8B and 9A - Peptides and Tertiary Structures Flashcards Preview

Intro to Biochemistry > 8B and 9A - Peptides and Tertiary Structures > Flashcards

Flashcards in 8B and 9A - Peptides and Tertiary Structures Deck (35):

What is glutathione?

A tripeptide found in most all organisms and is involved in protein and DNA synthesis, toxic substance metabolism (antioxidant) and amino acid transport


What is vasopressin?

An antidiuretic hormone that regulates water balance, appetite and body temperature


What is oxytocin?

A peptide that aids in uterine contraction and lactation


What are homologous Proteins?

Proteins that share a similar sequence and arose from the same ancestor gene


What is an invariant Amino Acid Sequence?

Those that are identical and presumed to be essential for function


What is a conservative Amino Acid Change in a polypeptide sequence?

A change to a chemically similar amino acid


What is the Variable Sequence Position in an amino acid sequence?

A less stringent sequence position, because they perform nonspecific functions


What are 7 Reasons to Sequence Proteins?

3D Structure Interpretation
Protein Engineering
Structure Prediction
To find the gene
Identify Post-Translational modification
Molecular evolution studies
Phylogeny (history or organismal lineages)


What genetic 'even't causes sickle cell anemia? Explain

Substitution of valine for a glutamic acid in β-globin subunit of hemoglobin. Valine is hydrophobic, unlike the charged amino acid will aggregate to form sickle shaped cells, low oxygen binding capacity and susceptibility to hemolysis is a result


What characterizes hydrogen Bonding in polypeptide α-helices? (eg. what bonds with what?)

N-H hydrogen bonding with a carbonyl four amino acids away


Which two amino acids do not foster α-helical formation?

glycine and proline


Which type of beta pleated sheet is most stable?

Antiparallel sheets are much more stable than parallel sheets


What are 4 examples of domains found in a large number of proteins?

Leucine Zippers (two alpha helices)
ATP binding domain or hexokinase
The α/β zinc binding motif


What do mosaic/modular Proteins consist of?

Repeated domains


What are 5 Interactions that stabilize tertiary structures?

Hydrophobic Interactions
Electrostatic Interactions (salt bridges)
Hydrogen Bonds
Covalent Bonds


What are oligomers

(In Quaternary Structures) Identical subunits in multisubunit proteins. Composed of protomers.


What are three reasons for multisubunit proteins?

Synthesis of subunits may be more efficient

In supramolecular complexes, replacement of worn-out components can be handled more effectively

Biological function may be regulated by complex interactions of multiple subunits


What type of interactions hold together polypeptide subunits?

Noncovalent interactions, covalent interactions like disulfide bridges are less common. Desmosine and lysinonorleucine linkages are also covalent (but rare as well)


What type of chemical bond is a disulfide bridge?



What is allostery?

Control of protein function by ligand binding. Ligands that do this are called effectors and modulators.


What is an allosteric transition?

Change of protein conformation in response to ligand binding.


What are two types of unstructured protein?

Intrinsically unstructured proteins (IUPs) or natively unfolded proteins


Proteins are categorized into families based on ___ and ____?

Proteins are categorized into families based on sequence and three dimensional shape (globular and fibrous)


What are conjugated proteins?

Proteins that have a protein and non-protein component (eg. lipoprotein or glycoprotein)


What are simple proteins?

Contain only amino acids


What are the four levels of protein structure?



Each beta strand (secondary structure of polypeptide) is stabilized by hydrogen bonding between what two groups?

Between N-H and carbonyl groups of adjacent strands. Parallel sheets ar much less stable than antiparallel sheets because of less hydrogen bonding.


What are five supersecondary structures (motifs) of proteins? (All have patterns of alpha-helix and beta-sheet structures).

1. βαβ unit (two beta sheets on either side of a helix)
2. β-meander (beta sheets side by side attached, like a closely space sin line)
3. αα unit (two alpha helices attached, extending next to each other)
4. β-barrel (a barrel formed by beta sheets wrapped into a cylinder
5. Greek key (beta sheets going up and down side by side to form a hollow S sort of)


Protein folding is defined as?

The process by which a nascent molecule acquires a highly organized structure. Information for folding is contained in the amino acid sequence


What does tertiary protein structure refer to?

The unique 3D structures formed by globular proteins, sometimes with prosthetic groups.
- Many proteins fold in a way to bring distant amino acids into close proximity
- Globular proteins are compact because of efficient packing


What is the core structural element of a domain called?

A fold


Domain modules are coded for by what type of genetic sequences?

Genetic sequences created by gene duplications


What is quaternary structure of proteins?

A protein that is composed of several polypeptide chains (subunits)
- Multisubunit proteins may be composed, at leas in part, of identical subunits and are referred to as oligomers (composed of protomers)


What are three reasons for the common occurrence of multisubunit proteins?

1. Synthesis of subunits may be more efficient
2. In supramolecular complexes replacement of worn-out components can be handled more effectively
3. Biological function may be regulated by complex interactions of multiple subunits.


Polypeptide subunits are mostly held together by what type of chemical interactions? What are some exceptions?

Noncovalent interactions
- Some exceptions are disulfide bridges (covalent) and desmosine and lysinonorleucine linkages (also covalent)