Biology Flashcards

All of these play an important role in human respiration EXCEPT

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.

Animal cells vary from plant cells in that they have

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.

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

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.

A symbiotic relationship is defined as which of the following?

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.

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

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.

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

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.

Which of the following is NOT true about meiosis?

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.

Which of the following characteristics of arteries is 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.

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

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.

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

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.

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

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.

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

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.

Which of the assertions regarding trypsin is untrue?

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.

The sympathetic nervous system stimulates all of the following EXCEPT

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.

The main site of glucose absorption is the

Answer: Proximal Convoluted Tubule

Explanation: 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.

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

Answer: The daughter cells fuse to form a zygote

Explanation: 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).

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

Answer: Nucleic acid and a capsid

Explanation: 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.

During reproduction, which of the following occurs

Answer: Ovulation

Explanation: 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).

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

Answer: Pyrimidine : Purine

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

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

Answer: Cell wall, DNA, and plasma membrane

Explanation: 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)