Nokea
Antigenic variation, a common strategy used by some viruses, allows them to:
- A. Produce toxins
- B. Evade the immune system
- C. Survive outside a host
- D. Replicate rapidly
Correct Answer: B
Rationale: Antigenic variation is a strategy used by some viruses to evade the host's immune response. By constantly changing their surface antigens, viruses can avoid recognition and destruction by the immune system. This allows the virus to persist in the host and continue replicating, leading to prolonged infection and potential transmission to other hosts. Antigenic variation does not directly involve the production of toxins, survival outside a host, or rapid replication, making options A, C, and D incorrect in this context.
You may also like to solve these questions
Which of the following nutrients is essential for muscle growth and repair?
- A. Vitamin C
- B. Protein
- C. Carbohydrates
- D. Fat
Correct Answer: B
Rationale: Protein is essential for muscle growth and repair as it provides the necessary building blocks (amino acids) for muscle tissue synthesis and repair. While vitamins and minerals are crucial for overall health, protein has a specific role in muscle development. Carbohydrates supply energy for workouts, and fats are important for general health but are less directly involved in muscle growth and repair compared to protein.
Which type of lens focuses parallel light rays to a single point?
- A. Concave lens
- B. Convex lens
- C. Cylindrical lens
- D. Plano lens
Correct Answer: B
Rationale: A convex lens focuses parallel light rays to a single point by causing them to converge. This lens is thicker in the center than at the edges, which helps in converging the light rays. Convex lenses are commonly used for tasks like magnification and focusing due to their ability to bring distant light rays to a single focal point. Choice A, the concave lens, diverges light rays rather than converging them, making it incorrect. Choice C, the cylindrical lens, is designed to focus light along one axis rather than converging parallel light rays to a single point. Choice D, the plano lens, has no curvatures to bend or focus light rays, so it does not converge parallel light rays.
What is the main component of sweat?
- A. Urea
- B. Glucose
- C. Water
- D. Electrolytes
Correct Answer: C
Rationale: - Sweat is primarily composed of water, making up the majority of its content. Water helps regulate body temperature by evaporating from the skin's surface, which cools the body down.
- While sweat does contain small amounts of other substances like urea, glucose, and electrolytes, water is the main component that is secreted by sweat glands to help regulate body temperature during physical activity or in response to heat.
Which organelle is responsible for packaging and secreting proteins into the extracellular space?
- A. Golgi apparatus
- B. Mitochondria
- C. Ribosomes
- D. Endoplasmic reticulum
Correct Answer: A
Rationale: A) Golgi apparatus: The Golgi apparatus is responsible for modifying, sorting, and packaging proteins into vesicles for secretion outside the cell or for use within the cell. It acts as a distribution and shipping department for the cell, ensuring proteins are properly processed and sent to their correct destinations like the extracellular space. Golgi apparatus is the correct answer because it directly handles the packaging and secretion of proteins.
B) Mitochondria: Mitochondria are known as the powerhouse of the cell and are responsible for generating energy in the form of ATP through cellular respiration. They are not involved in packaging and secreting proteins into the extracellular space.
C) Ribosomes: Ribosomes are responsible for protein synthesis, where they translate mRNA into proteins. They are not involved in packaging and secreting proteins into the extracellular space.
D) Endoplasmic reticulum: The endoplasmic reticulum (ER) plays a role in protein synthesis and folding, but it is the rough ER specifically that is involved in synthesizing proteins that are then transported to the Golgi apparatus for further processing and packaging. The Golgi apparatus is primarily responsible for packaging and secreting proteins, making it the correct answer for this question.
In ecology, what defines a closed system?
- A. Exchanges energy but not matter
- B. Exchanges both energy and matter
- C. Exchanges neither energy nor matter
- D. Recycles nutrients efficiently
Correct Answer: A
Rationale: In ecology, a closed system is one that does not exchange matter with its surroundings but can exchange energy. This means that while energy can enter or leave the system, the amount of matter within the system remains constant. Option A correctly defines a closed system in ecology. Choices B and C are incorrect as a closed system does not exchange matter or energy. Option D is unrelated to the concept of a closed system in ecology.