Bio chap 4 Flashcards
peptide bonds
successive amino acids in proteins are connected by PEPTIDE BONDS. The carboxyl group (COOH) of one amino acid rx with the amino group (NH3) of the next acid in line.
**molecule of H20 is released R groups t in different direction
polypeptide (protein)
a polymer of amino acids connected by peptide bonds
chaperones
evolved proteins, protect slow folding or denatured proteins until they can attain their proper structures
Denatured
most proteins can be unfolded, by chemical treatment or high temp. Chemicals removed, heat removed, all is good again…
Mutant proteins containing an amino acid that prevents proper folding are often devoid of their functional activity
Primary Structure
the sequence of amino acids in a protein, determines how a protein folds
secondary structure
interactions between stretches of amino acids in a protein—result from hydrogen bonding in the polypeptide backbone
tertiary structure
overall three dimensional shape….
the ability to carry out functions solely depends on shape
localized folding
hydrogen bonds can form between the carbonyl group
Which one of the following interactions is not a stabilizing force at the tertiary level of protein organization?
hydrogen bonding between a carbonyl oxygen of one peptide bond and an amide hydrogen of a nearby peptide bond
A cooperative effect often occurs in multi-subunit proteins, leading to improved function of the subunits when bound to each other.
true
Which one of the following statements about amino acids is incorrect?
The bridge between cysteines that connects parts of a protein is a stable, but non-covalent interaction.
Imagine that a researcher was able to travel back in time, shortly after the appearance of the first RNAs on Earth. What would she find?
precursors of tRNAs bound to nucleotides, and not amino acids
Alpha helices are coils with how many amino acids per complete turn?
3.6
Consider the following two statements about protein structure:
1 - All polypeptides have tertiary structure.
2 - All proteins have quaternary structure.
Which of the two statements above is correct?
Statement 1) is true; statement 2) is false.
Folding domains typically range in length from __________ amino acids.
25 to 100 or more
You are studying a protein that you call Protein X. There is an aspartic acid at a key position in Protein X which is important in the folding and stabilization of that protein. If this aspartic acid is changed to a different amino acid, which one of the following amino acid substitutions is most likely to allow the protein to fold normally?
glutamic acid
Imagine that a primary RNA transcript from your favorite gene was processed incorrectly, such that it has no 5’ cap. What would be the result?
The initiation complex would fail to form properly, and translation would not occur.
Secondary structures are stabilized by which type of interaction?
hydrogen bonding
All changes in gene sequence are mutations, but not all mutations decrease or increase in frequency over time.
true
Which one of the following statements about translation in eukaryotes is incorrect?
A single processed mRNA can possess multiple protein coding regions.
The bond between two amino acids is referred to as a(n) _____ bond.
peptide
A consecutive sequence of codons following a start codon is called a _______.
reading frame
False statements regarding glycine
- Glycine is an asymmetric amino acid.
- Glycine is a large, polar amino acid.
- Glycine is a relatively “inflexible” amino acid.
- Glycine is similar to tyrosine in terms of structure and chemical properties.
In metabolic processes that generate energy from six-carbon sugars like glucose, a molecule called NAD is often attached to an enzyme carrying out one of the metabolic reactions. Which one of the following folding domains is most likely to be found in the region of one of these enzymes where association with NAD occurs?
Rossman Folds
Which one of the following is specific to the synthesis of only one type of protein?
a messenger RNA
Members of a protein family often contain the same folding domain.
true
A(n) ________ is a group of functionally related genes transcribed as a polycistronic mRNA from a single promoter to a single terminator.
operon
Which one of the following ribosomal subunits has three different pieces of rRNA in it?
60S
One of your friends has decided to make it his life’s work to characterize all functional proteins, as he is convinced that all possible amino acid combinations can result in a protein. Is it possible to confirm his hypothesis in this way?
No, most amino acid sequences cannot produce functional proteins.
It is actually the 16S rRNA component of a 30S ribosomal subunit which is responsible for recognition of a Shine-Dalgarno sequence. Which one of the following sequences in the 16S rRNA would you predict is responsible for the interaction between a small subunit and mRNA?
3′-UCCUCCA-5’
Imagine that you have a unit of hemoglobin, a protein that is present in the aqueous environment of the human bloodstream. What type of folding domain does hemoglobin likely possess?
globin fold
Which one of the following types of proteins interacts directly with a stop codon?
release factor
Which of the following is not a possible function of a protein-folding domain
transfer of an amino acid to a ribosome
Scientists often utilize compounds resembling nucleic acids called “morpholinos,” which can effectively prevent translation of any part of an mRNA of interest. Which of the following statements is most likely true regarding morpholinos?
Morpholinos are complementary to the target mRNA sequence and bind to the region upstream of the initiation codon.
Which of the following statements is true regarding the development of pyrimethamine resistance in malaria parasites?
Full resistance to pyrimethamine is the result of four mutations that arose one at a time and together affected an enzyme present in malaria-causing parasites.
Which of the following processes occur in the cytoplasm of eukaryotic cells?
translation only
Imagine that a scientist is able to travel back in time to when the first proteins appeared. What would she not observe?
Proteins would be long compared to proteins today and would possess several folding domains
Which of the following represent possible functions for a protein folding domain (choose all that are applicable)?
catalysis
ligand binding
