6: Which of the following in cells may catalyze hydrogen peroxide processes, provide cellular energy, and create proteins in that order?

• Peroxisomes, mitochondria, and Golgi apparatus
• Lysosome, ribosome, mitochondria
• Peroxisomes, mitochondria, and ribosomes (Correct answer)
• Peroxisomes, mitochondria, and lysosomes

Correct answer: Peroxisomes, mitochondria, and ribosomes

Peroxisomes are organelles that contain enzymes like catalase, which catalyze the breakdown of hydrogen peroxide into water and oxygen. Mitochondria are known as the 'powerhouses' of the cell, responsible for producing the majority of cellular energy in the form of ATP through cellular respiration. Ribosomes are the cellular machinery responsible for protein synthesis, translating messenger RNA into polypeptide chains. Therefore, the correct sequence of organelles performing these functions is peroxisomes, mitochondria, and ribosomes.

Question 7: Which of the following is NOT true about meiosis?

• Homologous chromosomes join during synapsis
• Sister chromatids separate during meiosis I (Correct answer)
• Crossing-over increases genetic variation in gametes
• None of the above

Correct answer: Sister chromatids separate during meiosis I

During meiosis I, homologous chromosomes separate, but sister chromatids remain attached. Sister chromatids only separate during anaphase II of meiosis II. Therefore, the statement that sister chromatids separate during meiosis I is incorrect. The other statements correctly describe events in meiosis: homologous chromosomes pair during synapsis in Prophase I, and crossing-over increases genetic variation.

Question 8: Which of the following characteristics of arteries is correct?

• The Superior Vena Cava is an example of an artery
• They are thin-walled blood vessels
• They carry blood away from the heart (Correct answer)
• They always carry oxygenated blood

Correct answer: They carry blood away from the heart

Arteries are defined as blood vessels that carry blood away from the heart. While most arteries carry oxygenated blood, the pulmonary artery is an exception as it carries deoxygenated blood to the lungs. Arteries are also characterized by their thick, muscular, and elastic walls, which allow them to withstand the high pressure of blood pumped from the heart, distinguishing them from thin-walled veins.

Question 9: A change in the membrane potential of a neuron from +50 to -70 millivolts is considered

• Repolarization (Correct answer)
• Post-Synaptic Inhibition
• Hyperpolarization
• Action Potential

Correct answer: Repolarization

A neuron's resting membrane potential is typically around -70 millivolts. During an action potential, the membrane depolarizes, becoming positive (e.g., +50 mV). Repolarization is the phase where the membrane potential returns from its positive peak back to the negative resting potential. Therefore, a change in membrane potential from +50 mV to -70 mV represents the repolarization phase of an action potential.

Question 10: Which of the following factors has the greatest impact on a population's genetic variability?

• D) Vegetative propagation

Vegetative propagation is a form of asexual reproduction in plants, where new individuals arise from vegetative parts of the parent plant. This process produces offspring that are genetically identical to the parent, essentially clones. Consequently, vegetative propagation significantly reduces the genetic variability within a population, as it does not introduce new genetic combinations or alleles, unlike sexual reproduction or mutation.

Question 11: All enzymes in the synaptic cleft are shown to be denatured by a chemical agent. How will this agent affect acetylcholine?

• Acetylcholine will not diffuse across the cleft to the postsynaptic membrane
• Acetylcholine will not be degraded in the synaptic cleft (Correct answer)
• Acetylcholine will not be released from the presynaptic membrane
• Acetylcholine will not bind to receptor proteins on the postsynaptic membrane

Correct answer: Acetylcholine will not be degraded in the synaptic cleft

Acetylcholine (ACh) is a neurotransmitter that transmits signals across the synaptic cleft. After binding to receptors on the postsynaptic membrane, its action is terminated by the enzyme acetylcholinesterase (AChE), which degrades ACh in the synaptic cleft. If all enzymes in the synaptic cleft, including AChE, are denatured, they will lose their function. This means acetylcholine will not be broken down and will persist in the cleft, continuing to bind to receptors and prolonging its effect.

Question 12: In plant intercellular communication, which of the following is used?

