Carbohydrates: Structure and Function PDF

Carbohydrates are the most abundant biomolecules on Earth. Chemically, they are composed of carbon and water and often have the formula (CH₂O)n, where n represents the number of repeated units. They are called "carbohydrates" because they resemble "hydrated" carbon chains....

Carbohydrates are the most abundant biomolecules on Earth. Chemically, they are composed of carbon and water and often have the formula (CH₂O)n, where n represents the number of repeated units. They are called "carbohydrates" because they resemble "hydrated" carbon chains. Carbohydrates contain carbon, hydrogen, and oxygen, but some also contain nitrogen, phosphorus, or sulfur. Functions of carbohydrates: ○ Found in food sources. ○ Part of DNA and RNA, which store and transmit genetic information. ○ Provide strength in structures like cellulose (plants) and chitin (insects). ○ Serve as a primary energy storage in the form of starch and glycogen. Monosaccharides: Carbohydrates are also called saccharides (from Greek "sugar"). Monosaccharides are the simplest form of carbohydrates (simple sugars). They are building blocks for larger carbohydrates (polymers). Monosaccharides are named based on the number of carbon atoms: ○ Triose (3 carbons) ○ Tetrose (4 carbons) ○ Pentose (5 carbons) ○ Hexose (6 carbons) The most common hexose sugar is D-glucose, along with galactose (found in milk sugar lactose) and fructose(found in fruit). Sugars with 4+ carbon atoms are more stable as rings. Ring structures form due to a reaction between two specific groups: the carbonyl group and a distant hydroxyl group. Example: Glucose forms a six-membered ring. disaccharides: Definition: Disaccharides are formed when two monosaccharides (simple sugars) bond together. Bond Type: The bond between them is called a glycosidic bond. Formation Process: This bond forms through a process called dehydration synthesis, where a water molecule is removed. Example: ○ Monosaccharide + Monosaccharide → Disaccharide Common Disaccharides:  Maltose: Made of two glucose molecules (grain sugar). Lactose: Made of one galactose and one glucose molecule (milk sugar). Sucrose: Made of one glucose and one fructose molecule (table sugar) Polysaccharides Definition: Polysaccharides (or glycans) are large molecules made of hundreds of sugar units (monosaccharides). Properties: Not sweet like mono- and disaccharides. Generally not soluble in water. Made up of monosaccharides linked by glycosidic bonds. Types of Important Polysaccharides: Starch: Energy storage in plants. Glycogen: Energy storage in animals and bacteria. Cellulose: Structural component of plant cell walls. Structure: Cellulose: Straight chain of glucose. Glycogen and Starch: Branched structures. The different linkages in these polysaccharides affect their properties. Modified Glucose: Components like N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) are found in bacterial cell walls. Chitin: Made of NAG, found in fungal cell walls and insect exoskeletons.