Nokea
What is the primary organ responsible for filtering urine?
- A. Kidneys
- B. Bladder
- C. Ureters
- D. Urethra
Correct Answer: A
Rationale: The correct answer is A: Kidneys. The kidneys are the primary organs responsible for filtering urine. They filter waste products and excess substances from the blood to produce urine. Subsequently, urine travels from the kidneys through the ureters to the bladder. The bladder temporarily stores urine until it is expelled from the body through the urethra. The bladder's function is storage, the ureters transport urine, and the urethra is the exit pathway for urine expulsion. Therefore, the kidneys play a vital role in the filtration and production of urine within the urinary system.
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What protein complex controls the progression of mitosis through its activation and degradation?
- A. Ribosome
- B. Cyclin-dependent kinase (CDK)
- C. Centriole
- D. Microtubule
Correct Answer: B
Rationale: A) Ribosome: Ribosomes are cellular organelles responsible for protein synthesis and are not directly involved in controlling the progression of mitosis.
B) Cyclin-dependent kinase (CDK): CDKs are a family of protein kinases that regulate the cell cycle, including the progression of mitosis. CDK activity is controlled by cyclins, which bind to CDKs to activate them at specific points in the cell cycle. The activation and degradation of cyclins regulate the activity of CDKs, which in turn control the progression of mitosis.
C) Centriole: Centrioles are involved in organizing the microtubules of the mitotic spindle but do not directly control the progression of mitosis.
D) Microtubule: Microtubules are structural components of the cytoskeleton and are involved in various cellular processes, including mitosis, but they do not control
Which of the following properties is NOT characteristic of a covalent bond?
- A. Sharing of electrons between atoms
- B. High melting and boiling points
- C. Low electrical conductivity in solid state
- D. Directional bonding
Correct Answer: B
Rationale: Covalent bonds are formed by the sharing of electrons between atoms, leading to the formation of molecules with directional bonding. This means that the atoms are held together in a specific orientation. Covalent compounds generally exhibit low melting and boiling points compared to ionic compounds due to the weaker intermolecular forces present in covalent compounds. Furthermore, covalent compounds do not conduct electricity in the solid state because the electrons are localized between the atoms and are not free to move and carry charge. Hence, high melting and boiling points are not characteristic of covalent bonds. The correct answer is 'B' because high melting and boiling points are typically associated with ionic compounds due to their strong electrostatic interactions, while covalent compounds have lower melting and boiling points. Choices A, C, and D are all characteristics of covalent bonds, making them incorrect answers for this question.
What is the primary factor that determines whether a solute will dissolve in a solvent?
- A. Temperature
- B. Pressure
- C. Molecular structure
- D. Particle size
Correct Answer: C
Rationale: The primary factor that determines whether a solute will dissolve in a solvent is the molecular structure. The compatibility of the solute's molecules with the solvent's molecules is crucial for dissolution to occur. While temperature, pressure, and particle size can influence the rate of dissolution, they are not the primary factors determining solubility. Molecular structure plays a key role in determining if a solute will form favorable interactions with the solvent, which is essential for dissolution to take place effectively. Temperature can affect solubility by changing the kinetic energy of molecules, pressure typically has a minor effect on solubility except for gases, and particle size influences the rate of dissolution by increasing surface area, but none of these factors are as fundamentally important as molecular structure in determining solubility.
What are fingernails and toenails primarily made of?
- A. Collagen (Collagen is found in the dermis)
- B. Keratin
- C. Melanin (Melanin provides pigment, not structure)
- D. Sebum (Sebum is an oily substance)
Correct Answer: B
Rationale: Fingernails and toenails are primarily made of a protein called keratin. Keratin is a tough, fibrous protein that provides structure and strength to nails, hair, and the outer layer of skin. Collagen, as mentioned, is found in the dermis and is not the primary component of nails. Melanin provides pigment to the skin and hair, not the structure of nails. Sebum is an oily substance produced by the skin's sebaceous glands and is not a structural component of nails.
What is the significance of the nuclear envelope breaking down during mitosis?
- A. It allows the chromosomes to condense and become visible.
- B. It allows the spindle apparatus to form and attach to the chromosomes.
- C. It allows the sister chromatids to separate.
- D. It allows the nuclear material to be evenly distributed to the daughter cells.
Correct Answer: B
Rationale: A) The breakdown of the nuclear envelope does not directly cause the chromosomes to condense and become visible. Chromosome condensation is a separate process that occurs before mitosis begins.
B) The breakdown of the nuclear envelope is crucial for the formation of the spindle apparatus, a structure made of microtubules that helps separate the chromosomes during cell division. The spindle apparatus attaches to the chromosomes and helps move them to opposite poles of the cell.
C) The separation of sister chromatids occurs during anaphase, which is facilitated by the spindle apparatus. The breakdown of the nuclear envelope is not directly involved in this process.
D) The even distribution of nuclear material to daughter cells is achieved through the movement of chromosomes by the spindle apparatus, which is made possible by the breakdown of the nuclear envelope.