• Desmosomes
• Gap Junction
• Plasmodesmata (Correct answer)
• Hemidesmosomes

Correct answer: Plasmodesmata

Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, connecting the cytoplasm of adjacent cells. These channels allow for the direct transport of water, nutrients, and signaling molecules between cells, facilitating intercellular communication and coordination within plant tissues. Desmosomes, gap junctions, and hemidesmosomes are types of cell junctions found in animal cells, not plant cells.

Question 13: The energy that electrons give up as they go through the electron transport chain is used to

• Make glucose
• Product ATP (Correct answer)
• Use ATP
• Break down glucose

Correct answer: Product ATP

The electron transport chain (ETC) is a crucial part of cellular respiration where electrons are passed along a series of protein complexes. As these electrons move, they release energy, which is used to pump protons across the inner mitochondrial membrane, creating a proton gradient. This proton gradient then drives the enzyme ATP synthase to produce a large amount of ATP, the cell's primary energy currency. Therefore, the energy given up by electrons is used to produce ATP.

Question 14: Which of the assertions regarding trypsin is untrue?

• It is a catalyst that alters the rate of a reaction
• It converts Chymotrypsinogen to Chymotrypsin
• It is an organic compound made of proteins
• It is operative over a wide pH range (Correct answer)

Correct answer: It is operative over a wide pH range

Trypsin is a protease enzyme that functions optimally in the alkaline environment of the small intestine, typically around a pH of 7.5 to 8.5. Like most enzymes, trypsin is highly sensitive to pH changes and will denature and lose its activity outside of its specific optimal range. Therefore, the assertion that trypsin is operative over a wide pH range is untrue; it has a relatively narrow optimal pH range.

Question 15: The sympathetic nervous system stimulates all of the following EXCEPT

• Increased peristalsis in the gastrointestinal tract (Correct answer)
• Dilation of the pupil of the eye
• Constriction of blood vessels
• Increased secretion of the sweat glands

Correct answer: Increased peristalsis in the gastrointestinal tract

The sympathetic nervous system is responsible for the 'fight or flight' response, which prepares the body for stressful situations. This involves actions like dilating pupils, constricting blood vessels to redirect blood flow, and increasing sweat gland secretion. However, the sympathetic nervous system *inhibits* digestive processes, including peristalsis (the muscular contractions that move food through the gastrointestinal tract), to conserve energy for more immediate survival needs. Increased peristalsis is stimulated by the parasympathetic nervous system.

Question 16: The main site of glucose absorption is the

• Descending loop of Henle
• Ascending loop of Henle
• Glomerulus
• Proximal Convoluted Tubule (Correct answer)

Correct answer: Proximal Convoluted Tubule

Explanation: <br> The primary site of glucose reabsorption is the proximal convoluted tubule. The glomerulus, (C), is a tuft of capillaries that filters fluid into the Bowman's capsule. Choice (A) and (B), the loop of Henle, is the site of salt reabsorption. Choice (D), the collecting duct, is the site in which urine is concentrated.

Question 17: Which of the following is NOT a feature of animal asexual reproduction?

• Daughter cells are identical to the parent cell
• Daughter cells have the same number of chromosomes as the parent cell
• The daughter cells fuse to form a zygote (Correct answer)
• The parent cell produces diploid cells

Correct answer: The daughter cells fuse to form a zygote

Explanation: <br> There is no union of gametes in mitosis. Choices (B) and (D) are incorrect: Asexual reproduction involves the production of two new cells with the same number of chromosomes as the parent cell. If the parent cell is diploid, then the daughter cells will be diploid. The daughter cells are identical to each other and to the parent cell, so eliminate (A).

Question 18: At least one of these two main components is found in every virus. They are

• Nucleic acid and a capsid (Correct answer)
• DNA and cell membrane
• RNA and cell membrane
• RNA and cell wall

Correct answer: Nucleic acid and a capsid

Explanation: <br> Viruses are made up of nucleic acid surrounded by a protein coat called a capsid. They do not contain a cell wall, proteins, or cell membrane.

