1. Which hormone, produced by the thyroid gland, regulates calcium levels in the blood by enhancing calcium absorption in the intestines and reducing calcium loss in the kidneys?

A. Calcitonin
B. Parathyroid hormone (PTH)
C. Thyroxine
D. Insulin

Correct answer: a

Rationale: The correct answer is A: Calcitonin. Calcitonin is a hormone produced by the thyroid gland that plays a crucial role in regulating calcium levels in the blood. It works by enhancing calcium absorption in the intestines and reducing calcium loss in the kidneys. This helps to maintain the proper balance of calcium in the body. Parathyroid hormone (PTH) works in the opposite way, increasing calcium levels in the blood when they are low. Thyroxine is a hormone produced by the thyroid gland that regulates metabolism and growth, not calcium levels. Insulin is a hormone produced by the pancreas that regulates blood sugar levels, not calcium levels. Therefore, the correct hormone in this case is Calcitonin.

2. Which neurotransmitter is responsible for stimulating muscle contraction?

A. Dopamine
B. Acetylcholine
C. Serotonin
D. Norepinephrine

Correct answer: B

Rationale: Rationale: Acetylcholine is the neurotransmitter responsible for stimulating muscle contraction at the neuromuscular junction. When an action potential reaches the end of a motor neuron, acetylcholine is released into the synaptic cleft and binds to receptors on the muscle cell membrane, leading to muscle contraction. Dopamine, serotonin, and norepinephrine are neurotransmitters that have different functions in the nervous system and are not directly involved in stimulating muscle contraction.

3. What is the term for the particles moving around within a substance?

A. Ions
B. Atoms
C. Molecules
D. Kinetic energy

Correct answer: C

Rationale: In most cases, the particles moving within a substance are individual molecules or atoms, depending on the state of matter.

4. What is the process of cells becoming specialized to perform specific functions called?

A. Cell division
B. Cell differentiation
C. Cell growth
D. Cell regeneration

Correct answer: B

Rationale: Rationale: A) Cell division refers to the process by which a parent cell divides into two or more daughter cells. B) Cell differentiation is the process by which cells become specialized to perform specific functions. During differentiation, cells acquire specific structures and functions that allow them to carry out particular roles in the body. C) Cell growth is the process by which cells increase in size and number. D) Cell regeneration is the process by which new cells are produced to replace damaged or lost cells in an organism. In this context, the process of cells becoming specialized to perform specific functions is best described as cell differentiation.

5. When light reflects from a surface, what determines the angle of reflection?

A. The material of the surface
B. The wavelength of the light
C. The angle of incidence
D. The intensity of the light

Correct answer: C

Rationale: The angle of reflection is always equal to the angle of incidence according to the law of reflection, regardless of the material, wavelength, or intensity.

6. What type of molecule forms the cell membrane and controls what enters and exits the cell?

A. Proteins
B. Carbohydrates
C. Lipids
D. Nucleic acids

Correct answer: C

Rationale: The correct answer is C: Lipids. The cell membrane is primarily composed of a double layer of lipids called phospholipids. These phospholipids have a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, which arrange themselves to form a barrier that controls the passage of substances in and out of the cell. While proteins are also present in the cell membrane and play important roles in transport and cell signaling, lipids are the main structural component responsible for the selective permeability of the membrane. Carbohydrates are typically found on the outer surface of the membrane and are involved in cell recognition and communication. Nucleic acids are not a major component of the cell membrane; they are primarily responsible for storing and transmitting genetic information within the cell.