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Biomolecules Overview
Biomolecules Overview
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Biomolecules are the carbon based molecules that make up living things and allow cells to function. The four major classes are carbohydrates, lipids, proteins, and nucleic acids. Each class has a different structure and a different job in the body. Learning how they compare helps students connect chemistry to biology, nutrition, genetics, and cell structure.
These molecules are built from smaller units and organized by the types of atoms and bonds they contain. Carbohydrates often provide quick energy, lipids store energy and form membranes, proteins perform most cellular work, and nucleic acids store and transmit genetic information. Their shapes strongly affect their functions, especially in proteins and nucleic acids. A biomolecules overview shows how life depends on both molecular building blocks and molecular interactions.
Key Facts
- Carbohydrates are usually made of C, H, and O in an approximate 1:2:1 ratio, often written as (CH2O)n.
- Monosaccharides join by dehydration synthesis to form disaccharides and polysaccharides.
- Lipids are mostly nonpolar molecules such as fats, oils, phospholipids, and steroids, and they do not mix well with water.
- Proteins are polymers of amino acids linked by peptide bonds.
- A triglyceride = glycerol + 3 fatty acids.
- Nucleic acids are polymers of nucleotides, and each nucleotide contains a sugar, a phosphate group, and a nitrogenous base.
Vocabulary
- Monomer
- A monomer is a small molecular subunit that can join with others to build a larger polymer.
- Polymer
- A polymer is a large molecule made of many repeating monomer units bonded together.
- Enzyme
- An enzyme is a protein that speeds up a chemical reaction in a cell without being used up.
- Phospholipid
- A phospholipid is a lipid with a phosphate containing head and two fatty acid tails that helps form cell membranes.
- Nucleotide
- A nucleotide is the monomer of nucleic acids and includes a sugar, a phosphate group, and a nitrogenous base.
Common Mistakes to Avoid
- Thinking all biomolecules are polymers, which is wrong because many lipids are large biological molecules but are not true polymers made of repeating monomers.
- Confusing monomers with polymers, which is wrong because monomers are the small building blocks while polymers are the larger molecules built from them.
- Assuming carbohydrates are only for energy, which is wrong because some carbohydrates also provide structure, such as cellulose in plant cell walls.
- Saying DNA and RNA are proteins, which is wrong because they are nucleic acids made of nucleotides rather than amino acids.
Practice Questions
- 1 A polysaccharide is broken down into 12 glucose monomers. How many monomer units did the original carbohydrate contain, and what class of biomolecule is it?
- 2 A triglyceride molecule is made from 1 glycerol and 3 fatty acids. How many fatty acid molecules are needed to build 8 triglycerides?
- 3 Why are proteins able to perform many more different functions in cells than carbohydrates, even though both are large biological molecules?