Which of the following properties prevents the ligands of...

Which of the following properties prevents the ligands of cell-surface receptors from entering the cell? a. The molecules bind to the extracellular domain. b. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane. c. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells. d. The ligands are able to penetrate the membrane, directly influencing gene expression upon receptor binding.

Which of the following properties prevents the ligands of cell-surface receptors from entering the cell?
a. The molecules bind to the extracellular domain.
b. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.
c. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells.
d. The ligands are able to penetrate the membrane, directly influencing gene expression upon receptor binding.

Key Concepts

Hydrophilicity vs. Hydrophobicity

Molecular polarity determines a molecule's affinity for water. Hydrophilic (water-loving) molecules are polar and do not easily partition into the hydrophobic (water-repelling) interior of the plasma membrane, limiting their ability to diffuse through it.

Selective Membrane Permeability

Selective permeability refers to the ability of the plasma membrane to allow certain molecules to pass while restricting others. This property is largely determined by the lipid composition of the membrane, enabling the passage of small, non-polar, hydrophobic molecules while keeping larger or hydrophilic molecules out without specialized transport mechanisms.

Plasma Membrane Structure

The plasma membrane is a lipid bilayer embedded with proteins, where the interior is composed of hydrophobic fatty acid chains. This structure helps maintain distinct internal and external environments by selectively controlling which substances can cross the membrane.

Transcript

00:01 Okay, in order to solve this question, let's talk about the two types of receptors based on the location of them.

00:08 Okay, if we have this cell, okay, we can find receptors here on the cell's surface and also here in the intracellular part of the cell.

00:21 Okay.

00:22 And why not all the receptors are expressed here? well, it is because of the characteristics or the properties, the properties of ligands.

00:30 Ligands can be, ligands are particularly those molecules that are going to bind receptors and they are going to cause a biological response.

00:38 Okay, they can be toxins, for example, they can be hormones, they can be neurotransmitters, they can view drugs or others.

00:47 Okay, but they are going to bind receptors.

00:49 And so we have two different types of molecules here.

00:53 Or well, practically, this cell membrane first, remember that this cell membrane is made of phospholipids mainly.

01:01 So it is going to have a lipid core.

01:05 So the substances that are going to be able to move passively without the requirement of proteins, transporters, or other things are going to be substances that are lipid soluble, also substances that are small, and substances that are poorly charged.

01:30 So if a ligand is lipid soluble or if it is small or if it is poorly charged, they are going to be able to move directly in the cell memory without the use of transporters.

01:45 So if a ligand feels or has these characteristics, they are going to move directly and then they are not going to need or require a cell receptor here because they can diffuse the cell memory normally.

01:59 So the receptor for this type of ligands or the ligands with these characteristics are going to be found in the intracellular, the receptor for them.

02:11 And what if the ligand is water soluble? it means it is not lipid soluble.

02:19 Or if it is very big, like glucose, or if it is heavily charged.

02:29 If a ligand feels or has this characteristic or properties, then it is, you know, it is very big, like glucose, or if it is heavily charged.

02:34 They are not going to be able to cross the cell membrane passively, right? they are going to be, they are not going to be able to cross the cell membrane.

02:43 So it has sense if i say that the receptor for these ligands are going to be found here on the cell surface because as they cannot diffuse, they need to, at the end of the day, the ligand is a message, okay? so the cell needs to receive the message.

02:57 So if the ligand cannot get inside the cell directly, then in some way the cell needs to receive the message...

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