Chapter 4 - Macromolecules
- Oxygen and sulfur both have six valence electrons and normally form two bonds.
* Oxygen may be present in all macromolecules.
* %%Sulfur is frequently present in proteins.%% - Nitrogen and phosphorus have five valence electrons apiece, and they normally form three bonds.
* Nucleic acids and proteins contain nitrogen.
* %%Phosphorus may be present in nucleic acids as well as certain lipids.%% - Hydrogen contains a single valence electron and just one bond.
* Hydrogen may be present in all macromolecules.
* In fact, hydrogen atoms are so common that they are frequently overlooked in molecular structures. - Carbon serves as the molecules' "backbone."
* Carbon contains four valence electrons and may connect to a wide variety of other elements.
* It has the ability to create single, double, and even triple bonds. - Carbon can also take the form of linear, branching, or ring-shaped formations.
* Carbon can be present in all macromolecules.
* Carbohydrates are sugar monomer polymers."
* The structure and function of carbohydrate are determined by the type of sugars utilized to form it and how the sugars are connected. - Sugars can be linked in either linear or branched chains.
* Carbohydrates can be utilized to store energy (as in starch or glycogen) as well as provide structural roles (such as in cellulose).
* ^^The types of connections found between sugars in carbs that store energy differ from those found in carbohydrates that have a structural purpose.^^ - Lipids are nonpolar polymers that have important roles in energy storage, cell membranes, and insulation." (As seen in the image attached below.)
- Fatty acids are one of the building components of lipids.
* Saturated fatty acids have the greatest amount of C–H single bonds, are solid at room temperature, and are often derived from animals. 
- Unsaturated fatty acids have at least one C=C double bond, are liquid at room temperature, and are often derived from plants.
* The saturation level of a lipid determines how it operates in a cell. - Phospholipids play a critical role in cell membranes.
* A glycerol molecule, two fatty acids, and a phosphate group make up their structure.
* Because the fatty acids are nonpolar and the phosphate is polar, phospholipids are amphipathic, which means they have both hydrophobic and hydrophilic properties.
* The term Nucleic acids refer to polymers of nucleotides and function as the carriers of genetic information.
* Nucleotides will be discussed in more detail later in this chapter.” - Steroids are another kind of lipid.
* Steroids are nonpolar, rather flat molecules.
* Many steroids are created by altering the molecules of cholesterol.
* Estradiol, testosterone, and cortisol are examples of steroids.
* Proteins are amino acid polymers.
* As illustrated in the image above, amino acids have an amino group, a carboxylic acid group, a hydrogen atom, and a side chain (R-group) connected to a central carbon. - The R-group is unique to each amino acid; it defines the amino acid's identity as well as whether it is nonpolar, polar, acidic, or basic.
* Proteins have roles in enzyme catalysis, cell structure maintenance, cell signaling, cell recognition, and other processes.
* Peptide bonds connect amino acids, as seen in the image attached above.
* The resultant polypeptide chains have a carboxyl (COOH) terminus and an amino (NH2) terminus. - The main structure of the protein is determined by the order of the amino acids in the polypeptide chain.
* Tertiary structure refers to the protein's three-dimensional folded form, which is frequently governed by hydrophobic/hydrophilic interactions between R-groups in the polypeptide.
* The most stable tertiary structures will feature hydrophilic R-groups on the protein's surface (in touch with the aqueous environment of the cell's cytosol), whereas hydrophobic R-groups will be found in the protein's core (away from the watery cytosol).
* Disulfide bridges between sulfur atoms may also be seen in tertiary structures.