Chemistry of Life and Cell Biology Flashcards

Vocabulary practice flashcards covering key topics in biochemistry, nucleic acids, protein structure, and cellular organization from the lecture notes.

Chemical reactions

Changes in covalent bonds that alter molecular structures.

Covalent bond

A strong chemical association in which atoms share one or more pairs of electrons to fill their outer electron shells and achieve stability.

Electronegativity hierarchy

The relative affinity for electrons among major biological elements, expressed as $\text{Oxygen} > \text{Nitrogen} > \text{Carbon} = \text{Hydrogen}$.

Polar covalent bond

A covalent bond in which shared electrons spend more time near one nucleus than another due to differences in electronegativity, creating partial positive and partial negative charges.

Ionic bond

An attraction between oppositely charged ions that readily dissociates and is relatively weak under physiological, watery conditions.

Hydrophilic

The property of a molecule that allows it to readily interact with water through participation in noncovalent hydrogen bonds.

Hydrogen bond

A weak noncovalent interaction between opposite partial charges, where a partial positive charge on a hydrogen atom in a polar covalent bond interacts with a partial negative charge on another atom.

Hydrophobic interactions

Weak noncovalent associations between nonpolar covalent molecules that occur when placed in a polar environment like water.

Ribozymes

RNA molecules that catalyze chemical reactions in a manner similar to protein enzymes.

Purines

Nitrogenous bases characterized by a two-ring chemical structure, which include adenine and guanine.

Pyrimidines

Nitrogenous bases characterized by a single-ring chemical structure, which include cytosine, thymine, and uracil.

Nucleoside

A molecule composed of a nitrogenous base covalently linked to a pentose sugar, lacking any phosphate groups.

$2'$ Carbon (pentose sugar)

The specific carbon position on the sugar ring that distinguishes RNA (which possesses a reactive hydroxyl group, $-\text{OH}$) from DNA (which lacks an oxygen atom and possesses only a hydrogen atom, $-\text{H}$).

Complementary base pairing

Specific hydrogen bonding between nitrogenous base pairs, where Guanine pairs with Cytosine using $3$ hydrogen bonds, and Adenine pairs with Thymine using $2$ hydrogen bonds.

Amino acid ionization forms

Structures showing (a) the non-ionized form of an amino acid with an uncharged amino group ($-\text{NH}_2$) and carboxyl group ($-\text{COOH}$), and (b) the ionized form in aqueous solution with a positively charged amino group ($-\text{NH}_3^+$) and a negatively charged carboxyl group ($-\text{COO}^-$).

Residue

A generic term for a monomer subunit after it has been incorporated into a polymer chain.

Dehydration reaction

An energy-requiring chemical reaction that removes a water molecule to synthesize a covalent peptide bond between amino acids.

Hydrolysis

An energetically favorable chemical reaction that adds a water molecule to break a chemical bond.

Primary structure

The linear sequence of amino acids in a single polypeptide chain, which does not constitute a three-dimensional shape on its own.

Secondary structure

Local three-dimensional structural patterns (such as alpha helices and beta pleated sheets) stabilized by regularly repeating hydrogen bonds along the polypeptide backbone.

Tertiary structure

The overall three-dimensional shape of a single polypeptide chain, stabilized by noncovalent interactions among side chains and occasional covalent disulfide bonds.

Quaternary structure

The overall functional protein structure formed by the assembly of two or more individual polypeptide chains.

Chaperone proteins

Specialized proteins that protect unfolded or folding polypeptides to ensure they achieve their correct three-dimensional structure.

Cytosol

The fluid component of the cytoplasm in which cellular organelles are suspended.

Cytoplasm

All contents within the cell membrane excluding the nucleus.

Dynein

A motor protein that hydrolyzes ATP to transport cellular cargo directionally toward the negative ($-$) end of a microtubule.

Kinesin

A motor protein that hydrolyzes ATP to transport cellular cargo directionally toward the plus ($+$) end of a microtubule.

Myosin

The motor protein associated with actin microfilaments that uses ATP binding and hydrolysis to generate force during muscle contraction.

Intermediate filaments

Cytoskeletal structures composed of antiparallel tetramers that lack directional polarity and function strictly in providing structural support to cells.