Mastering Biology 4: Flashcards

Carbohydrates and Related Molecules

• Lipid is identified as a non-carbohydrate molecule, contrasting with starch, cellulose, and glycogen which are all carbohydrates.
• Monosaccharides, basic units of carbohydrates, consist of carbon, hydrogen, and oxygen and can be classified based on the arrangement of their atoms.
• Peptidoglycan is a polysaccharide unique to bacteria, highlighting its structural role in bacterial cell walls.
• Amylose, a component of starch, contains only α-1,4-glycosidic linkages, differentiating it from other polysaccharides like cellulose and glycogen.
• Cellulose serves as the structural component of plant cell walls, providing rigidity and support, whereas amylose is the main energy storage form for plants.

Functions and Properties of Polysaccharides

• Peptidoglycan features modified monosaccharides, essential for bacterial structure.
• The branching difference between starch and glycogen defines their structural properties and energy storage capabilities.
• A molecule represented by the formula C6H12O6 indicates a monosaccharide, often recognized as glucose.
• Starch and cellulose are polymers of glucose, each serving distinct biological functions in energy storage and structural roles respectively.

Human Digestion of Carbohydrates

• Starch can be digested by humans due to the presence of enzymes capable of hydrolyzing its α-glycosidic linkages, contrasting with cellulose's β-glycosidic linkages which humans cannot digest.

Proteins and Amino Acids

• Proteins are polymers composed of amino acids, essential for a myriad of biological functions.
• An amino acid's central carbon connects to four groups, including a carboxyl group, amino group, a side chain ("R group"), but not an oxygen.
• The carboxyl functional group of amino acids is always acidic and plays a critical role in peptide bond formation during protein synthesis.

RNA and Nucleotides

• RNA is composed of nucleotides, emphasizing the importance of these units as the building blocks of genetic material.
• Polypeptides form through the condensation reaction between the carboxyl group of one amino acid and the amino group of another, facilitated by dehydration synthesis.

Enzymatic Reactions

• Enzymes in the digestive tract catalyze hydrolysis reactions, aiding in the breakdown of complex molecules for absorption.

General Characteristics of Polymers

• Polymers are always composed of monomers, refuting any notions that they may be formed through hydrolysis.
• DNA exemplifies a polymer made of nucleotides, crucial for heredity and cellular function.

Specific Carbohydrate Examples

• Glycogen is a polysaccharide found in animals used for energy storage, while cellulose is the most abundant organic compound on Earth.
• Sucrose, a disaccharide, forms through the glycosidic linkage of glucose and fructose.
• Plant cell walls primarily consist of cellulose, an important source of dietary fiber, often referred to as insoluble fiber.

Classification of Sugars

• Lactose is categorized as a disaccharide, derived from one glucose and one galactose molecule.
• Complex sugars represent a category of carbohydrates, while simple sugars have a basic composition of carbon, hydrogen, and oxygen.

Misconceptions About Carbohydrates

• The incorrect statement that all carbohydrates adhere to the general formula Cn(H₂O)n indicates a common misconception in carbohydrate chemistry.