Chemistry in Living Organisms: Atoms to Macromolecules

Vocabulary flashcards covering key concepts from the lecture notes on atoms, bonds, water, pH, and macromolecules.

Atom

The basic unit of matter; the smallest unit of an element, composed of protons and neutrons in the nucleus and electrons orbiting around it.

Element

A pure substance made of one kind of atom; defined by its number of protons (atomic number) and distinct properties.

Atomic number

Number of protons in the nucleus; determines the identity of an element.

Mass number

Total number of protons and neutrons in the nucleus.

Isotope

Atoms of the same element with different numbers of neutrons; same atomic number, different mass number.

Radioisotope

An unstable isotope that undergoes radioactive decay over time.

Electron

Negatively charged subatomic particle that orbit the nucleus; extremely fast.

Proton

Positively charged subatomic particle located in the nucleus.

Neutron

Electrically neutral subatomic particle located in the nucleus.

Nucleus

Center of the atom containing protons and neutrons.

Electron shell

Concentric regions around the nucleus where electrons are found; first shell holds up to 2 electrons; second up to 8.

Ionic bond

Bond formed by transfer of electrons; resulting ions attract each other.

Covalent bond

Bond formed by sharing electrons between atoms.

Hydrogen bond

Weak bond between a hydrogen atom of one molecule and an electronegative atom (usually O or N) of another molecule.

Water as solvent

Water’s polarity makes it a good solvent; dissolves many solutes; salts dissociate; lipids are not soluble.

pH

Potential of hydrogen; measure of acidity or basicity of a solution; scale 0–14; 7 is neutral.

Acid

Substance that increases hydrogen ion concentration in solution.

Base (alkaline)

Substance that increases hydroxide ion concentration; raises pH.

Buffer

Substance that resists changes in pH by donating or accepting hydrogen ions as needed.

Salt

Ionic compound that dissolves in water into ions but does not increase hydrogen or hydroxide ion concentration.

Organic molecule

Molecule containing carbon; has a carbon backbone and includes macromolecules.

Macromolecule

A large organic molecule built from smaller units (monomers); four main types: carbohydrates, lipids, proteins, nucleic acids.

Carbohydrate

Macromolecule with carbon, hydrogen, and oxygen; general formula CH2O; primary energy source for cells.

Monosaccharide

Single sugar unit (e.g., glucose, fructose, galactose).

Disaccharide

Two monosaccharides joined by a glycosidic bond (e.g., sucrose, lactose, maltose).

Polysaccharide

Long chains of monosaccharides; examples include starch, glycogen, cellulose, chitin.

Starch

Plant storage polysaccharide consisting of glucose units.

Glycogen

Animal storage polysaccharide consisting of glucose units.

Cellulose

Plant cell wall polysaccharide made of glucose; structural.

Chitin

Glucose-based polysaccharide found in fungi cell walls and arthropod exoskeletons.

Lipid

Hydrophobic macromolecule with high energy content; includes fats, oils, phospholipids, waxes, steroids; not soluble in water.

Saturated fat

Fat with no double bonds between carbon atoms; typically solid at room temperature.

Unsaturated fat

Fat with one or more double bonds causing kinks; typically liquid at room temperature; generally healthier.

Trans fat

Man-made unsaturated fat with trans double bonds; associated with higher health risks than saturated fats.

Phospholipid

Lipid with glycerol, two fatty acid tails (hydrophobic) and a phosphate head (hydrophilic); forms cell membranes as a bilayer.

Wax

Hydrophobic lipid with long-chain components; protects surfaces and reduces water loss.

Steroid

Lipid with four fused carbon rings; includes hormones like estrogen and testosterone; cholesterol is a key example.

Cholesterol

Sterol component of cell membranes; modulates membrane fluidity and is a precursor to steroid hormones and vitamin D.

Protein

Macromolecule made of amino acids; performs many functions including enzymes, antibodies, transport, hormones, and structure.

Amino acid

Monomer of proteins; contains amino group, carboxyl group, central carbon, hydrogen, and a variable R group (20 types).

Peptide bond

Bond between the carboxyl group of one amino acid and the amino group of the next.

Primary structure

Linear sequence of amino acids in a protein; the initial level of protein structure.

Secondary structure

Local folded structures like alpha helices and beta pleated sheets formed by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein; stabilized by various interactions and disulfide bonds.

Quaternary structure

Arrangement of multiple polypeptide subunits into a functional protein (e.g., hemoglobin).

Denaturation

Unfolding of a protein from loss of its three-dimensional structure, resulting in loss of function.

Nucleic acid

Macromolecule made of nucleotides; stores and transmits genetic information (DNA, RNA); ATP is also a nucleotide.

Nucleotide

Monomer of nucleic acids; composed of a sugar, phosphate, and a nitrogenous base.

DNA

Deoxyribonucleic acid; double-stranded helix storing hereditary information; bases: A-T and C-G.

RNA

Ribonucleic acid; typically single-stranded; bases: A-U and C-G; involved in protein synthesis and regulation.

ATP

Adenosine triphosphate; main energy currency of the cell; energy released from terminal phosphate bond powers cellular work.