1.4a Co-ordination NEED TO GO OVER

Question 1

Extracellular Signalling molecules

Answer 1

Multicellular organisms signal between cells using extracellular signalling molecules. Steroid hormones, peptide hormones, and neurotransmitters are examples of extracellular molecules.

Question 2

What are receptor molecules?

Answer 2

Receptor molecules of target cells are proteins with a binding site for a specific signal molecule. Binding changes the conformation of the receptor, which initiates a response within the cell.

Question 3

Specific signals

Answer 3

Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor. Signalling molecules may have different effects on different target cell types due to differences in the intracellular signalling molecules and pathways that are involved.

Question 4

Different Cell types

Answer 4

In a multicellular organism, different cell types may show a tissue-specific response to the same signal.