Macromolecules Notes - Chapter 5

Macromolecules carbon, and life Chapter 5  Stanley Miller’s Experiment (1953) Can organic molecules form under conditions believed to simulate those on the early Earth? Yes! Figure 4.2 Seven functional groups (that are most important in the chemistry of life: Hydroxyl group Carbonyl g...

Macromolecules carbon, and life Chapter 5  Stanley Miller’s Experiment (1953) Can organic molecules form under conditions believed to simulate those on the early Earth? Yes! Figure 4.2 Seven functional groups (that are most important in the chemistry of life: Hydroxyl group Carbonyl group Carboxyl group Amino group Sulfhydryl group Phosphate group Methyl group Figure 4.10  The (LARGE) Molecules of Life: Macromolecules Macromolecules are large and complex molecules that are composed of many covalently connected atoms: carbohydrates; lipids; proteins; nucleic acids (the 4 classes) Molecular structure dictates function Figure 5.1 Why is the structure of a protein important for its function? Concept: Macromolecules are Polymers, Built from Monomers Polymer: a long molecule consisting of many similar building blocks The smaller, repeating molecules that serve as building blocks are called monomers Three of life’s organic molecules are polymers: Carbohydrates Proteins Nucleic acids And they are made of monomers (glucose, Amino acids, nucleotides  Disaccharides and Polysaccharides A disaccharide forms when a dehydration reaction joins two monosaccharides: This bond is called a glycosidic linkage Figure 5.5b Polysaccharides are polymers of sugar that have storage and structural roles The structure and function of a polysaccharide are determined by Sugar monomers Positions of its glycosidic linkages  Storage Polysaccharides (examples) Starch, a storage polysaccharide of plants, consists entirely of glucose monomers (e.g. Plants store surplus starch as granules within chloroplasts and other organelles) Figure 5.6a Polysaccharides of plants and animals.  Structural Polysaccharides The glycosidic linkages of cellulose differ from those of starch because the ring forms of glucose in the two polymers are slightly different Beta (β) bonds between glucose in cellulose (straight) instead of alpha (α) glucose as in starch (largely helical) Figure 5.7 Starch and cellulose structures.  Structural Polysaccharides Enzymes that hydrolyze (or digest) α linkages in starch cannot hydrolyze β linkages in cellulose: Cellulose in human food passes through as insoluble fibre Some microbes have enzymes that digest cellulose: Herbivores, from cows to termites, have symbiotic relationships with these microbes Concept: Lipids are a Diverse Group of Hydrophobic Molecules Lipids are the one class of large biological molecules that does not form polymers Unifying feature of lipids is little or no affinity for water Lipids are hydrophobic because they consist mostly of hydrocarbons which are nonpolar Biologically important lipids include triglycerides, fatty acids, phospholipids, and steroids  Fats Fats are constructed from glycerol and fatty acids Glycerol is a three-carbon alcohol with a hydroxyl attached to each carbon Fatty acids consist of a carboxyl group linked to a long hydrocarbon chain Figure 5.9a The synthesis and structure of a fat, or triacylglycerol.  Fats Fatty acids vary in length (number of carbons), number and location of double bonds Saturated fatty acids do not have double bonds Solid at room temperature Most animal fats are saturated Unsaturated fatty acids have one or more double bonds Liquid at room temperature Plant fats and fish fats are usually unsaturated Figure 5.10a  Phospholipids In phospholipids, two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic The phosphate head group is hydrophilic Figure 5.11a and b The structure of a phospholipid. Phospholipids: major component of cell membranes When added to water, they spontaneously self- assemble into a bilayer Steroids Steroids are lipids with a carbon skeleton consisting of four fused rings Cholesterol is a component in animal cell membranes Although cholesterol is an essential component of animal cell membranes, high levels in blood may contribute to cardiovascular disease Figure 5.12 Cholesterol, a steroid. Concept: Proteins Include a Diversity of Structures, Resulting in a Wide Range of Functions Proteins account for more than 50% of the dry mass of most cells Protein functions include: Speeding up (catalyzing) chemical reactions Structural support Storage Transport Cellular communications Movement Defense against foreign substances  Proteins are Polymers of Amino Acids All proteins are polymers constructed from the same set of 20 amino acids… linked together into unbranched polymers called polypeptides (few to >1000 monomers) A protein is a biologically functional molecule that consists of one or more polypeptide Four Levels of Protein Structure: Primary structure of a protein is its unique amino acids sequence Secondary structure are coils and folds within the polypeptide chain Tertiary structure is determined by interactions among various side chains (R groups) Quaternary structure is when a protein consists of multiple polypeptide chains Figure 5.14  Protein Structure and Function A functional protein consists of one or more polypeptides folded precisely into a unique shape, or conformation Protein function relies on intricate three-dimensional architecture Figure 5.16 Visualizing Proteins  Protein Structure and Function The sequence of amino acids determines a protein’s three- dimensional structure Protein structure determines its function Function usually depends on ability to recognize and bind other molecule(s) Figure 5.17 Complementarity of shape between two protein surfaces. What Happens if we have an amino acid change (mutation)?  Protein Functions: Enzymatic proteins Figure 5.13  Protein Functions: Storage proteins Figure 5.13  An Overview of Protein Functions Figure 5.13  An Overview of Protein Functions Figure 5.13  An Overview of Protein Functions Figure 5.13  An Overview of Protein Function Figure 5.13  An Overview of Protein Functions Figure 5.13  An Overview of Protein Functions Figure 5.13 Concept: Nucleic Acids Store, Transmit, and Help Express 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 made of monomers called nucleotides Two type: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Gene expression DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis  DNA → RNA → Protein Figure 5.22 The Components of Nucleic Acids Nucleic acids are polymers called polynucleotides Each polynucleotide is made of monomers called nucleotides Nucleoside = nitrogenous base + sugar Figure 5.23abc Animation: DNA and RNA Structure  The Structures of DNA and RNA Molecules DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix In DNA double helix, two backbones run in opposite 5→ 3 directions from each other, an arrangement referred to as antiparallel One DNA molecule includes many genes Figure 5.24a1