Cell Signaling

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Questions and Answers

What is the primary purpose of a hormone?

To regulate blood pressure

To create and effect in a cell (correct)

To aid in digestion

To maintain body temperature

How do peptide hormones typically transmit their message?

By affecting the cytoplasm directly

By diffusing through the plasma membrane

By entering the cell nucleus

By binding to a membrane receptor (correct)

What is the solubility characteristic of peptide hormones?

Soluble in both water and lipids

Water soluble (correct)

Insoluble in both water and lipids

Lipid soluble

How do steroids travel through the bloodstream?

Attached to a protein carrier Signup and view all the answers

What allows steroids to enter the plasma and nuclear membranes?

Lipid solubility Signup and view all the answers

What is necessary for a hormone to initiate a response?

Binding to a receptor Signup and view all the answers

How do peptide hormones typically interact with cells?

By using a transmembrane receptor protein Signup and view all the answers

What is the role of peptide hormones as first messengers?

They bind to the receptor on the outside of the cell Signup and view all the answers

What is the term for a conformational change in the receptor that creates change inside the cell?

Second messenger Signup and view all the answers

What initiates the conformational change in ligand-gated ion channels?

Binding of a specific molecule to the extracellular domain Signup and view all the answers

Which type of hormone pathways are faster but last for a shorter amount of time?

Membrane-bound receptors Signup and view all the answers

What is the role of the alpha subunit in G proteins?

It can bind GDP and GTP Signup and view all the answers

What are the structural components of G proteins?

beta and gamma subunits Signup and view all the answers

G proteins can either be _ or _.

Stimulatory, inhibitory Signup and view all the answers

What is the second messenger for most G-Protein receptors?

cAMP Signup and view all the answers

Which type of G-protein receptor stimulates the production of cAMP?

Gs receptor Signup and view all the answers

What is the main function of Gi receptors in G-protein signaling?

Inhibit production of cAMP Signup and view all the answers

What is a key characteristic of G-proteins?

Signal amplification Signup and view all the answers

You notice on a graph of receptor affinity that the curve has shifted to the left and up. What does this mean for the binding ability of the hormone to the receptor?

Quick to bind and a higher affinity Signup and view all the answers

A weak binding ligand which blocks the receptor site for the target hormone is pushed out of the way and target hormone binds. This is an example of what?

Competitive inhibition Signup and view all the answers

What is a permissive hormone?

A hormone that needs the permission from another hormone in order to exert its effects effectively Signup and view all the answers

How long do the effects of amine hormones typically last?

Minutes to hours Signup and view all the answers

How can we differentiate between Type 1 from Type 2 diabetes or assess the efficacy of a treatment?

By measuring the levels of C-peptide in the blood Signup and view all the answers

What does up-regulation refer to in the context of hormones?

An increase in the number of receptors for a hormone Signup and view all the answers

Study Notes

Hormones and Their Functions

The primary purpose of a hormone is to act as a chemical messenger that regulates physiological processes in the body.
Peptide hormones typically transmit their message by binding to specific receptors on the cell surface, triggering a cascade of intracellular signaling events.
Peptide hormones are generally water-soluble, allowing them to circulate freely in the bloodstream.

Steroid Hormones

Steroid hormones travel through the bloodstream bound to carrier proteins due to their lipophilic nature.
They can easily enter plasma and nuclear membranes because they are lipid-soluble and can diffuse through the lipid bilayer.
For a hormone to initiate a response, it must bind to a specific receptor that activates intracellular mechanisms.

Interaction of Peptide Hormones

Peptide hormones interact with cells by binding to surface receptors, leading to changes in cellular activity.
As first messengers, peptide hormones initiate the signal transduction process that communicates the message inside the cell.
A conformational change in the receptor that leads to a cellular response is referred to as a signal transduction event.

G-Protein Coupled Receptors

The conformational change in ligand-gated ion channels is initiated by the binding of a specific ligand to the receptor.
Hormone pathways involving peptide hormones are typically faster but have shorter-lasting effects compared to steroid hormone pathways.
The alpha subunit in G proteins is responsible for activating or inhibiting downstream signaling pathways.
G proteins consist of three structural components: alpha, beta, and gamma subunits.
G proteins can either be stimulatory or inhibitory.

Second Messengers and Receptor Mechanisms

The second messenger for most G-protein receptors is cyclic adenosine monophosphate (cAMP).
G-protein receptors that stimulate the production of cAMP are known as Gs receptors.
The main function of Gi receptors is to inhibit the production of cAMP, counteracting the effects of Gs activity.
A key characteristic of G-proteins is their ability to switch between active and inactive states, facilitating signal relay.

Receptor Affinity and Interaction

A leftward and upward shift in a receptor affinity graph indicates an increased binding ability of the hormone to its receptor.
When a weak binding ligand is displaced from a receptor site, allowing the target hormone to bind, this exemplifies competitive inhibition.

Hormonal Effects and Regulation

A permissive hormone is one that enhances or enables the action of another hormone, often by increasing receptor availability.
The effects of amine hormones generally last longer than those of peptide hormones but shorter than steroid hormones.
Differentiating Type 1 from Type 2 diabetes or assessing treatment efficacy typically involves monitoring blood glucose levels and insulin responses.
Up-regulation in the context of hormones refers to an increase in the number or sensitivity of hormone receptors, enhancing cellular responsiveness to the hormone.

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