Q

QuestionAnatomy and Physiology

- Cell membranes are present in only two of the three domains of life. This statement is false because cell membranes are present in all three domains of life: Archaea, Bacteria, and Eukarya. - In water, phospholipids spontaneously arrange into a bilayer. This statement is true. Phospholipids have a hydrophilic head and hydrophobic tails. In water, they arrange in a way that the hydrophilic heads face outward, and the hydrophobic tails face inward, forming a bilayer. - The area within a phospholipid bilayer, near the fatty acid tails, is hydrophilic. This statement is false. The area within a phospholipid bilayer, near the fatty acid tails, is hydrophobic due to the nonpolar nature of the fatty acid tails. - Steroids in cell membranes allow the membrane to be more fluid. This statement is false. Steroids, such as cholesterol, actually help restrict the fluidity of the cell membrane by occupying space between phospholipids. - Phospholipid bilayers surround all eukaryotic cells. This statement is true. In eukaryotic cells, the plasma membrane is a phospholipid bilayer, and so are the membranes of organelles like the nucleus, mitochondria, and endoplasmic reticulum. - Membrane proteins offer structural support to the membrane but have no other function. This statement is false. Membrane proteins have various functions, including transporting molecules, acting as enzymes, and providing recognition sites for other molecules. - Both plant and animal cell membranes are considered fluid mosaics. This statement is true. The fluid mosaic model describes the cell membrane as a fluid structure composed of phospholipids, cholesterol, and proteins that can move laterally in the plane of the membrane.