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2.3 Carbon-Based Molecules KEY CONCEPT Carbon-based molecules are the foundation of life. 2.3 Carbon-Based Molecules Carbon atoms have unique bonding properties. • Carbon forms covalent bonds with up to four other atoms, including other carbon atoms. • Carbon-based molecules have three general types of structures. – straight chain – branched chain – ring 2.3 Carbon-Based Molecules • Many carbon-based molecules are made of many small subunits bonded together. – Monomers are the individual subunits. – Polymers are made of many monomers. 2.3 Carbon-Based Molecules Integrating Chemistry – Types of reactions • Some polymers form through a process of dehydration, that is, a molecule of water is released as one or more monomer bonds to another. One provides a hydrogen (H) and the other provides a hydroxyl group (OH). • Some polymers can also be broken down in a reverse reaction called hydrolysis. The bonds between the monomers are broken by the addition of water molecules (H2O). 2.3 Carbon-Based Molecules Four main types of carbon-based molecules are found in living things. • Carbohydrates are made of carbon, hydrogen, and oxygen. – C, H and O are combined in a ratio of 1:2:1 2.3 Carbon-Based Molecules Four main types of carbon-based molecules are found in living things. • 1. Carbohydrates are made of carbon, hydrogen, and oxygen. – Carbohydrates include sugars and starches. – Monosaccharides are simple sugars like glucose and fructose. – Disaccharides include sucrose, maltose and lactose – Polysaccharides include starches, cellulose, and glycogen. 2.3 Carbon-Based Molecules • Carbohydrates can be broken down to provide energy for cells (starch and glycogen). Glycogen is made by animals and stored in their liver. • Some carbohydrates are part of cell structure (cellulose). Polymer (starch) Polymer (cellulose) monomer Starch is a polymer of glucose monomers that often has a branched structure. Starch is made and stored by plants. They break it down for energy. Cellulose is a polymer of glucose monomers that has a straight, rigid structure. It is used and the building block of plant cell structure. It is the tough outer covering of plant cells. 2.3 Carbon-Based Molecules • 2. Lipids are nonpolar molecules that include fats, oils, and cholesterol. – Many contain carbon chains called fatty acids. – Fats and oils contain fatty acids bonded to glycerol. Triglyceride 2.3 Carbon-Based Molecules • Lipids have several different functions. – broken down as a source of energy (fats and oils) – make up cell membranes (phospholipids and cholesterol) – used to make hormones (cholesterol makes steroid hormones like testosterone and estrogen) 2.3 Carbon-Based Molecules • Fats and oils have different types of fatty acids. – saturated fatty acids (common in animal fats) – unsaturated fatty acids 2.3 Carbon-Based Molecules • Phospholipids make up all cell membranes. – Polar phosphate “head” – Nonpolar fatty acid “tails” Phospholipid How would the polar head of a phospholipid respond to water molecules? How would the nonpolar tails respond to water molecules? 2.3 Carbon-Based Molecules • 3. Proteins are polymers of amino acid monomers. – Twenty different amino acids are used to build proteins in organisms. – They are the most varied of the carbon-based molecules and function in movement, eyesight or digestions and many other things. Fig. Serine is one of 20 amino acids that make up proteins in organisms 2.3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers. – Twenty different amino acids are used to build proteins in organisms. – Amino acids differ in side groups, or R groups. 2.3 Carbon-Based Molecules • Proteins are polymers of amino acid monomers. – Twenty different amino acids are used to build proteins in organisms. – Amino acids differ in side groups, or R groups. – Amino acids are linked by peptide bonds. 2.3 Carbon-Based Molecules • Proteins differ in the number and order of amino acids. – Amino acids interact to give a protein its shape. Primary structure (amino acid chain), secondary structure (folds, alpha or beta), tertiary structure (overall shape). Hemoglobin hydrogen bond – Incorrect amino acids change a protein’s structure and function. 2.3 Carbon-Based Molecules Hemoglobin and Sickle Cell Anemia • Hemoglobin in red blood cells transports oxygen. Just one amino acid change causes red blood cells to have the curved shape characteristic of sickle cell anemia. (colored SEM; magnification 3500 X) 2.3 Carbon-Based Molecules • 4. Nucleic acids are polymers of monomers called nucleotides. • They carry detailed instructions to build proteins. 2.3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides. – Nucleotides are made of a sugar, phosphate group, and a nitrogen base. A phosphate group deoxyribose (sugar) nitrogen-containing molecule, called a base 2.3 Carbon-Based Molecules • Nucleic acids are polymers of monomers called nucleotides. – Nucleotides are made of a sugar, phosphate group, and a nitrogen base. – DNA stores genetic information. DNA – RNA builds proteins. RNA Apply: What is the relationship between proteins and nucleic acids?