chapter 05

Bio1151 Chapter 5 9

Macromolecules are polymers that are made from linking building blocks ( ) with bonds by , and can disassemble by .
- Dehydration synthesis.
  Polymers are formed by connecting monomers with covalent bonds through loss of a water molecule.
  This is called a dehydration, or condensation, reaction.
- Hydrolysis reaction.
  Polymers are disassembled to monomers by hydrolysis.
  Covalent bonds are broken by the addition of water molecules.
  Making and Breaking Polymers:
Carbohydrates are and serve as fuel and building material.
- Carbohydrates (sugars) are molecules made of mostly carbon (C) and water (H[2]O). Note: many H atoms opposite the OH groups are not shown in this simplified diagram.
- Monosaccharides such as glucose are sugar monomers and can be linked to form .
  - Monosaccharides are the simplest carbohydrates.
    Aldoses and ketoses are structural isomers.
  - Aldoses have a carbonyl at the end of the carbon skeleton.
  - Ketoses have the carbonyl within the skeleton.
    Glucose and galactose each has an asymmetric carbon and are
  - + stereo isomers.
  - Glucose is a 6-carbon monosaccharide, or hexose. When dissolved in water, it usually circularizes into a ring structure where the orientation of the hydroxyl groups on the 1 and 2 carbons result in a (alpha) and b (beta) structural isomers. Models of Glucose:
- consist of two monosaccharides.
  - Disaccharides are formed by dehydration synthesis from two monosaccharides.
  - Sucrose
  - Maltose Review:
  - Dehydration synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose monomers. Notice that fructose, though a hexose like glucose, forms a five-sided ring.
  - Dehydration reaction in the synthesis of maltose. Maltose is a disaccharide formed from 2 glucose monomers.
- contain many monosaccharide monomers.
- Polysaccharides.
- Cellulose
- Starch
- Glycogen
- Chitin
- Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups of glucose monomers.
  Cellulose is a major component of the tough cell walls in plants, and is difficult to digest.
- Starch is a digestible polysaccharide consisting entirely of glucose monomers and is stored in chloroplasts of plants.
- Glycogen is a glucose polymer with highly branched structures.
  Animals stockpile glycogen in granules within organelles called mitochondria in liver and muscle cells.
- Chitin is made of glucose monomers whose 2 carbon has a nitrogen group.
  The polymer is a strong but flexible structural polysaccharide of insect exoskeletons and can also make biodegradable surgical threads.
are mostly neutral hydrocarbons and thus are .
- Fats can be with no double bonds in the hydrocarbon chains, or with double bonds.
  - Lipids (fats) are constructed from a single glycerol molecule and usually 3 fatty acids by dehydration synthesis.
    The fatty acid tails are nonpolar hydrocarbon chains that are hydrophobic.
    Such lipids may also be called triglycerides.
  - • A saturated fat has no double bonds in the hydrocarbon chains: they are "saturated" with the maximum number of hydrogen atoms possible.
    The straight geometry of saturated fat allow them to pack tightly and they are usually solids at room temperature.
    Most animal fats are saturated.
  - Unsaturated fats have one or more double bonds.
    The mostly cis double bonds cause the molecule to bend.
    Unsaturated fats pack loosely and are usually liquid (oils) at room temperature.
    However, trans double bonds can cause a Lipids to behave like a saturated fat.
    Review:
  - Alpha-linolenic acid is a omega-3 fatty acid with a cis double bond in the ω-3 position.
  - Trans unsaturated fats such as elaidic acid have large components on opposite sides relative to the double bond, and are geometrically similar to saturated fats.
    Cis unsaturated fats have large components on the same side.
- Two important classes of in cells are phospholipids and steroids.
- Phospholipids are diglycerides with a phosphate group and two fatty acid chains. The phosphate heads are hydrophilic while the fatty acid tails are hydrophobic. These polymers form a lipid bilayer in the membranes of cells called plasma membrane.
- Phospholipid bilayer. Two layers of phospholipids form the membrane (plasma membrane) of cells. The hydrophilic phosphate heads orient to the outside and inside aqueous environments; the hydrophobic fatty acid tails pack the middle of the membrane.
- The steroid lipid cholesterol is embedded in cell membranes and is also a precursor for sex hormones such as estradiol and testosterone.
Proteins consist of one or more chains, which are polymers of amino _ani_5,7 acids.
- Proteins are polypeptides composed of amino acid monomers linked by peptide bonds.
  Most proteins fold into a specific 3-dimensional shape (conformation) with four levels of structure.
- primary structure
- secondary structure
- tertiary structure
- quaternary structure
- Amino acids possess both carboxyl and amino groups and an asymmetric carbon atom called the alpha (a) carbon, and can form enantiomers.
  Each amino acid has a different side chain (R group).
- Dehydration synthesis of a polypeptide.
  Peptide bonds formed by dehydration reactions link the carboxyl group of one amino acid to the amino group of the next.
  The polypeptide has a repetitive backbone to which the side chains are attached.
- The sequence of amino acids of a polypeptide, linked by covalent bonds, determines its primary structure.
  Review:
- Secondary structure is the folding of the polypeptide, due to hydrogen bonds, into repeating patterns of an alpha helix or a beta pleated sheet. Review:
- Tertiary structure determines the final three-dimensional shape of a polypeptide, and results from various reactions between amino acids as well as interactions with the aqueous environment. Review:
- Some proteins possess quaternary structure that results from the aggregation of two or more polypeptide chains.
  Review:
- An is a protein that acts as a , speeding up chemical _ANI_5,17 reactions.
- Conformation of a protein.
  Present in our sweat, tears, and saliva, lysozyme is an enzyme that prevents infection by destroying molecules in bacteria cell walls.
  The groove in the protein recognizes and binds to target molecules on bacterial walls.
  To be active, the enzyme must be in a specific 3-dimensional shape, or conformation.
- Enzymes as catalysts. The enzyme sucrase accelerates hydrolysis of its substrate (sucrose) into products (glucose and fructose) by binding the substrate to its active site. As a catalyst, the protein is not consumed during the cycle; it can be used for further catalysis.
Nucleic acid polymers called are made of monomers.
- A polynucleotide is made of nucleotide monomers.
- A nucleotide monomer is composed of a nitrogenous base, a sugar, and a phosphate group. The nitrogenous base and sugar comprise a nucleoside. A nucleoside and a phosphate group make up a nucleotide.
- The components of a nucleoside include a nitrogenous base and a pentose sugar (deoxyribose in DNA, ribose in RNA).
  The carbon atoms on the sugar are given prime numbers: 1' through 5'.
  The nitrogenous base is either a pyrimidine - Cytosine (C), Thymine (T), and Uracil (U) - or a purine - Adenine (A) and Guanine (G).
  Thymine is found in DNA (Deoxyribonucleic Acid), while Uracil is found in RNA (Ribonucleic Acid).
- The nitrogenous base of a nucleotide is attached to the 1' carbon of the sugar; together these form a nucleoside.
  The phosphate group is attached to the 5' carbon, forming a nucleotide.
- DNA is usually composed of two polynucleotide strands wound around each other in a helix.
- DNA double helix.
  A DNA molecule is usually double-stranded, with the sugar-phosphate backbone of two polynucleotide strands on the outside of the helix.
  Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds.
  Adenine (A) can pair only with Thymine (T).
  Guanine (G) can pair only with Cytosine (C).