Biological Macromolecules: Monomers, Polymers, and Carbohydrates

Section 3.2: Monomers, Polymers, and Chemical Reactions

Monomers vs. Polymers

Biological macromolecules are large molecules essential for life, and they are typically formed by linking smaller units called monomers into long chains known as polymers.

• Monomer: A small, repeating molecular unit that can join with other similar units to form a polymer. Examples include glucose, amino acids, and nucleotides.

• Polymer: A large molecule composed of many monomers bonded together. Examples include starch, proteins, and DNA.

• Example: Glucose (monomer) units join to form starch (polymer).

Dehydration Synthesis vs. Hydrolysis

Polymers are formed and broken down by specific chemical reactions involving water.

• Dehydration Synthesis (Condensation Reaction): A chemical reaction in which two monomers are joined together by removing a molecule of water. This process builds polymers from monomers.

• Hydrolysis: A chemical reaction in which a polymer is broken down into monomers by adding a molecule of water.

• Equation for Dehydration Synthesis:

$\text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{Dehydration}} \text{Polymer} + \text{H}_2\text{O}$

• Equation for Hydrolysis:

$\text{Polymer} + \text{H}_2\text{O} \xrightarrow{\text{Hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2$

• Example: The breakdown of starch into glucose during digestion is a hydrolysis reaction.

Section 3.3: Carbohydrates

Monosaccharides

Monosaccharides are the simplest carbohydrates and serve as the building blocks for more complex sugars.

• Definition: Single sugar molecules with the general formula $C_nH_{2n}O_n$ (commonly $C_6H_{12}O_6$ for glucose).

• Functions: Provide immediate energy for cellular processes; serve as monomers for larger carbohydrates.

• Examples: Glucose, Fructose, Galactose.

• Application: Glucose is the primary energy source for most organisms.

Disaccharides

Disaccharides are carbohydrates formed by the joining of two monosaccharides via a specific covalent bond.

• Definition: Sugars composed of two monosaccharide units.

• Functions: Serve as energy sources and transport forms of sugars in plants and animals.

• Examples: Sucrose (glucose + fructose), Lactose (glucose + galactose), Maltose (glucose + glucose).

• Type of Bond Formed: Glycosidic bond—a covalent bond formed between two monosaccharides during dehydration synthesis.

• Equation for Disaccharide Formation:

$\text{Glucose} + \text{Fructose} \xrightarrow{\text{Dehydration}} \text{Sucrose} + \text{H}_2\text{O}$

• Application: Sucrose is common table sugar and is used for energy transport in plants.

Polysaccharides

Polysaccharides are large carbohydrates composed of many monosaccharide units linked together. They serve as storage and structural molecules in living organisms.

• Definition: Polymers of monosaccharides, typically containing hundreds to thousands of sugar units.

Storage Polysaccharides

These polysaccharides store energy for later use.

• Examples and Functions:

Polysaccharide	Organism	Function
Starch	Plants	Energy storage
Glycogen	Animals	Energy storage in liver and muscles

• Application: Glycogen is rapidly mobilized to meet energy demands in animals.

Structural Polysaccharides

These polysaccharides provide structural support to cells and organisms.

• Examples and Functions:

Polysaccharide	Organism	Function
Cellulose	Plants	Main component of cell walls
Chitin	Fungi, Arthropods	Structural support in fungal cell walls and exoskeletons of insects/crustaceans

• Application: Cellulose is the most abundant organic polymer on Earth and is important for plant rigidity.

Additional info: The notes have been expanded to include definitions, examples, and applications for each carbohydrate type, as well as the chemical equations for synthesis and breakdown reactions.