Basics of cell communication — Select the correct statement about how cells communicate in different organisms

Introduction:
Intercellular communication relies on chemical messengers that travel between cells to coordinate growth, defense, and homeostasis. This question asks you to identify the correct general statement about communication modes in biology.

Given Data / Assumptions:

• Multicellular organisms require long range and local signaling.
• Unicellular organisms also communicate, but they do not use antibodies in typical signaling.
• Signals can be secreted into extracellular spaces or blood.

Concept / Approach:
In multicellular organisms, extracellular signaling molecules (hormones, neurotransmitters, cytokines, growth factors) mediate endocrine, paracrine, and synaptic communication. Intracellular molecules transmit signals within a cell, not between cells. Antigens and antibodies are components of adaptive immunity, not the basic language of unicellular communication.

Step-by-Step Solution:

Verification / Alternative check:
Examples abound: insulin (endocrine), acetylcholine (synaptic), interleukins (paracrine/autocrine). In bacteria, quorum sensing uses extracellular autoinducers rather than antibodies.

Why Other Options Are Wrong:

• Unicellular communication via antigen/antibody: incorrect; antibodies are produced by vertebrate B cells.
• Intracellular only in multicellular organisms: ignores intercellular hormones and neurotransmitters.
• Intracellular antigen/antibody in unicellular organisms: not a recognized mechanism.
• No chemical communication: contradicted by fundamental physiology and microbiology.

Common Pitfalls:
Confusing intracellular signaling (within a cell) with intercellular signaling (between cells). The question targets intercellular mechanisms.

Final Answer:
Cell communicate with one another in multicellular organisms using extracellular signaling molecules or hormones.