Protein Structure and the Genetic Code (G) Flashcards
What is a polypeptide?
A chain of covalently linked amino acids
What does each mRNA specify?
It specifies a particular amino acid sequence of a particular polypeptide
What is a protein in comparison to a polypeptide?
It is a structure made of one or more polypeptides that has a distinct function within an organism
What is E. coli RNA polymerase?
It is a protein made of six interacting polypeptides
What is the function of RNA polymerase?
To synthesize RNA
What are amino acids?
They are individual monomers that make up a polypeptide
What is the basic structure of all amino acids?
There is a central carbon atom that is covalently bonded to a hydrogen atom, an amino group, a carboxyl group, and a side chain/R group
What is the purpose of a side chain/R group?
The side chain is variable in the composition of amino acids
This variation distinguishes one amino acid from another
How many different amino acids are there?
20 amino acids, all with a different side chain
Certain side chains share similar chemical properties. What are the four broad groups amino acids are separated into?
- Acidic side chains
- Basic side chains
- Uncharged polar (hydrophilic)
- Nonpolar (hydrophobic)
How are amino acids linked together?
Peptide bonds
How is a peptide bond formed?
By linking the carboxyl group of one amino acid to the amino group of another
How many peptide bonds can each amino acid make? Why?
Two peptide bonds
This is because each amino acid has one carboxyl and one amino group
What is the orientation of all amino acids and polypeptides?
The amino groups are directed toward one end of the polypeptide and the carboxyl groups are directed toward the other end
What is found at the ends of a polypeptide?
There is an amino acid with a free amino group in one end
There is an amino acid with a free carboxyl group at the other end
What is the end with a free amino group called?
Amino terminus
N terminus
What is the end with a free carboxyl group called?
Carboxyl group
C terminus
What is a polypeptide’s conformation?
It acquires a unique 3D shape after being synthesized (i worded this weird mb)
How are conformations formed in polypeptides?
By interactions between different functional groups within the amino acids
What is the conformation of polypeptides dependent on?
On the amino acid sequence of the polypeptide
What is considered the primary structure of a polypeptide? Why?
The amino acid is considered the primary structure because conformation is dependent on it
What are the different levels of conformation?
Secondary
Tertiary
Quarternary
What is secondary structure?
The conformation within a particular area of one polypeptide
What is tertiary structure?
The overall conformation of one polypeptide
What is quarternary structure?
The overall conformation of a protein that contains two or more polypeptides
What kind of structures are found on a protein consisting of one polypeptide?
Primary
Secondary
Tertiary
(NO quarternary)
Where is a protein’s function acquired?
From its conformation
What happens to a protein’s function if its conformation is lost?
The function will also be lost
How is each amino acid specified?
It is specified by a group of three bases called a codon
What are the other names for codons?
Triplet codons
Triplets
Why is the order of bases in codons important?
Each codon specifies a different amino acid
EX: The codon CCA specifies a different amino acid than CAC or ACC
If codons are a genetic language, what are the bases in the gene/mRNA and what are the codons?
The bases would be considered the alphabet and the codons would be the words
What do codons (the “words”) make up?
The genetic code
What does translation do to the genetic code?
It turns it into the amino acid sequence of a polypeptide
How mano possible codons exist?
64 codons
How many codons code for amino acids?
61 codons
There are 61 codons for amino acids but only 20 amino acids. What does that mean?
That means most amino acids are encoded by more than one codon
Which amino acids are encoded by a single codon?
Methionine and tryptophan
Why is the genetic code considered to be degenerate?
Because an amino acid may be encoded by more than one codon
Which codons do not encode amino acids?
UGA
UAA
UAG
What is the function of the three codons that do not encode amino acids?
They function as translation termination signals
STOP codons
What does the codon AUG labeled as?
Methionine
Start
What is the rule for the codon AUG?
All AUG codons specify methionine, but not all AUG codons are translation start signals
Which AUG codon is considered the START codon?
Only the first AUG in an mRNA can be the start codon
Any other AUG is considered to be methionine
What is the genetic code sometimes referred to as? Why?
The universal code
This is because the genetic code is almost identical in all organisms
What are some exceptions to the universal code?
Variations have been found in the mitochondrial DNA of many eukaryotes, and in some bacterial and protists species
