macromolecules
CARBON AND MOLECULAR DIVERSITY
Chapter 5: The Structure and Function of Macromolecules: Polymerization
Objectives
Familiarize with how polymers are assembled/dismantled.
Understand that most macromolecules are polymers of smaller units.
Describe the properties of each class of macromolecule.
Distinguish between different types of macromolecules and provide examples.
Know the functions of each macromolecule in cells.
Complex Structures Make Living Systems
Macromolecules: Large molecules formed from smaller organic molecules or subunits called:
Monomers: Individual units that make up a macromolecule.
Polymers: Chains of monomers bonded together.
Polymer Principles
Most macromolecules are polymers built from smaller units called monomers.
Synthesis and breakdown of polymers typically involves water:
Synthesis occurs via dehydration or condensation (also referred to as polymerization).
Breakdown occurs via hydrolysis (also known as depolymerization).
An immense variety of polymers can be constructed from a limited set of monomers.
The Structure and Function of Macromolecules: Further Objectives
Familiarize with assembly and dismantling of each macromolecule class.
Identify and provide examples of macromolecule types.
Understand what macromolecules are used for and their functional importance.
Carbohydrates: Fuel and Building Material
Carbohydrates are composed of monomer units, each with the chemical formula CH₂O.
Depending on their size and configuration, carbohydrates can function as:
Energy molecules (fuel).
Structural building blocks.
Three categories of carbohydrates:
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides: Fuel and Building Material
Monosaccharides: The smallest carbohydrates, serving as fuel and carbon sources.
Example Types:
Aldose: A monosaccharide with a carbonyl group at the end of the carbon chain.
Ketose: A monosaccharide with a carbonyl group in the middle of the carbon chain.
In aqueous solutions, many sugars often form ring structures.
Monosaccharides provide a major fuel source for cells and serve as raw materials for larger molecules.
Disaccharides
Formed when two monosaccharides are linked via a glycosidic linkage.
This linkage occurs through dehydration or condensation synthesis.
The monosaccharides must be in ring form for this process.
The structure of the disaccharide (types of monosaccharides used and glycosidic linkage position) is critical for its functional role.
Polysaccharides
Polysaccharides result from many monosaccharides linked together.
Functions include:
Energy Storage
Glycogen: Storage in animals.
Starch: Storage in plants.
Structural Support
Chitin: Found in arthropods and fungal cell walls.
Cellulose: Found in plant cell walls.
The type of monosaccharide and the structure of the glycosidic linkages are vital in determining a polysaccharide's functionality.
Storage Polysaccharides
Starch is a plant storage polysaccharide, consisting entirely of glucose monomers:
Plants store excess starch as granules within chloroplasts and other plastids.
The simplest form of starch is amylose.
Lipids: Diverse Hydrophobic Molecules
Functions of Fats:
Energy storage, cushioning, insulation.
Lipids can store large amounts of energy, approximately 9 kcal/gram due to energy-rich fatty acid chains.
Characteristics of Fat:
Hydrophobic due to nonpolar fatty acid chains.
Fluid nature allows them to cushion and disperse shockwaves.
Proximity of lipid molecules contributes to their efficiency as insulators.
What are Lipids?
Characteristics:
Tend to be hydrophobic, as they consist of nonpolar components (predominantly hydrocarbons derived from C-H bonds).
Constructs composed from isoprene units combined to form chains.
Chains gain polarity through the addition of a carboxyl group, forming a Fatty Acid.
Kinds of Lipids
Triglycerides (Triacylglycerols):
Comprise many dietary oils and fats.
Functional differences arise due to variances in the type and positioning of the hydrophobic chain.
Saturated vs Unsaturated Fats:
Saturated Fatty Acids: Maximum number of single bonds.
Unsaturated Fatty Acids: One or more double bonds, allowing for the formation of additional bonds.
Phospholipids:
Major components of plasma or cell membranes:
Amphipathic nature due to a polar phosphate group attached to nonpolar hydrocarbon chains.
Steroids:
Characterized by a 17-carbon ring system formed from isoprene chains.
Variations among steroid types depend on the composition and position of attached groups on the ring.
Includes hormones such as testosterone, estradiol, cortisol, and aldosterone.
Proteins: Molecular Tools of the Cell
Amino Acids: Monomer building blocks of proteins.
Comprised of:
Amino Group (NH₂)
Carboxyl Group (COOH)
Side Chain (R group)
Amino Acids Become Charged in Polar Environments
In non-ionized form, an amino acid contains:
Amino group, a carboxyl group, and a side chain.
In ionized form, an amino acid may gain a charge due to the polar environment.
Peptide Bonds Linking Amino Acids
Peptide Bond Formation:
Forms through dehydration (condensation) synthesis between two amino acids:
The covalent bond is referred to as a Peptide Bond, facilitating linkage of amino acids.
Protein Structure and Flexibility
Proteins exhibit flexibility due to the ability of peptide bonds to rotate around single bonds, leading to complex three-dimensional shapes.
Protein Structure Levels
Primary Level of Organization:
Sequence of amino acids defined; unique combinations characterize each protein.
Secondary Level of Organization:
Formation of α helices and β pleated sheets through hydrogen bonding.
α helices involve hydrogen bonds between every 4th amino acid.
β pleated sheets involve hydrogen bonds along parallel protein regions.
Tertiary Level of Organization:
Interactions of R-groups create an overall three-dimensional shape.
Stabilizing interactions include:
Disulfide Bridges (Covalent Bonds)
Ionic Bonds
Hydrogen Bonds
Hydrophobic Interactions
Reinforced by van der Waals interactions.
Quaternary Level of Organization:
Complex proteins are formed from interactions between multiple polypeptide chains.
Examples include collagen and hemoglobin.
Changes in Protein Conformation
Denaturation: Loss of a protein’s shape influenced by factors such as:
pH: Disruption of hydrogen bonds.
Temperature: Potential disruption of disulfide bonds.
Large Biological Molecules Overview
Components, examples, and functions of biological molecules emphasize the diversity in macromolecule structure and function:
Carbohydrates: Fuel and building materials; includes monosaccharides, disaccharides, polysaccharides.
Lipids: Hydrophobic molecules, including triglycerides, phospholipids, steroids.
Proteins: Diverse structural functions, enzymes, and transport proteins.
Nucleic Acids: Store and transmit hereditary information via DNA and RNA.
Nucleic Acids: Informational Polymer
Nucleic Acids:
Polymers composed of monomers called nucleotides.
Functions include storage and transmission of genetic information (genes).
Nucleotide Structure
Composed of 3 parts:
Phosphate Group
Sugar:
Ribose (RNA)
Deoxyribose (DNA)
Nitrogenous Base:
Purines (A, G) and Pyrimidines (C, T, U).
Nucleic Acids Polymers
Nucleotide polymers are formed via phosphodiester linkages between the phosphate of one nucleotide and the sugar of another.
Synthesis occurs from the 5’ to 3’ end due to enzyme action.
Nucleic Acids Structure
DNA Structure:
Pyrimidines are attracted to purines in an adjacent chain via hydrogen bonds.
RNA Structure:
RNA is synthesized from nucleosides, with ribose sugar and uracil replacing thymine.
Functions as a single polymer but may form double helices through complementary base pairing.
Notes
Mon- finished Mono, di, poly-
Tues- stopped lipids.
Announcements
Lecture Exam 1: In-class, Tuesday 2/15, covering Chapters 1-5.
Required materials: #2 pencil with eraser, calculator.