Week 7 Flashcards
(36 cards)
translation
process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins after the process transcription of DNA to RNA in the cell’s nucleus. The entire process is called gene expression
amino acid
organic compounds that contain amine and carboxyl functional groups, along with a side chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen
amino group
nitrogen atom and two hydrogen atoms, amine
carboxyl group
organic, functional group consisting of a carbon atom that’s double-bonded to an oxygen atom and singly bonded to a hydroxyl group
peptide bonds
chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). This is a dehydration synthesis reaction (also known as a condensation reaction), and usually occurs between amino acids
peptides
a short chain of amino acids. The amino acids in a peptide are connected to one another in a sequence by bonds called peptide bonds. Typically, peptides are distinguished from proteins by their shorter length
polypeptide
short chains of between two and fifty amino acids, linked by peptide bonds. Chains of fewer than ten or fifteen amino acids are called oligopeptides
proteins
made from a long chain of these amino acids, each linked to its neighbor through a covalent peptide bond. Proteins are therefore also known as polypeptides. Each type of protein has a unique sequence of amino acids
wobble
a pairing between two nucleotides in RNA molecules that does not follow Watson-Crick base pair rules. The four main wobble base pairs are guanine-uracil, hypoxanthine-uracil, hypoxanthine-adenine, and hypoxanthine-cytosine
ribosomes
macromolecular machines, found within all living cells, that perform biological protein synthesis. Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains
anticodon
a sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA.
start codon
the first codon of a messenger RNA transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and Archaea and a modified Met in bacteria, mitochondria and plastids. The most common start codon is AUG. The start codon is often preceded by a 5’ untranslated region
Shine-Dalgarno sequence
a ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. The RNA sequence helps recruit the ribosome to the messenger RNA to initiate protein synthesis by aligning the ribosome with the start codon
release factor
a protein that allows for the termination of translation by recognizing the termination codon or stop codon in an mRNA sequence. They are named so because they release new peptides from the ribosome
polysome
a group of ribosomes bound to an mRNA molecule like “beads” on a “thread”. It consists of a complex of an mRNA molecule and two or more ribosomes that act to translate mRNA instructions into polypeptides
cistron
an alternative term for “gene”. The word cistron is used to emphasize that genes exhibit a specific behavior in a cis-trans test; distinct positions within a genome are cistronic
protease
enzyme that catalyzes proteolysis, the breakdown of proteins into smaller polypeptides or single amino acids. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds.
transfer-messenger RNA (tmRNA)
a bifunctional RNA that has properties of a tRNA and an mRNA. tmRNA uses these two functions to release ribosomes stalled during translation and target the nascent polypeptides for degradation
primary structure
the linear sequence of amino acids in a peptide or protein. By convention, the primary structure of a protein is reported starting from the amino-terminal end to the carboxyl-terminal end
secondary structure
local interactions between stretches of a polypeptide chain and includes α-helix and β-pleated sheet structures
tertiary structure
three dimensional shape of a protein. The tertiary structure will have a single polypeptide chain “backbone” with one or more protein secondary structures, the protein domains.
quaternary structure
number and arrangement of multiple folded protein subunits in a multi-subunit complex. It includes organizations from simple dimers to large homooligomers and complexes with defined or variable numbers of subunits
alpha helix
a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located three or four residues earlier along the protein sequence
beta strand/ sheet
a common motif of regular secondary structure in proteins. Beta sheets consist of beta strands connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet
