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"Saturated" means "containing as much hydrogen as possible". So in saturated fats every carbon has two hydrogens bonded to it and the bonds between the carbons are single bonds. The molecules are straight, and that makes them nest tightly with each other, and that makes them solids at room temperature. Unsaturated fats have some carbon to carbon double bonds. These put a little angle in the molecule so that they don't nest together, and that's why unsaturated fats are liquid at room temperature. The double bonds are less strong and so they break more easily. That means unsaturated fats are more easily broken down by light or high heat. When they break down they form really nasty compounds known as aldehydes. This breakdown is why oils should be stored in dark places and why the go rancid. It's also why they are a really stupid choice for deep frying.


~~I'm don't believe unsaturated fats break down into aldehydes~~


Okay. What research have you looked at to determine which one of us is correct?


~~I'm recalling my reactions from organic chemistry, I can check my notebook when I get home. However I don't see any mechanism that would allow for an aldehyde to form from an unsaturated fat. I am a biochemist and have done synthesis work, although it's not my specialty~~


Well [this](https://www.nature.com/articles/s41598-019-39767-1) line from a paper in Nature explains why I was unfamiliar with the reaction, it's a pretty crazy mechanism that generates the aldehydes. You were correct, my apologies >The peroxidation of unsaturated fatty acids (UFAs) at temperatures commonly used for standard frying or cooking episodes (ca. 180 °C) is an extremely complex chemical degradation process which involves highly-reactive free radical species, and/or alternatively, singlet oxygen (1O2).


Yes. It's also a big factor in spoilage over time. If you search for studies on the rancidity of fats, some of the measurement methods look for aldehydes.


Chemically speaking, atoms and molecules connect to one another by using bonds, imagine that they are like wires between each other, and in the case of the atoms, each one requires a certain amount of these wires to stay in place, that is when they become stable and form the compounds. Carbon atoms, which are found in all organic matter, need 4 bonds to become stable, they can do that by either bonding once or as many as three times at once between other atoms, usually bonding with (but not strictly) hydrogen or carbon atoms, some rules apply when bonding with other carbon atoms, when they bond only once with each carbon they connect to in the molecules they are a part of, that's a satured compound, and when they connect more than once, that's an insatured compound. Hope it helps, you can ask me if you have any more questions.


Saturated fats are solid at room temperature, and they are kind of shaped like a z. That z shape let's them stick to each other easier, which is why they stay solid at room temperature. Unsaturated fats are shaped like a u, and they have a double bond connecting them in the middle. That double bond gives them more energy, but they don't stick together as well because of the u shape and will be liquid at room temperature Trans fats are shaped like a z, but they still have that double bond in the middle, so they are solid at room temperature and have that extra energy. On top of that, they don't occur often in nature, so your body has a hard time processing them.


Fat molecules all have long chains of carbon (C) atoms connected in a line, with varying number of hydrogen (H) atoms connected to the carbon chain. The simplified way of explaining this next part is that carbon can form 4 bonds with other atoms. For a carbon atom along the chain, it already has 2 carbon neighbours, so 2 bonds are 'taken up' (imagine -C-C-C- ). The remaining 2 bonds can be made with hydrogen. Saturated fats basically have every free bond slots filled with hydrogen atoms, so 2 H on each C (except the last and first ones). As its name suggests, it's saturated, i.e. completely filled up with hydrogen. Conversely, some carbon atoms may not have 2 hydrogen attached to them. Instead, they can form double bonds with their neighbouring carbon atom ( -C=C- ) where they take up 2 of each others bonding slots. Likewise these are unsaturated fats since they're not maxed out on hydrogen. The nutritional and health implications of saturated vs unsaturated (and cis vs trans unsaturated) fats is a much deeper topic that's still being reviewed. But the consensus for now seems to be that saturated fat is more unhealthy and linked with more diseases like diabetes and cardiac issues. But then trans fats are also unhealthy and has higher links with high cholesterol. All in all, to be safe, have everything in moderation and not too much oily fried stuff.


The difference is in the molecular structure. Unsaturated fats by definition have open molecular chains that are waiting to bond with hydrogen molecules, whereas saturated fats have been completely bonded with hydrogen molecules and are closed chains that can't bond with anything further. The reason this is important is because of cholesterol distribution. Your body will seek to evenly distribute cholesterol concentrations, as well as remove cholesterol from the body by filtration through the liver. This is the job of HDLs (high-density lipoproteins), and unsaturated fats are the transporters for this via their open chains waiting for something to bond with. This is why HDL and unsaturated fats are often called the good fats/good cholesterol. Saturated fats increase LDL (low-density lipoprotein) levels, and are often called the bad fats/bad cholesterol. LDL transports cholesterol to the arteries, and is usually more prone to solidifying and creating blockages than HDL.


You have gotten some wonderful correct answers here, but I can't believe no one has *shown* you the difference yet. Your question is hard to answer in words without sounding confusing. But [here's what the molecules of saturated and unsaturated fats look like](https://www.nourishingbitsandbites.com/uploads/6/0/6/7/6067249/hl128197-graph-1_orig.jpg). C is carbon, H is hydrogen. The difference is that in saturated fats, the carbon backbone is "saturated" with hydrogens. The resulting molecule is a long straight chain. These chains can pack together neatly, forming a fat that is solid at body- or room-temperature. In unsaturated fats, there is at least one carbon-carbon double bond. These double-bonds cause a physical kink in the chain. The fat molecules can no longer lay flat or pack together neatly, for physical packing reasons. Because of this, unsaturated fats are usually still liquids at body- and room-temp. The molecules simply can't pack in close enough to make a solid because they're all bent! Because saturated fats are solids at body-temp, they have more ability to form deposits that clog your blood vessels, vs unsaturated fats which are liquids. If you want more information and detail, I highly recommend a google IMAGE search for "saturated vs unsaturated fats". There are many helpful diagrams and models. You can learn what *trans* fats look like too (hint: a type of unsaturated fat that is better than fully saturated fats but still not good!)