Chemical Bonds & Biological Macromolecules

Flashcards covering chemical bonds, properties of water, acids/bases, and biological macromolecules (carbohydrates, lipids) as discussed in the lecture notes.

Covalent Bonds

Atoms equally share electrons to fill their outermost shells; can be single, double, or triple bonds.

Nonpolar Covalent Bond

Atoms share electrons equally, and the electronegativity values of the two atoms are equal (e.g., H-H, O=O).

Polar Covalent Bond

Unequal sharing of valence electrons due to different electronegativity values of the two atoms.

Ionic Bond

Involves the transfer of electrons (not sharing) and forms an intramolecular attraction between positive and negative ions (typically metal and non-metal).

Hydrogen Bond

An intermolecular attraction between an H atom and a highly electronegative element (like O, N, F); only polar molecules form H bonds.

Polarity

The distribution of electrical charge over the atoms joined by a bond; influenced by molecular shape.

Ion formation

Occurs when an atom, initially having an equal number of electrons and protons with no net charge, gains or loses electrons.

Cation

An atom that loses electrons and becomes positively charged.

Anion

An atom that gains electrons and becomes negatively charged.

Liquid Water

Hydrogen bonds are 50% longer than covalent bonds and break and reform easily.

Vapor Water

Heat energy disrupts hydrogen bonds, and lower temperatures cause condensation.

Hydrophilic

Describes molecules that 'like' and form bonds with H2O molecules.

Hydrophobic

Describes molecules that repel H2O molecules.

Water (as a solvent)

An excellent solvent because it is a polar molecule, allowing many other molecules to dissolve in it.

Acids

Substances that donate H+ (protons).

Bases

Substances that remove H+.

pH Scale

Measures the 'Power of Hydrogen,' ranging from 0 (acidic) to 7.5 (neutral) to 14 (basic).

Strong Acids & Bases

Substances that completely ionize in solution.

Macromolecules

Large molecules built by cells from smaller molecules, with 3 classes of polymers made by joining monomers through covalent bonds.

Polymer Synthesis

Polymers are built through condensation reactions (releasing H2O, requiring ATP, and aided by enzymes).

Polymer Breakdown

Polymers are taken apart through hydrolysis reactions (requiring H2O, releasing energy, and aided by enzymes).

Carbohydrates

Consist of C/H/O in a 1:2:1 ratio; serve as structural material (plant/bacterial cell walls) and energy sources, with monosaccharides as their monomer.

Monosaccharide

A simple sugar, such as glucose or fructose, which is typically a 6-carbon sugar and serves as a monomer for carbohydrates.

Disaccharide

Two monosaccharides linked together by a condensation reaction (e.g., Glucose + Fructose = Sucrose).

Starch

A large carbohydrate and storage molecule of glucose in plants, a polymer made of monomers linked by alpha bonds (digestible by humans).

Glycogen

Energy storage in animals (stores glucose), functionally equivalent to starch; stored in liver and muscle cells with alpha 1,4 bonds and beta 1,6 branches.

Cellulose

Tightly coiled form that constitutes the structural part of plant cell walls; made of glucose chains linked by beta bonds, not digestible by humans, and highly resistant to degradation.

Chitin

A modified glucose polymer that strengthens the exoskeleton of crabs, lobsters, insects, and fungi cell walls; not digestible by humans due to beta bonds and an N-containing group attached to glucose.

Lipids

Non-polar and insoluble molecules that form cell membranes, provide insulation, and serve as an energy source; cannot form hydrogen bonds with H2O.

Fatty Acid

A carboxylic acid (COOH) with a long hydrocarbon chain; a common component of lipids, having a hydrophilic head and a hydrophobic tail.

Phospholipids

Main components of cell membranes, consisting of a glycerol backbone, two fatty acid tails, and a phosphate head.

Phospholipid Head

The carboxyl group (COOH) portion of a phospholipid; it is polar and hydrophilic.

Phospholipid Tail

The long chain of hydrocarbons (HC) in a phospholipid; it is non-polar and hydrophobic.