Chapter 6: The Structures and Functions of Proteins Flashcards
What are amino acids?
There are 20 proteinogenic acid building blocks. Humans can only synthesize.
N-C-C
Amino group, alpha carbon, carboxyl group
True or False:
Only the L form of amino acids are found in cells
True
Amino acids are categorize in five groups. What are they?
- Nonpolar, aliphatic (open-chains)
- Aromatic (nonpolar and polar, resonance)
- Polar, uncharged
- Positively charged (basic)
- Negatively charged (acidic)
Examples of nonpolar, aliphatic amino acids
Buried within a protein or membrane, Will not be exposed to water. All contribute to protein folding except glycine.
-Glycine
-Alanina
-Proline
-Valine
-Leucine
Isoleucine
-Methinonie
Examples of aromatic amino acids
Absorbs at 280 nm
- Phenylaline
- Tyrosine
- Trytophan
Tyrosine
aromatic and amphiphatic . It can h-bond, ionize, and participate in acid-base reactions
Examples of polar amino acid
Polar because they’re asymmetrical. Imporatnt for interacting with DNA
- Serine
- Theronine
- Cystine
- Asparagine
- Glutamine
Examples of positively charged amino acid
Can form H-bonds and salt bridges. Can be found interacting DNA
- Lysine
- Arginine
- Histidine
Examples of negatively charged amino acids
Can form H bonds and salt bridges. Interacts with positively charged molecules
- Aspartate
- Glutamate
What amino acid would be found in the transmembrane portion of a protein?
Non polar amino acids
What is the direction of peptide bond formation?
N –> C
Peptide bonds
primary covalent linkage between amino acids in polypeptides
Partial double bond
Rotation around the peptide bond is limited due delocalization of the pi electron orbitals over the O-C-N
True or False:
Steric hindrances cab limit structures (cis vs trans)
True
True or false:
Peptide bond has resonance between the N and C=O of two amino acids
True
True or False:
Peptide bonds links the amino group and carboxyl group to the R group
FALSE
What are four levels of protein structures?
- Primary (sequence)
- Secondary (local folding)
- Tertiary (long range folding)
- Quaternary (multimeric organization)
Describe the primary structure of protein structure
linear sequence of amino acids held together by peptide binds, covalent and strong
Describe the secondary structure of protein structure
Interactions between the parts that make up polypeptide backbone, primarily alpha-helix and beta-sheet, which maximize hydrogen bonding
Describe the tertiary structure of protein structure
Overall conformation stabilized by weak interactions from often distant amino acids, final folding in 3D space
Describe the tertiary structure of protein structure
Proteins consist of multiple polypeptides
True of False:
Primary structure often determines secondary, tertiary, and quaternary structures
True
Molecular chaperone
Prevent improper folding by providing a hydrophobic chamber for refolding. Example id PDF
What is the purpose of PDF (Protein disulfide isomerase)
forms and breaks disulfide bonds in the ER to assist folding
Alpha helix is the _____ stable arrangement, _____-handed helix
Most, right
Alpha helix is the _____ stable arrangement, _____ -handed helix
Most, right
Regarding the alpha-helix, why are proline and glycine not found in alpha-helix?
Proline cannot form H-Bonds and cause turns. Glycine is too flexible
Regarding the alpha-helix, sequence determines if there is stabilization
kk
Alpha- helix supercoiling has 3.6 turns, giving it a twist. Alpha helices interact at 18 degree angle from parallel.
Allows side groups to interact with onpther helix helix
Alpha- helix supercoiling has 3.6 turns, giving it a twist. Alpha helices interact at 18 degree angle from parallel.
Allows side groups to interact with another helix
What are the two types of beta-sheets?
Parallel and anti parallel
Define Parallel Beta-sheet
Adjacent chains run in the same N–>C direction
Define antiparallel Beta-sheet
Adjacent chains run in opposite N–>C
Antiparallel Beta-sheets are more or less stable than Alpha-helices?
More bc of their 180 degree H bonds
In regards to beta-helices, Type 1 turn
Contains proline
In regards to Beta-helices, Type 2 turn
Contains glycine
Turns are very _____ to minimize the number of unfilled H bonds
short
What are the four types of bonds or interactions that contributes to tertiary structure stability?
Hydrogen bonds
Disulfide bridges
Ionic bonds
hydrophobic interactions
