Question

Match the hormone to the mechanism of signaling.

neurotransmitter Acetylcholine

      [ Choose ]            binds to a receptor tyrosine kinase, causing dimerization and activation            binds to a histone acetylase to activate transcription            binds a nuclear receptor which is a DNA binding protein            opens a ligand-gated ion channel in skeletal muscle      

steroid like progesterone

      [ Choose ]            binds to a receptor tyrosine kinase, causing dimerization and activation            binds to a histone acetylase to activate transcription            binds a nuclear receptor which is a DNA binding protein            opens a ligand-gated ion channel in skeletal muscle      

thyroid hormone

      [ Choose ]            binds to a receptor tyrosine kinase, causing dimerization and activation            binds to a histone acetylase to activate transcription            binds a nuclear receptor which is a DNA binding protein            opens a ligand-gated ion channel in skeletal muscle      

growth hormone

      [ Choose ]            binds to a receptor tyrosine kinase, causing dimerization and activation            binds to a histone acetylase to activate transcription            binds a nuclear receptor which is a DNA binding protein            opens a ligand-gated ion channel in skeletal muscle      

Answers can only be used once.

Answer 1

• Membrane receptor proteins facilitates the binding of ligand molecules, in form of hormones, neurotransmitters, etc., to bind to them and trigger specific effector activities in the cells.
• These ligands, on binding to receptors, (sometimes through second messengers) initiate a signal transduction pathway.

1.Neurotransmitter Acetylcholine-opens a ligand-gated ion channel in skeletal muscle      

• Synaptic vesicles of pre-synaptic neuron store neurotransmitters, on activation they fuse to membrane and release neurotransmitter by exocytosis.
• The released neuron binds to neuron receptor on post-synaptic membrane or effector cell membrane.
• The skeletal muscles have motor end plate with receptors for binding of neurotransmitters. The activation open the ligand-gated channels causing muscular stimulation.

2. Steroid like progesterone- binds a nuclear receptor which is a DNA binding protein.

• · Steroid hormones are hydrophobic and soluble in lipid.
• On crossing the membrane, steroid hormones bind to specific intracellular receptors called the nuclear receptors.
• The receptor has three basic components: Activation function domain, DNA-binding domain, Ligand binding domain.

3. Thyroid hormone-binds to a histone acetylase to activate transcription

• Thyroid hormines regulates metabolic processes in cell.
• Thus, they needs to activate and express several proteins for metabolism.
• They bind to receptors modulating histones and gene regulation.

4. Growth hormone- binds to a receptor tyrosine kinase, causing dimerization and activation

• The receptors for growth hormone are cytosine kinase receptors.
• On binding they activate a tyrosine kinase receptor or Jak2 (Janus Kinase 2) receptor.