Nokea
Which statement about white blood cells is true?
- A. B cells are responsible for antibody production.
- B. White blood cells are produced in the bone marrow before entering the bloodstream.
- C. Platelets, a specialized class of blood cells, function to clot blood and stop bleeding.
- D. The majority of white blood cells are active throughout life, providing immunity across all age groups.
Correct Answer: A
Rationale: The correct answer is A: B cells, a type of white blood cell, are responsible for producing antibodies in response to pathogens. Antibodies play a crucial role in identifying and neutralizing foreign substances like bacteria and viruses in the body, aiding in the immune response and protecting against infections. This function is essential for maintaining a healthy immune system. White blood cells, including B cells, are produced in the bone marrow before entering the bloodstream. Platelets, not white blood cells, are a specialized class of blood cells that function to clot blood and stop bleeding. While white blood cells provide immunity, not all of them are active throughout life as some have specific lifespans and functions.
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Which of the following inventions likely had the greatest impact on combating nutrition deficiencies in developing countries?
- A. Food products fortified with dietary vitamins and minerals
- B. Integrated statistical models of fish populations
- C. Advances enabling microscopes to use thicker tissue samples
- D. Refrigerated train cars for transportation of food
Correct Answer: A
Rationale: Food products fortified with dietary vitamins and minerals have had the greatest impact on combating nutrition deficiencies in developing countries. By fortifying food products with essential nutrients such as vitamins and minerals, it becomes easier to address specific deficiencies in populations that may not have access to a diverse range of foods. This innovation has been particularly impactful in addressing common deficiencies like vitamin A, iron, zinc, and folic acid, improving overall health outcomes in populations with limited access to nutrient-rich foods. Choices B, C, and D are incorrect. Integrated statistical models of fish populations, advances in microscopy, and refrigerated train cars, while important in their own right, do not directly address combating nutrition deficiencies in developing countries as effectively as food fortification with essential nutrients.
Which of the following is responsible for carrying electrical impulses in the nervous system?
- A. Platelets
- B. Neurons
- C. Red blood cells
- D. White blood cells
Correct Answer: B
Rationale: Neurons are the correct answer as they are specialized cells in the nervous system that transmit electrical impulses throughout the body. Neurons have structures like axons and dendrites that enable the transmission of electrical signals. Platelets are responsible for blood clotting, red blood cells carry oxygen, and white blood cells are part of the immune system; however, none of these cell types play a role in carrying electrical impulses in the nervous system.
What are chromosomes made of?
- A. DNA and RNA
- B. DNA and protein
- C. Protein and RNA
- D. DNA and lipids
Correct Answer: B
Rationale: Chromosomes are made up of DNA and associated proteins. These proteins help package and organize the DNA within the cell, playing a crucial role in gene regulation and cell division. While RNA is involved in various cellular processes, it is not a primary component of chromosomes. Lipids are not a fundamental component of chromosomes, which primarily consist of DNA and proteins.
Which organ in the human body is responsible for filtering blood and producing urine?
- A. Liver
- B. Kidneys
- C. Pancreas
- D. Heart
Correct Answer: B
Rationale: The correct answer is B: Kidneys. The kidneys are vital organs in the human body responsible for filtering blood to remove waste products and excess substances, producing urine as a result. The liver plays a role in detoxification and metabolism. The pancreas is involved in digestion and blood sugar regulation. The heart pumps blood throughout the body but does not filter blood or produce urine.
What is an electrically charged atom called?
- A. Ion
- B. Isotope
- C. Molecule
- D. Compound
Correct Answer: A
Rationale: An ion is an atom that has gained or lost electrons, resulting in a positive or negative charge, making it electrically charged. This term specifically refers to atoms with a net electrical charge. Isotopes are atoms of the same element with different numbers of neutrons, not electrically charged. Molecules are formed when atoms bond together, but they are not necessarily charged. Compounds are substances composed of different elements bonded together, but they may not be electrically charged.