Nokea
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.
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Which hormone plays a key role in stimulating the release of milk from breast tissue after childbirth?
- A. Follicle-stimulating hormone (FSH)
- B. Luteinizing hormone (LH)
- C. Prolactin
- D. Estrogen
Correct Answer: C
Rationale: Prolactin is the hormone responsible for stimulating the release of milk from breast tissue after childbirth. It is produced by the pituitary gland and plays a crucial role in lactation. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are involved in the menstrual cycle and reproductive processes, not milk production. Estrogen is a female sex hormone with various functions but is not directly involved in milk production.
Which type of joint allows for the most movement?
- A. Ball-and-socket joint (shoulder)
- B. Hinge joint (elbow)
- C. Fibrocartilaginous joint (wrists)
- D. Suture joint (skull)
Correct Answer: A
Rationale: The correct answer is A: Ball-and-socket joint (shoulder). Ball-and-socket joints, exemplified by the shoulder joint, provide the widest range of movement among joint types. These joints facilitate flexion, extension, abduction, adduction, and rotation, allowing for versatile mobility. In a ball-and-socket joint, the rounded end of one bone fits into the socket of another bone, enabling extensive motion capabilities. Choice B, Hinge joint (elbow), allows movement in one plane, limiting its range compared to ball-and-socket joints. Choice C, Fibrocartilaginous joint (wrists), like the intervertebral discs, is meant for stability rather than extensive movement. Choice D, Suture joint (skull), found in the skull bones, is immovable and provides structural support rather than movement.
What is the scientific name for the building blocks of proteins?
- A. Residues
- B. Monomers
- C. Macromolecules
- D. Peptides
Correct Answer: B
Rationale: Rationale:
- Proteins are made up of long chains of amino acids.
- Amino acids are the building blocks of proteins and are considered monomers.
- Monomers are the individual units that can be linked together to form larger molecules called polymers.
- In the context of proteins, amino acids are the monomers that are linked together through peptide bonds to form polypeptide chains, which then fold into functional proteins.
- Residues refer to the specific amino acids within a protein after certain modifications or cleavages have occurred, so it is not the correct term for the building blocks of proteins.
- Macromolecules are large molecules made up of smaller subunits, such as proteins, nucleic acids, and carbohydrates, but they are not the specific building blocks of proteins.
- Peptides are short chains of amino acids linked by peptide bonds, but they are not the fundamental building blocks of proteins.
In nuclear physics, the term 'barn' is a unit commonly used to quantify:
- A. Energy
- B. Radioactivity
- C. Nuclear cross-section
- D. Half-life
Correct Answer: C
Rationale: In nuclear physics, the term 'barn' is a unit used to quantify nuclear cross-section. Nuclear cross-section is a measure of the probability of a nuclear reaction occurring when an atomic nucleus interacts with a particle or another nucleus. The barn is a unit of area equal to 10^-28 square meters; it is commonly used to describe the cross-sectional area of atomic nuclei for nuclear reactions. Choice A, 'Energy,' is incorrect because a barn is not a unit for measuring energy; it is a unit of area. Choice B, 'Radioactivity,' is incorrect as radioactivity is typically measured in units like becquerels. Choice D, 'Half-life,' is also incorrect as half-life is a measure of the time it takes for half of a substance to decay, not related to the concept of a barn as a unit of nuclear cross-section.
Which type of tissue is characterized by tightly packed cells with minimal extracellular matrix and provides structural support and protection?
- A. Epithelial tissue
- B. Connective tissue
- C. Muscle tissue
- D. Nervous tissue
Correct Answer: A
Rationale: Epithelial tissue is the correct answer as it aligns with the description provided in the question. Epithelial tissue is characterized by tightly packed cells with minimal extracellular matrix, which allows it to form protective barriers on the body's surface and line internal organs, providing structural support and protection. Connective tissue, while important for support and connection between tissues and organs, does not fit the description in the question of being tightly packed with minimal extracellular matrix. Muscle tissue is responsible for movement, and nervous tissue transmits signals throughout the body, neither of which are primarily involved in providing structural support and protection as described. Therefore, based on the characteristics described in the question, epithelial tissue best fits the description of tissue that provides structural support and protection.