Chapter 3,17 Flashcards
How does each amino acid differ from one another?
from the molecular structure of their R-group
why is the α carbon in glycine not asymmetrical?
glycine only has 3 unique groups
how does cysteine differ from other amino acids?
has a sulfhydryl functional group, can form disulphide bonds
what kind of turn can a protein with glycine make?
tight turns b/c of how small glycine is
what is special about proline’s shape?
R-group connects to amino group in backbone
what does proline do in proteins?
affects flexibility, found in permanently locked turns
what kind of bonds are between double bonded carbon and peptide bonds in polypeptides?
a partial double bond
why can’t peptide bonds rotate?
peptide bonds have 2nd resonance form, C=O and N-H reside in a single plane
what is the difference between proteins and polypeptides?
proteins - correctly folded
polypeptides - not correctly folded
what bonds are present in primary structures?
peptide bonds
what bonds are present in secondary structures?
hydrogen bonds between peptide backbones, which determine polypeptide orientation (a helices or b pleated sheets)
what bonds are present in tertiary structures?
ionic, hydrogen, and covalent bonds (such as disulfide bonds) between R-groups, as well as hydrophobic forces in nonpolar interior
what bonds are present in quaternary structures?
weak bonds
is a polypeptide’s primary structure disrupted when denatured?
No, peptide bonds are polar covalent, hard to break
how is a polypeptide’s primary structure read?
from amino end to carboxyl end
what is an α helix?
tightly twisted coil, stabilized by hydrogen bonds btwn an amino acid’s carbonyl group and an amino acid’s amino group 4 residues away
what is a β sheet?
pleated sheet stabilized by hydrogen bonds between carbonyl groups in one chain and amino groups in other chain
what is a tertiary structure?
protein’s 3D shape, made of several secondary structures, formed from weak bonds and interactions btwn R-groups
how is the ball-and-stick model useful for illustrating tertiary structures?
shows atoms and bonds
how is the ribbon model useful for illustrating tertiary structures?
shows a helices and b sheets of secondary structures in proteins
how is the space-filling model useful for illustrating tertiary structures?
shows actual size, shape, and contour of protein
the tertiary structure determines a protein’s function by:
contours and distribution of charge on outside
presence of cavities
what are functions of proteins?
enzymes, defense, storage, transport, hormonal, structural, contractile and motor, receptor and communication
what factors causes a protein to denature?
pH, temp, salt conc.
how is renaturation possible in proteins?
intact primary structure,
optimal conditions return
what components are required for translation?
mRNAs, tRNAs, Ribosomes, Aminoacyl-tRNA-synthetase, release factor
what is translation?
mRNA sequence specifies order of amino acids in a polypeptide
how is genetic code universal?
all codons specify same amino acids in all organisms
how is genetic code unambiguous?
each codon codes for only one amino acid
how is genetic code redundant?
many amino acids are specified by more than one codon
how is genetic code being universal useful?
biotechnology, genetic engineering
what do ribosomes facilitate?
process of translation
what three sites does the large subunit of a ribosome contain?
A, P, and E sites
what is the A site?
aminoacyl - holds aminoacyl tRNA
what is the P site?
peptidyl - holds tRNA with growing polypeptide attached
what is the E site?
exit, holds a tRNA that will exit
what are codons?
continuous, non-overlapping groups of three nucleotides
what are tRNAs?
transfer RNAs bind to amino acids and bring them to mRNA at ribosome during translation
what is an aminoacyl-tRNA or charged-tRNA?
tRNA that is linked to its amino acid
what is an anticodon?
sequence in tRNA that is complementary to codon sequence in mRNA
how do the anticodon and codon pair?
in an antiparallel direction
what do aminoacyl-tRNA-synthetases do?
catalyze addition of amino acids to tRNAs
how many aminoacyl-tRNA-synthetases are there?
20, one for each amino acid in proteins
how is genetic code redundant?
wobble hypothesis - only the first 2 bases of codon have precise pairing with the bases of anticodon of tRNA, while pairing btwn 3rd bases of codon and anticodon may wobble
what are the four main wobble base pairs?
G-U
I-U
I-A
I-C
what does the wobble hypothesis allow?
phenomenon permits a single tRNA to recognize more than 1 codon, allows mRNA codons to be translated w/ fewer than 61 tRNAs required w/o wobble
what are 3 separate processes of translation?
initiation, elongation, termination
what is process of initiation in translation?
- mRNA binds to small subunit
- Initiator aminoacyl-tRNA binds
- Large subunit of ribosome binds
what is process of elongation in translation?
- incoming aminoacyl tRNA
- peptide-bond formation
- translocation
what is process of termination in translation?
- release factor binds to stop codon
- polypep. & uncharged tRNAs release
- ribosome subunits separate
what is cotranslational folding?
protein folding occurs simultaneously as polypeptide chain extended during elongation
what is a release factor?
protein that binds to A site of ribosome when stop codon is encountered
