Everyday Chemistry of Life - Summary Notes

Our Universe is Made of Chemicals

Biology relies on chemistry.
Chemical interactions dictate life processes.
Chemistry is integral to daily activities.

Life's Unique Chemistry

Primarily composed of: Oxygen, Carbon, Hydrogen, and Nitrogen.
Also contains Calcium, Phosphorus, Sulfur, Sodium, Chlorine, Magnesium, and trace elements.

Atomic Structure

Elements are made of atoms.
Atoms: smallest unit of an element that form compounds and molecules.
Structure:
- Nucleus: Protons (positive charge) and Neutrons (no charge).
- Electron cloud: Negatively charged electrons orbiting the nucleus.
Electromagnetic attraction between protons and electrons maintains electron orbit.
Neutral atoms: Number of electrons equals the number of protons.

Orbitals

Orbitals: Clouds of electrons surrounding the nucleus with different energy levels.
Valence shell: Outermost energy level.
Valence electrons: Electrons in the valence shell.

Atomic Number and Mass

Atomic Symbol examples:
- Carbon = C
- Oxygen = O
- Sodium = Na
Atomic Number: Number of protons in the nucleus (e.g., $_{6}C$ ).
Atomic Mass: Weight of protons and neutrons (e.g., $^{12}C$ ). Protons and neutrons weigh about 1 atomic mass unit (amu).

Isotopes

Isotopes: atoms with the same number of protons but different neutrons.
Isotopes are chemically identical but have different masses.
Unstable isotopes release energy (radiation).

Periodic Table

Organizes elements by atomic number and reactivity.
Elements in the same column have similar valence electrons and reactivity.

Chemical Bonding

Atoms bond to form molecules and compounds.
Molecule: two or more atoms (e.g., $H_2$ ).
Compound: molecule with different atoms (e.g., $CO_2$ ).
Types of Bonds:
- Ionic
- Covalent
- Hydrogen

Valence Shells and Bonds

Filled valence shells (8 electrons) are stable (Noble gases).
Unfilled valence shells form bonds by sharing or moving electrons.
Atoms losing electrons become positive ions.
Atoms gaining electrons become negative ions.

Ionic Bonds

Formed by attraction between positive and negative ions (e.g., $Na^+$ and $Cl^−$ in NaCl).
Example: Sodium (Na) loses an electron to become $Na^+$ , Chlorine (Cl) gains an electron to become $Cl^−$ .

Covalent Bonds

Atoms share valence electrons to fill shells.
Non-polar Covalent Bonds : electrons are shared equally
Single bond: one electron pair shared (e.g., $H_2$ ).
Double bond: two electron pairs shared (e.g., $O_2$ ).
Triple bond: three electron pairs shared (e.g., $N_2$ ).

Polar Covalent Bonds

Electrons unequally shared.
One atom attracts electrons more strongly, becoming slightly negative.
Other atom becomes slightly positive (e.g., water).

Hydrogen Bonds

Weak bonds between slightly positive hydrogen and slightly negative atoms.
Important for:
- Holding water molecules together.
- DNA structure.
- Protein shape.

Van der Waals Forces

Weak forces from temporary electromagnetic interactions.

Energy in Bonds

Exothermic Reaction: Energy released when bonds form. Example: $C + O<em>2 = CO</em>2$
Endothermic Reaction: Energy absorbed when bonds form (e.g., forming long-chain sugars).

Water's Importance

Water: 60-70% of body weight.
Needed for digestion, excretion, respiration, and circulation.

Water Properties

Liquid at Room Temp: Forms polar covalent bonds and hydrogen bonds.
Solvent: Dissolves hydrophilic (charged) substances.
Cohesive and Adhesive: Fills vessels and provides lubrication.
High Specific Heat: Stabilizes body temperature.
High Heat of Vaporization: Cooling through sweating.
Ice Floats: Provides insulation and protection.

pH Scale

Measures H+ concentration (0-14).
Lower pH: Higher H+ concentration (acidic).
pH 7: Equal H+ and OH- (neutral).
Higher pH: Lower H+ concentration (alkaline).
Logarithmic scale: Each unit is a tenfold change.

Hydrogen Ion Concentration

Affects chemical reactions and concentrations.
Blood pH must be between 7.4 and 7.5.
Buffers stabilize pH by absorbing or releasing H+.

Organic Compounds

Contain carbon atoms that covalently bind with up to four other atoms.
Four Categories:
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids

Carbohydrates

Composed of carbon, hydrogen, and oxygen (1:2:1 ratio e.g., $C<em>6H</em>{12}O_6$ ).
Energy source.

Saccharides (Sugars)

Monosaccharides: simple sugars (e.g., glucose, fructose).
Disaccharides: two monosaccharides (e.g., sucrose, lactose).
Polysaccharides: long chains of monosaccharides (e.g., glycogen, starch, cellulose).

Lipids

Hydrophobic compounds (fats, oils, sterols, waxes).
Fatty acids: Energy-storing lipids. Can bind to glycerol to form triglycerides and phospholipids.

Fatty Acids

Unsaturated: At least one double bond, liquid at room temperature (oils).
Saturated: No double bonds, straight shape, solid at room temperature (butter).

Phospholipids

Hydrophilic polar head and hydrophobic fatty acid tails.
Form bilayers in water (cell membranes).

Steroids

Four-ring structure (cholesterol, sex hormones).
Cholesterol: Membrane flexibility.
Sex hormones: Estrogen and Testosterone.

Proteins

Made from 20 amino acids.
Amino Acid Structure: central carbon atom, amino group, carboxyl group, and R group.

Amino Acids & Proteins

Peptide bonds join amino acids.
Dipeptide: two amino acids.
Polypeptide: linear sequence of amino acids.
Proteins require a 3D shape to function, determined by amino acid sequence.

Protein Function & Shape

Shape (globular or fibrous) determines function.
- Globular: round, water-soluble.
- Fibrous: stringy, insoluble.
Amino acid sequence determines the final shape.

Enzymes

Catalysts that speed up chemical reactions.
Active site binds to a specific substrate.

Nucleic Acids

DNA: hereditary information in the nucleus to build proteins, regulate processes, and maintain homeostasis.
RNA: messenger molecule that Regulates metabolism, produces proteins, and governs development.

Life Requires Energy

Energy stored as glycogen, triglycerides, and ATP (adenosine triphosphate).
ATP powers cellular activity.