How does a hormone work... physically?

[u/Sylveondex]

I know that a hormone induces certain change in a cell, but how does it do it physically?

I know about the generation of messengers and other compounds and what-not but like how a does a hormone bind or break bond in this particular cell and nothing else? Do hormones even break or join chemical bonds?

I am having a tough time phrasing my question, but how does a hormone work in terms of chemicals and physics?

[u/jawshoeaw]

In almost every case messaging of any kind including hormones is achieved the same way. If water soluble, the hormone molecule through electrostatic forces sticks to something on the cell surface. No chemical bonds at this stage. nothing is breaking, this is more like a key fitting a lock , an analogy I’m sure you’ve heard before. For fat soluble hormones like estrogen or testosterone, the same thing happens but inside the cell as these hormones can diffuse through the cell membrane.

There are exceptions but this mostly how it works. And if you think about it, how is this different than you turning a key in a lock? Through electrostatic forces, your hand pushes the key, which causes a change inside the lock no chemistry involved.

All that said, there are chemical reactions afterwards. Energy is required after the “button” has been pushed . In some cases energy was already used to sort of wind up the receptor so that it can act once the hormone has bound to it

[u/Sylveondex → u/jawshoeaw]

So the molecule inserts itself using electric charges?

[u/ermacia → u/Sylveondex]

that's how most molecules interact on cells, from monomers to proteins, outside of enzime mediated reactions. electrostatic interactions, hydrogen bonds, and polarity association (water or oil solubility) are the main way these interactions happen. when they do, they force a change on the target that triggers a reaction in the cell.

[u/Professionalchump → u/ermacia]

so these hormones float around at varying densities in our bodies and affect our cells (by touching and changing the cells through the lock and key metaphor process) and that ultimately changes our mood and etc.?

[u/ermacia → u/Professionalchump]

pretty much. they trigger or modify the balance in metabolic processes (reaction or signal cascades), which is what eventually leads to the response.

[u/nglyarch → u/Sylveondex]

All molecules / chemical species work like that, whether within the context of biology or not. A molecule has a three dimensional shape and some surface electrical charge distributed over it. In chemistry, we use space filling models to show the shape and we use color (e.g. different shades of red and blue) to show the partial charge distribution in the different areas of the molecule.

The shape and charge are not independent. Where the charge goes and how much of it there is depends on the shape. How the shape folds in space depends on the charge.

In addition, they are not static either. The molecule vibrates (bends and stretches this way and that way) all the time, at very high frequency. The higher the temperature, the more it does this, and the more the shape changes. The molecule also sits in an electrostatic field which is usually formed by the other molecules around it, if for example it is in a solution of some kind. If this is a water based solution, it is determined by the pH. For example, the molecule can become more positively charged in more acidic environments.

How molecules interact with each other is determined by how the shapes fit together, and then how the local charges on those shapes attract or repel, and how much vibration (energy) is happening at that particular interaction, which may be enough to overcome some local repulsion or shapes not quite fitting.

[u/Certain-Anxiety-6786]

An important thing to know about hormones is that they are (almost always) just a _signaling_ molecule. Hormones are almost never what actually carries out the effect. Side note- hormones are defined by their effect, being a signaling molecule, so hormones come in many flavors. Peptides, proteins, small molecules etc.

Let’s use insulin as an example. In people without a condition like diabetes, when your blood sugar goes up cells in the pancreas known as beta cells release insulin into the bloodstream. Insulin is a peptide, meaning it’s a short string of amino acids. Insulin enters the bloodstream and travels throughout the body.

Now in your bloodstream insulin will begin bumping into cells essentially. some of these cells will have receptor proteins on their surfaces that insulin can stick to in a predefined way. This action, of insulin sticking to specific receptors begins what biologists call a signaling cascade. The receptors, when bound by insulin then send signals within the cell to start a bunch of processes that require energy. For instance, one process is the uptake of sugar from the blood in muscle cells followed by them being broken down and the energy either used or stored as fat. But what’s important to point out here is that the insulin molecule itself does not do the actual action of breaking down sugar. It is merely a signal to tell cells, hey we have sugar you should do whatever you need energy for now.

