1. Autoimmune diseases occur when the immune system mistakenly attacks healthy body tissues. What is a potential cause of autoimmune diseases?

A. Deficiency in essential vitamins and minerals
B. Exposure to environmental toxins
C. Breakdown in immune cell self-tolerance mechanisms
D. All of the above

Correct answer: C

Rationale: The correct answer is C. Autoimmune diseases are triggered by a breakdown in immune cell self-tolerance mechanisms, where the immune system fails to recognize 'self' from 'non-self' cells, leading to attacks on healthy tissues. While deficiencies in essential vitamins and minerals or exposure to environmental toxins can impact immune function, the root cause of autoimmune diseases is primarily attributed to the breakdown in self-tolerance mechanisms. This breakdown can be influenced by genetic predisposition, environmental factors, and other triggers, leading to the development of autoimmune conditions.

2. The protective fluid surrounding the brain and spinal cord is called:

A. Blood
B. Cerebrospinal fluid
C. Plasma
D. Myelin

Correct answer: B

Rationale: The correct answer is B: Cerebrospinal fluid. Cerebrospinal fluid is a clear, colorless liquid that surrounds the brain and spinal cord, providing cushioning and protection against physical impact. It also helps to maintain a stable environment for the central nervous system by regulating pressure and removing waste products. Blood (option A) is not the fluid that directly surrounds the brain and spinal cord. Plasma (option C) is the liquid component of blood and is not specific to the central nervous system. Myelin (option D) is a fatty substance that forms a protective sheath around nerve fibers but is not the fluid surrounding the brain and spinal cord.

3. What is the primary difference between ionic and metallic bonding?

A. Ionic bonds involve electron sharing, while metallic bonds involve electron transfer.
B. Ionic bonds are weak and directional, while metallic bonds are strong and non-directional.
C. Ionic bonds exist between metals and non-metals, while metallic bonds exist only between metals.
D. Ionic bonds form discrete molecules, while metallic bonds form extended structures.

Correct answer: B

Rationale: Ionic bonds form discrete molecules, while metallic bonds form extended structures. Ionic bonds involve complete electron transfer between specific atoms, resulting in discrete molecules. Metallic bonds involve a "sea" of delocalized electrons shared across all metal atoms, leading to strong, non-directional bonding throughout the entire material.

4. The term "double circulation" in the cardiovascular system refers to

A. The separation of oxygenated and deoxygenated blood flow within the heart.
B. The regulation of blood pressure through vasoconstriction and vasodilation
C. The cyclic contraction and relaxation of the heart muscle.
D. The existence of two separate circulatory pathways, one for the lungs and one for the body.

Correct answer: D

Rationale: The term 'double circulation' in the cardiovascular system refers to the existence of two separate circulatory pathways, one for the lungs (pulmonary circulation) and one for the body (systemic circulation). In pulmonary circulation, deoxygenated blood is pumped from the heart to the lungs to pick up oxygen and release carbon dioxide. Then, oxygenated blood returns to the heart to be pumped out to the rest of the body in systemic circulation. This separation of oxygenated and deoxygenated blood flow in different pathways is what distinguishes the double circulation system. Therefore, option D is the correct answer as it accurately describes the concept of double circulation in the cardiovascular system.

5. Which type of cell division is responsible for sexual reproduction?

A. Mitosis
B. Meiosis
C. Amitosis
D. Cytokinesis

Correct answer: B

Rationale: Rationale: Meiosis is the type of cell division responsible for sexual reproduction. During meiosis, a single cell undergoes two rounds of division to produce four daughter cells, each with half the number of chromosomes as the parent cell. This reduction in chromosome number is essential for sexual reproduction, as it ensures that when two gametes (sperm and egg) combine during fertilization, the resulting zygote will have the correct number of chromosomes. Mitosis, on the other hand, is a type of cell division that produces two daughter cells with the same number of chromosomes as the parent cell and is involved in growth, repair, and asexual reproduction. Amitosis is a rare form of cell division that does not involve the typical processes of mitosis or meiosis. Cytokinesis is the process of dividing the cytoplasm of a cell after mitosis or meiosis.