High school biology
- Elements and atoms
- Introduction to carbohydrates
- Introduction to proteins and amino acids
- Introduction to lipids
- Introduction to nucleic acids and nucleotides
- Introduction to vitamins and minerals
- Biological macromolecules review
- Biological macromolecules
Introduction to lipids
Introduction to lipids like fats and phospholipids.
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- This is sort of a dark question but... If fats are hydrophobic, is that why 1. our fingers prune in water and 2. dead bodies decompose faster in water?(25 votes)
- Kind of... Your fingers prune up because the cells in your fingers have absorbed too much water. What he means with "Hydrophobic" is that water is repelled away from the Lipid Tails which allows certain particles and substances to pass through the Lipid Bilayer.(17 votes)
- does sal really have a six pack?(17 votes)
- big mystery my friend.(8 votes)
- When describing the difference between micro and macro molecules, it was explained that macro molecules are defined by the number of atoms they are made of. Is there any particular threshold after which a molecule has enough atoms to be considered macro, or is it more of a general term in the same way most people describe things as big or small?(7 votes)
- It is really easy -
Most macromolecules are polymers, which are long chains of subunits called monomers. These subunits are often very similar to each other, and for all the diversity of polymers (and living things in general), there are only about 40 - 50 common monomers.
It is not defined size per se, but the fact that they are polymers.
To define polymers, you first have to define monomers.
So, once you have a monomer unit, you can easily define polymers - macromolecules.
- I don't understand this saturated/unsaturated fats thing. Sal is repeating the same thing
"If the carbons are bonded to as many hydrogens as they can, it's a saturated fat. If it's not bounded (double) then its unsaturated". what does that mean?(4 votes)
- When carbons have double bonds to one hydrogen, they are "wasting" one bond that could be used to bond to another hydrogen on bonding with only one. Therefore, the carbon is not reaching its maximum hydrogen bonding potential, i.e. not completely saturated with hydrogens.(6 votes)
- is hormones always sexual if not what are they(1 vote)
- Hormones are signaling molecules that are transported by fluids within a multicellular organism (e.g. in the blood in vertebrates).
Most hormones have nothing to do with sex — some examples are insulin (which helps control blood sugar), melatonin (which helps control circadian rhythms and sleep), and cortisol (which is a steroid hormone, but is involved in responding to stress).(12 votes)
- How can I visually recognize a hydrophobic chain and hydrophilic chain? I couldn't see much of a difference as they appear to be bonded together.(3 votes)
- A lot of polar groups in polymer (-OH, =NH, =C=O, -C(O)OH, -CN, -C-O-C-, -C-N-C-, and so forth) - hydrophilic polymer.
A few polar groups in polymer - hydrophobic polymer.
Structure of both:
Hydrophobic https://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=16372120(1 vote)
- 0:12, Are all fats lipids but not all lipids fats?? Or are only some fats lipids and only some lipids fats??(3 votes)
- Lipids are compounds that are insoluble in water but are soluble in organic solvents such as ether and chloroform
Fats and oils are esters of glycerol and three fatty acids.
Meaning that all fats are lipids, but not all lipids are fats.
- What does water soluble mean?
How does it affect molecules? Please give an example.(2 votes)
- Water soluble means that a thing can dissolve in water. Because of the charge of water it can pull some molecules apart but not all, e.g. salt dissolves in water but oil doesn't. Look up the video: "Water as a solvent" if you want a more in depth explanation.(2 votes)
- Can someone please explain to me about the "What makes triglyceride not so soluble in water" part? (2:35) I get a bit confused there :/(1 vote)
- How soluble a molecule is in water depends to a large extent on the degree of polarity seen in that molecule.
A very polar molecule like a sugar (has lots of hydroxyl groups) can from strong interactions (hydrogen bonds) with water molecules and this makes it easy for a sugar molecule to stay in solution.
In contrast, a hydrocarbon chain (like the fatty acid tails) has very low polarity and so has very weak interactions with water molecules — thus hydrocarbons are very happy to stick together. This means that if you try to dissolve a hydrocarbon in water the molecules tend to stick to each other rather than the water — i.e. they have low solubility.
A triglyceride is mostly nonpolar hydrocarbon chains and so sticks to other triglycerides much better than it sticks to water.
Does that help?
