Basic Chemistry

1. Basic Chemistry Chapter 2 – Part 4

2. Carbohydrates • Carbohydrates - Compounds made up of carbon, hydrogen, and oxygen atoms • Usually in a ratio of 1 : 2 : 1. • Examples: sugars and starches.

3. Classification of Sugars • Monosaccharides • Disaccharides • Polysaccharides

4. Monosaccharides • Monosaccharides - Single sugar molecules • Referred to as simple sugars • Single-chain or single-ring structures • Contain 3 to 7 carbon atoms • Examples in the body: Glucose, Galactose, Fructose, ribose, and deoxyribose • Glucose (also called blood sugar) is the universal cellular fuel. • Fructose and galactose are converted to glucose for use by body cells. • Ribose and deoxyribose form part of the structure of nucleic acids.

5. Disaccharides • Disaccharides – Double sugar molecules • Formed when two simple sugars are joined by a synthesis reaction known as dehydration synthesis. • In this reaction, a water molecule is lost as the bond forms. • Examples: • Glucose + Fructose = Sucrose (cane sugar) • Glucose + Galactose = Lactose (found in milk) • Glucose + Glucose = Maltose (malt sugar)

6. Disaccharides • Double sugars are too large to pass through cell membranes. • They must be broken down (digested) to their monosaccharide unit to be absorbed by the blood. • This is accomplished by hydrolysis. • As a water molecule is added to each bond, the bond is broken, and the simple sugar units are released.

7. Polysaccharides • Polysaccharides – More than two sugar molecules • Because they are large, insoluble molecules, they: • Are ideal storage products. • Lack the sweetness of the simple and double sugars. • Examples: • Starch - The storage polysaccharide formed by plants; Humans ingest it in the form of “starchy” foods such as potatoes and carrots. • Glycogen – Polysaccharide found in animal tissues (mainly in the liver and muscles); Formed by linked glucose units.

9. Uses of Carbohydrates • Living things use carbohydrates as: • Main source of energy (starches and sugars) • Plants and some animals also use carbohydrates for structural purposes (only 1-2% of animal cell mass) • Some sugars are found in our genes. • Some sugars are attached to outer surfaces of cell membranes, where they act as road signs to guide cellular interactions.

10. How Do We Get Energy From Glucose? • When glucose is oxidized (combined with oxygen) in a complex set of chemical reactions, it is broken down to carbon dioxide and water. • Some of the energy released as the glucose bonds are broken is trapped in the bonds of high-energy ATP molecules. • If not immediately needed for ATP synthesis, carbohydrates are converted to glycogen or fat and stored.

11. Lipids • Common categories of lipids are: • Neutral Fats (Triglycerides) • Phospholipids • Steroids • Enter the body in the form of fat-marbled meats, egg yolks, milk products, and oils. • Generally not soluble in water but readily dissolve in other lipids and other in organic solvents such as alcohol and acetone.

12. General Structure of Lipids • Large and diverse group of organic compounds. • Contains carbon, hydrogen, and oxygen atoms, but in lipids, carbon and hydrogen atoms far outnumber oxygen atoms. • Example: The formula for a typical fat named tristearin is C57H110O6.

13. Neutral Fats • Neutral Fats or Triglycerides contain the following structure: • Glycerol molecule + 3 fatty acids • The glycerol backbone is the same in all neutral fats, but the fatty acid chains vary and results in different kinds of neutral fats. • Exists as a solid or liquid.

14. Saturated and Unsaturated Lipids • Saturated - If each carbon atom in a lipid's fatty acid chains is joined to another carbon atom by a single bond. • “Saturated” is used because the fatty acids contain the maximum possible number of hydrogen atoms. • Animal fats tend to be saturated. • Unsaturated - If there is at least one carbon-carbon double bond or triple bond in a fatty acid. • Have the ability to bind with more hydrogen atoms or atoms of a different type. • Plant oils tend to be unsaturated (such as corn oil, canola oil, sesame oil, and peanut oil).

15. Saturated and Unsaturated Fatty Acids

16. Function of Neutral Fats • Represent the body’s most abundant and concentrated source of usable energy. • When they are oxidized, they yield large amounts of energy. • They are stored chiefly in fat deposits beneath the skin and around organs, where they: • Help insulate the body • Protect deeper body tissues from heat loss and bumps.

17. Phospholipids • Glycerol molecule + 2 fatty acids + phosphorus-containing group • The phosphorus-containing portion (the “head”) bears an electrical charge and therefore gives phospholipids special chemical properties and polarity. • The charged region attracts and interacts with water and ions, but the fatty acid chains (the “tail”) do not. • Allows cells to be selective about what may enter or leave the membrane.

19. Steroids • Steroids – Basically flat molecules formed by four interlocking rings. • Cholesterol is the single most important steroid molecule. • Enters the body in animal products such as meat, eggs, and cheese. • A certain amount is also made by the liver, regardless of dietary intake. • Uses: • Found in all cell membranes (particularly abundant in the brain). • Raw material used to form vitamin D, some hormones (sex hormones and cortisol), and bile salts.

21. Saturated Fats • Saturated fats and cholesterol have been implicated as substances that encourage atherosclerosis (deposit of fatty substances in our artery walls) and eventual arteriosclerosis (hardening of the arteries). • As a result olive oil and liquid spreads made from polyunsaturated fats are being promoted as good-tasting substitutes that do not damage our arteries.