Which part of the cell is composed of two layers of phospholipids?
Cell nucleus
Cell membrane
Endoplasmic reticulum
Cell mitochondria
The Correct Answer is B
A. The cell nucleus contains genetic material (DNA) and is surrounded by a nuclear envelope, which also has a double lipid bilayer. However, the question refers to the general structural component of the cell, and the nucleus is not considered the primary barrier separating the cell from its environment.
B. The cell membrane, also called the plasma membrane, is composed of a phospholipid bilayer. This structure has hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward, creating a semi-permeable barrier that regulates the entry and exit of substances. The cell membrane also contains proteins, cholesterol, and carbohydrates that support signaling, transport, and structural stability.
C. The endoplasmic reticulum (ER) is a membrane-bound organelle involved in protein and lipid synthesis. While it contains lipid membranes, the ER is an internal structure, not the primary boundary of the cell, and its membrane is continuous with the nuclear envelope.
D. Mitochondria are double-membrane organelles responsible for energy production via ATP synthesis. Although they have an inner and outer membrane, the question refers to the cell component composed of a phospholipid bilayer that serves as the main barrier of the cell, which is the plasma membrane.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Fortified grains and cereals are excellent sources of folic acid, the synthetic form of folate (vitamin B9). Adequate folic acid intake before conception and during early pregnancy is crucial for proper neural tube development, which forms the baby’s brain and spinal cord. Consuming folic acid-rich foods or supplements has been shown to significantly reduce the risk of neural tube defects such as spina bifida and anencephaly.
B. While fresh citrus fruits contain some natural folate, the amounts are generally lower than in fortified grains and cereals. Relying solely on citrus fruits may not provide sufficient folic acid to meet the recommended daily intake for pregnant women.
C. Simple carbohydrates, such as sugar and refined starches, provide energy but do not contain significant amounts of folic acid or other essential micronutrients needed to prevent neural tube defects.
D. Linoleic and alpha-linolenic acids are essential fatty acids important for overall health, including brain and eye development, but they do not provide folic acid and are not effective in preventing neural tube defects.
Correct Answer is ["B","D","E"]
Explanation
A. Blood does not produce hormones; endocrine glands such as the thyroid, adrenal glands, and pancreas produce hormones. Blood serves as a transport medium for hormones but is not their source.
B. Blood helps maintain body temperature by distributing heat generated by metabolism throughout the body and by constricting or dilating blood vessels to conserve or release heat as needed.
C. Blood itself does not heal injuries. While it carries platelets and clotting factors essential for clot formation, the actual tissue repair process occurs through cellular and tissue mechanisms, not the blood directly.
D. Blood plays a critical role in regulating the immune system by transporting white blood cells, antibodies, and other immune components to sites of infection or injury, helping defend the body against pathogens.
E. Blood transports essential substances such as nutrients, oxygen, and hormones to tissues and carries waste products like carbon dioxide and urea to organs such as the lungs and kidneys for excretion, supporting overall homeostasis.
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