Exhaustive Guide to Biological Macromolecules and Chemical Processes

Overview of Biological Macromolecules

Biomolecules, also known as organic molecules or macromolecules, are the foundational building blocks of living organisms. These molecules are significantly larger than simple inorganic molecules; for instance, a macromolecule contains at least $24$ atoms, whereas a water molecule ($H_2O$) contains only $3$ atoms.

There are four primary classes of biological molecules:

• Carbohydrates

• Proteins

• Lipids

• Nucleic Acids

Each class is characterized by its basic structure, specific monomers (subunits), polymers (complex chains), functions/uses, and the elements present within them.

Lipids (Fats)

Chemical Composition and Structure

• Elements Present: Carbon, Hydrogen, and Oxygen ($CHO$). Lipids are characterized by having an abundance of Hydrogen and Carbon atoms and relatively few Oxygen atoms.

• Monomers: Lipids are composed of Glycerol and Fatty acids.

• Polymers: Saturated fats and Unsaturated fats (the two primary types).

• Properties: Lipids are non-polar. Because water is polar and "like dissolves like," lipids do not dissolve in water. While substances like salt and sugar are polar and dissolve easily in water, fats must be physically broken down into smaller pieces rather than chemically dissolved in the bloodstream.

Classification of Fats

• Saturated Fats: These consist of glycerol and tails with all single-bond carbon chains, which results in straight tails. These are typically animal lipids and are solid yet squishy at room temperature (e.g., the white part of steak or the white/yellow fat in chicken). These are often referred to as "bad" fats because they can clog arteries (blood vessels that carry blood away from the heart), similar to how bacon grease solidifies in a tube.

• Unsaturated Fats: These contain at least one double bond between carbon atoms. These double bonds create a "kink" or bend in the fatty acid tail.

  • Monounsaturated: Contains one double bond.

  • Polyunsaturated: Contains more than one double bond.

• Plant Lipids: These are typically liquid oils such as vegetable oil, sunflower oil, and olive oil. They are considered "okay/good" compared to saturated fats because they do not clog arteries as easily; liquid oil flows through the tubes of the circulatory system more effectively than solid fat.

Functions of Lipids

• Long-term energy storage.

• Insulation: They contribute to the structure of cell membranes and provide thermal insulation.

Carbohydrates

Chemical Composition and Structure

• Elements Present: Carbon, Hydrogen, and Oxygen ($CHO$).

• Elemental Ratio: They maintain a strict $1:2:1$ ratio of $C:H:O$.

• Naming Convention: Carbohydrates almost always end in the suffix "-ose" (e.g., glucose, sucrose, fructose, maltose).

• Monomer: Monosaccharides (simple sugars). Key examples include Glucose and Fructose.

• Polymer: Polysaccharides (many sugars linked together). Key examples include Starch (storage in plants) and Glycogen (storage in animal tissues).

Uses and Examples

• Quick Energy:

  • Plant Example: Glucose

  • Animal Example: Lactose

• Backup/Stored Energy:

  • Plant Example: Starch

  • Animal Example: Glycogen

• Structure:

  • Plant Example: Cellulose (found in cell walls and serves as dietary fiber for humans).

  • Animal Example: Chitin (found in exoskeletons).

Proteins

Chemical Composition and Structure

• Elements Present: Carbon, Hydrogen, Oxygen, and Nitrogen ($CHON$).

• Monomer: Amino acids. There are $20$ common amino acids used by living organisms.

  • $9$ of these amino acids cannot be manufactured by the human body and must be acquired through the diet.

• Polymer: Polypeptide (also referred to simply as a protein).

• The Importance of Order: Proteins are formed from chains of amino acids where the specific sequence of amino acids determines the protein's identity and function. If the amino acids are viewed as "letters," the resulting protein is the "word." For example, changing the order of the letters R, T, and A results in different words (RAT, ART, TAR), just as changing the sequence of amino acids results in different proteins.

• Structure = Function: The specific shape of a protein is integral to its ability to perform its job.

Biological Roles of Proteins

• Proteins run all chemical reactions in the body. Using a construction analogy:

  • Carbohydrates and Lipids represent the gasoline or electricity (energy).

  • DNA represents the blueprints.

  • Proteins represent the workers and builders.

• Structural Support: Found in muscle, bone, and connective tissue (e.g., Keratin).

• Communication: Hormones, such as Insulin, which controls blood sugar levels.

• Metabolism: Enzymes, such as Pepsin, which acts as a digestive enzyme.

Denaturation

• Definition: Denaturation is the process where a protein loses its specific structure and, consequently, its functionality.

• Causes: High temperatures or deviations from the protein's optimum $pH$.

• Molecular Impact: The process can break hydrogen bonds, causing the protein to unfold or break apart, leaving the polypeptide chains disordered and non-functional.

• Observable Examples:

  • Boiling an egg: The proteins denature and become hard.

  • Cooking meat: The proteins denature, causing the meat to become firm.

Nucleic Acids

Chemical Composition and Structure

• Elements Present: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus.

• Monomer: Nucleotide. A nucleotide consists of three parts:

  1. Phosphorus Group

  2. $5$-C Sugar

  3. Nitrogen Group

• Polymers: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).

DNA vs. RNA Comparison

Formation and Destruction of Organic Compounds

Dehydration Synthesis

• Definition: The process of combining two monomers to form a larger molecule using enzymes.

• Etymology: "Dehydrate" (to remove water) and "Synthesis" (to make).

• Process: Water ($H_2O$) is lost as a byproduct of the reaction.

• Example: Glucose + Fructose $\rightarrow$ Sucrose + Water ($H_2O$).

Hydrolysis

• Definition: The process of breaking down a polymer into its subunits (monomers) using enzymes and water.

• Etymology: "Hydro" (water) and "Lysis" (to cut).

• Process: A water molecule is used to facilitate the breaking of the chemical bonds.

• Example: Sucrose + Water ($H_2O$) $\rightarrow$ Glucose + Fructose.