Lecture 2 Flashcards
Most abundant macromolecule in the cell?
Proteins
What determines the structure/function of a given protein?
The amino acid sequence of a protein determines it structure which ultimately determines how it is folded (3D structure) and what its function will be
What are proteins?
Polymers which are made up of amino acids monomers
Describe the structure of amino acids?
- Amino group
- alpha-carbon (bound to 4 atoms)
- Carboxyl group
- Side chain
T/F: At pH 7 the carboxyl and amino group of the amino acids are ionized ?
True, the amino group is positive and the carboxyl group is negative
How do the amino acid side chains differ?
- Polar/ Charged/ Hydrophobic
- Small/Large
- Covalently linked to polypeptides
Name the 5 polar amino acids?
- Asparagine
- Glutamine
- Serine
- Threonine
- Tyrosine
Least polar of the five amino acids and why ?
Tyrosine , has a hydrophobic ring that is more difficult for H-bonding
Characteristics of Polar amino acids?
- No charge
- Form H-bonding(non-covalent)
-Found near the cytosol
Name the three basic amino acids?
- Lysine
- Arginine
- Histidine
Histidine?
Only partially positive at a neutral pH because its nitrogens do not have high affinity for hydrogen
Characteristics of acidic and basic amino aicds?
can form ionic interactions between each other
10 Hydrophobic amino acids?
- Alanine
- Valine
- Proline
- Phenylalanine
- Glycine
- Cysteine
- Leucine
- Isoleucine
- Methionine
- Tryptophan
Characteristics of non polar amino acids?
Interact through hydrophobic interactions (exclusion of water molecules)
Cysteines?
Form disulfide bonding but not in the cytosol because it is a reduced environment
Link between two amino acids?
Peptide bond
What type of bonds can peptide bonds engage in?
Can engage in h-bonding
T/F: Both the polypeptide backbone and side chains can engage in non-covalent bonding?
True, polypeptide back bonde can for H-bonds with peptide bonds and side chains can form non-covalent bonds via H-bodning with polar amino acids
Flexibility of peptide bond?
Does not allow for free rotation due to the bond being planar and it has double bond character
Can the polypeptide backbone rotate at all?
Yes it can rotate around the alpha-carbon
Non-covalent interactions ?
- Hydrogen Bonds
- Van der Waals interactions(transient dipoles between all atoms)
- Ionic bonds
- Hydrophobic Interactions
How do hydrophobic interactions increase the entropy of the environment?
Hydrophobic molecules aggregate together meaning they require less water molecules to surround them . The excess water molecules are released to the environment and increase the entropy of it
Disulfide bonding?
-Covalent bonding
-Between cysteines
-Occurs in the extracellular proteins/secretory organelles
-Does not occur in the cytoso, nucleus or mitochondria
Purpose of disulfide bonding?
Reinforces structure of proteins with other proteins