Humans cannot digest cellulose due to the absence of the enzyme cellulase, which is necessary to break down cellulose into glucose units. Cellulose is a complex carbohydrate found in the cell wall of plants and is a major component of dietary fiber. Although humans lack the enzyme to digest it, bacteria in the human gut can partially break down cellulose, contributing to the fermentation process that produces short-chain fatty acids beneficial for colon health. However, most of the cellulose passes through the digestive system unchanged, aiding in the digestive process by adding bulk to the stool and helping prevent constipation.

Viruses do not possess a polysaccharide coat as part of their basic structure. Typically, viruses are composed of a protein capsid that encases their genetic material (DNA or RNA). Some viruses also have an outer envelope derived from the host cell membrane. However, there are no known viruses with a polysaccharide layer similar to the capsule found in some bacteria. Polysaccharide capsules are primarily associated with bacteria, where they function as protective barriers and aid in immune system evasion. Although viruses lack this specific feature, they employ other strategies to evade detection and replicate effectively within host organisms.

Yes, positive amino acids are attracted to negative amino acids due to electrostatic interactions. Amino acids can be classified based on the polarity and charge of their side chains. Positively charged amino acids, like lysine and arginine, carry a positive charge under physiological pH, while negatively charged amino acids, such as glutamate and aspartate, carry a negative charge. When these amino acids come into close proximity, the oppositely charged side chains are attracted to each other, forming salt bridges. This type of interaction is a key factor in the folding and stability of proteins, influencing their 3D structure and function. These electrostatic attractions are crucial for protein-protein interactions, enzyme-substrate recognition, and the stabilizing forces of tertiary and quaternary protein structures.