Campbell Biology, Chapter 5: Macromolecules PDF

Chapter 5: The Structure and Function of Large Biological Molecules Campbell Biology, 12th Edition  Overview: The Molecules of Life All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids. Within cells, small organi...

Chapter 5: The Structure and Function of Large Biological Molecules Campbell Biology, 12th Edition  Overview: The Molecules of Life All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids. Within cells, small organic molecules are joined together to form larger molecules. Macromolecules are large molecules composed of thousands of covalently connected atoms. Molecular structure and function are inseparable.  Concept 5.1: Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks. Loading… These small building-block molecules are called monomers Three of the four classes of life’s organic molecules are polymers: Carbohydrates Proteins Nucleic acids  The Synthesis and Breakdown of Polymers A condensation reaction or more specifically a dehydration reaction occurs when two monomers bond together through the loss of a water molecule. Enzymes are macromolecules that speed up the dehydration process. Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction. HO 1 2 3 H HO H Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new H2 bond O HO 1 2 3 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer HO Loading… 1 2 3 4 H Hydrolysis adds a water H2 molecule, breaking a bond O HO 1 2 3 H HO H (b) Hydrolysis of a polymer  The Diversity of Polymers 2 3 Each cell has thousands of different kinds of H HO macromolecules. Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species. An immense variety of polymers can be built from a small set of monomers. Concept 5.5: Nucleic acids store and transmit hereditary information The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene. Genes are made of DNA, a nucleic acid.  The Roles of Nucleic Acids There are two types of nucleic acids: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA provides directions for its own replication. DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis. Protein synthesis occurs in ribosomes.  DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into Ribosome cytoplasm via nuclear pore 3 Synthesis of protein Amin Polypeptide o acids  The Structure of Nucleic Acids Nucleic acids are polymers called polynucleotides. Each polynucleotide is made of monomers called nucleotides. Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group. The portion of a nucleotide without the phosphate & group is called a nucleoside.  5 - end Nitrogenous bases 8 Pyrimidines 5 C 3 C Nucleoside - Nitrogenous base Cytosine Thymine (T, in DNA) Uracil (U, in RNA) (C) Purines 5 C Loading… Phosphate group Sugar (pentose) Adenine Guanine 3 (b) Nucleotide (A) (G) C Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars Nucleotide Monomers Nucleoside = nitrogenous base + sugar There are two families of nitrogenous bases: Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines Double (adenine and guanine) have a six- riny membered ring fused to a five-membered ring In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Nucleotide = nucleoside + phosphate group  Nucleotide Polymers Nucleotide polymers are linked together to build a polynucleotide. Adjacent nucleotides are joined by covalent bonds that form between the –OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next. These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages. The sequence of bases along a DNA or mRNA polymer is unique for each gene.  The DNA Double Helix A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix. In the DNA double helix, the two backbones run in opposite 5 → 3 directions from each other, an arrangement referred to as antiparallel. One DNA molecule includes many genes. The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C).  5' end 3' end Sugar- phosphate backbones Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand 3' end 5' end New strands 3' end 5' end 5' end 3' end Fig. 5-UN2