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.