Biology Lecture Notes: Macromolecules, DNA Replication, Transcription, and Translation

Vocabulary flashcards covering key terms from the lecture notes.

Hydrolysis

Addition of water to break a covalent bond; opposite of dehydration synthesis; used to break down polymers such as polysaccharides, proteins, and nucleic acids.

Dehydration synthesis

Removal of water to form covalent bonds between monomers; builds polymers (e.g., joining amino acids into proteins).

Dipeptide

A molecule composed of two amino acids linked by a single peptide bond formed during dehydration synthesis.

Peptide bond

A covalent bond that links amino acids together in a protein; formed by dehydration synthesis between the carboxyl group of one amino acid and the amino group of the next.

Polysaccharide

A polymer of monosaccharides; can be hydrolyzed by hydrolysis; serves roles in storage and structure.

Translation

Process by which a ribosome reads mRNA and synthesizes a polypeptide (protein) using tRNA as adaptors.

Initiation (translation)

Stage where the ribosome assembles with the initiator tRNA and start codon to begin protein synthesis.

Elongation (translation)

Stage where amino acids are added one by one to the growing polypeptide via A-site tRNA, forming peptide bonds.

Termination (translation)

Stage where a stop codon is reached; a release factor promotes dissociation of ribosomal subunits and release of the finished polypeptide.

Prokaryote

Simple, single-celled organism lacking a nucleus and membrane-bound organelles; transcription and translation occur in the cytoplasm.

Eukaryote

Organism with a nucleus and membrane-bound organelles; transcription occurs in the nucleus and translation in the cytoplasm.

Leading strand

The DNA strand synthesized continuously in the 5' to 3' direction; template runs 3' to 5' toward the fork.

Lagging strand

The DNA strand synthesized discontinuously as Okazaki fragments; primers are needed and fragments are joined by ligase.

Primer

Short RNA sequence laid down by primase to provide a 3' hydroxyl group for DNA polymerase to begin synthesis.

DNA polymerase

Enzyme that adds nucleotides to a growing DNA strand in the 5' to 3' direction; replaces RNA primers during replication.

DNA ligase

Enzyme that seals nicks between Okazaki fragments by forming phosphodiester bonds to create a continuous strand.

Topoisomerase

Enzyme that relieves torsional strain ahead of the replication fork by cutting and rejoining DNA.

Helicase

Enzyme that unwinds the DNA double helix by breaking hydrogen bonds between base pairs.

Single-stranded binding protein (SSB)

Protein that stabilizes unwound DNA during replication to prevent reannealing; non-enzymatic.

Phosphodiester bond

Covalent bond linking the sugar of one nucleotide to the phosphate of the next, forming the sugar–phosphate backbone of DNA/RNA.

Base pairing

Complementary pairing between DNA strands: A binds T (2 hydrogen bonds) and G binds C (3 hydrogen bonds).

Base stacking

Hydrophobic interactions and Van der Waals forces between adjacent bases that stabilize the DNA double helix.

Antisense strand

The template DNA strand used for RNA synthesis; read 3' to 5' during transcription.

Promoter

DNA sequence where transcription factors bind to initiate transcription; determines where RNA polymerase begins.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template during transcription; does not require a primer and reads DNA 3' to 5'.

Transcription

Process of copying a segment of DNA into RNA (mRNA) by RNA polymerase; occurs in the nucleus in eukaryotes.

R group

The side chain of an amino acid; determines properties such as polarity, charge, and hydrophobicity.

Hydrophobic interactions

Nonpolar regions avoid water and tend to cluster together, contributing to protein folding and base stacking in DNA.

Van der Waals forces

Weak intermolecular attractions due to transient partial charges that contribute to molecular stability.

Neutral lipids

Nonpolar lipids (e.g., fats, oils, triglycerides) that are hydrophobic and store energy.

Phospholipids

Lipids with a phosphate-containing head and two fatty acid tails; amphipathic and form lipid bilayers in membranes.

Sterols

Lipids with four fused rings (e.g., cholesterol); components of membranes and precursors to steroid hormones.