Water, Chemistry of Life, and Nucleic Acids

Flashcards covering key vocabulary related to water chemistry, pH, and the structure and properties of nucleic acids (DNA and RNA) from lecture notes.

Covalent Bonds

Bonds formed by the sharing of electrons between atoms.

Hydrogen Bonds

Bonds formed between molecules with differences in electronegativity, such as between water molecules.

Polar Covalent Bonds

Covalent bonds within a water molecule, where electrons are unequally shared due to differences in electronegativity.

Energy and Bonds

Breaking bonds requires energy; covalent bonds require more energy than hydrogen bonds to break because they are stronger.

Heat

Motion of molecules, which provides energy, speeds up reactions, and allows more bonds to break and form due to increased atomic interactions.

Boiling Water

The process where hydrogen bonds between water molecules break, as they are much weaker than the covalent bonds within individual water molecules.

Evaporation of Water

Requires a significant amount of energy to break all the hydrogen bonds between water molecules, aiding in cooling processes like sweating.

High Specific Heat of Water

Due to the large amount of hydrogen bonds that need to be broken to increase water's temperature.

High Surface Tension of Water

Caused by the hydrogen bonds between water molecules holding the surface together.

Cohesion

The property of water molecules sticking together via hydrogen bonds.

Adhesion

The property of water molecules sticking to other polar molecules via hydrogen bonds.

Non-polar Molecules (in water)

Molecules that cause hydrogen bonds between water molecules to break without being reformed, making the situation thermodynamically unfavorable, leading to clustering.

Hydrophobic

Meaning 'water-fearing,' describing non-polar or very large, weakly polar molecules that are excluded by polar molecules and cluster together in water.

Hydrophilic

Meaning 'water-loving,' describing polar molecules that readily dissolve in water because they can break and reform hydrogen bonds, making it energetically favorable.

pH

A measure of the hydrogen ion (H+) concentration in a solution, calculated as -log[H+].

Neutral pH

A pH of 7, indicating an equal amount of H+ and OH- ions, as found in pure water.

Acidic Solution

A solution with a pH less than 7, indicating more H+ ions than OH- ions.

Basic Solution

A solution with a pH greater than 7, indicating fewer H+ ions than OH- ions.

Nucleotides

The monomers of nucleic acids, composed of a phosphate group, a nitrogenous base, and a pentose sugar group.

Phosphate Group (in Nucleotides)

Attached to the 5’ carbon of the sugar; it loses hydrogen atoms in water, increasing H+ concentration and making solutions with nucleotides acidic.

DNA (Deoxyribonucleic Acid)

A polymer of nucleotide monomers, typically a double helix, containing deoxyribose sugar (with one OH group on 3' carbon and no oxygen on 2' carbon) and bases Adenine, Guanine, Cytosine, and Thymine.

RNA (Ribonucleic Acid)

A polymer of nucleotide monomers, typically a single strand, containing ribose sugar (with OH groups on both 2' and 3' carbons) and bases Adenine, Guanine, Cytosine, and Uracil (instead of Thymine).

Nucleic Acid Backbone

Formed by alternating phosphate and sugar groups; it is polar with a 5’ phosphate end and a 3’ hydroxyl end.

Antiparallel Strands

The orientation of the two strands in a DNA double helix, running in opposite 5' to 3' directions.

Base Pairing Rules

In DNA, Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via 3 hydrogen bonds. In RNA, Uracil (U) replaces Thymine and pairs with Adenine.

Rosalind Franklin

Used X-ray diffraction to determine that DNA has a double helix structure, its width, and the distance between repetitions.

Watson and Crick

Co-discovered the double helical structure of DNA, realizing the specific A-T and C-G base pairing rules.