Nokea
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 cell membrane is primarily composed of lipids, specifically phospholipids, which form a lipid bilayer. This lipid bilayer controls what enters and exits the cell, providing a barrier that is selectively permeable. While proteins are also important components of the cell membrane and play various roles, lipids are the main structural component responsible for the membrane's permeability and function. Carbohydrates and nucleic acids are not the primary components of the cell membrane and do not have the same structural role as lipids.
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What is the function of the cell membrane?
- A. To protect the cell and control what enters and exits
- B. To store energy
- C. To produce proteins
- D. To synthesize lipids
Correct Answer: A
Rationale: The cell membrane, also known as the plasma membrane, serves as a protective barrier for the cell, separating the internal environment of the cell from the external environment. It is selectively permeable, meaning it controls the passage of substances in and out of the cell. This regulation of what enters and exits the cell is crucial for maintaining the cell's internal environment and ensuring proper functioning. Options B, C, and D are incorrect because storing energy, producing proteins, and synthesizing lipids are functions carried out by other cellular structures such as mitochondria, ribosomes, and endoplasmic reticulum, respectively, not the cell membrane.
Which state of matter has a definite shape and volume but can flow?
- A. Solid
- B. Liquid
- C. Gas
- D. Plasma
Correct Answer: B
Rationale: A liquid is the state of matter that has a definite volume but can flow and take the shape of its container. Solids have a definite shape and volume but do not flow as liquids do. Gases do not have a definite shape or volume but can flow to fill their container. Plasma is a state of matter where the particles are highly energized and do not have a definite shape or volume, thus not fitting the description of having a definite shape and volume while being able to flow.
Memory B cells and memory T cells are crucial for immunological memory. How does immunological memory enhance the immune response upon re-exposure to a pathogen?
- A. It increases the production of the same ineffective antibodies.
- B. It allows for a quicker and more robust immune response.
- C. It suppresses the immune system to prevent overreaction.
- D. It triggers a completely different immune response.
Correct Answer: B
Rationale: Immunological memory enhances the immune response upon re-exposure to a pathogen by allowing for a quicker and more robust immune response. Memory B cells and memory T cells are primed to recognize the pathogen quickly and mount a faster and more effective response, leading to a more efficient clearance of the pathogen. Choice A is incorrect because immunological memory does not increase the production of ineffective antibodies but rather promotes the production of specific antibodies that are effective against the pathogen. Choice C is incorrect as immunological memory does not suppress the immune system; instead, it enhances the response. Choice D is incorrect because immunological memory leads to a recall of the specific immune response mounted during the initial exposure, not a completely different response.
What is the term for the shedding of the outermost layer of the epidermis?
- A. Desquamation
- B. Exfoliation
- C. Keratinization
- D. Epidermolysis
Correct Answer: A
Rationale: Desquamation is the correct term for the shedding of the outermost layer of the epidermis. This process is essential for skin renewal, allowing the removal of dead skin cells from the skin's surface. Exfoliation, on the other hand, involves the removal of dead skin cells through mechanical or chemical methods. Keratinization refers to the process where skin cells produce the protein keratin, contributing to the skin's protective barrier. Epidermolysis is a condition characterized by the separation of the epidermis from the dermis due to a structural defect in the skin.
What is the difference between a ventral and dorsal root of a spinal nerve?
- A. Ventral carries motor, dorsal carries sensory information.
- B. Ventral carries sensory, dorsal carries motor information.
- C. Ventral is larger, dorsal is smaller.
- D. Ventral is located anteriorly, dorsal is posteriorly.
Correct Answer: A
Rationale: The correct answer is A: Ventral carries motor, dorsal carries sensory information. In the spinal nerve, the ventral root carries motor information from the spinal cord to the muscles, while the dorsal root carries sensory information from the peripheral sensory receptors to the spinal cord. Therefore, other choices are incorrect. Choice B is incorrect as it states the opposite roles of ventral and dorsal roots. Choice C is incorrect as the size comparison between ventral and dorsal roots is not related to their functions. Choice D is incorrect as the terms 'anteriorly' and 'posteriorly' are not commonly used to describe the locations of ventral and dorsal roots in relation to each other.