Question

remaining time: 13 minutes, 59 seconds. question completion status: biological membranes are composed of a. phospholipids and proteins. b. monosaccharides. c. fatty acids. d. nucleotides and enzymes. question 2 in a biological membrane, the phospholipids are arranged in a __, with the __. a. single layer; fatty acids facing the interior of the cell b. bilayer; fatty acid tails pointing toward each other c. single layer; fatty acids facing outward d. bilayer; fatty acids facing outward question 3 a selectively permeable membrane ensures that a. a cell can maintain its ion concentrations by diffusion. b. fluids can be obtained rapidly. c. essential macromolecules cannot leave the cell by diffusion. d. macromolecules can be obtained through active transport.

Explanation:

1. Biological membranes are primarily made of phospholipids and proteins. Phospholipids form the structural framework and proteins have various functions like transport and signaling.
2. Phospholipids in a biological membrane arrange in a bilayer with their hydrophobic fatty - acid tails pointing toward each other to avoid water.
3. A selectively permeable membrane allows some substances to pass through while restricting others. It ensures essential macromolecules cannot leave the cell by diffusion to maintain cell integrity.

Answer:

1. A. phospholipids and proteins.
2. B. bilayer; fatty acid tails pointing toward each other
3. C. essential macromolecules cannot leave the cell by diffusion.