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.