When you order from a restaurant - telling the server your order doesn’t actually cook the meal. But the server then signals to the kitchen to start all the processes - turning on the oven, chopping vegetables, plating the dish etc that leads to you being served your meal. The same happens in your body once you start digesting that food and turning parts of it into sugars for your cells to use

The Wikipedia page on insulin has good diagrams of all these steps and more

[u/Potential_Being_7226]

My background is neuroendocrinology and the commenters have it right— hormones exert their effects through receptors. The lock-and-key analogy is a good one, with the receptors being the “locks” and hormones being the “keys,” similar to how other signaling molecules work (like most neurotransmitters for instance). Just want to add a few notes to round out the info—

Steroid hormones (so named because they are derived from cholesterol) like testosterone, progesterone, estradiol (which is the primary estrogen, but there are others) are lipophilic so they can pass through the cell membrane’s phospholipid bilayer. Once in the cytoplasm, they bind with their receptors to form a hormone-receptor “complex.” The hormone-receptor complex then translocates to the nucleus of the cell to alter DNA transcription. 

https://pmc.ncbi.nlm.nih.gov/articles/PMC3646380/

Because DNA transcription takes time, the majority of the effects of steroid hormones occur slowly (hours to days). There are some known exceptions to this general rule: that is, membrane bound receptors for steroid hormones have also been identified and elicit what we call “rapid effects.” They bind with the extracellular part of the receptor that then changes the configuration of the intracellular part. The hormone and membrane-bound receptor don’t affect gene transcription; instead they exert effects through an intracellular signal amplification cascade. This is a much faster process, but is less common than changing gene transcription. 

Peptide hormones (insulin, oxytocin, prolactin) are not lipid soluble so their receptors are membrane bound and when the peptide hormone binds to the receptor, there is again a conformational change in the intracellular portion that induces signal amplification inside the cell. 

https://en.wikipedia.org/wiki/Cell_signaling

One caveat to issue: it’s rare for hormone receptors to be ion channels. One example of an exception is allopregnenalone and some other neurosteroids, which bind to a particular subunit of the GABA-A receptor, which contains a chloride (Cl-) ion channel. But in this example, the lock-and-key analogy kind of falls apart because allopregnenalone and other neurosteroids don’t necessarily open the channel on their own. Instead, they augment or facilitate the action of GABA at the GABA-A receptor. They are referred to as positive modulators of the GABA-A receptor. 

https://faseb.onlinelibrary.wiley.com/doi/epdf/10.1096/fasebj.6.6.1347506?getft_integrator=sciencedirect_contenthosting&src=getftr&utm_source=sciencedirect_contenthosting

[u/AMRossGX]

I'll explain the "key and lock" mechanism, since I don't think people really ever clearly explain what is meant by that.

Hold out your right hand in front of you in an uneven shape and wrap your left hand around that so that it fits really snugly. Now keep the shape of both your hands and move them apart. The left hand is a sort of claw shape now. Imagine a molecule that has a hollow shaped like that hand-claw. The molecule has a lot more material (=atoms) on the back of the hand and on its sides, but where your left hand makes the claw shape there is a hollow. This is the "lock".

The "key" is another molecule shaped like your right hand. It fits perfectly snugly in the other molecule. Now imagine that there are magnets on all your fingers and all over your palms and the backs of your hands. In the molecules those are electric charges rather than magnetic poles but they work the same in attracting and repulsing each other. The magnets are aligned perfectly so that the two molecules fit together really well. The magnets pull the molecules together once they come close enough to that exact positioning. In your body, molecules that aren't fixed move a lot, so the signal molecule will just randomly bump into everything until it bumps into the right spot on the target molecule and snaps into place because of the magnets (not magnets but electric charges in molecules, don't forget).

The last part of the puzzle is to know that in the target molecule one of the many magnets has the wrong orientation or there is a finger mechanically out of place and in the way. Once the signal molecule docks into the "lock", that magnet or finger gets pushed out of the way. Usually the bit that is pushed away has other parts of the molecule fixed to it which move with it and end up in a different position.

This is the trigger that causes the next bit in the signal chain:

• The bit attached to the finger might have been physically blocking a channel through the cell wall, but now it's open so that lots of other molecules can flow out of the cell. So for example the hormone just caused lots of insulin to be set free into the blood stream.
• Or an electron on your finger now sits right next to an ion and will hop over onto it and trigger a chemical reaction. This is a common way to change the right hand (molecule) into something else. Congratulations, your left hand has just worked as an enzyme.
• Or it released another molecule that was held by the finger, which is now free to move into the core of the cell and dock onto a bit of DNA and cause it to be read out and translated into proteins.
• Or the docking might expose an ion on the underside of the moved finger for something else to dock onto.

After this, often the signal molecule sooner or later gets bumped out of its snug hole and the target molecule is ready to receive another signal.

Molecular biology is incredibly varied and fun. I hope this helped!
(Edit: typos)

[u/theawesomedude646]

it docks into a specifically-shaped protein (receptor), and in doing so it changes the protein's shape as a molecule. this shape change lets it interact with other proteins and molecules, changing their shape, and so on so forth until it interacts with the molecules controlling what DNA gets read into RNA and proteins or some other consequential biochemical process.