A spherical bacterium is called a:

Bacterial cell membranes are composed of a phospholipid bilayer in which the hydrophilic (water-attracting) heads face outward toward the aqueous environment both inside and outside the cell, while the hydrophobic (water-repelling) tails are buried in the interior of the membrane, away from water. This arrangement creates a selectively permeable barrier that regulates the movement of substances into and out of the cell. The correct orientation of phospholipids is critical for maintaining membrane integrity, fluidity, and proper function of embedded proteins, transport systems, and signaling molecules.

A. semisynthetic drugs: Semisynthetic drugs are chemically modified natural antibiotics. They may have improved stability, spectrum, or pharmacokinetics compared to their natural counterparts, but the term does not define the range of microbial types they affect.

B. narrow-spectrum drugs: Narrow-spectrum drugs are effective against a limited group of microorganisms, such as only Gram-positive bacteria or a specific genus. They are preferred when the causative agent is known to reduce disruption of normal microbiota and minimize resistance development.

C. broad-spectrum drugs: Broad-spectrum drugs are effective against a wide variety of microorganisms, including both Gram-positive and Gram-negative bacteria, and sometimes other microbial types. They are useful for empirical therapy when the causative agent is unknown but carry a higher risk of promoting resistance and disrupting normal flora.

D. antibiotics: Antibiotics are substances produced by microorganisms that inhibit or kill other microbes. This term describes the source or mechanism rather than the range of effectiveness; some antibiotics can be narrow- or broad-spectrum.

E. synthetic drugs: Synthetic drugs are entirely chemically synthesized rather than derived from natural sources. Like semisynthetic drugs, the term indicates origin, not the spectrum of activity.