Chapter 2: Chemistry Comes Alive – Comprehensive Study Notes

Chapter 2: Chemistry Comes Alive

Subatomic Particles and Atomic Structure

Atoms are the fundamental units of matter, composed of three main subatomic particles: protons, neutrons, and electrons. Understanding their properties is essential for grasping chemical behavior.

• Proton: Positively charged particle found in the nucleus; determines atomic number.

• Neutron: Neutral particle found in the nucleus; contributes to atomic mass.

• Electron: Negatively charged particle orbiting the nucleus; involved in chemical bonding.

• Atomic Number: Number of protons in an atom; defines the element.

• Mass Number: Sum of protons and neutrons in the nucleus.

• Valence Shell Electrons: Electrons in the outermost shell; determine chemical reactivity.

Isotopes and Radioisotopes

Isotopes are variants of elements with different neutron numbers. Radioisotopes are unstable isotopes that emit radiation.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Half-life: Time required for half the atoms in a sample to decay.

• Radioisotope: Isotope that undergoes radioactive decay, emitting energy.

• Difference: Radioisotopes are unstable; other isotopes may be stable.

Electron Arrangement and the Octet Rule

Electron configuration determines chemical properties. The octet rule states that atoms tend to fill their outer shell with eight electrons.

• Octet Rule: Atoms are most stable when their valence shell contains eight electrons.

• Electron Arrangement: Electrons fill shells in order of increasing energy.

Ions and Ionic Bonds

Ions are charged atoms formed by gaining or losing electrons. Ionic bonds result from the attraction between oppositely charged ions.

• Ion: Atom or molecule with a net charge.

• Cation: Positively charged ion (loss of electrons).

• Anion: Negatively charged ion (gain of electrons).

• Common Body Ions: Na+, K+, Ca2+, Cl-, HCO3-

• Formation: Atoms become ions by transferring electrons.

• Ionic Bond: Electrostatic attraction between cation and anion (e.g., NaCl).

Covalent Bonds and the Octet Rule

Covalent bonds involve sharing electrons to satisfy the octet rule. They are common in organic molecules.

• Covalent Bond: Sharing of electron pairs between atoms.

• Formation: Atoms share electrons to achieve stable electron configuration.

• Single Bond: One pair of shared electrons (e.g., H2).

• Double Bond: Two pairs of shared electrons (e.g., O2).

• Triple Bond: Three pairs of shared electrons (e.g., N2).

Polar, Nonpolar, and Hydrogen Bonds

Bond polarity affects molecular properties. Hydrogen bonds are weak attractions important in biological molecules.

• Polar Covalent Bond: Unequal sharing of electrons; creates partial charges (e.g., H2O).

• Nonpolar Covalent Bond: Equal sharing of electrons (e.g., CH4).

• Hydrogen Bond: Weak attraction between hydrogen and electronegative atom (e.g., between water molecules).

Elements in the Human Body

Four elements make up most of the human body.

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

Properties of Water

Water is essential for life due to its unique properties.

• High heat capacity

• High heat of vaporization

• Polar solvent properties

• Reactivity

• Cushioning

Mixtures and Concentration Expressions

Mixtures are combinations of substances. Concentration is expressed in various ways.

• Solution: Homogeneous mixture (e.g., salt water).

• Colloid: Heterogeneous mixture with dispersed particles (e.g., cytosol).

• Suspension: Large particles settle out (e.g., blood).

• Concentration: Percentage, weight/volume (mg/dL).

Hydrophilic, Hydrophobic, Amphipathic

Molecules interact with water differently based on their structure.

• Hydrophilic: Water-loving; dissolves in water.

• Hydrophobic: Water-fearing; does not dissolve in water.

• Amphipathic: Contains both hydrophilic and hydrophobic regions (e.g., phospholipids).

Chemical Reactions: Types and Energy Flow

Chemical reactions transform substances. Energy flow distinguishes reaction types.

• Catabolism: Breakdown of molecules; releases energy.

• Anabolism: Synthesis of molecules; requires energy.

• Endergonic: Absorbs energy.

• Exergonic: Releases energy.

• Factors Influencing Rate: Temperature, concentration, particle size, catalysts.

Organic vs Inorganic Chemistry

Organic compounds contain carbon; inorganic compounds do not.

• Organic: Carbohydrates, lipids, proteins, nucleic acids.

• Inorganic: Water, salts, acids, bases.

Acids, Bases, Salts, and pH

Acids, bases, and salts are important for maintaining homeostasis. pH measures hydrogen ion concentration.

• Acid: Releases H+ ions.

• Base: Releases OH- ions.

• Salt: Ionic compound from acid-base reaction.

• pH Scale: $\text{pH} = -\log_{10}[\text{H}^+]$

• Normal Blood pH: 7.35–7.45

• Acidosis: pH < 7.35

• Alkalosis: pH > 7.45

• Buffer: Substance that resists pH changes.

Inflammation and Aspirin

Inflammation is a response to injury. Aspirin has therapeutic effects.

• Signs/Symptoms: Redness, heat, swelling, pain, loss of function.

• Aspirin Effects: Anti-inflammatory, analgesic, antipyretic, antiplatelet.

Carbohydrates

Carbohydrates are energy sources and structural molecules.

• Monosaccharides: Glucose, fructose, galactose.

• Disaccharides: Sucrose, lactose, maltose.

• Polysaccharides: Glycogen, starch, cellulose.

• Function: Provide energy, store energy, structural support.

Hydrolysis vs Dehydration Reactions

These reactions build and break down biomolecules.

• Hydrolysis: Addition of water to break bonds.

• Dehydration: Removal of water to form bonds.

Lipids

Lipids are diverse molecules with various functions.

• Types: Triglycerides, phospholipids, steroids, eicosanoids.

• Functions: Energy storage, membrane structure, signaling, insulation.

Proteins and Amino Acids

Proteins are polymers of amino acids, essential for structure and function.

• Amino Acid: Contains amino group, carboxyl group, and R group.

• Chemical Backbone: $\text{NH}_2$–$\text{CH}$–$\text{COOH}$

• Peptide Bond: Covalent bond between amino acids.

• Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helix, beta sheet.

  • Tertiary: 3D folding.

  • Quaternary: Multiple polypeptides.

• Denaturation: Loss of structure due to heat, pH, chemicals.

Enzymes

Enzymes are biological catalysts that speed up reactions.

• Function: Lower activation energy.

• Mechanism: Bind substrate, convert to product.

Nucleic Acids

Nucleic acids store and transmit genetic information.

• Nucleotide: Composed of sugar, phosphate, and nitrogenous base (A, T, C, G).

• DNA vs RNA: DNA is double-stranded, contains thymine; RNA is single-stranded, contains uracil.

• DNA Structure: Double helix.

ATP: The Energy Molecule

ATP is the primary energy carrier in cells.

• Structure: Adenosine triphosphate.

• Role: Stores and releases energy for cellular processes.

• Equation: $\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$