Nokea
What type of bond links amino acids together to form proteins?
- A. Hydrogen bond
- B. Ionic bond
- C. Disulfide bond
- D. Covalent bond
Correct Answer: D
Rationale: Amino acids are linked together by covalent bonds to form proteins. Specifically, the bond that links amino acids together is called a peptide bond, which is a type of covalent bond. The peptide bond forms between the amino group of one amino acid and the carboxyl group of another amino acid, resulting in the formation of a peptide chain. While hydrogen bonds, ionic bonds, and disulfide bonds are important for protein structure and stability, the primary bond responsible for linking amino acids in a protein chain is the covalent peptide bond. Hydrogen bonds are involved in maintaining the secondary structure of proteins, such as alpha helices and beta sheets. Ionic bonds and disulfide bonds contribute to tertiary and quaternary structures of proteins by stabilizing interactions between different parts of the protein or between different protein subunits, respectively.
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The neutral theory of molecular evolution proposes that:
- A. Most mutations in DNA are selectively neutral and do not affect an organism's fitness.
- B. All mutations are beneficial and contribute to the adaptation of a population.
- C. The rate of evolution is primarily driven by strong directional selection pressures.
- D. Genetic drift plays a negligible role in shaping genetic variation within populations.
Correct Answer: A
Rationale: Rationale:
A) The neutral theory of molecular evolution, proposed by Motoo Kimura in the 1960s, suggests that the majority of mutations that occur in DNA are selectively neutral, meaning they do not have a significant impact on an organism's fitness. These neutral mutations are not subject to natural selection and are allowed to accumulate in populations over time. This theory helps explain the high levels of genetic variation observed within populations.
B) Option B is incorrect because not all mutations are beneficial. Mutations can be neutral, harmful, or beneficial, and the neutral theory specifically focuses on the idea that many mutations are neutral in their effects.
C) Option C is incorrect because the neutral theory suggests that evolution is not primarily driven by strong directional selection pressures. Instead, it emphasizes the role of genetic drift and the accumulation of neutral mutations in shaping genetic variation.
D) Option D is incorrect because
What is the Aufbau principle?
- A. The principle that electrons fill orbitals in order of increasing energy.
- B. The principle that electrons cannot occupy the same orbital with the same spin.
- C. The principle that the maximum number of electrons in an orbital is 2n^2, where n is the energy level of the orbital.
- D. The principle that the attractive force between an electron and the nucleus is inversely proportional to the distance between them.
Correct Answer: A
Rationale: The Aufbau principle states that electrons fill orbitals in order of increasing energy. This principle helps to explain the electron configuration of atoms and how electrons are distributed within the energy levels and sublevels of an atom. By following the Aufbau principle, one can determine the electron configuration of an atom by sequentially adding electrons to orbitals in order of their increasing energy levels, starting with the lowest energy level. Choice B is incorrect as it describes the Pauli Exclusion Principle, which states that no two electrons in an atom can have the same four quantum numbers. Choice C is incorrect as it refers to the formula for calculating the maximum number of electrons that can occupy an energy level. Choice D is incorrect as it relates to Coulomb's law, which describes the electrostatic interaction between charged particles.
Which mineral is crucial for bone strength and is stored in bones and teeth?
- A. Calcium
- B. Iron
- C. Magnesium
- D. Potassium
Correct Answer: A
Rationale: Calcium is crucial for bone strength as it is a major mineral stored in bones and teeth. It plays a vital role in maintaining bone density and strength, making it essential for overall bone health. Calcium is essential for various physiological functions, including muscle contraction, nerve transmission, and blood clotting. Inadequate calcium intake can lead to conditions like osteoporosis, where bones become weak and brittle. Iron (Choice B) is important for transporting oxygen in the blood, but it is not stored in bones and does not play a significant role in bone strength. Magnesium (Choice C) is essential for bone health, but it is not primarily stored in bones and teeth. Potassium (Choice D) is crucial for various physiological functions, such as fluid balance and muscle function, but it is not a major mineral stored in bones and teeth for bone strength.
The number of protons in an atom determines its:
- A. Mass number
- B. Atomic number
- C. Atomic weight
- D. Valence electron count
Correct Answer: B
Rationale: The number of protons in an atom is known as the atomic number. The atomic number uniquely identifies an element and determines its position on the periodic table. It is a fundamental property of an element and directly influences its chemical behavior and interactions. The mass number, on the other hand, is the sum of protons and neutrons in the nucleus of an atom, not just protons. Atomic weight is the average mass of an element's isotopes considering their relative abundance, not solely based on the number of protons. Valence electron count refers to the number of electrons in the outermost energy level of an atom, influencing its ability to form bonds and participate in chemical reactions, but it is not determined by the number of protons in the atom.
Which hormones are responsible for stimulating the development of sex organs and secondary sex characteristics during puberty?
- A. Growth hormone
- B. Testosterone (in males) and Estrogen (in females)
- C. Insulin
- D. Thyroid hormone
Correct Answer: B
Rationale: Testosterone and estrogen are the primary sex hormones responsible for the development of male and female sex organs, respectively, and the emergence of secondary sex characteristics during puberty. Growth hormone, insulin, and thyroid hormone do not directly influence the development of sex organs and secondary sex characteristics during puberty. Growth hormone primarily regulates growth and metabolism, insulin regulates blood sugar levels, and thyroid hormone controls metabolism and energy levels. Therefore, choices A, C, and D are incorrect for this question.