Chapter 5: The Structure and Function of Macromolecules IB Topic 3.2

Organic vs. Inorganic Compounds Carbohydrates, lipids, and proteins are examples of compounds of carbon. Carbon is the 2 nd most abundant element in cells and organisms Compounds containing carbon that are found in living organisms are called organic Exceptions: CO2, hydrogen carbonates,  Non-organic carbon compounds

Why Carbon is so Cool! Carbon  Able to form four strong, stable, covalent bonds  Able to react with each other to form extended chains Straight, branched, or rings  Bonds covalently with other atoms Oxygen, hydrogen, nitrogen, sulphur  Very many of the organic chemicals of living things fall into four categories Carbohydrates, lipids, proteins, and nucleic acids

Most Macromolecules are Polymers Carbohydrates, lipids, and proteins are chainlike molecules called polymers  Polymer is a long molecule consisting of many similar or identical building blocks linked by covalent bonds  Monomers

Condensation Reaction (or Dehydration Synthesis ) The process of connecting monomers to create a polymer  This process requires energy and is aided by enzymes  Removes water molecules  One monomer provides a hydroxyl group and the other provides a hydrogen  Figure 5.2

Hydrolysis The process of disassembling polymers into monomers  Addition of water, aided by enzymes  Example, digestion of food

Carbohydrates Largest group of organic compounds found in living things Sugars, starch, glycogen, cellulose Contain only three elements: C, H, O  Hydrogen and oxygen in a 2:1 ratio Monosaccharides, disaccharides, polysaccharides Function:  Carried by blood to transport energy to cells  Energy storage (stored in the form of glycogen)

Monosaccharides Relatively small; taste sweet and soluble in water Examples:  Glucose: made by green leaves using light energy, our bodies transport it in our blood, respiration, building block for larger molecules  Galactose  Fructose

Disaccharides Made of 2 monosaccharide molecules Examples:  Sucrose (glucose + fructose)  Maltose (glucose + glucose)  Lactose (galactose + glucose)  See Figure 5.5 pg. 63

Polysaccharides Built from many monosaccharide molecules connected by glycosidic links Examples  Starch (polymer of glucose)  Glycogen (polymer of glucose)  Cellulose (polymer of glucose)

Carbohydrates Important in Plants and Animals AnimalsPlants Monosaccharides Glucose: transported to cells in the blood plasma; used as a respiratory substrate for cellular respiration Galactose: used in the production of lactose Glucose: a first product of photosynthesis Fructose: used in the production of sucrose

Carbohydrates Important in Plants and Animals AnimalsPlants Disaccharides Lactose: produced in mammary glands & secreted into the milk; important for young mammals Sucrose: produced in green leaves from glucose and fructose Maltose: Breakdown product in the hydrolysis of starch

Carbohydrates Important in Plants and Animals AnimalsPlants Polysaccharides Glycogen: storage carbohydrate from glucose in the liver when glucose is not immediately required for cellular respiration Cellulose: main component of cell walls Starch: storage carbohydrate

Lipids Lipids occur in living things as animal fats, plant oils, phospholipids of cell membranes, and steroids At room temperature, oils are liquid and fats are solid Contain C, O, and H (like carbs), but proportion of oxygen is much less Insoluble in water; hydrophobic  Can be dissolved in organic solvents (alcohol)

Lipids Fats and oils are compounds called triglycerides  Formed when water is removed between fatty acids and glycerol Long hydrocarbon tails

Functions of Lipids 1. Energy storage  Less oxygen atoms/more concentrated source 2. Metabolic water source 3. Thermal insulation and buoyancy 4. Water proofing of hair and feathers 5. Electrical insulation  Myelin sheath

Carbohydrates vs. Lipids LipidsRoleCarbohydrate More energy per gram than from a carbohydrate. Energy storageLess energy per gram than from lipids Much metabolic water is produced on oxidation Metabolic water source Less metabolic water is produced on oxidation InsolubleSolubilitySugars are highly soluble in water Not quickly digestedEase of breakdownEasily hydrolyzed; quick energy

Amino Acids, peptides, and proteins Contain nitrogen, sulfur, hydrogen, carbon and oxygen  Amino group: NH2 Carboxyl group: COOH Amino acids  peptides and proteins  Polypeptide and protein are used interchangeably Once the chain is constructed, it takes a specific shape –shape matters with proteins  Shape  function