Biological Molecules (A-level Biology)
Biological Molecules
Biological Molecules
- Biological molecules are the building blocks of biology. Biological molecules is a term that is typically used to characterise most molecules and ions in living organisms that contribute to various biological processes (e.g. metabolism, cell division, etc).
- Most biological molecules are organic compounds. Meaning that they are mostly made up of the atom carbon.
- Biological molecules consist of many elements. In addition to carbon, these molecules also consist of oxygen, nitrogen, and hydrogen, which along with carbon makeup 96% of the human body’s mass!
- There are four major classes of biological molecules. Although there are thousands of various biological molecules, the four major classes we will concern ourselves with in this chapter are carbohydrates, lipids, proteins, and nucleic acids. Together, these four are the most crucial molecules for sustaining life and are made up of the following elements:
- Carbohydrates – C, H, O
- Lipids – C, H, O
- Proteins – C, H, O, N, S
- Nucleic acids – C, H, O, N, P
Monomers and Polymers
- Monomers are small units that form larger molecules. Monosaccharides, amino acids, and nucleotides are key monomers, important in making up some important polymers (see table 2).
- Polymers consist of a chain of monomers. Polymers are simply very large, long, and complex molecules which consist of smaller and simpler monomers strung together in a chain (Fig. 1).
- Polymers can be homogenous or heterogenous. Homogenous means that all of their monomers are the same, and heterogenous means that their monomeric subunits are different. Examples of homogenous polymers are carbohydrates and proteins, and heterogenous polymers include lipids. In later sections of this chapter, we will come across various homogenous and heterogenous polymers.
- Most biological molecules are polymers. Carbohydrates, lipids, proteins, and nucleic acids are all examples of polymers.
Biological molecules are the chemical compounds found in living organisms that are essential for the growth, maintenance, and functioning of cells and tissues. These molecules include carbohydrates, lipids, proteins, and nucleic acids.
Carbohydrates are the primary source of energy for the body. They are broken down into glucose which is used by the body’s cells for energy. They also have a structural function in cell walls.
Lipids are important for energy storage and insulation in the body. They also have a structural role in cell membranes.
Proteins have many important functions in the body, including serving as enzymes that catalyze chemical reactions, transporting molecules, providing structure to cells, and regulating gene expression.
Nucleic acids are the genetic material of the cell. They include DNA and RNA, which are responsible for storing and transmitting genetic information.
Carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio. They can be simple sugars or complex carbohydrates, such as starch.
Lipids are made up of fatty acids and glycerol. They are non-polar molecules, meaning they do not mix well with water.
Proteins are made up of amino acids, which are linked together by peptide bonds to form long chains. The sequence of amino acids determines the protein’s structure and function.
Nucleic acids are composed of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. The sequence of nucleotides determines the genetic information stored in DNA and RNA.
Enzymes are proteins that catalyze chemical reactions in the body. Enzymes are specific to certain substrates and act to break down or build up biological molecules such as carbohydrates, lipids, and proteins.
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