Questions about stuff I am not confident with:
- Why do amphipathic molecules make lipids soluble? Do they make all hydrophobic molecules hydrophilic or how exactly does it work?
- Why is it that teritiary structures are said to have a 3d shape? Aren't they all 3d?
- What is a good term (umbrella term) that I can use to group all proteins found on a membrane?
With regards to protein structure, is the following correct?
- Primary structure: Long chains of amino acids that only form peptide bonds to create a polypeptide.
- Secondary structure: Amino acids are linked together via peptide and hydrogen bonds. They come in Alpha helices, Beta pleated sheets and random coiling.
- Teritiary structure: Amino acids are linked via peptide, hydrogen, covalent (disulfide bridges/bonds) and ionic bonds.
- Quaternary structure: Are composed of 2 or more peptides bonded together.
Also if there is anything you think I should then feel free to comment.
Thanks!
1. Detergents are tricky to explain, because they're really similar to phospholipids. Basically though, the key difference between detergents and phospholipids is that detergents like to form balls, whereas phospholipids prefer to form bilayers. Not going to go into why that's the case, other than to say it has to do with the shape of the molecules.
What detergents basically do is bind fats by their hydrophobic tail and bind water by the hydrophilic head, much like phospholipids. This allows them to form balls called micelles that dissolve in water (because the heads are on the outside of the micelle) and that store lipids in their core. This is what they do to fats, what they do to phospholipids is much the same and is shown above. Rather than the phospholipid being stored in the core of the micelle, it is stored in the micelle itself, substituting a detergent molecule.
If this doesn't make sense, don't worry about it too much—it's beyond VCE. Just know that they can disrupt fat droplets and bilayers and you're sweet.
2. A true point. Tertiary structure gives the toplogy of the molecule, its functional shape as it were. So tertiary structure describes how all of the secondary structures fold into each other to make a particular shape.
3. Membrane proteins (genuinely what they're called technically)
4. Each level of structure is a distinct unit. So secondary structure, for instance, doesn't include the peptide bonds between amino acids. That is the protein's primary structure. So secondary structure doesn't describe a state that the protein is in, it describes some of the elements of the protein's structure.
If that doesn't make sense, think of it this way. A protein simultaneously has primary, secondary and tertiary structure. Its primary structure is the order of amino acids (linked by peptide/amide bonds), its secondary structure arises from hydrogen bonding between hte peptide backchain forming alpha-helices, beta-sheets and random coils and its tertiary structure is the overall topology of the protein, formed by a host of interactions between R-groups, including salt bridges, hydrogen bonds, disulphide bridges etc etc.
Yo its me again. Just wanted to know what the differences are between the nuclear membrane (or nuclear envelope) and the plasma membrane. Do both follow the fluid mosaic model? Or is the nuclear membrane different?
Your help is very much appreciated 
Nuclear membranes are double folded, whereas plasma membranes aren't. Google some images, will make sense
Home
Help
Search
Login
