BIO181_Ch2_S25 (2)
Chapter 2: The Chemistry of Life
Page 1: Introduction
Computer-generated image: One strand of DNA.
Page 2: Elements - The Components of Matter
Major Elements (96%): Essential for life, including Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).
Mineral Elements (<4%): Include elements such as calcium (Ca), potassium (K), and sodium (Na).
Trace Elements (0.01%): Include elements like iron (Fe), iodine (I), and zinc (Zn) which are crucial in minute amounts.
Periodic Table: Metals on the left and nonmetals on the right, with a red staircase dividing them.
Page 3: Atoms - Single Elemental Units
Nucleus: Contains protons (p+) and neutrons (nº).
Electron Shells: The outer shells contain electrons (e¯).
Example - Carbon Atom: 6 protons, 6 neutrons, 6 electrons.
Page 4: Filling Electron Orbitals
Electron Shell Capacity:
1st shell: Holds 2 electrons.
2nd shell: Holds 8 electrons.
3rd shell: Can hold up to 18 electrons but is stable with 8.
Chlorine: Has 7 valence electrons.
Page 5: Covalent Bonding – Sharing of Electron Pairs
Hydrogen Molecule Formation:
Each hydrogen atom has one electron.
The protons attract each other's electrons, merging shells to form H₂ molecule while obeying the duet rule.
Page 6: Nonpolar vs. Polar Covalent Bonds
Nonpolar Covalent Bond (H₂): Electrons are evenly shared between the two hydrogen atoms.
Polar Covalent Bond (H₂O): Electrons spend more time near the oxygen atom, giving it a partial negative charge and the hydrogen atoms partial positive charges.
Page 7: Multiple Covalent Bonds
Example: Carbon can form multiple covalent bonds by sharing more than one pair of electrons.
Page 8: Hydrogen Bonding and Surface Tension
Hydrogen Bonds: Weak attractions between polar covalent compounds.
Surface Tension: Hydrogen bonds create surface tension in water, allowing droplets to form.
Page 9: Ionic Bonds
Definition: Result from electron transfer between a metal (which becomes positively charged) and a nonmetal (which becomes negatively charged).
Ionic Bond Formation: E.g., Sodium ion (Na+) transfers an electron to Chlorine (Cl-) to form NaCl.
Page 10: Some Helpful Vocabulary
Solvent: Fluid in which substances dissolve; in the human body, the solvent is always water.
Solute: Substance that is dissolved; can be hydrophilic or hydrophobic.
Solution: Mixture of solute in solvent.
Page 11: Ionic Molecules
Ionic Compounds: Such as sodium (Na+) and chloride (Cl-) ions are attracted to water molecules.
Page 12: Polar Covalent Molecules
Example: Carbon monoxide (CO) has polarity allowing interaction with water.
Page 13: Nonpolar Covalent Compounds
Example: Methane (CH₄) molecules lack charge, having no interaction with water.
Page 14 & 15: Potential Energy and Kinetic Energy
Potential Energy: Stored energy (e.g. stationary ball).
Kinetic Energy: Energy of motion (e.g. moving ball).
Chemical Bonds: Bonds represent potential energy in molecules.
Page 16: Classes of Chemical Reactions
Dehydration Synthesis: Formation of complex molecules by removal of water (e.g. Glucose + Fructose = Sucrose).
Hydrolysis: Breakdown of molecules by the addition of water.
Page 17: Classes of Chemical Reactions Continued
Anabolic: Synthesis process (A + B → AB).
Catabolic: Breakdown process (AB → A + B).
Exchange Reaction: Rearrangement of components (AB + CD → AC + BD).
Page 18: Activation Energy
Energy required to start a chemical reaction.
Transition State: Point at which reactants are transformed into products.
Page 19: The Effect of Enzymes on Activation Energy
Enzymes lower activation energy, speeding up reactions.
Page 20: Enzyme-Substrate Interaction
Process: Enzymes bind to substrates, altering their shape and forming products before dissociating back to their original state.
Page 21: The Behavior of Acids and Bases in Water
Water dissociation: H₂O ↔ H⁺ + OH⁻ (Pure water has equal concentrations)
Acidic Solution: When an acid, like HCl, releases H⁺.
Basic Solution: When a base, like NaHCO₃, accepts H⁺.
Page 22: The pH Scale
pH Levels: Ranges from 0 (acidic) to 14 (basic); pure water is neutral at 7.
Page 23: The pH Scale Details
Negative Exponential Scale: Each increment of pH represents a tenfold change in hydrogen ion concentration.
Page 24: Carbohydrates - Monosaccharides
Types: Pentoses (5 carbon sugars) and Hexoses (6 carbon sugars), examples include ribose and glucose.
Page 25: Carbohydrates - Disaccharides
Formation: Disaccharides are formed through dehydration synthesis from two monosaccharides (e.g., Glucose + Fructose = Sucrose).
Page 26: Carbohydrates - Polysaccharides
Structure: Polysaccharides consist of many monosaccharide units linked together.
Page 27: Proteins - Monomers (Amino Acids)
Basic Structure: Contains carboxylic acid group, amino group, and variable R group that determines properties.
Page 28: Proteins - Dipeptides
Peptide Bond Formation through dehydration synthesis.
Hydrolysis: Splitting of dipeptides into amino acids.
Page 29: Levels of Protein Structure
Primary Structure: Amino acid sequence.
Secondary Structure: Formation of alpha helices and beta-pleated sheets through hydrogen bonding.
Tertiary Structure: 3D folding due to interactions of R groups.
Quaternary Structure: Assembly of multiple polypeptide chains.
Page 30: Nucleic Acids - Monomers (Nucleotides)
Structure of Nucleotide: Composed of a nitrogenous base, pentose sugar, and phosphate group.
Base Types: Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Thymine, Uracil).
Page 31: ATP - a Nucleic Acid
Structure: Adenosine triphosphate (ATP) consists of adenine, ribose, and three phosphate groups.
Energy Transfer: ATP carries energy; conversion to ADP releases energy.
Page 32: Lipids - Hydrophobic Organic Molecules
Classification: Saturated, monounsaturated, and polyunsaturated fatty acids; hydrophobic in nature.
Page 33: Lipids - Triglycerides
Formation: Glycerol linked to three fatty acids through dehydration synthesis creates triglycerides.
Page 34: Lipids - Phospholipids
Structure: Consist of hydrophilic phosphate "head" and hydrophobic fatty acid "tails".
Page 35: Lipids - Steroids
Steroid Structure: Characterized by a common steroid nucleus, examples include cholesterol.