Foundations of Cell Biology - Protein Structure and Enzymes (VOCABULARY)

Vocabulary flashcards covering protein structure levels, key terms, and enzyme concepts from the lecture notes.

Primary structure

The linear sequence of amino acids in a protein (polypeptide), directed by the gene sequence.

Secondary structure

Regular local structures formed by hydrogen bonds between backbone atoms, including alpha helices and beta sheets.

Alpha helix

A right-handed coiled secondary structure stabilized by intra-chain hydrogen bonds.

Beta pleated sheet

A sheet-like secondary structure formed by hydrogen bonds between adjacent polypeptide strands.

Tertiary structure

The overall three-dimensional folding of a single polypeptide due to interactions among its R groups and the environment.

Quaternary structure

The assembly of two or more polypeptide chains into a functional protein.

Polypeptide

A chain of amino acids linked by peptide bonds.

Peptide bond

The covalent bond that links amino acids together in a polypeptide.

N-terminus

The amino-terminal end of a polypeptide (the start of the sequence).

C-terminus

The carboxyl-terminal end of a polypeptide (the end of the sequence).

Amino acid

The monomer units that make up proteins, each with an amino group, a carboxyl group, and a side chain (R group).

Gene

DNA segment that encodes the amino acid sequence of a protein.

DNA

Deoxyribonucleic acid; carries genetic information.

RNA

Ribonucleic acid; carries information from DNA and participates in protein synthesis.

Transcription

Process of copying a gene's DNA sequence into RNA.

Translation

Process by which ribosomes synthesize a protein from mRNA.

Denaturation

Disruption of a protein’s structure and function due to heat, pH change, or chemicals.

Renaturation

Reversal of denaturation; refolding of a protein to functional form under favorable conditions.

Enzyme

A protein that acts as a biological catalyst to accelerate chemical reactions.

Catalyst

Substance that increases the rate of a reaction by lowering activation energy.

Activation energy

Energy barrier that must be overcome for a reaction to proceed.

Substrate

The molecule(s) that bind to an enzyme’s active site and are transformed into products.

Active site

The region of an enzyme where the substrate binds.

Enzyme-substrate complex

Temporary complex formed when a substrate binds to an enzyme at the active site.

Lock-and-key model

Concept that the substrate fits the enzyme’s active site like a key fits a lock, with little or no conformational change.

Induced fit

Concept that the enzyme changes shape slightly to accommodate the substrate for better binding.

Amylase

Enzyme that hydrolyzes starch into glucose.

Protease

Enzyme that digests proteins into amino acids.

Hydrophilic

R groups that are polar and interact with water; often exposed on the protein surface.

Hydrophobic

R groups that are nonpolar and avoid water; tend to be buried inside the protein.

Salt bridge

Ionic interaction between oppositely charged R groups that helps stabilize structure.

Disulfide bond

Covalent bond between sulfur atoms in cysteine residues, stabilizing tertiary structure.

Hydrogen bond

Non-covalent bond important for stabilizing secondary and tertiary structures.

Polypeptide backbone

The repeating N–Cα–C sequence of the protein chain excluding side chains.

Globular protein

A compact, roughly spherical protein with a folded tertiary structure, often enzyme-like.

R group (side chain)

The variable group on an amino acid that determines its identity and behavior (polar/nonpolar, charged).

Secondary structure motifs

Common patterns such as alpha helices and beta sheets formed by backbone interactions.

Primary structure direction by genes

The amino acid sequence of a protein is determined by the encoded gene (DNA).

Denatured protein

Protein that has lost its native structure and function due to environmental changes.

Renaturation

Reformation of a functional protein structure after denaturation under favorable conditions.

Enzyme specificity

Enzymes act on particular substrates due to the shape and chemistry of their active sites.