Molecules of Life

Comprehensive vocabulary flashcards covering the molecular biology of water, carbohydrates, lipids, proteins, and nucleic acids as presented in the Chapter 1 lecture notes.

Properties of Water: Polarity

A condition where a molecule, such as water, has no net charge but carries an unequal distribution of electrical charge, resulting in opposite ends of the molecule having opposite charges.

Structure of Water Molecule

Consists of one oxygen atom and two hydrogen atoms joined by covalent bonds spreading apart at an angle of $104.5^\circ$.

Hydrogen Bond

A weak bond formed when the partially positive charged hydrogen atoms ($\delta+$) of one water molecule are attracted to the partially negative charged oxygen atoms ($\delta-$) of nearby water molecules.

Hydrophilic

Water-loving substances, such as sugar or salt, that are attracted to the polarity of water molecules.

Hydrophobic

Water-hating substances, such as oil, that consist of non-polar molecules and are repelled by water.

Specific Heat Capacity of Water

The amount of heat that must be absorbed or lost to change the temperature of $1\,g$ of water by $1^\circ C$, which for water is $1\,cal/g^\circ C$.

Hydration Shell

A sphere of water molecules that surrounds each dissolved ion, separating and shielding them from one another.

Latent Heat of Vaporization

The quantity of heat that must be absorbed by $1\,g$ of water to vaporize it from a liquid to a gas.

Cohesion

The attraction between water molecules that causes them to be held together, often resulting in high surface tension.

Adhesion

The attraction between water molecules and other different polar substances, such as the cell walls of xylem.

Maximum Density of Water

The unique property where water reaches its highest density at $4^\circ C$, causing ice at $0^\circ C$ to be less dense and float.

Monosaccharides

The basic units of carbohydrates and simplest sugar molecules which are sweet-tasting, soluble in water, and can be crystallized.

Aldose

A monosaccharide where the carbonyl group is located at the end of the carbon skeleton, such as glucose.

Ketose

A monosaccharide where the carbonyl group is located in the middle of the carbon skeleton, such as fructose.

Glycosidic Linkage

A covalent bond formed between two monosaccharides through a condensation process.

Maltose

A disaccharide formed from two molecules of $\alpha-glucose$ joined by an $\alpha-1,4$ glycosidic bond.

Amylopectin

A branched starch polymer of $\alpha-glucose$ units held by $\alpha-1,4$ glycosidic bonds with branches occurring at $\alpha-1,6$ glycosidic bonds.

Cellulose

A polymer of $\beta-glucose$ that serves as the main structural component of plant cell walls, featuring $\beta-1,4$ glycosidic linkages.

Triglycerides

A type of lipid consisting of three fatty acids linked to one glycerol molecule by ester bonds.

Saturated Fatty Acids

Fatty acids that have only single bonds in the hydrocarbon chain and tend to be solid at room temperature.

Unsaturated Fatty Acids

Fatty acids that have one or more double bonds ($-C=C-$) between carbon atoms, causing bending and typically remaining liquid at room temperature.

Phospholipids

Lipids consisting of a hydrophilic head and two hydrophobic tails, which form the bilayer of cell membranes.

Steroids

Organic compounds characterized by a carbon skeleton with four fused rings and a variable side chain.

Zwitterions

Bipolar ionic molecules, like amino acids at $pH\,7.4$, that possess both positive and negative charges on the same molecule.

Primary Structure of Protein

The linear chain of amino acids joined exclusively by peptide bonds.

Secondary Structure of Protein

Regions of a polypeptide stabilized by hydrogen bonds between the atoms of the backbone, taking forms like $\alpha-helix$ or $\beta-pleated\,sheet$.

Tertiary Structure of Protein

The three-dimensional shape of a single polypeptide chain stabilized by interactions between side chains, including disulfide bridges and ionic bonds.

Quaternary Structure of Protein

The overall protein structure resulting from the association of two or more polypeptide chains or subunits.

Denaturation

A process where a protein loses its original conformation and biological activity due to the breakage of chemical bonds caused by extreme pH or high temperature.

Nucleotide

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

Purines

Nitrogenous bases consisting of a double-ring structure, specifically Adenine ($A$) and Guanine ($G$).

Pyrimidines

Nitrogenous bases consisting of a single-ring structure, specifically Cytosine ($C$), Uracil ($U$), and Thymine ($T$).

Phosphodiester Linkage

The covalent bond that joins nucleotides together to form the sugar-phosphate backbone of a polynucleotide.

mRNA (Messenger RNA)

A single-stranded polynucleotide that carries genetic information copied from DNA to act as a template for protein synthesis.

tRNA (Transfer RNA)

An RNA molecule responsible for transferring specific amino acids to the ribosome during protein synthesis.