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","B","E"]
Explanation
A. Breast milk contains antibodies, particularly immunoglobulin A (IgA), which help protect infants from infections such as respiratory and gastrointestinal illnesses. This passive immunity is a key advantage of breastfeeding.
B. Breastfeeding reduces the infant’s exposure to potential contaminants, preservatives, or additives that may be present in formula or other foods. Breast milk is naturally sterile when produced and provides optimal nutrition.
C. While breastfeeding is legally protected in many places, public acceptance in American society varies and can still be a barrier for some mothers. Social acceptance is not a biological advantage of breastfeeding.
D. Harmful drugs, alcohol, and certain infections can be passed through breast milk. Mothers must be cautious with medications, substances, or illnesses that can affect the infant.
E. Breastfeeding increases maternal energy expenditure, which can help some mothers return to their pre-pregnancy weight more quickly. It also stimulates uterine contractions, which can aid postpartum recovery.
Correct Answer is D
Explanation
A. This describes behaviors associated with binge-eating disorder, where individuals consume large amounts of food without engaging in compensatory behaviors such as purging or excessive exercise.
B. This describes bulimia nervosa, which involves recurrent binge eating followed by compensatory behaviors like self-induced vomiting, laxative use, or over-exercising to prevent weight gain.
C. Frequent overeating and rapid weight gain are not characteristic of anorexia nervosa. This pattern is more consistent with binge-eating disorder or general obesity-related behaviors.
D. Anorexia nervosa is a potentially fatal eating disorder characterized by self-starvation, extreme restriction of caloric intake, intense fear of gaining weight, and excessive weight loss. Clinical features often include emaciation, bradycardia, hypotension, hypothermia, electrolyte imbalances, amenorrhea in females, and hair or skin changes. Anorexia nervosa carries a high risk of medical complications, including cardiovascular collapse, osteoporosis, and death if untreated.
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