proteins Flashcards
describe the peptide chain formation.
- Initiation
- Begins with the binding of mRNA to ribosome
- start codon AUG signals the beginning of translation
- Initiator tRNA carrying methionine binds to the AUG start codon - Elongation
- Incoming tRNA molecules carrying amino acids bind to the ribosome.
- Peptide bond formation: The amino acid carried by the incoming tRNA forms a peptide bond with the growing polypeptide chain.
- Translocation: Ribosome moves along the mRNA, shifting by one codon.
- Empty tRNA is released from the ribosome. - Termination
- When a stop codon (UAA, UAG, or UGA) is reached, a release factor binds to the ribosome.
- The release factor causes the polypeptide chain to be released from the ribosome.
- Ribosome dissociates into its subunits.
- Polypeptide folds into its functional 3D structure, often assisted by chaperone proteins.
what is the genetic code?
- Triplet Code: The genetic code is read in sets of three nucleotides called codons. Each codon corresponds to a specific amino acid or a signal for the start or end of protein synthesis.
- Degeneracy: Most amino acids are encoded by more than one codon. For example, the amino acid leucine is encoded by six different codons (e.g., UUA, UUG, CUU, CUC, CUA, and CUG).
- Start and Stop Codons: The start codon, AUG (encoding methionine), signals the beginning of protein synthesis.
There are three stop codons (UAA, UAG, and UGA) that signal the termination of protein synthesis. - Universal: The genetic code is nearly universal, meaning that the same codons typically specify the same amino acids in all organisms. This universality allows for the exchange of genetic information across different species.
- Non-Overlapping: The codons are read in a non-overlapping manner, meaning that each nucleotide is part of only one codon.
- Redundancy: Due to degeneracy, some amino acids are specified by multiple codons. This redundancy helps protect against errors in DNA replication or mutation.
secondary structure refers to a basic pattern of _______ bonding.
give 2 examples.
hydrogen
2 examples: alpha-helix, beta-strand/sheet
which structure (pri,sec,ter,qua) refers to the 3D structure of the protein as defined by its atomic coordinates.
eg. a type or class of protein fold.
tertiary structure
what size are proteins?
5-10nm
pKa describes molecule’s what?
acidity
if pKa is less than pH of system, does molecule get deprotonated or protonated? give 1 example.
deprotonated
eg. COOH (pKa 2) when in physiological pH 7, donates proton (H+) and becomes COO-
which 2 amino acids have R group with pKa similar to physiological pH?
histidine, cysteine
what is a zwitterion?
molecule with both (+) and (-) chrges, and net charge of 0.
name 3 amino acids that are nonpolar, hydrophobic (usually found in core of protein) and aliphatic (linear, non-aromatic)?
glycine
alanine
leucine
proline
valine
isoleucine
methionine
which aliphatic (linear, non-aromatic) amino acid has an R group covalently bonded to amino group (NH2) and making a 5-membered ring?
proline
name 2 amino acids that have side chains that can H bond? (polar, uncharged)
serine
threonine
cysteine
asparagine
glutamine
name the 3 basic amino acids (positively charged).
which one is the most basic?
lysine
arginine (most basic)
histidine
name the 2 acidic amino acids (negatively charged).
which one is the most acidic
aspartate (most acidic)
glutamate
acidic amino acids can __________ protons while basic amino acids can __________ protons.
donate; accept
