Chapter 2 : Proteins Flashcards
What are proteins
A molecule composed of amino acids joined together by peptide bonds
How many amino acids are there in total
20
What is the basic monomer of proteins
amino acids
What are the three major groups of an amino acid ?
amino group (NH2) , carboxyl group ( COOH) and the side chain
What group gives the identity of the amino acid
the side chain
What kind of shape do amino acids have ?
tetrahedral shape
True or false , the central carbon on an amino acid is not chiral
False , the central carbon is chiral
What are the two enantiomers of all amino acids ?
L and D
Between the L and the D isomer, which one is mostly found in proteins
The L isomer
How many different types of amino acids are there?
5
Non-polar Aliphatic Amino acids
- Nonpolar
- Water insoluble ( CH bonds)
- 7 amino acids
Aromatic Amino Acids
- Contain an aromatic group
- nonpolar
- Able to absorb UV light
- 2 amino acids
Polar Uncharged Amino Acids
- Contain polar bonds ( OH, SH, or NH)
- contain no charges
- more soluble in water
- 6 amino acids
Acidic Amino Acids
- side chain is a COOH group
- weak acids but exist as COO- at neutral pH
- 2 amino acids
Basic Amino Acids
- Contain net positive charges at neutral pH
- contain amine group as side chain which is protonated
- 3 amino acids
How many dissociable hydrogens does every amino acid have AT LEAST ?
2 hydrogens
pK1
1/2 of the amino acid molecules have lost H from the COOH
- falls between pH of 2.0-2.4
pK2
1/2 of amino acid molecules have lost H+ from NH3 group
- falls between pH of 9.0-9.8
Where do peptide bonds form?
Between the carboxyl group of the 1st aa and the amine group of the 2nd amine
What is a biproduct of a peptide bond
water, dehydration synthesis
True or False, the peptide bond is a single bond which has resonance form in a double bond
True, the double bond inhibits rotation creating stability and polarity in the protein backbone
How many levels of protein structure are there ?
4
Primary structure
sequence of amino acids
Secondary structure
hydrogen bonding between adjacent amino acids to create α-helix or β-pleated sheet
Teritary structure
complete 3D shape of the polypeptide chain
Quarternary structure
structure that results after two or more interacting polypeptide chains come together
True or false, the primary structure contains all the info for the final 3D shape
True
True or false, the backbone of the protein is 3D
False, the backbone of a protein is planar
α-Helix
- found in secondary structure
- All H bonds are parallel to the axis
- helices can be right or left handed
β –pleated sheet
- formed from the protein backbone
- can either be parallel or antiparallel
- side chains extend out perpendicularly
β-turn
When the β-sheet is formed , the turn allows fo the backbone to bend, turn or reorient
Hydrophobic protein interactions
Nonpolar side chains cluster to avoid interaction resulting in protein folding
Ionic protein interactions
Attractions or repulsions between opposite or like charges on the side chains
Van Der Waal protein interactions
- quick dipole-dipole reactions resulting in fluctuations in electron distribution
Denaturation
the process which protein function begins to degrade due to the surrouding eniorment
