General Biology I Unit 2 Review: The Chemical Foundation of Life

Key Concepts

• Matter consists of atoms, the fundamental units of elements
• Atoms bond together to form molecules through chemical reactions
• Water is a vital molecule with unique properties essential for life
• Carbon forms the backbone of organic molecules due to its ability to form four stable covalent bonds
• Macromolecules are large molecules composed of smaller organic molecules linked together
  • Includes carbohydrates, lipids, proteins, and nucleic acids
• Energy is required for chemical reactions to occur and is often stored in chemical bonds
• Understanding the chemical foundation of life has practical applications in fields such as medicine, agriculture, and biotechnology

Atoms and Elements

• Atoms are the basic units of matter composed of protons, neutrons, and electrons
  • Protons have a positive charge, neutrons have no charge, and electrons have a negative charge
• Elements are substances composed of only one type of atom distinguished by their atomic number
  • Atomic number represents the number of protons in an atom's nucleus
• Isotopes are variations of an element with different numbers of neutrons
• Electrons occupy specific energy levels called orbitals surrounding the nucleus
  • Valence electrons in the outermost shell participate in chemical bonding
• Periodic table organizes elements based on their atomic number and chemical properties
  • Includes metals (sodium), nonmetals (oxygen), and metalloids (silicon)

Chemical Bonds

• Chemical bonds form when atoms share or transfer electrons to achieve a more stable electron configuration
• Ionic bonds involve the transfer of electrons between atoms resulting in positively and negatively charged ions
  • Occurs between metals and nonmetals (sodium chloride)
• Covalent bonds involve the sharing of electrons between atoms
  • Nonpolar covalent bonds have equal sharing of electrons (methane)
  • Polar covalent bonds have unequal sharing of electrons due to electronegativity differences (water)
• Hydrogen bonds are weak attractions between hydrogen atoms and electronegative atoms (oxygen, nitrogen)
  • Contributes to the unique properties of water and the structure of macromolecules (DNA)

Water and Its Properties

• Water is a polar molecule with a bent geometry due to the unequal sharing of electrons between hydrogen and oxygen
• Hydrogen bonding between water molecules leads to cohesion, adhesion, and surface tension
  • Cohesion allows water to maintain column strength in xylem tissue for transpiration
  • Adhesion enables capillary action in narrow spaces (soil)
• Water has a high specific heat capacity, requiring significant energy to change its temperature
  • Moderates temperature fluctuations in living organisms and aquatic environments
• Water is an excellent solvent for polar and ionic compounds due to its polarity
  • Enables transport of nutrients and waste products in living systems
• Ice is less dense than liquid water, allowing aquatic life to survive under frozen surfaces

Carbon and Organic Molecules

• Carbon is the basis for organic molecules due to its ability to form four stable covalent bonds
• Carbon can form single, double, or triple bonds with other carbon atoms or elements
  • Leads to a vast diversity of organic molecules with different structures and functions
• Hydrocarbons are organic molecules composed of only carbon and hydrogen (methane, propane)
• Functional groups are specific arrangements of atoms that give organic molecules their unique properties
  • Includes hydroxyl (alcohol), carboxyl (carboxylic acid), amino (amine), and phosphate groups
• Isomers are compounds with the same molecular formula but different structural arrangements
  • Structural isomers have different bonding patterns (butane and isobutane)
  • Stereoisomers have the same bonding but different spatial arrangements (cis and trans fats)

Macromolecules

• Macromolecules are large molecules composed of smaller organic molecules linked together by covalent bonds
• Carbohydrates are composed of monosaccharides (simple sugars) linked together
  • Includes disaccharides (sucrose) and polysaccharides (starch, cellulose)
  • Serve as energy storage (glucose) and structural components (chitin in arthropod exoskeletons)
• Lipids are hydrophobic molecules that do not dissolve in water
  • Includes triglycerides (fats), phospholipids (cell membranes), and steroids (hormones)
• Proteins are composed of amino acids linked by peptide bonds
  • Primary structure is the sequence of amino acids
  • Secondary structure involves local folding patterns (alpha helices and beta sheets)
  • Tertiary structure is the overall 3D shape stabilized by interactions between amino acids
  • Quaternary structure involves multiple polypeptide chains (hemoglobin)
• Nucleic acids are composed of nucleotides containing a sugar, phosphate group, and nitrogenous base
  • DNA (deoxyribonucleic acid) stores genetic information
  • RNA (ribonucleic acid) plays a role in protein synthesis and gene regulation

Energy in Chemical Reactions

• Chemical reactions involve the breaking and forming of chemical bonds, which requires or releases energy
• Endergonic reactions require an input of energy to proceed and are non-spontaneous
  • Anabolic reactions that build complex molecules from simpler ones (photosynthesis)
• Exergonic reactions release energy and are spontaneous
  • Catabolic reactions that break down complex molecules into simpler ones (cellular respiration)
• Enzymes are biological catalysts that lower the activation energy of chemical reactions
  • Specific to particular substrates and reactions
  • Affected by factors such as temperature, pH, and substrate concentration
• ATP (adenosine triphosphate) is the primary energy currency in living systems
  • Hydrolysis of ATP to ADP (adenosine diphosphate) and inorganic phosphate releases energy for cellular processes

Practical Applications

• Understanding the chemical foundation of life has led to advancements in medicine
  • Drug design targets specific molecules and pathways (enzyme inhibitors)
  • Gene therapy utilizes nucleic acids to treat genetic disorders
• Agriculture benefits from knowledge of plant physiology and biochemistry
  • Genetically modified crops with enhanced nutrient content or pest resistance
  • Fertilizers and pesticides designed to optimize plant growth and protect against pests
• Biotechnology harnesses biological processes for industrial and environmental applications
  • Bioremediation uses microorganisms to degrade pollutants
  • Biosensors detect specific molecules using biological components (enzymes, antibodies)
• Forensic science relies on chemical analysis of biological evidence
  • DNA profiling identifies individuals based on unique genetic markers
  • Toxicology screens detect the presence of drugs or poisons in body fluids
• Biofuels are renewable energy sources derived from organic matter
  • Ethanol produced from fermentation of plant sugars (corn, sugarcane)
  • Biodiesel synthesized from vegetable oils or animal fats