Nokea
Which level of protein structure is defined by the folds and coils of the protein's polypeptide backbone?
- A. Primary
- B. Secondary
- C. Tertiary
- D. Quaternary
Correct Answer: B
Rationale: The correct answer is B: Secondary. The secondary structure of a protein is defined by the folds and coils of the protein's polypeptide backbone. This level of structure is characterized by the formation of alpha helices and beta sheets, which are stabilized by hydrogen bonds between amino acids along the polypeptide chain. Choice A, Primary, refers to the linear sequence of amino acids in the protein. Choice C, Tertiary, involves the 3D folding of the entire polypeptide chain. Choice D, Quaternary, pertains to the arrangement of multiple polypeptide subunits in a protein complex.
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What is the first event to occur in a primary immune response?
- A. Macrophages phagocytose pathogens and present their antigens.
- B. Neutrophils aggregate and act as cytotoxic, nonspecific killers of pathogens.
- C. B lymphocytes make pathogen-specific antibodies.
- D. Helper T cells secrete interleukins to activate pathogen-fighting cells.
Correct Answer: A
Rationale: The correct answer is A. The initial event in a primary immune response is the phagocytosis of pathogens by macrophages and the subsequent presentation of their antigens, which is crucial for initiating the adaptive immune response. Neutrophils (Choice B) are also involved in the innate immune response, but they typically respond after macrophages. B lymphocytes (Choice C) produce antibodies later in the adaptive immune response, and Helper T cells (Choice D) help in coordinating the immune response but are not the first cells to act in a primary immune response.
What is the responsibility of the somatic nervous system?
- A. Breathing
- B. Thought
- C. Movement
- D. Fear
Correct Answer: C
Rationale: The somatic nervous system is responsible for controlling voluntary movements of skeletal muscles. This system communicates sensory information and controls voluntary movements, such as walking or reaching for objects. Breathing is primarily regulated by the autonomic nervous system, which functions involuntarily. Thought processes involve complex interactions between various regions of the brain and are not directly controlled by the somatic nervous system. Fear is an emotional response that involves the limbic system of the brain and the autonomic nervous system, not the somatic nervous system.
Which of the following best defines the term amphoteric?
- A. A substance that conducts electricity due to ionization when dissolved in a solvent
- B. A substance that can act as an acid or a base depending on the properties of the solute
- C. A substance that, according to the Br¸nsted-Lowry Acid-Base Theory, is a proton-donor
- D. A substance that donates its proton and forms its conjugate base in a neutralization reaction
Correct Answer: B
Rationale: An amphoteric substance can act as both an acid or a base depending on the environment. It can donate a proton (act as an acid) or accept a proton (act as a base), showing versatility in its behavior. Choice A is incorrect as it describes an electrolyte rather than an amphoteric substance. Choice C is incorrect as it defines an acid based on the Br¸nsted-Lowry Acid-Base Theory. Choice D is incorrect as it specifically refers to a substance donating a proton in a neutralization reaction, not capturing the dual behavior of an amphoteric substance.
How many daughter cells are formed from one parent cell during meiosis?
- A. One
- B. Two
- C. Three
- D. Four
Correct Answer: D
Rationale: During meiosis, one parent cell produces four genetically distinct daughter cells. This occurs through two rounds of cell division, resulting in four haploid cells with half the number of chromosomes as the parent cell. Each daughter cell is genetically unique due to processes like crossing over and independent assortment during meiosis. Choice A is incorrect because meiosis results in multiple daughter cells. Choice B is incorrect because meiosis yields more daughter cells. Choice C is incorrect because meiosis produces four, not three, daughter cells.
Blood type is a trait determined by multiple alleles, with IA and IB being co-dominant: IA codes for A blood and IB codes for B blood, while i codes for O blood and is recessive to both. If an A heterozygote individual and an O individual have a child, what is the probability that the child will have A blood?
- A. 25%
- B. 50%
- C. 75%
- D. 100%
Correct Answer: B
Rationale: If an A heterozygote (IAi) and an O individual (ii) have a child, there is a 50% chance the child will inherit the IA allele and have A blood. The A heterozygote can pass on either the IA or i allele, while the O individual can only pass on the i allele. Therefore, the possible genotypes for the child are IAi (A blood) or ii (O blood), resulting in a 50% chance of the child having A blood. Choice A (25%) is incorrect as it does not take into account the possibility of inheriting the IA allele. Choice C (75%) and Choice D (100%) are incorrect as they overestimate the probability of the child having A blood.