Biomolecules: Proteins and Nucleic Acids

Practice vocabulary flashcards covering the structure, bonding, behavior, and functions of proteins and nucleic acids from Chapter 3 of Becker's World of the Cell.

Protein

A large, complex biomolecule that makes up approximately $\sim 50\%$ of a cell's dry weight and performs varied functions including catalysis, structural support, movement, regulation of cell processes, transport, communication, and defense.

Amino Acid

The monomer of proteins; $20$ amino acids are common to all life, possessing the same base structure and differing only by their R-group (side chain).

R-group (Side Chain)

The variable group attached to the central carbon of an amino acid that determines its specific chemical structure, reactivity, and behavior in aqueous solution.

Nonpolar Amino Acids

A group of $9$ hydrophobic amino acids (Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan, and Proline) that do not dissolve in aqueous solution.

Polar, Uncharged Amino Acids

A group of $6$ hydrophilic amino acids (Serine, Threonine, Cysteine, Tyrosine, Asparagine, and Glutamine) that dissolve in aqueous solution without bearing a net electric charge on their side chains.

Polar, Charged Amino Acids

A group of $5$ hydrophilic amino acids that dissolve in aqueous solution and carry an electrical charge, categorized into acidic amino acids (Aspartate, Glutamate) and basic amino acids (Lysine, Arginine, Histidine).

Alanine (ALA)

A nonpolar amino acid with a methyl ($-CH_3$) side chain that is insoluble in aqueous solution.

Threonine (THR)

A polar, uncharged amino acid with a side chain containing a hydroxyl group ($-CH(OH)CH_3$) that is soluble in aqueous solution.

Aspartic Acid (ASP)

An acidic, polar amino acid with a negatively charged ($-$) carboxyl-containing side chain that is soluble in aqueous solution.

Lysine (LYS)

A basic, polar amino acid with a positively charged ($+$) amino-containing side chain that is soluble in aqueous solution.

Peptide Bond

A strong covalent bond formed by a condensation reaction that links the carbon of the carboxyl group of one amino acid to the nitrogen of the amino group of another.

Polypeptide

A polymer formed by linking many amino acid monomers together via peptide bonds.

Primary Structure

The specific linear sequence of amino acids linked together in a polypeptide chain.

Secondary Structure

Localized folding of a polypeptide backbone into repeating patterns, specifically $\alpha$-helices and $\beta$-pleated sheets.

Tertiary Structure

The final three-dimensional shape of a polypeptide resulting from additional bonding among the amino acid side chains.

Quaternary Structure

The higher-level structure formed when two or more polypeptide subunits join together to make a larger protein complex.

Fibrous Proteins

Proteins that adopt elongated, structural shapes, such as elastin, collagen, and keratin.

Globular Proteins

Compact, folded proteins that execute physiological functions, such as hemoglobin and lactase enzyme.

Denaturation

The disruption of a protein's proper folding caused by environmental factors such as changes in temperature or pH, rendering it nonfunctional.

Deoxyribonucleic Acid (DNA)

A type of nucleic acid that stores and transmits genetic information, which codes for the synthesis of RNA and proteins.

Ribonucleic Acid (RNA)

A type of nucleic acid that functions in transmitting genetic information, acting as a catalyst, transporting biomolecules, and regulating cellular processes.

Nucleotide

The monomer of nucleic acids, each composed of a phosphate group, a $5\text{-carbon}$ sugar, and a nitrogenous base.

Purines

Double-ring nitrogenous bases found in nucleotides, consisting of Adenine (A) and Guanine (G).

Pyrimidines

Single-ring nitrogenous bases found in nucleotides, consisting of Thymine (T), Cytosine (C), and Uracil (U).

Deoxyribose

The $5\text{-carbon}$ sugar found in DNA nucleotides.

Ribose

The $5\text{-carbon}$ sugar found in RNA nucleotides.

Phosphodiester Bridge

The covalent bond formed via a condensation reaction between the $3'\text{ -OH}$ group of one nucleotide and the phosphate group of the next nucleotide.

Sugar-Phosphate Backbone

The repeating structural chain of alternating sugar and phosphate groups in a polynucleotide strand.

Directionality (Nucleic Acids)

The orientation of a polynucleotide strand possessing a distinct $5'$ end and $3'$ end, with the strand growing from the $3'$ end.

Complementary Base Pairing

Specific hydrogen bonding between nitrogenous bases in polynucleotides, where Adenine pairs with Thymine (or Uracil) and Guanine pairs with Cytosine.

Hairpin (RNA)

A secondary structure formed when a single-stranded RNA molecule self-pairs via complementary base pairing.

Ribozyme

An RNA molecule capable of acting as a biological catalyst, such as catalyzing its own polymerization.

RNA World Hypothesis

The hypothesis proposing that early RNA served as a precursor to life by fulfilling both genetic information storage and catalytic functions before DNA and proteins evolved to assume these roles.