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Chapter 13: Problem 2

What are the three major classes of membrane receptors?

Short Answer

Expert verified
The three major classes are Ion Channel-Linked Receptors, G-Protein-Coupled Receptors, and Enzyme-Linked Receptors.

Step by step solution

01

Understanding Membrane Receptors

Membrane receptors are proteins that are located within or on the surface of a cell membrane. Their primary function is to facilitate communication between the cell and its external environment, often through the binding of signaling molecules.
02

Identifying Major Classes

The three major classes of membrane receptors can largely be divided based upon their structure and function. These are Ion Channel-Linked Receptors, G-Protein-Coupled Receptors, and Enzyme-Linked Receptors.
03

Ion Channel-Linked Receptors

These receptors form channels through the cell membrane that can open or close in response to a chemical signal. They are typically involved in the transmission of nerve impulses by allowing specific ions to pass through the membrane.
04

G-Protein-Coupled Receptors (GPCRs)

GPCRs are a large family of receptors that interact with G-proteins in the cell. Upon ligand binding, these receptors activate a cascade of intracellular signaling pathways via the interaction with G-proteins.
05

Enzyme-Linked Receptors

These receptors, upon binding with a ligand, often trigger enzyme activity within the cell. A common example is receptor tyrosine kinases, which phosphorylate tyrosine residues on certain proteins leading to a signaling cascade.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Ion Channel-Linked Receptors
Ion channel-linked receptors are fascinating proteins that form gateways in the cell membrane. These gateways can open or close in response to specific signals, often coming from neurotransmitters. Their primary role is crucial in the transmission of nerve impulses. Imagine them as doorways for ions like sodium, potassium, or calcium to enter or exit a cell.

- When a signaling molecule binds to these receptors, they change shape, allowing ions to flow through the membrane.
- This flow of ions generates an electrical signal that can be used in processes like muscle contraction or neuron communication.

Ion channel-linked receptors are paramount in brain function and are an essential component in how nerves communicate with each other.
G-Protein-Coupled Receptors (GPCRs)
G-protein-coupled receptors, or GPCRs, are some of the most diverse and versatile membrane receptors in our body. They play a key role in transmitting signals from various stimuli such as light, hormones, and neurotransmitters.

- Upon binding to their specific ligand, GPCRs undergo a change that activates an associated G-protein inside the cell.
- This G-protein can then trigger multiple downstream signaling pathways, leading to a variety of cellular responses.

GPCRs are involved in many physiological processes, including vision, taste, and mood regulation. They're also a major target for a large percentage of modern pharmaceuticals, highlighting their importance in medicine.
Enzyme-Linked Receptors
Enzyme-linked receptors are unique because they combine the actions of a receptor and an enzyme. When a signaling molecule binds to this type of receptor, it activates an enzymatic function within the cell. A well-known example is receptor tyrosine kinases.

- These receptors often phosphorylate themselves or other proteins when activated.
- This phosphorylation initiates a cascade of signaling events within the cell, affecting functions like cell growth, division, and metabolism.

Enzyme-linked receptors are critical in processes such as cell communication and immune response. They are also significant in cancer research, as malfunctions in these receptors can lead to uncontrolled cell growth.

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Most popular questions from this chapter

At steady state, intracellular levels of \(\mathrm{Ca}^{2+}\) must be kept low to prevent the precipitation of carboxylated and phosphorylated compounds, which form poorly soluble salts with \(\mathrm{Ca}^{2+} .\) The cytoplasmic level of \(\mathrm{Ca}^{2+}\) is approximately \(100 \mathrm{nM},\) several orders of magnitude lower than the concentration in the extracellular medium. How might the cell maintain such low levels of intracellular \(\mathrm{Ca}^{2+}\) ? How does the cell take advantage of the difference in intracellular and extracellular \(\mathrm{Ca}^{2+}\) concentrations?

What are some of the structural features common to all membrane-bound receptors?

A scientist wishes to determine the number of receptors specific for a ligand \(\mathrm{X},\) which he has in both radioactive and nonradioactive form. In one experiment, he adds increasing amounts of the radioactive \(\mathrm{X}\) and measures how much of it is bound to the cells. The result is shown as total activity in the adjoining graph. Next, he performs the same experiment, except that he includes a several hundredfold excess of nonradioactive \(\mathrm{X}\). This result is shown as nonspecific binding. The difference between the two curves is the specific binding. (GRAPH CANNOT COPY) (a) Why is the total binding not an accurate representation of the number of receptors on the cell surface? (b) What is the purpose of performing the experiment in the presence of excess nonradioactive ligand? (c) What is the significance of the fact that specific binding attains a plateau?

Suppose that each \(\beta\) -adrenergic receptor bound to epinephrine converts 100 molecules of \(G_{\alpha s}\) into their GTP-bound forms and that each molecule of activated adenylate cyclase produces 1000 molecules of \(\mathrm{cAMP}\) per second. With the assumption of a full response, how many molecules of cAMP will be produced in \(1 \mathrm{s}\) after the formation of a single complex between epinephrine and the \(\beta\) -adrenergic receptor?

You prepare a cell line that overexpresses a mutant form of EGFR in which the entire intracellular region of the receptor has been deleted. Predict the effect of overexpression of this construct on EGF signaling in this cell line.
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