🔬General Biology I Unit 3 – Biological Macromolecules

What Are Biological Macromolecules?

• Biological macromolecules are large, complex molecules essential for life
• Composed of smaller subunits called monomers that are covalently bonded together to form polymers
• Play critical roles in cellular structure, function, and metabolism
• Include carbohydrates, lipids, proteins, and nucleic acids
• Macromolecules are formed through dehydration synthesis reactions that remove water molecules to join monomers
  • Polymers can be broken down into monomers through hydrolysis reactions that add water molecules
• Exhibit diverse structures and functions depending on their specific monomers and arrangements
• Macromolecules interact with each other and with other cellular components to maintain homeostasis and support life processes

Types of Biological Macromolecules

• Carbohydrates are composed of monosaccharides (simple sugars) and serve as energy sources and structural components
• Lipids include fats, oils, waxes, and steroids, providing energy storage, insulation, and cell membrane structure
• Proteins are made up of amino acids and perform a wide range of functions, such as catalyzing reactions, transporting molecules, and providing structural support
• Nucleic acids, DNA and RNA, store and transmit genetic information and direct protein synthesis
• Each type of macromolecule has unique chemical properties and structures that enable their specific functions
• Macromolecules can be further classified based on their monomers, linkages, and overall structure (linear, branched, or ring-shaped)
• The diversity and complexity of biological macromolecules allow for the incredible variety of life on Earth

Carbohydrates: Structure and Function

• Carbohydrates are composed of carbon, hydrogen, and oxygen atoms, typically in a 1:2:1 ratio
• Monosaccharides are the simplest carbohydrates and include glucose, fructose, and galactose
  • Monosaccharides can be linked together to form disaccharides (sucrose, lactose) and polysaccharides (starch, cellulose, glycogen)
• Carbohydrates serve as the primary energy source for most organisms, with glucose being the most common fuel molecule
• Polysaccharides like starch and glycogen are used for energy storage in plants and animals, respectively
• Structural polysaccharides, such as cellulose in plant cell walls and chitin in arthropod exoskeletons, provide support and protection
• Carbohydrates also play roles in cell signaling, immune function, and cell-cell recognition
• The structure of carbohydrates determines their function, solubility, and reactivity
  • For example, the branching of glycogen allows for rapid energy release, while the linear structure of cellulose provides strength and rigidity

Lipids: More Than Just Fat

• Lipids are a diverse group of hydrophobic molecules that include fats, oils, waxes, steroids, and phospholipids
• Triglycerides, composed of a glycerol backbone and three fatty acid chains, serve as energy storage molecules and insulation
  • Saturated fatty acids have single bonds between carbon atoms, while unsaturated fatty acids have one or more double bonds
• Phospholipids are the main components of cell membranes, with a hydrophilic head and two hydrophobic tails that form a bilayer
• Steroids, such as cholesterol and hormones (testosterone, estrogen), have a characteristic four-ring structure and play important roles in cell signaling and regulation
• Waxes, like beeswax and cuticle wax in plants, provide waterproofing and protection against desiccation
• Lipids are essential for the absorption and transport of fat-soluble vitamins (A, D, E, and K)
• The structure and composition of lipids influence their melting points, solubility, and biological functions

Proteins: The Workhorses of Cells

• Proteins are linear polymers of amino acids joined by peptide bonds
  • There are 20 different amino acids, each with a unique side chain that determines the protein's properties
• Protein structure is organized into four levels: primary (amino acid sequence), secondary (alpha helices and beta sheets), tertiary (3D folding), and quaternary (multiple polypeptide subunits)
• Enzymes are catalytic proteins that speed up chemical reactions without being consumed, lowering activation energy
  • Enzymes have specific active sites that bind to substrates, and their activity can be regulated by factors like pH, temperature, and inhibitors
• Structural proteins, such as collagen and keratin, provide support and strength to tissues and organs
• Transport proteins, like hemoglobin and ion channels, move molecules and ions across membranes or throughout the body
• Signaling proteins, such as hormones and receptors, are involved in cell communication and regulation
• Antibodies are specialized proteins produced by the immune system to recognize and neutralize foreign invaders
• The structure and folding of proteins determine their function, stability, and interactions with other molecules

Nucleic Acids: The Blueprint of Life

• Nucleic acids, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), store and transmit genetic information
• DNA is a double-stranded helix composed of nucleotides with a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases (adenine, thymine, guanine, or cytosine)
  • Complementary base pairing (A-T and G-C) allows for the precise replication and transmission of genetic information
• RNA is typically single-stranded and contains ribose sugar and the base uracil instead of thymine
  • There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)
• DNA serves as the blueprint for protein synthesis, with genes encoding the amino acid sequence of proteins
• The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to proteins
  • Transcription is the process of synthesizing RNA from a DNA template, while translation is the process of synthesizing proteins from mRNA
• Mutations in DNA can lead to changes in protein structure and function, potentially causing genetic disorders or contributing to evolutionary change
• DNA replication ensures the accurate transmission of genetic material during cell division, with enzymes like DNA polymerase and DNA ligase playing key roles

Macromolecules in Action: Cellular Processes

• Macromolecules work together to carry out essential cellular processes, such as energy production, cell division, and cell signaling
• Carbohydrates are broken down through glycolysis and cellular respiration to generate ATP, the energy currency of the cell
  • Glucose is oxidized in the presence of enzymes and electron carriers, with the released energy used to power cellular work
• Lipids, particularly phospholipids, form the basis of cell membranes, which control the movement of molecules in and out of the cell
  • Membrane proteins, such as receptors and channels, facilitate communication and transport across the membrane
• Proteins catalyze the vast majority of chemical reactions in cells, including those involved in metabolism, DNA replication, and cell division
  • Enzymes often work in cascades or pathways, with the product of one reaction serving as the substrate for the next
• Nucleic acids direct the synthesis of proteins through the processes of transcription and translation
  • The genetic code, a triplet of nucleotides (codon) corresponding to a specific amino acid, ensures the accurate translation of genetic information
• Cell signaling involves the interaction of macromolecules, such as hormones, receptors, and second messengers, to coordinate cellular activities
  • Signal transduction pathways amplify and transmit signals from the cell surface to the nucleus, resulting in changes in gene expression and cell behavior

Real-World Applications and Current Research

• Understanding biological macromolecules has led to numerous advances in fields like medicine, agriculture, and biotechnology
• Recombinant DNA technology allows for the production of human proteins, such as insulin and growth hormone, in bacteria or other organisms
  • This has revolutionized the treatment of diabetes and other hormonal disorders
• Genetically modified crops have been developed to increase yield, resist pests, and tolerate harsh environmental conditions
  • Examples include Bt corn, which produces a bacterial toxin that kills insect pests, and Roundup Ready soybeans, which are resistant to the herbicide glyphosate
• Personalized medicine uses an individual's genetic information to tailor treatments and predict disease risk
  • Pharmacogenomics studies how genetic variations influence drug response, allowing for more targeted and effective therapies
• CRISPR-Cas9 is a powerful gene-editing tool that allows researchers to make precise changes to DNA sequences
  • This technology has the potential to treat genetic disorders, create disease-resistant crops, and even bring extinct species back to life
• Synthetic biology aims to design and construct new biological systems or organisms with specific functions
  • This field combines principles from engineering, computer science, and biology to create novel proteins, metabolic pathways, and even entire genomes
• Research on biological macromolecules continues to expand our understanding of life processes and opens up new possibilities for improving human health and well-being