Chapter 11 Flashcards
What is the amino acid structure?
A central carbon atom attached to a hydrogen, carboxyl group (-COOH), amino group (-NH2), and an organic side chain (R group)
What is a polypeptide?
A continuous, unbranched chain of amino acids joined by peptide bonds. When amino acids are linked together to form polymers (which are called polypeptides)
What are peptide bonds?
The covalent linkage between amino acids
What are the four levels of protein structure and what do they do?
- Primary structure- its sequence of amino acids
- Secondary structure- interactions between amino acids cause primary structure to fold into a secondary structure, such as an alpha helix
- Tertiary structure- secondary structure folds further into tertiary structure
- Quaternary structure- two or more polypeptide chains may associate to create a quaternary structure
What is a codon? How many possible codons are there?
Three nucleotides in a row in the protein-coding region of a mRNA. Because there are 4 nucleotide bases (A, G, C, U), 3 in a row allows for 4^3 or 64 possible codons.
What are the 4 common features of the genetic code?
- Reading frame: The protein coding sequence can be read in groups of three nucleotides
- Nonoverlapping: It’s just three nucleotides in a row, then on to the next three- no overlap
- No punctuation: Nucleotides are not skipped
- The universality of the code: near universal, with some exceptions (very minor alterations, slightly different mitochondria)
What is the tRNA structure?
What are the 3 types of codons, how many of each are there, and what do they do?
Sense codons (61): encoding amino acid
Initiation codon (1 but can also act as sense codon): AUG
Termination codon (3): UAA, UAG, UGA
What is aminoacyl-tRNA synthetase?
attach the correct amino acid to its tRNA. Required for tRNA charging, must occur before translation
What does wobble mean?
Wobble occurs on the third position of the base pair.
The wobble position of a codon refers to the 3rd nucleotide in a codon. This nucleotide has two major characteristics: Binding of a codon in an mRNA the cognate tRNA is much “looser” in the third position of the codon.
How do proteins fold?
Primary, secondary, tertiary, and quaternary structures. Folding allows for specific proteins to carry out their specific function.
Where does transcription and translation occur in prokaryotic and eukaryotic cells?
Prokaryotic transcription occurs in the cytoplasm alongside translation. Prokaryotic transcription and translation can occur simultaneously.
In eukaryotes, transcription occurs in a membrane-bound nucleus while translation occurs outside the nucleus in the cytoplasm
What are the three main requirements for translation?
Initiation: Kozak’s sequence or Shine-Dalgarno/met-tRNA or fmet-tRNA, start codon, GTP, and IFs
Elongation: APE sites on ribosomes (70s or 80s) and elongation factors
Termination: Stop codon and Release factors
What are the required components of initiation during translation?
mRNA, ribosomes, 3 initiation factors, initiator tRNA with N formylmethionine attached to fmet-tRNA, energy molecule: GTP
What are the subunits of prokaryotic and eukaryotic ribosomes? What amount of ‘S’ does each type have?
Prokaryotic Ribosomes- 70S, 50S subunit and 30S subunit
Eukaryotic Ribosomes- 80S, 60S subunit and 40S subunit
