**Core Concept**
G-proteins, or guanine nucleotide-binding proteins, are a family of proteins that play a central role in signal transduction pathways in cells. They act as molecular switches, facilitating the transmission of signals from the cell surface to the interior of the cell, influencing various cellular processes such as metabolism, gene expression, and cell growth.

**Why the Correct Answer is Right**
G-proteins act as molecular switches by binding to guanosine triphosphate (GTP) or guanosine diphosphate (GDP), changing their conformation and activating or inhibiting downstream effectors. This process is mediated by the interaction between the G-protein and the receptor it is associated with, such as G-protein-coupled receptors (GPCRs). The activated G-protein then stimulates or inhibits various enzymes, such as adenylyl cyclase or phospholipase C, leading to the production of secondary messengers like cAMP or inositol trisphosphate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incomplete, but assuming it's a blank space, it's an incorrect answer.
**Option B:** This option might be a distractor, but without its text, it's hard to determine why it's incorrect.
**Option C:** This option might be a distractor, but without its text, it's hard to determine why it's incorrect.

**Clinical Pearl / High-Yield Fact**
G-proteins are involved in numerous diseases, including various types of cancer, where their abnormal function can lead to uncontrolled cell growth. Understanding the role of G-proteins in signal transduction is crucial for developing targeted therapies for these diseases.

**Correct Answer:** C.