Question 19: During reproduction, which of the following occurs

• Implantation
• Neurelation
• Ovulation (Correct answer)
• Fertilization

Correct answer: Ovulation

Explanation: <br> Ovulation is the first to occur of those mentioned in the question. Ovulation is the release of an egg from the ovary into the fallopian tube. It is followed by fertilization (D) in the fallopian tubes. The zygote will then undergo a series of steps before implantation into the endometrium (A), neurulation (B).

Question 20: DNA's base composition differs between species. Which of the following ratios do you think will stay the same in DNA?

• Pyrimidine : Purine (Correct answer)
• Cytosine : Adenine
• Guanine : Deoxyribose
• Adenine : Guanine

Correct answer: Pyrimidine : Purine

Explanation: <br> The ratio of purines to pyrimidines should be constant because purines always bind with pyrimidines, no matter which ones they may be.

Question 21: Which of the following features are shared by bacteria and fungi?

• Plasma membrane, multicellularity, and Golgi apparatus
• Cell wall, DNA, and plasma membrane (Correct answer)
• Cell wall, unicellularity, and mitochondria
• Nucleus, organelles, and unicellularity

Correct answer: Cell wall, DNA, and plasma membrane

Explanation: <br> They both contain genetic material (DNA), a plasma membrane, and a cell wall. Unlike fungi, bacteria lack a definite nucleus. Therefore, eliminate (D). Bacteria are unicellular, whereas fungi are both unicellular and multicellular. Therefore, eliminate (A), (C). All those options contain membrane-bound organelles (mitochondria and golgi)

Question 22: Metafemale syndrome, a condition in which a woman has an extra X chromosome. This could be caused by a failure in

• Metaphase II
• Metaphase I
• Anaphast II (Correct answer)
• Telophase I

Correct answer: Anaphast II

Explanation: <br> The failure in oogenesis that could produce this syndrome would occur in anaphase I or anaphase II. Anaphase refers to the stage of meiosis in which chromatids separate from each other. If the chromosomes or chromatids fail to separate during anaphase, one egg cell will contain two X chromosomes instead of one.

Question 23: In DNA replication, which of the following does NOT happen?

• RNA polymerase is used to elongate both chains of the helix (Correct answer)
• Helicase unwinds the double helix
• Topoisomerase is used to prevent over winding and underwinding
• DNA ligase links the Okazaki fragments

Correct answer: RNA polymerase is used to elongate both chains of the helix

Explanation: <br> DNA polymerase, not RNA polymerase, is the enzyme that causes the DNA strands to elongate. DNA helicase unwinds the double helix, so (A) is true and therefore incorrect. Choice (B), DNA ligase seals the discontinuous Okazaki fragments, is also true. Eliminate it. In the presence of DNA polymerase, DNA strands always grow in the 5' to 3' direction as complementary bases attach. Therefore, (D) is also incorrect. Topoisomerase is used to prevent over-winding and underwinding, (E) is incorrect.

Question 24: Which of the following statements about organisms that are the first to establish an ecologically successional habitat is correct?

• They change the habitat in a way that makes it more habitable for other organisms (Correct answer)
• They are the fiercest competitors in the area
• They maintain the habitat as it is for their own kind
• None of the above

Correct answer: They change the habitat in a way that makes it more habitable for other organisms

Explanation: <br> Pioneer organisms colonize an area that is not habitable by other organisms and alter it over time in a way that makes the area habitable for other organisms. Pioneer organisms are producers, such as lichens that are symbionts—an intertwined relationship of a fungus and an algae.

Question 25: A frameshift mutation is which of the following?

• CAT HAS HIS → CAT HIS HAT
• CAT HAS HIS → CAT WAS HIT
• CAT HAS HIS → CAT HSH ISA (Correct answer)
• CAT HAS HIS → CAT HIT WAS

Correct answer: CAT HAS HIS → CAT HSH ISA

Explanation: <br> A frameshift mutation is one in which the reading frame for the protein construction machinery is shifted. It is a deletion or addition of nucleotides in a number that is not a multiple of 3. Often this can lead to premature stop codons, which lead to nonfunctional proteins.