Question

True or false and why?: All receptors change their shape when their ligand binds to them

Answer 1

False.

Receptors are protein molecules. They are seen on the surface of target cell or inside the target cell. It recieves chemical signals.

A ligand is a molecule which forms a complex with biomolecule.It is considered to be signaling molecules. Receptors and Ligands exist in several varieties; and, a specific ligand will be having a specific receptor which binds only to that ligand.

When a ligand binds to its specific receptor, it changes its shape or activity, thus allow to transmit a signal or it directly produces a change inside the cell

There are several types of receptors

INTERNAL RECEPTORS

Intracellular receptors seen in the cytoplasm.

Respond to hydrophobic ligand molecules which can cross the plasma membrane.

When ligand binds to receptor there will be a change in shape which exposes DNA binding site on the receptor protein.

ligand-receptor complex goes into nuceus and produce mRNA from specific genes

CELL-SURFACE RECEPTORS
They are transmembrane receptors

Attached to plasma membrane of the cell

Bind to external ligand molecules and perform signal transduction(extracellular signal converted to intracellular signal)

There are 3 types of cell surface receptors,They are

1.Ion channel-linked receptors
2.G-protein-linked receptors
3.Enzyme-linked receptors

Ion channel-linked receptors when bind to ligand it will open a channel. Specific ions can pass through these channel. When ligand binds to the protein, there will be a conformational change in the protein structure.

G-protein-linked receptors when bind to the ligand,it activates G protein which is a membrane protein. This G protein binds to the receptor & changes its shape and becomes active.

Enzyme-linked receptors have intracellular domains associated with the enzyme. When a ligand binds to extracellular domain of these type of receptors, a signal is tansferred through the membrane and it will activate the enzyme.It will lead to desired response in the cell.