Chemical Composition of the Body

Complete vocabulary flashcards for Chapter 2: Chemical Composition of the Body, covering atomic logic, solutions, acids/bases, and the four major classes of organic molecules.

Ion

An atom that results from gaining or losing one or more electrons, causing a mismatch in the number of protons and electrons and making it electrically charged.

Covalent Bond

A strong chemical bond formed when atoms share electrons, such as in methane ($CH_4$).

Ionic Bond

A chemical bond formed by the attraction between opposite charges, such as in sodium chloride ($Na^+Cl^-$).

Hydrogen Bond

A weak electrostatic attraction between a hydrogen atom and an oxygen ($O$) or nitrogen ($N$) atom.

van der Waals forces

Weak local forces that act as interactions between molecules, such as between lipid molecules.

Polarity

The unequal distribution of electrical charge in a molecule, resulting in one side being slightly positive and the other side slightly negative.

Chemical Concentration

The amount of a solute present in a given volume of solvent.

Molecular Weight (MW)

The total mass of all atoms in a molecule; it is the number of grams of a solute added to $1\,L$ of solvent to produce a $1$-molar ($1\,M$) solution.

Mole

The amount of a compound equivalent to its molecular weight ($MW$); for example, $180\,g$ of glucose ($C_6H_{12}O_6$) equals $1$ mole.

Hydrophilic

Literally "water loving"; refers to polar compounds, such as $NaCl$, that dissolve readily in water.

Hydrophobic

Literally "water fearing"; refers to non-polar compounds, like fats, that do not dissolve readily in water but dissolve in non-polar solvents.

Amphipathic

Molecules that possess both a hydrophobic region and a hydrophilic region, such as phospholipids in cell membranes.

pH

A value indicating the acidity of a solution based on the concentration of free hydrogen ions, calculated as $pH = -\log[H^+]$.

Acidic

A solution with a $pH < 7$ caused by a high concentration of $[H^+]$.

Alkaline (basic)

A solution with a $pH > 7$.

Carbohydrates

Organic molecules containing $C$, $H$, and $O$ in the general formula $C_n H_{2n} O_n$, primarily used for energy storage and production.

Glycogen

A polysaccharide that serves as a high-energy storage molecule made up of glucose units.

Lipids

Nonpolar organic molecules composed of $H$ and $C$; types include fatty acids, triglycerides, phospholipids, and steroids.

Saturated Fatty Acid

A fatty acid, such as palmitic acid, where all carbons are linked by single bonds.

Unsaturated Fatty Acid

A fatty acid, such as linolenic acid, containing one or more double bonds.

Phospholipids

Amphipathic lipids formed from glycerol, two fatty acids, and one or more charged phosphate groups; they are key components of cell membranes.

Micelles

Aggregates of amphipathic molecules (like phospholipids) that spontaneously arrange in water so that polar regions face the water.

Cholesterol

A steroid lipid that promotes membrane fluidity and serves as a starting material for steroid hormones.

Proteins

Macromolecules containing $C$, $H$, $O$, $N$, and small amounts of sulfur, formed from amino acid ($AA$) monomers.

Peptide bonds

Covalent bonds that connect neighboring amino acids together to form a polypeptide chain.

Primary Structure (Protein)

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure (Protein)

The folded or twisted shape of a protein, such as an alpha helix or beta pleated sheet, determined by hydrogen bonds.

Tertiary Structure (Protein)

The overall three-dimensional shape of a functional protein resulting from the folding and bending of a polypeptide chain.

Quaternary Structure (Protein)

The multimeric structure formed when two or more polypeptides bond together, such as in hemoglobin.

Nucleic Acids

Organic molecules responsible for information storage, composed of a sugar, a base, and a phosphate group; examples include DNA and RNA.

DNA (Deoxyribonucleic acid)

A double-chained nucleic acid containing deoxyribose sugar and the bases Adenine, Guanine, Cytosine, and Thymine.

RNA (Ribonucleic acid)

A single-chained nucleic acid containing ribose sugar and the bases Adenine, Guanine, Cytosine, and Uracil.