If you want to understand this material better, I strongly encourage you to work through the Chemistry material on Khan Academy starting here:
That may look like a lot of work, but you've probably watched many of the videos already under "Chemistry of life". A deep understanding of chemistry is essential to anyone interested in modern biological sciences or medicine, so I really encourage you to take the time to work though all of the chemistry material (including the Organic Chemistry section: https://www.khanacademy.org/science/organic-chemistry).(4 votes)
- 0:47So is detergent a lipid?(2 votes)
- [Instructor] What we are going to do in this video is talk a little bit about lipids. Now, a lot of times, lipids are strongly associated with fats, and that's not incorrect. Fats are lipids, but not all lipids are fats. A better definition or a better association for lipids would be a class of molecules that you often see in biological systems that are not so water soluble. And I didn't say outright hydrophobic, which means not attracted to water, because there are definitely lipids that have parts that are hydrophobic, that are trying to get away from the water. But there is other parts that are hydrophilic, that like the water, that would be attracted to water molecules. Now, in terms of roles they play in the body, and we can think of fat molecules here, well, they definitely play a role in terms of energy storage. Whenever I look at my belly, I just like to think of all that energy that is there covering my six-pack. They could be involved in signaling. In future videos, we're going to study hormones, and hormones are nothing but molecules that help transmit a signal from one part of the body to another part of the body. And many of these hormones are lipids. They're also involved in membranes. So a lot of the time in biology, we're gonna talk about cellular membranes and how they're formed with these phospholipids. And we'll see these phospholipids, in particular, have one end that's trying to get away from the water and another end that is attracted to the water. And that's actually what makes them good for membranes. Just going back to fats, let's actually take a look at what some of these lipid molecules look like. So this right over here is an example of a fat molecule, but the general structure you're going to have is these three fatty acids. So that's one right over there, one fatty acid, two fatty acids, and three fatty acids that are connected to a glycerol. And don't worry too much about the words here. You'll study them more when you get to an organic chemistry class. But that's where this word triglyceride comes from, tri- for your three fatty acids and -glyceride from a glycerol. And triglyceride is, in fact, another word for fat. And what makes a triglyceride not so soluble in water? Look at these long hydrocarbon chains where you just essentially have a bunch of carbons and hydrogens. Those parts, remember, things that are soluble in water, they tend to be polar molecules, things that have a partial charge on one end or another or even a full charge. But when we look at these hydrocarbon chains, they tend to not have these partial charges on one side or another, and so that doesn't make them so soluble in water. And another word that you sometimes hear associated with fats, saturated or unsaturated fat. That's really referring to what's going on on these hydrocarbon chains. If the carbons are as bonded to as many hydrogens as they can, well, then you're talking about a saturated fat. It's saturated with hydrogens. If it's not bounded, if it, in theory, it could bond to more hydrogens because it has some double bonds in there, well, then it's unsaturated. Maybe in a future video, we'll talk about the health issues of saturated versus unsaturated fat. Sometimes in popular culture, fat gets a bad name because everyone's trying to get their six-packs or whatever else, but it's very important to realize that without fats you would die. Many vitamins, which are not so soluble in water, making them, in fact, lipids, need fat in order to be absorbed into the body properly. But as I also mentioned, all lipids are not fats. Here are more examples of lipids, and I'm not gonna go into detail into their molecular structure. But you see something similar here. They all have long chains of hydrocarbons that aren't so soluble in water. These parts right over here would be hydrophobic, hydrophobic. But what's interesting, especially about this sphingomyelin, which is involved in your myelin sheath in the brain, it helps electrically insulate neurons, it's also involved in membranes, it makes up a substantial part of the phospholipids in membranes, is that this sphingomyelin right over here has a part that actually is hydrophilic. And as we'll see later on, that's what makes things, molecules like this, phospholipids, this is a sphingophospholipid, makes them good for membrane structures. Because the part that's attracted to the water could be on the outside, and the part that's not attracted to the water could be on the inside. And so you can form these membranes that a cross-section of which would look something like this where the circular parts are the part that want, the parts that want to be around the water, while these tails right over here, these are the hydrophobic chains that want to go away from the water. And this is, in fact, what cellular membranes actually look like if you were zoom really, really, really far in. I'll leave you there. Between lipids, carbohydrates, proteins, nucleic acids, we've really covered the major macromolecules that you will see in biological systems. Once again, what makes them macromolecules? Well, they can be composed of many, many, many, many, many atoms. They aren't small molecules.